You've seen it before-they did it in Japan and they did it in the US. But those were one-off cars. Who else but HASport would competently engineer the first readily available K-series engine swap for the new GD or Fit chassis?
Though it's been in Asia for some time as either the Jazz or the Fit, America just got the Fit for the 2007 model year as an attempt to compete with Scion and position beneath the ever-bloating Civic. While you might wish that the Fit weighs as little as it looks (so this would truly be a big engine in a small car), today's emissions and safety regs mean it's just not the case. The Fit weighs about 2450 pounds, right in the ballpark of the old EK chassis.
But it's new, has all that safety tech, looks like a trendy micro-car and, given the power levels tuners are achieving with the K-series engines, could really haul some ass with this swap.
Picking The Chassis
Not a whole lot to choose from here, the Fit is the Fit. There's a Sport model, but it's really a mild cosmetic and suspension change. You'll be starting with a fairly new car with lots of fancy sensors and electronics to sort through. You don't want to try this with a Fit that has the CVT (continuously variable transmission), since you'll need a proper shifter on the floor. Plus, it's cheaper-list price for a basic Fit is $13,850 at the time of writing.
Picking The Engine
The choices are endless since Honda has so many versions of the new K-series engine. For this particular swap, HASport used a K20Z3-the engine from the new 2006 Civic Si. It also used its six-speed tranny with its excellent ratios and factory limited-slip differential, something absolutely necessary for something with this much power and oddball weight distribution. But any 2.4-liter K-series from the Accord or TSX can be used-they'll all fit under the Fit's tall hood.
Keep in mind the good K-series engines are from the RSX-S, TSX and the 2006-up Si. Unfortunately, the other K-series don't have real iVTEC and make considerably less power. They are a good deal cheaper, though, and with new cams from companies like Brian Crower or Skunk2, it's possible to make credible power with these engines. You decide: budget or baller.
The transmission is a little more trouble, but one from the previous generation 2002 to 2005 EP3 Civic Si or 2002 to 2006 Acura RSX or RSX-S is cool. Right now, the TSX and all other K24 transmissions have a different housing so they aren't compatible with the bolt-in HASport kit. The 2006-up Si will also work, but, like the '05-up RSX, it uses a different speed sensor. The earlier one is easy to work with, the newer one is different and gives most gauges trouble.
Engine Removal
First, getting the shop manual from www.helminc.com is highly recommended and it's usually cheaper than from the dealer. Start by removing the bumper fascia, radiator, condenser and fans. Then, remove the lower subframe. Disconnect the lower suspension arms, then the front lower transmission mount, then the rear mount at the back of the subframe. There's no reason to remove the Electric Power Steering (EPS) from the car. Just unbolt the rack from the subframe so it stays on the chassis. Drop out the subframe and then remove the axles.
Next, discharge the A/C system, since at least one of the hard lines will need to come off. Do it the right way and evacuate it with the proper equipment. According to the Fit manual, you can use a hoist to support the engine from the top, but you can also support it from the bottom on a 10-inch or taller cart. Then instead of lowering the engine to the floor, the car can be raised off the engine. Test fitting is much easier this way and is how the swap is illustrated.
Wiring: The Fork In The Road
As with most modern engine swaps, electronics and wiring present the main problem. The Fit engine has uses a drive-by-wire (DBW) electronic throttle body and an SOHC VTEC system, not the DOHC iVTEC found on K-series engines. So modifying the stock ECU to run the new engine isn't even an option. Problem two, the Fit's dash, like most new Hondas, is controlled by CAN-bus communication via the ECU. But since each car has its own CAN protocol, a K-series ECU cannot just be plugged in and expected to run the Fit gauge cluster. The level of integration is so high that there's really no way of getting the Fit dash to work without the original ECU.
This is the fork in the road for the swap. Use a Hondata K-Pro ECU and run the engine, but have no gauges, or use the Fit's ECU and lose the iVTEC. The only way to have your cake and eat it is to do both. As a prototype for this swap only, Hondata and HASport have worked together to piggyback a K-Pro ECU onto the Fit's ECU. The K-Pro controls the engine in terms of fuel, ignition, closed loop operation and cams, while the Fit's ECU talks to the gauges, go pedal, e-throttle and the rest of the car. It requires a custom jumper harness, which the two companies are looking into selling, that lets the two computers coexist in relative harmony. Unfortunately, at this point there is no plan for Hondata to offer the wiring harness as a kit, since it's far from a plug-and-play affair, but customer demand might just change that.
To keep it simple, a K-Pro, an E plug to add some inputs and outputs that aren't in the stock engine harness plugs, and a rack of gauges is all that's required, just as we've seen in previous K24 swaps. You will need a speedo, engine temp, check engine indicator, tach and fuel level, at a minimum. For about $750, Racepak's 250-DS-UDXSR street dash has all the above, plus oil temp and pressure, high beam, odometer, brake and turn signals.
Going this route means a lot of re-wiring. Hondata has K-Series swap wiring listed on www.hondata.com/images/k20awiring.gif. The Fit factory service manual is needed to build a subharness that integrates with the cabin harness. The harness needs a starter signal, then power for the main relay, fuel pump relay, O2 sensor relay and ECU. With a dash like the Racepak, a lot of the connections are available from the ECU. Just add the missing sensors. Lots to do, but possible.
Which way you go determines what you will use as an engine harness. The Hondata way uses the original engine harness. Add another cam sensor and wiring, wires for the VTC cam actuator and stretching it here and there is all that needs to be done. If you're going K-Pro only, use the K20's engine harness. Slight modifications and the cabin subharness are needed as mentioned above.
It's also rare to find a K20 engine with the starter and alternator harness. For some reason, these are on a separate harness that also connects to the battery. If you have it, great, modify it to, um, fit. If not, strip the four alternator wires, starter wire and charging wire from the stock harness and integrate them to the engine harness you have. Don't forget the K-series uses a wideband primary O2 sensor. If you didn't get it with your swap, you'll need to buy one.
If all this sounds too complicated, HASport is working on the solution. It will offer a complete harness made from the K20 and L15 engine harnesses along with all that's needed to connect to the Fit's cabin harness, including the O2 sensor connection (but not the sensor).
Engine Mounting
This is probably one of the hairiest engine shoehorn swaps we've done. Although the drive configuration is similar, the stock L15 Fit engine is narrow, and so the engine bay is narrow, even though it has plenty of height. The K20 and trans, on the other hand, is pretty wide. To make the fit, a number of things need to be moved around and the left-side frame rail needs a circular hole cut into it. Other than that, the HASport kit uses the stock mounts resourcefully, with new brackets. In the future, replacement mounts will be offered for less engine movement or even getting racy with the stock engine.
The first thing to do is move the brake lines along the passenger side and back of the engine bay. They will need to come out of the white locator clips and be gently bent by hand to hug the firewall and move along the wheel well above the frame rail. This, in conjunction with removing the hard A/C lines, opens up the right side of the engine bay completely.
While you're there, do the same type of operation to the ABS modulator. It needs to be much closer to the headlight to make room for the idler pulley of the K-series and a HASport bracket. It will take modifying the stock hold-down brackets to reposition the modulator securely.
Moving to the driver side of the engine bay, clearance needs to be made on the chassis frame rail for the transmission case. Measure 10.5 inches back from the bulkhead and cut a notch 2.5 inches in diameter. A hole-saw is recommended. Double-check the notch by lowering the car on top of the engine and checking the clearance. The notch should only be about 0.25 to 0.375 inches deep. Make sure to reinforce the frame rail after removing the material.
Double-check the notching again, this time with the mount in place. This will give you an idea of how much material to remove from one edge of the notch for clearance. Under acceleration, the engine will move forward and up an inch or more. Make sure there is room for that, because when aluminum from the transmission case comes into contact with the steel of the frame rail, steel wins.
The last place to make some room is out front. The radiator core support needs to be trimmed just a bit to clear the intake manifold. Again, lowering the car to the engine will show the amount to remove. Allow at least an inch of clearance, because the stock mounts let the engine move under hard acceleration.
Now the engine bay of your squeaky-new Fit has been hacked into a work of modern industrial art, there's another problem. The only intake manifold that works with this swap is from the 2002 to 2006 RSX Type-S, EP3 Si or JDM Civic or Integra Type-R. They have the large flat front and the letters RBB or RBC cast into them. The longer Euro R, TSX or 2006-up Si manifolds stick out farther and will hit the radiator. The RBB and RBC manifolds will interfere with the alternators from the Accord, TSX and 2006 to 2007 Civic Si. An alternator from a 2002 to 2005 EP3 Si, any RSX or CR-V can be substituted. In addition, on some heads (mostly K24), you will need to plumb the thermostat bypass passage in the head, just to the side of the number one intake runner, back into the coolant system. HASport makes an adaptor plate for this. Don't just block it off, as this is a coolant passage.
Now clean up the K-series engine and take off all the accessories. If you have an engine with power steering, you'll need to replace it with an idler pulley and bracket from an EP3 Si, since the Fit has EPS. To retain the A/C, use the compressor from the EP3 or RSX, because it has a single wire control for the clutch like the Fit. Most K24s have a three-wire setup, not compatible with the Fit. You'll also need to redo the suction and receiver hoses.
Accessory belt size varies, depending on several factors. For K24s and the K20A3, you can use the EP3 (2002 to 2005 Civic Si) belt. On a K20A2, Z1, Z3 or any of the K20A Type-R engines, the crank pulley is smaller, so a shorter belt than the EP3 is required. No A/C? Start with a belt about 1.5 inches smaller than an EP3 and go from there.
If the engine harness is not on, install it. Install the half-shaft from an EP3 Si or RSX, which have 6MN, S5T30 or SNG30 stamped on them. These are the only Honda axles with the proper length and mounting flange pattern. Bolt the HASport right-hand engine bracket to the block using two of the stock bolts and one of the HASport-supplied bolts. With the engine and transmission on the support stand, lower the car over it. Keep a close watch on the VTEC solenoid on the rear of the engine, the clutch actuator fork, and the slave cylinder on the front of the transmission. You may need to twist the engine while lowering the car to avoid contact. This is a two-man job.
Once the car has been lowered and the engine is within a few inches of where the mounts are, install the left-hand transmission bracket using the HASport hardware. Then place a spacer under the bracket on the outside rear mount hole, so the bracket mounts flush. Leave the bolts finger-tight at this time. Continue to lower the car until you can bolt the transmission bracket to the mount. Use the stock bolt and HASport-supplied nylon lock nut.
The Fit's left-hand upper engine mount will need to be modified for clearance. Grind down the small nub on the top, near the upright stud. Notch the mount on the left inside edge to clear the engine-mounted HASport bracket. Put a couple bolts in the right-hand mount (passenger side) and check for clearance (0.25 inches).
Leaving those bolts loose, attach the HASport top bracket with the supplied two bolts. If the hole on the mount end doesn't match up, try moving the engine around until it does. Torque the two HASport brackets to spec and finger-tighten the factory nut at the top of the Fit's right-side mount. Finger-tighten all three factory mount bolts. If nothing looks bound up, torque the top nut on the Fit mount to spec and then do the same for the three bolts around its base. Go to the right side and torque all those fasteners as specified in the HASport directions.
Drivetrain Hook-Up & Engine Accessories
Attaching the two side mounts will hold the engine for now. The swap needs custom-length driveshafts. HASport and the Driveshaft Shop plan to have these available. Install the driveshafts and then attach the lower subframe. After that, the lower control arms can be bolted to the knuckles.
Bolt the steering rack and gearbox back to the subframe. Finger-tighten the Fit's rear mount to the HASport bracket, using the stock rear mount bolt and HASport-provided nylon lock nut. Install the bracket and mount into the subframe together as a unit. You may need to lift the front of the engine to make room for both parts to be installed and line up properly. Install the rear mount using the factory hardware. Don't tighten yet.
Next, bolt the HASport rear bracket to the engine and transmission. The front hole will use the stock bolt you removed earlier from the transmission. The other two holes will use the HASport-provided hardware. Once all three bolts are in, torque the mount and bracket to HASport installation manual specs.
The Fit's radiator fans will no longer work, but the car needs at least one 12-inch electric pusher fan (two, if you keep A/C) on the front of the radiator. Connect it to the stock harness, so the K-Pro can control it. A lower GSR radiator hose, properly cut, will connect both the top and the bottom of the Fit's radiator.
Attach the alternator, connecting it to the alternator/starter-specific harness. Bolt on the EP3 idler pulley and bracket and, whether or not you're using A/C, install it along with the correct belt and new lines.
If you plan to keep the e-throttle (like the HASport Fit), install the HASport adaptor plate and the throttle body (the TSX unit is the largest at 2.44 inches). Most won't be doing this, so the Fit must be converted to drive-by-cable. The pedal assembly will need to get swapped with something from another Honda or custom-fabricated. It will also take some experimentation to find the right length of throttle cable.
Because HASport had a 2006 Si at its disposal, it used the car's K20Z3 engine and transmission. If, by some enormous amount of luck, you can find one of these gearboxes, you can use the Fit's shifter assembly with shortened 2003-up Accord shifter cables. For the rest of us, only a tranny from an EP3 Si or any RSX will work. For these gearboxes, you also need the original shifter cables and shifter box from the chassis. TSX, Accord and other gearboxes have different casings and the HASport mounts won't line up.
The Fit's shifter box won't work because the way it operates the cables is the reverse of the EP3 Si or any RSX gearbox. That's why you'll need the cables and shifter box that match your tranny. The shifter box will also need to be modified. The center tunnel has a big bump that will need working around. But once installed, simply pass the cables through the floor in the stock location.
Fuel System
Luckily for us, Honda's streamlining process means that both the L15 and the K20 use similar quick-disconnect system fuel lines and connectors. With hardly any adjustment, the Fit's fuel line will snap right onto the K20 returnless system fuel line.
Tuners have found the RSX's fuel pump will support up to about 400 wheel-hp, but the Fit's pump is an unknown. Anyone going turbo or using large injectors may want to replace the stock fuel pump. For a mostly stock K-series, the Fit pump will work fine.
Intake And Exhaust System
For an intake, any of the aftermarket RSX short ram units work well. For true cold air, though, you'll need to make one. The exhaust is a bit more complicated, because the Fit has a flat floor with the gas tank under the front seats. Jackson Racing has come to the rescue and will be manufacturing headers that will clear the EPS, the subframe and then terminate just before the exhaust, making a sharp right turn to go down the side.
The header seen here is the prototype for the Jackson Racing unit and should be nearly identical to a production version. Jackson Racing is also working on an exhaust, including a version that should flow well enough to support forced induction.
Measure Twice, Cut Once
This is a complicated swap. The electronics and wiring make it a real challenge. Bending the brake lines gently and getting some new A/C lines, plus cutting and reinforcing a frame rail, means you need to be a competent mechanic.
Any K-series engine will work, but the best is one from an EP3 Si or an RSX. If the engine is still in the car, here's a check list of what the junkyard needs to pull out: engine, transmission, shifter cables, shifter box, primary O2 sensor, ECU, alternator, engine harness, battery/starter/ charging harness and, if you want A/C, the compressor and suction hose. If the engine doesn't have the RBB or RBC manifold, it'll also need one of those.
Decide up front if you're going to do this with just a K-Pro or hope HASport or Hondata makes the harness that lets you keep the Fit's ECU so it can run the dash and a few other creature features.
| K-Series Engine Codes & Chassis | ||
| Engine | Year | Model |
| K20A | 2001-up | Euro/JDM ITR and CTR, JDM Accord Euro-R |
| K20A2 | 2002-2004 | RSX-S |
| K20A3 | 2002-2005 | USDM Civic Si, |
| 2002-2006 | RSX | |
| K20Z1 | 2005-2006 | RSX-S |
| K20Z2 | 2006-up | Acura CSX (Canada), |
| 2006-up | JDM Civic | |
| 2006-up | Euro Accord | |
| K20Z3 | 2006-up | USDM Civic Si |
| 2007-up | Acura CSX Type-S (Canada) | |
| K23A1 | 2007-up | RSX |
| K24A1 | 2002-2006 | CR-V |
| K24A2 | 2003-up | TSX |
| K24A3 | 2003-2006 | Accord (Japan, Europe & Australia) |
| K24A4 | 2003-2005 | Accord & Element |
| K24A8 | 2006-up | Accord |
The Basics
*Use any K-series engine
*Only RSX (all models) and EP3 transmission
*Requires Hondata K-Pro
*Fit's dash will not work without Fit ECU, requires lots of gauges
*Hondata or HASport may have harnesses for both K-*Pro and modified Fit ECU, which allows Fit dash to function
*Custom axles and specific half-shaft
*Custom header and exhaust (Jackson Racing-supplied)
*RBB or RBC intake manifold required
*EP3 idler pulley assembly
*Minor cutting, welding and fabrication required
While the three to four Impreza-based project cars we've been involved with in the past were built to be edgy, pissed-off machines, capable of doing double duty on both track and street, we wanted something different with our Project 2006 WRX. The response from the new variable-cam 2.5-liter EJ25 engine easily eclipses the horrendous lag of the old 2.0-liter. Since the engine physically moves more air, boost is instantaneous and linear, and is much more suited to city acceleration than the peaky old EJ20-or the constant insanity of the STI.
The new WRX's steering feel is also improved, on-center vagueness is reduced. The transmission update means there's no more guessing about whether or not the car's in gear, or double-clutching to get into reverse. With so many improvements applied throughout, we decided to focus on tightening the suspension first.
Initially, our hope was to show that, for a pure street car on street tires, lowering springs and upgraded dampers are just as good as the fancy-pants coilovers we mount on just about every one of our project cars. We just needed slightly stiffer spring rates for our plans to use Project WRX as a tire-test platform.
The only problem was, the lowering springs we initially picked were too low and, when coupled with the stock dampers, created a severely under-damped system. Despite our findings, the manufacturer claimed the springs were designed to work with stock damping rates. Umm... sure. In retrospect, the better option would have been to pick a set of high-quality sport dampers with more low-speed damping to better control body motion and to increase the roll rate with aftermarket anti-roll bars. This is a pretty good idea, since most stock springs are engineered by OEMs to give a good ride frequency and NVH for the street when coupled with stock bushings. Instead of wasting time looking around for the right damper/spring combo, we changed plans and went with coilovers, since, for the most part, a coilover's damping range is specifically designed to work with the included spring's rates.
Coilovers from Down Under
Over the years, we've tried just about every notable make of coilover suspension available in America. It's often a crapshoot-one brand might make a great set-up for a given application, yet feel like crap on another. We decided to try a set from Whiteline Automotive, based in Australia. One look at its product line-up shows that Whiteline doesn't just make springs and dampers. It takes a holistic approach to suspension tuning by addressing critical issues, like proper geometry whenever a car is lowered.
We got a set of Whiteline's top-of-the-line G4 coilovers through its American distributor, Global Performance Parts. The G4 suspension for the WRX/STI uses a steel-bodied upright monotube design with a 46mm diameter piston, and anodized aluminum threaded bodies with spring perches for height adjustment.
All four corners use a small tender spring to maximize droop travel, an important thing on the WRX when running soft street-spring rates that require more suspension stroke. Chassis like the WRX, which have some off-road roots, seem to be happier with more suspension travel in street trim, since limited travel means almost no camber gain with its MacPherson strut suspension. This is why the stock '06 rolled so much.
Our first experience with the G4s was an eye-opener. We rarely experience such a comfortable street ride, especially one that maintains such composure on the skidpad or the figure eight. Merely add one or two clicks to the 12-position damping adjustment and the difference can be instantly felt between a nice, under-damped street ride and a responsive track feel, all on spring rates that don't beat your brains out. After some pleading with Whiteline's proficient engineers, we finagled some shock dyno data out of them-data which compared the G4's damping profile to the stock STI and to various leading aftermarket suspension kits. What was immediately apparent is that Whiteline uses an extremely linear damping profile. This means damping resistance increases consistently as piston speeds increase. Most modern dampers we've experienced use a digressive damping profile that emphasizes more low- and mid-speed damping to control body roll and surface undulations, while having relatively low high-speed damping to reduce all the bumps and jiggles your ass feels on the freeway.
It seems counterintuitive, since we like cars that don't roll or pitch (which is the reasoning behind digressive damping), but Whiteline engineers explained that they use a near-linear damping profile because: "We don't get hung up on low-speed compression, as our packages always use anti-roll bar upgrades for better roll control, which partially negates the need for higher transient spring rate effects." They also make anti-lift bushing kits to control some conditions of pitch. We're not entirely convinced, since damping typically has to do with how fast each wheel moves relative to the chassis, while spring/roll/pitch rates relate to how much force has to act on the wheel to move it. Either way, it works and it does a damn good job.
Since the G4's piston design is an adjustable bleed bypass system, both compression and rebound damping profiles change when adjusted. The majority of the damping force change occurs in the rebound side, since (according to many) rebound is the larger component of force and has a larger impact on ride quality. We did notice that, unlike many dampers where the effects of damping adjustments are only apparent at mid-to-high piston speeds, Whiteline's shock dyno chart shows an immediate jump in rebound damping resistance, even at ultra-low piston speeds, making any change to the damping adjustment immediately noticeable in the ride.
We didn't bother corner-balancing our WRX, as it's street-bound only and constantly loaded with various numbers of fat-ass passengers looking to bum a ride. We just set the car roughly an inch lower than stock, maxed out the front camber within the stock adjustment range, and used a set of Whiteline 14mm rear eccentric camber bolts to max out the rear camber to above -1 degrees. Toe was set to 1/16th inch out up front and zero in the rear. We also cut the rear bumpstops in half after a couple days of fooling around-we realized the stock rear 4kg/mm springs had some issues with bottoming out when passengers were on board. Depending on your preference, we'd suggest changing the rear springs for a set of 5kg/mm pieces, although this will affect the balance of front-to-rear ride frequencies.
Now here's the bad news. It seems every time we find a really good suspension set-up, it's not available to the public (for example, our bad-ass but discontinued TRD suspension for Project MR2). As of this writing, Whiteline has decided to discontinue the G4 line and sell out its existing inventory. We've seen group buys online, but chances are, people are going to start wanting these in a bad way. So now's the time to e-mail and convince the Whiteline people Down Under to change their minds.
All Types Of Bars
Unlike some Japanese suspension tuners, who increase roll stiffness by just using kidney-busting springs, Whiteline shares the same mentality as many American tuners (and probably similarly rough roads). The G4 kit anticipates the use of anti-roll bars. While Whiteline also makes an entire line of adjustable anti-roll bars, beefed-up endlinks and anti-roll bar mounts, we went with a set of 22mm front-and-rear chromoly Sustec Stabilizers from Tanabe.
The idea (on a street car) is that most people don't want to get underneath to make adjustments. We also wanted a predictable balance of front and rear roll rates that didn't set the car into a spin on the interchange if you had to lift and brake for traffic, or lift the inside rear wheel up over every driveway. The WRX bars were designed for 2004 models, but we didn't have any fitting issues on our '06, nor did the bars bind against the stock end-links at our ride height.
We also added front-and-rear strut tower braces to make sure the suspension does the work, not the chassis. Although we're usually skeptical about the effectiveness of strut tower braces, especially on super-stiff modern chassis, we've never been able to come up with a test accurate enough to measure the change in chassis deflection. The DC Sports titanium pieces we added did make a difference we could see in terms of more front tire shoulder wear during extreme cornering. Part of why it works so well is that the non-hinged single piece design doesn't have an added degree of rotational freedom between the mounts and the actual bar that transfers the load. At a weight penalty of only 2.7 pounds in front and 1.6 pounds in back, it wasn't something we'd sweat.
Testing Month
You can imagine how many tires we'd be able to test in one month if we weren't SCC. But to us, getting a true street tire impression isn't just a matter of putting on a bunch of new tires during one long day at the track and banging out performance numbers. It actually has more to do with spending time on the street to learn all the little things you'd never notice while flogging it on track. So we got through just one set, the Maxxis MA-Z1 Victra UHP tire.
To make the test fair, the people at Discount Tire Direct supplied us with two sets of 17x7 Enkei J10 wheels with a +38mm offset, chosen because they can mount the same-size tires as stock. The original 215/45/17 Bridgestone RE92 tires were re-mounted onto one set, while the identically sized Maxxis MA-Z1s were mounted onto the other, so we could baseline the stock tire against the test tire on the same day under the same conditions.
We also came across a pressure-sensitive film made by Sensor Products Inc. and used that to get a contact patch for each tire. The Pressurex Pre-Scale Pressure Indicating Film is basically a sheet of material placed between two touching surfaces. Once there is pressure, the film will leave an impression of the contact. It sounds like an expensive way to get an impression of a contact patch, but Pressurex actually has a lot of applications for automotive use, ranging from brake pads to manifolds. Once an imprint is made, the film can be sent back to Sensor Products for post-processing that can break down pressure distribution so you can see how much pressure is acting on which spot and just how uniform it really is.
Stock Bridgestone RE92
The worn stock RE92s blew us away once we made the suspension changes. We didn't think showroom stock tires could work this well, especially when you look at the decidedly un-sporty tread pattern. But the technology and development time spent on the RE92s is clear. The tire is quiet, decent in steering response, communicates wheel motion well, and has a progressive breakaway limit.
Maxxis MA-Z1 Victra
One look at the Maxxis MA-Z1 makes several things apparent. The shoulder blocks are larger, which should mean more cornering grip, and the center V-tread pattern is set at an aggressive angle, which helps with water evacuation. Tread grooves are deep and cut at 90-degree angles, which hold more water, but have more tread squirm and scaling issues under intense heat.
This is exactly what we felt on the street and the track. Although the MA-Z1s physically generated more grip, they're as loud as some R-compound tires at highway speeds, had mild groove tracking characteristics, didn't communicate well how close to or past the limit of grip we were, and had some steering vagueness in the first couple degrees of turn-in. We think these traits were concessions made by the manufacturer for increased wet performance, which we didn't get the chance to test, except at the car wash. We also noted a shorter sidewall on the Bridgestones, even though both tires were the same size, which added to the steering and suspension edge while the car was on the RE92s.
Our figure-eight and skidpad numbers give an idea of the hairs we're splitting here. While none of the configurations even broke 0.9g or posted eye-popping times, the end result is that the combination of a Whiteline/Tanabe suspension, Maxxis street tires and wide torque band puts our 2006 Project WRX at the top of the list for the best street project car in terms of fun, driveability, durability, practicality, civility and just about anything else that matters in a car you'll be commuting in.
| Stock suspension WRX | Project WRX w/ | Project WRX w/ | |
| w/Bridgestone RE92 | Bridgestone RE92 | Maxxis MA-Z1 | |
| Skidpad (g) | 0.79 | 0.85 | 0.87 |
| Figure 8 time (sec.) | 26.91 | 26.58 | 26.47 |
You've seen it before-they did it in Japan and they did it in the US. But those were one-off cars. Who else but HASport would competently engineer the first readily available K-series engine swap for the new GD or Fit chassis?
Though it's been in Asia for some time as either the Jazz or the Fit, America just got the Fit for the 2007 model year as an attempt to compete with Scion and position beneath the ever-bloating Civic. While you might wish that the Fit weighs as little as it looks (so this would truly be a big engine in a small car), today's emissions and safety regs mean it's just not the case. The Fit weighs about 2450 pounds, right in the ballpark of the old EK chassis.
But it's new, has all that safety tech, looks like a trendy micro-car and, given the power levels tuners are achieving with the K-series engines, could really haul some ass with this swap.
Picking The Chassis
Not a whole lot to choose from here, the Fit is the Fit. There's a Sport model, but it's really a mild cosmetic and suspension change. You'll be starting with a fairly new car with lots of fancy sensors and electronics to sort through. You don't want to try this with a Fit that has the CVT (continuously variable transmission), since you'll need a proper shifter on the floor. Plus, it's cheaper-list price for a basic Fit is $13,850 at the time of writing.
Picking The Engine
The choices are endless since Honda has so many versions of the new K-series engine. For this particular swap, HASport used a K20Z3-the engine from the new 2006 Civic Si. It also used its six-speed tranny with its excellent ratios and factory limited-slip differential, something absolutely necessary for something with this much power and oddball weight distribution. But any 2.4-liter K-series from the Accord or TSX can be used-they'll all fit under the Fit's tall hood.
Keep in mind the good K-series engines are from the RSX-S, TSX and the 2006-up Si. Unfortunately, the other K-series don't have real iVTEC and make considerably less power. They are a good deal cheaper, though, and with new cams from companies like Brian Crower or Skunk2, it's possible to make credible power with these engines. You decide: budget or baller.
The transmission is a little more trouble, but one from the previous generation 2002 to 2005 EP3 Civic Si or 2002 to 2006 Acura RSX or RSX-S is cool. Right now, the TSX and all other K24 transmissions have a different housing so they aren't compatible with the bolt-in HASport kit. The 2006-up Si will also work, but, like the '05-up RSX, it uses a different speed sensor. The earlier one is easy to work with, the newer one is different and gives most gauges trouble.
Engine Removal
First, getting the shop manual from www.helminc.com is highly recommended and it's usually cheaper than from the dealer. Start by removing the bumper fascia, radiator, condenser and fans. Then, remove the lower subframe. Disconnect the lower suspension arms, then the front lower transmission mount, then the rear mount at the back of the subframe. There's no reason to remove the Electric Power Steering (EPS) from the car. Just unbolt the rack from the subframe so it stays on the chassis. Drop out the subframe and then remove the axles.
Next, discharge the A/C system, since at least one of the hard lines will need to come off. Do it the right way and evacuate it with the proper equipment. According to the Fit manual, you can use a hoist to support the engine from the top, but you can also support it from the bottom on a 10-inch or taller cart. Then instead of lowering the engine to the floor, the car can be raised off the engine. Test fitting is much easier this way and is how the swap is illustrated.
Wiring: The Fork In The Road
As with most modern engine swaps, electronics and wiring present the main problem. The Fit engine has uses a drive-by-wire (DBW) electronic throttle body and an SOHC VTEC system, not the DOHC iVTEC found on K-series engines. So modifying the stock ECU to run the new engine isn't even an option. Problem two, the Fit's dash, like most new Hondas, is controlled by CAN-bus communication via the ECU. But since each car has its own CAN protocol, a K-series ECU cannot just be plugged in and expected to run the Fit gauge cluster. The level of integration is so high that there's really no way of getting the Fit dash to work without the original ECU.
This is the fork in the road for the swap. Use a Hondata K-Pro ECU and run the engine, but have no gauges, or use the Fit's ECU and lose the iVTEC. The only way to have your cake and eat it is to do both. As a prototype for this swap only, Hondata and HASport have worked together to piggyback a K-Pro ECU onto the Fit's ECU. The K-Pro controls the engine in terms of fuel, ignition, closed loop operation and cams, while the Fit's ECU talks to the gauges, go pedal, e-throttle and the rest of the car. It requires a custom jumper harness, which the two companies are looking into selling, that lets the two computers coexist in relative harmony. Unfortunately, at this point there is no plan for Hondata to offer the wiring harness as a kit, since it's far from a plug-and-play affair, but customer demand might just change that.
To keep it simple, a K-Pro, an E plug to add some inputs and outputs that aren't in the stock engine harness plugs, and a rack of gauges is all that's required, just as we've seen in previous K24 swaps. You will need a speedo, engine temp, check engine indicator, tach and fuel level, at a minimum. For about $750, Racepak's 250-DS-UDXSR street dash has all the above, plus oil temp and pressure, high beam, odometer, brake and turn signals.
Going this route means a lot of re-wiring. Hondata has K-Series swap wiring listed on www.hondata.com/images/k20awiring.gif. The Fit factory service manual is needed to build a subharness that integrates with the cabin harness. The harness needs a starter signal, then power for the main relay, fuel pump relay, O2 sensor relay and ECU. With a dash like the Racepak, a lot of the connections are available from the ECU. Just add the missing sensors. Lots to do, but possible.
Which way you go determines what you will use as an engine harness. The Hondata way uses the original engine harness. Add another cam sensor and wiring, wires for the VTC cam actuator and stretching it here and there is all that needs to be done. If you're going K-Pro only, use the K20's engine harness. Slight modifications and the cabin subharness are needed as mentioned above.
It's also rare to find a K20 engine with the starter and alternator harness. For some reason, these are on a separate harness that also connects to the battery. If you have it, great, modify it to, um, fit. If not, strip the four alternator wires, starter wire and charging wire from the stock harness and integrate them to the engine harness you have. Don't forget the K-series uses a wideband primary O2 sensor. If you didn't get it with your swap, you'll need to buy one.
If all this sounds too complicated, HASport is working on the solution. It will offer a complete harness made from the K20 and L15 engine harnesses along with all that's needed to connect to the Fit's cabin harness, including the O2 sensor connection (but not the sensor).
Engine Mounting
This is probably one of the hairiest engine shoehorn swaps we've done. Although the drive configuration is similar, the stock L15 Fit engine is narrow, and so the engine bay is narrow, even though it has plenty of height. The K20 and trans, on the other hand, is pretty wide. To make the fit, a number of things need to be moved around and the left-side frame rail needs a circular hole cut into it. Other than that, the HASport kit uses the stock mounts resourcefully, with new brackets. In the future, replacement mounts will be offered for less engine movement or even getting racy with the stock engine.
The first thing to do is move the brake lines along the passenger side and back of the engine bay. They will need to come out of the white locator clips and be gently bent by hand to hug the firewall and move along the wheel well above the frame rail. This, in conjunction with removing the hard A/C lines, opens up the right side of the engine bay completely.
While you're there, do the same type of operation to the ABS modulator. It needs to be much closer to the headlight to make room for the idler pulley of the K-series and a HASport bracket. It will take modifying the stock hold-down brackets to reposition the modulator securely.
Moving to the driver side of the engine bay, clearance needs to be made on the chassis frame rail for the transmission case. Measure 10.5 inches back from the bulkhead and cut a notch 2.5 inches in diameter. A hole-saw is recommended. Double-check the notch by lowering the car on top of the engine and checking the clearance. The notch should only be about 0.25 to 0.375 inches deep. Make sure to reinforce the frame rail after removing the material.
Double-check the notching again, this time with the mount in place. This will give you an idea of how much material to remove from one edge of the notch for clearance. Under acceleration, the engine will move forward and up an inch or more. Make sure there is room for that, because when aluminum from the transmission case comes into contact with the steel of the frame rail, steel wins.
The last place to make some room is out front. The radiator core support needs to be trimmed just a bit to clear the intake manifold. Again, lowering the car to the engine will show the amount to remove. Allow at least an inch of clearance, because the stock mounts let the engine move under hard acceleration.
Now the engine bay of your squeaky-new Fit has been hacked into a work of modern industrial art, there's another problem. The only intake manifold that works with this swap is from the 2002 to 2006 RSX Type-S, EP3 Si or JDM Civic or Integra Type-R. They have the large flat front and the letters RBB or RBC cast into them. The longer Euro R, TSX or 2006-up Si manifolds stick out farther and will hit the radiator. The RBB and RBC manifolds will interfere with the alternators from the Accord, TSX and 2006 to 2007 Civic Si. An alternator from a 2002 to 2005 EP3 Si, any RSX or CR-V can be substituted. In addition, on some heads (mostly K24), you will need to plumb the thermostat bypass passage in the head, just to the side of the number one intake runner, back into the coolant system. HASport makes an adaptor plate for this. Don't just block it off, as this is a coolant passage.
Now clean up the K-series engine and take off all the accessories. If you have an engine with power steering, you'll need to replace it with an idler pulley and bracket from an EP3 Si, since the Fit has EPS. To retain the A/C, use the compressor from the EP3 or RSX, because it has a single wire control for the clutch like the Fit. Most K24s have a three-wire setup, not compatible with the Fit. You'll also need to redo the suction and receiver hoses.
Accessory belt size varies, depending on several factors. For K24s and the K20A3, you can use the EP3 (2002 to 2005 Civic Si) belt. On a K20A2, Z1, Z3 or any of the K20A Type-R engines, the crank pulley is smaller, so a shorter belt than the EP3 is required. No A/C? Start with a belt about 1.5 inches smaller than an EP3 and go from there.
If the engine harness is not on, install it. Install the half-shaft from an EP3 Si or RSX, which have 6MN, S5T30 or SNG30 stamped on them. These are the only Honda axles with the proper length and mounting flange pattern. Bolt the HASport right-hand engine bracket to the block using two of the stock bolts and one of the HASport-supplied bolts. With the engine and transmission on the support stand, lower the car over it. Keep a close watch on the VTEC solenoid on the rear of the engine, the clutch actuator fork, and the slave cylinder on the front of the transmission. You may need to twist the engine while lowering the car to avoid contact. This is a two-man job.
Once the car has been lowered and the engine is within a few inches of where the mounts are, install the left-hand transmission bracket using the HASport hardware. Then place a spacer under the bracket on the outside rear mount hole, so the bracket mounts flush. Leave the bolts finger-tight at this time. Continue to lower the car until you can bolt the transmission bracket to the mount. Use the stock bolt and HASport-supplied nylon lock nut.
The Fit's left-hand upper engine mount will need to be modified for clearance. Grind down the small nub on the top, near the upright stud. Notch the mount on the left inside edge to clear the engine-mounted HASport bracket. Put a couple bolts in the right-hand mount (passenger side) and check for clearance (0.25 inches).
Leaving those bolts loose, attach the HASport top bracket with the supplied two bolts. If the hole on the mount end doesn't match up, try moving the engine around until it does. Torque the two HASport brackets to spec and finger-tighten the factory nut at the top of the Fit's right-side mount. Finger-tighten all three factory mount bolts. If nothing looks bound up, torque the top nut on the Fit mount to spec and then do the same for the three bolts around its base. Go to the right side and torque all those fasteners as specified in the HASport directions.
Drivetrain Hook-Up & Engine Accessories
Attaching the two side mounts will hold the engine for now. The swap needs custom-length driveshafts. HASport and the Driveshaft Shop plan to have these available. Install the driveshafts and then attach the lower subframe. After that, the lower control arms can be bolted to the knuckles.
Bolt the steering rack and gearbox back to the subframe. Finger-tighten the Fit's rear mount to the HASport bracket, using the stock rear mount bolt and HASport-provided nylon lock nut. Install the bracket and mount into the subframe together as a unit. You may need to lift the front of the engine to make room for both parts to be installed and line up properly. Install the rear mount using the factory hardware. Don't tighten yet.
Next, bolt the HASport rear bracket to the engine and transmission. The front hole will use the stock bolt you removed earlier from the transmission. The other two holes will use the HASport-provided hardware. Once all three bolts are in, torque the mount and bracket to HASport installation manual specs.
The Fit's radiator fans will no longer work, but the car needs at least one 12-inch electric pusher fan (two, if you keep A/C) on the front of the radiator. Connect it to the stock harness, so the K-Pro can control it. A lower GSR radiator hose, properly cut, will connect both the top and the bottom of the Fit's radiator.
Attach the alternator, connecting it to the alternator/starter-specific harness. Bolt on the EP3 idler pulley and bracket and, whether or not you're using A/C, install it along with the correct belt and new lines.
If you plan to keep the e-throttle (like the HASport Fit), install the HASport adaptor plate and the throttle body (the TSX unit is the largest at 2.44 inches). Most won't be doing this, so the Fit must be converted to drive-by-cable. The pedal assembly will need to get swapped with something from another Honda or custom-fabricated. It will also take some experimentation to find the right length of throttle cable.
Because HASport had a 2006 Si at its disposal, it used the car's K20Z3 engine and transmission. If, by some enormous amount of luck, you can find one of these gearboxes, you can use the Fit's shifter assembly with shortened 2003-up Accord shifter cables. For the rest of us, only a tranny from an EP3 Si or any RSX will work. For these gearboxes, you also need the original shifter cables and shifter box from the chassis. TSX, Accord and other gearboxes have different casings and the HASport mounts won't line up.
The Fit's shifter box won't work because the way it operates the cables is the reverse of the EP3 Si or any RSX gearbox. That's why you'll need the cables and shifter box that match your tranny. The shifter box will also need to be modified. The center tunnel has a big bump that will need working around. But once installed, simply pass the cables through the floor in the stock location.
Fuel System
Luckily for us, Honda's streamlining process means that both the L15 and the K20 use similar quick-disconnect system fuel lines and connectors. With hardly any adjustment, the Fit's fuel line will snap right onto the K20 returnless system fuel line.
Tuners have found the RSX's fuel pump will support up to about 400 wheel-hp, but the Fit's pump is an unknown. Anyone going turbo or using large injectors may want to replace the stock fuel pump. For a mostly stock K-series, the Fit pump will work fine.
Intake And Exhaust System
For an intake, any of the aftermarket RSX short ram units work well. For true cold air, though, you'll need to make one. The exhaust is a bit more complicated, because the Fit has a flat floor with the gas tank under the front seats. Jackson Racing has come to the rescue and will be manufacturing headers that will clear the EPS, the subframe and then terminate just before the exhaust, making a sharp right turn to go down the side.
The header seen here is the prototype for the Jackson Racing unit and should be nearly identical to a production version. Jackson Racing is also working on an exhaust, including a version that should flow well enough to support forced induction.
Measure Twice, Cut Once
This is a complicated swap. The electronics and wiring make it a real challenge. Bending the brake lines gently and getting some new A/C lines, plus cutting and reinforcing a frame rail, means you need to be a competent mechanic.
Any K-series engine will work, but the best is one from an EP3 Si or an RSX. If the engine is still in the car, here's a check list of what the junkyard needs to pull out: engine, transmission, shifter cables, shifter box, primary O2 sensor, ECU, alternator, engine harness, battery/starter/ charging harness and, if you want A/C, the compressor and suction hose. If the engine doesn't have the RBB or RBC manifold, it'll also need one of those.
Decide up front if you're going to do this with just a K-Pro or hope HASport or Hondata makes the harness that lets you keep the Fit's ECU so it can run the dash and a few other creature features.
| K-Series Engine Codes & Chassis | ||
| Engine | Year | Model |
| K20A | 2001-up | Euro/JDM ITR and CTR, JDM Accord Euro-R |
| K20A2 | 2002-2004 | RSX-S |
| K20A3 | 2002-2005 | USDM Civic Si, |
| 2002-2006 | RSX | |
| K20Z1 | 2005-2006 | RSX-S |
| K20Z2 | 2006-up | Acura CSX (Canada), |
| 2006-up | JDM Civic | |
| 2006-up | Euro Accord | |
| K20Z3 | 2006-up | USDM Civic Si |
| 2007-up | Acura CSX Type-S (Canada) | |
| K23A1 | 2007-up | RSX |
| K24A1 | 2002-2006 | CR-V |
| K24A2 | 2003-up | TSX |
| K24A3 | 2003-2006 | Accord (Japan, Europe & Australia) |
| K24A4 | 2003-2005 | Accord & Element |
| K24A8 | 2006-up | Accord |
The Basics
*Use any K-series engine
*Only RSX (all models) and EP3 transmission
*Requires Hondata K-Pro
*Fit's dash will not work without Fit ECU, requires lots of gauges
*Hondata or HASport may have harnesses for both K-*Pro and modified Fit ECU, which allows Fit dash to function
*Custom axles and specific half-shaft
*Custom header and exhaust (Jackson Racing-supplied)
*RBB or RBC intake manifold required
*EP3 idler pulley assembly
*Minor cutting, welding and fabrication required
While the three to four Impreza-based project cars we've been involved with in the past were built to be edgy, pissed-off machines, capable of doing double duty on both track and street, we wanted something different with our Project 2006 WRX. The response from the new variable-cam 2.5-liter EJ25 engine easily eclipses the horrendous lag of the old 2.0-liter. Since the engine physically moves more air, boost is instantaneous and linear, and is much more suited to city acceleration than the peaky old EJ20-or the constant insanity of the STI.
The new WRX's steering feel is also improved, on-center vagueness is reduced. The transmission update means there's no more guessing about whether or not the car's in gear, or double-clutching to get into reverse. With so many improvements applied throughout, we decided to focus on tightening the suspension first.
Initially, our hope was to show that, for a pure street car on street tires, lowering springs and upgraded dampers are just as good as the fancy-pants coilovers we mount on just about every one of our project cars. We just needed slightly stiffer spring rates for our plans to use Project WRX as a tire-test platform.
The only problem was, the lowering springs we initially picked were too low and, when coupled with the stock dampers, created a severely under-damped system. Despite our findings, the manufacturer claimed the springs were designed to work with stock damping rates. Umm... sure. In retrospect, the better option would have been to pick a set of high-quality sport dampers with more low-speed damping to better control body motion and to increase the roll rate with aftermarket anti-roll bars. This is a pretty good idea, since most stock springs are engineered by OEMs to give a good ride frequency and NVH for the street when coupled with stock bushings. Instead of wasting time looking around for the right damper/spring combo, we changed plans and went with coilovers, since, for the most part, a coilover's damping range is specifically designed to work with the included spring's rates.
Coilovers from Down Under
Over the years, we've tried just about every notable make of coilover suspension available in America. It's often a crapshoot-one brand might make a great set-up for a given application, yet feel like crap on another. We decided to try a set from Whiteline Automotive, based in Australia. One look at its product line-up shows that Whiteline doesn't just make springs and dampers. It takes a holistic approach to suspension tuning by addressing critical issues, like proper geometry whenever a car is lowered.
We got a set of Whiteline's top-of-the-line G4 coilovers through its American distributor, Global Performance Parts. The G4 suspension for the WRX/STI uses a steel-bodied upright monotube design with a 46mm diameter piston, and anodized aluminum threaded bodies with spring perches for height adjustment.
All four corners use a small tender spring to maximize droop travel, an important thing on the WRX when running soft street-spring rates that require more suspension stroke. Chassis like the WRX, which have some off-road roots, seem to be happier with more suspension travel in street trim, since limited travel means almost no camber gain with its MacPherson strut suspension. This is why the stock '06 rolled so much.
Our first experience with the G4s was an eye-opener. We rarely experience such a comfortable street ride, especially one that maintains such composure on the skidpad or the figure eight. Merely add one or two clicks to the 12-position damping adjustment and the difference can be instantly felt between a nice, under-damped street ride and a responsive track feel, all on spring rates that don't beat your brains out. After some pleading with Whiteline's proficient engineers, we finagled some shock dyno data out of them-data which compared the G4's damping profile to the stock STI and to various leading aftermarket suspension kits. What was immediately apparent is that Whiteline uses an extremely linear damping profile. This means damping resistance increases consistently as piston speeds increase. Most modern dampers we've experienced use a digressive damping profile that emphasizes more low- and mid-speed damping to control body roll and surface undulations, while having relatively low high-speed damping to reduce all the bumps and jiggles your ass feels on the freeway.
It seems counterintuitive, since we like cars that don't roll or pitch (which is the reasoning behind digressive damping), but Whiteline engineers explained that they use a near-linear damping profile because: "We don't get hung up on low-speed compression, as our packages always use anti-roll bar upgrades for better roll control, which partially negates the need for higher transient spring rate effects." They also make anti-lift bushing kits to control some conditions of pitch. We're not entirely convinced, since damping typically has to do with how fast each wheel moves relative to the chassis, while spring/roll/pitch rates relate to how much force has to act on the wheel to move it. Either way, it works and it does a damn good job.
Since the G4's piston design is an adjustable bleed bypass system, both compression and rebound damping profiles change when adjusted. The majority of the damping force change occurs in the rebound side, since (according to many) rebound is the larger component of force and has a larger impact on ride quality. We did notice that, unlike many dampers where the effects of damping adjustments are only apparent at mid-to-high piston speeds, Whiteline's shock dyno chart shows an immediate jump in rebound damping resistance, even at ultra-low piston speeds, making any change to the damping adjustment immediately noticeable in the ride.
We didn't bother corner-balancing our WRX, as it's street-bound only and constantly loaded with various numbers of fat-ass passengers looking to bum a ride. We just set the car roughly an inch lower than stock, maxed out the front camber within the stock adjustment range, and used a set of Whiteline 14mm rear eccentric camber bolts to max out the rear camber to above -1 degrees. Toe was set to 1/16th inch out up front and zero in the rear. We also cut the rear bumpstops in half after a couple days of fooling around-we realized the stock rear 4kg/mm springs had some issues with bottoming out when passengers were on board. Depending on your preference, we'd suggest changing the rear springs for a set of 5kg/mm pieces, although this will affect the balance of front-to-rear ride frequencies.
Now here's the bad news. It seems every time we find a really good suspension set-up, it's not available to the public (for example, our bad-ass but discontinued TRD suspension for Project MR2). As of this writing, Whiteline has decided to discontinue the G4 line and sell out its existing inventory. We've seen group buys online, but chances are, people are going to start wanting these in a bad way. So now's the time to e-mail and convince the Whiteline people Down Under to change their minds.
All Types Of Bars
Unlike some Japanese suspension tuners, who increase roll stiffness by just using kidney-busting springs, Whiteline shares the same mentality as many American tuners (and probably similarly rough roads). The G4 kit anticipates the use of anti-roll bars. While Whiteline also makes an entire line of adjustable anti-roll bars, beefed-up endlinks and anti-roll bar mounts, we went with a set of 22mm front-and-rear chromoly Sustec Stabilizers from Tanabe.
The idea (on a street car) is that most people don't want to get underneath to make adjustments. We also wanted a predictable balance of front and rear roll rates that didn't set the car into a spin on the interchange if you had to lift and brake for traffic, or lift the inside rear wheel up over every driveway. The WRX bars were designed for 2004 models, but we didn't have any fitting issues on our '06, nor did the bars bind against the stock end-links at our ride height.
We also added front-and-rear strut tower braces to make sure the suspension does the work, not the chassis. Although we're usually skeptical about the effectiveness of strut tower braces, especially on super-stiff modern chassis, we've never been able to come up with a test accurate enough to measure the change in chassis deflection. The DC Sports titanium pieces we added did make a difference we could see in terms of more front tire shoulder wear during extreme cornering. Part of why it works so well is that the non-hinged single piece design doesn't have an added degree of rotational freedom between the mounts and the actual bar that transfers the load. At a weight penalty of only 2.7 pounds in front and 1.6 pounds in back, it wasn't something we'd sweat.
Testing Month
You can imagine how many tires we'd be able to test in one month if we weren't SCC. But to us, getting a true street tire impression isn't just a matter of putting on a bunch of new tires during one long day at the track and banging out performance numbers. It actually has more to do with spending time on the street to learn all the little things you'd never notice while flogging it on track. So we got through just one set, the Maxxis MA-Z1 Victra UHP tire.
To make the test fair, the people at Discount Tire Direct supplied us with two sets of 17x7 Enkei J10 wheels with a +38mm offset, chosen because they can mount the same-size tires as stock. The original 215/45/17 Bridgestone RE92 tires were re-mounted onto one set, while the identically sized Maxxis MA-Z1s were mounted onto the other, so we could baseline the stock tire against the test tire on the same day under the same conditions.
We also came across a pressure-sensitive film made by Sensor Products Inc. and used that to get a contact patch for each tire. The Pressurex Pre-Scale Pressure Indicating Film is basically a sheet of material placed between two touching surfaces. Once there is pressure, the film will leave an impression of the contact. It sounds like an expensive way to get an impression of a contact patch, but Pressurex actually has a lot of applications for automotive use, ranging from brake pads to manifolds. Once an imprint is made, the film can be sent back to Sensor Products for post-processing that can break down pressure distribution so you can see how much pressure is acting on which spot and just how uniform it really is.
Stock Bridgestone RE92
The worn stock RE92s blew us away once we made the suspension changes. We didn't think showroom stock tires could work this well, especially when you look at the decidedly un-sporty tread pattern. But the technology and development time spent on the RE92s is clear. The tire is quiet, decent in steering response, communicates wheel motion well, and has a progressive breakaway limit.
Maxxis MA-Z1 Victra
One look at the Maxxis MA-Z1 makes several things apparent. The shoulder blocks are larger, which should mean more cornering grip, and the center V-tread pattern is set at an aggressive angle, which helps with water evacuation. Tread grooves are deep and cut at 90-degree angles, which hold more water, but have more tread squirm and scaling issues under intense heat.
This is exactly what we felt on the street and the track. Although the MA-Z1s physically generated more grip, they're as loud as some R-compound tires at highway speeds, had mild groove tracking characteristics, didn't communicate well how close to or past the limit of grip we were, and had some steering vagueness in the first couple degrees of turn-in. We think these traits were concessions made by the manufacturer for increased wet performance, which we didn't get the chance to test, except at the car wash. We also noted a shorter sidewall on the Bridgestones, even though both tires were the same size, which added to the steering and suspension edge while the car was on the RE92s.
Our figure-eight and skidpad numbers give an idea of the hairs we're splitting here. While none of the configurations even broke 0.9g or posted eye-popping times, the end result is that the combination of a Whiteline/Tanabe suspension, Maxxis street tires and wide torque band puts our 2006 Project WRX at the top of the list for the best street project car in terms of fun, driveability, durability, practicality, civility and just about anything else that matters in a car you'll be commuting in.
| Stock suspension WRX | Project WRX w/ | Project WRX w/ | |
| w/Bridgestone RE92 | Bridgestone RE92 | Maxxis MA-Z1 | |
| Skidpad (g) | 0.79 | 0.85 | 0.87 |
| Figure 8 time (sec.) | 26.91 | 26.58 | 26.47 |
While the three to four Impreza-based project cars we've been involved with in the past were built to be edgy, pissed-off machines, capable of doing double duty on both track and street, we wanted something different with our Project 2006 WRX. The response from the new variable-cam 2.5-liter EJ25 engine easily eclipses the horrendous lag of the old 2.0-liter. Since the engine physically moves more air, boost is instantaneous and linear, and is much more suited to city acceleration than the peaky old EJ20-or the constant insanity of the STI.
The new WRX's steering feel is also improved, on-center vagueness is reduced. The transmission update means there's no more guessing about whether or not the car's in gear, or double-clutching to get into reverse. With so many improvements applied throughout, we decided to focus on tightening the suspension first.
Initially, our hope was to show that, for a pure street car on street tires, lowering springs and upgraded dampers are just as good as the fancy-pants coilovers we mount on just about every one of our project cars. We just needed slightly stiffer spring rates for our plans to use Project WRX as a tire-test platform.
The only problem was, the lowering springs we initially picked were too low and, when coupled with the stock dampers, created a severely under-damped system. Despite our findings, the manufacturer claimed the springs were designed to work with stock damping rates. Umm... sure. In retrospect, the better option would have been to pick a set of high-quality sport dampers with more low-speed damping to better control body motion and to increase the roll rate with aftermarket anti-roll bars. This is a pretty good idea, since most stock springs are engineered by OEMs to give a good ride frequency and NVH for the street when coupled with stock bushings. Instead of wasting time looking around for the right damper/spring combo, we changed plans and went with coilovers, since, for the most part, a coilover's damping range is specifically designed to work with the included spring's rates.
Coilovers from Down Under
Over the years, we've tried just about every notable make of coilover suspension available in America. It's often a crapshoot-one brand might make a great set-up for a given application, yet feel like crap on another. We decided to try a set from Whiteline Automotive, based in Australia. One look at its product line-up shows that Whiteline doesn't just make springs and dampers. It takes a holistic approach to suspension tuning by addressing critical issues, like proper geometry whenever a car is lowered.
We got a set of Whiteline's top-of-the-line G4 coilovers through its American distributor, Global Performance Parts. The G4 suspension for the WRX/STI uses a steel-bodied upright monotube design with a 46mm diameter piston, and anodized aluminum threaded bodies with spring perches for height adjustment.
All four corners use a small tender spring to maximize droop travel, an important thing on the WRX when running soft street-spring rates that require more suspension stroke. Chassis like the WRX, which have some off-road roots, seem to be happier with more suspension travel in street trim, since limited travel means almost no camber gain with its MacPherson strut suspension. This is why the stock '06 rolled so much.
Our first experience with the G4s was an eye-opener. We rarely experience such a comfortable street ride, especially one that maintains such composure on the skidpad or the figure eight. Merely add one or two clicks to the 12-position damping adjustment and the difference can be instantly felt between a nice, under-damped street ride and a responsive track feel, all on spring rates that don't beat your brains out. After some pleading with Whiteline's proficient engineers, we finagled some shock dyno data out of them-data which compared the G4's damping profile to the stock STI and to various leading aftermarket suspension kits. What was immediately apparent is that Whiteline uses an extremely linear damping profile. This means damping resistance increases consistently as piston speeds increase. Most modern dampers we've experienced use a digressive damping profile that emphasizes more low- and mid-speed damping to control body roll and surface undulations, while having relatively low high-speed damping to reduce all the bumps and jiggles your ass feels on the freeway.
It seems counterintuitive, since we like cars that don't roll or pitch (which is the reasoning behind digressive damping), but Whiteline engineers explained that they use a near-linear damping profile because: "We don't get hung up on low-speed compression, as our packages always use anti-roll bar upgrades for better roll control, which partially negates the need for higher transient spring rate effects." They also make anti-lift bushing kits to control some conditions of pitch. We're not entirely convinced, since damping typically has to do with how fast each wheel moves relative to the chassis, while spring/roll/pitch rates relate to how much force has to act on the wheel to move it. Either way, it works and it does a damn good job.
Since the G4's piston design is an adjustable bleed bypass system, both compression and rebound damping profiles change when adjusted. The majority of the damping force change occurs in the rebound side, since (according to many) rebound is the larger component of force and has a larger impact on ride quality. We did notice that, unlike many dampers where the effects of damping adjustments are only apparent at mid-to-high piston speeds, Whiteline's shock dyno chart shows an immediate jump in rebound damping resistance, even at ultra-low piston speeds, making any change to the damping adjustment immediately noticeable in the ride.
We didn't bother corner-balancing our WRX, as it's street-bound only and constantly loaded with various numbers of fat-ass passengers looking to bum a ride. We just set the car roughly an inch lower than stock, maxed out the front camber within the stock adjustment range, and used a set of Whiteline 14mm rear eccentric camber bolts to max out the rear camber to above -1 degrees. Toe was set to 1/16th inch out up front and zero in the rear. We also cut the rear bumpstops in half after a couple days of fooling around-we realized the stock rear 4kg/mm springs had some issues with bottoming out when passengers were on board. Depending on your preference, we'd suggest changing the rear springs for a set of 5kg/mm pieces, although this will affect the balance of front-to-rear ride frequencies.
Now here's the bad news. It seems every time we find a really good suspension set-up, it's not available to the public (for example, our bad-ass but discontinued TRD suspension for Project MR2). As of this writing, Whiteline has decided to discontinue the G4 line and sell out its existing inventory. We've seen group buys online, but chances are, people are going to start wanting these in a bad way. So now's the time to e-mail and convince the Whiteline people Down Under to change their minds.
All Types Of Bars
Unlike some Japanese suspension tuners, who increase roll stiffness by just using kidney-busting springs, Whiteline shares the same mentality as many American tuners (and probably similarly rough roads). The G4 kit anticipates the use of anti-roll bars. While Whiteline also makes an entire line of adjustable anti-roll bars, beefed-up endlinks and anti-roll bar mounts, we went with a set of 22mm front-and-rear chromoly Sustec Stabilizers from Tanabe.
The idea (on a street car) is that most people don't want to get underneath to make adjustments. We also wanted a predictable balance of front and rear roll rates that didn't set the car into a spin on the interchange if you had to lift and brake for traffic, or lift the inside rear wheel up over every driveway. The WRX bars were designed for 2004 models, but we didn't have any fitting issues on our '06, nor did the bars bind against the stock end-links at our ride height.
We also added front-and-rear strut tower braces to make sure the suspension does the work, not the chassis. Although we're usually skeptical about the effectiveness of strut tower braces, especially on super-stiff modern chassis, we've never been able to come up with a test accurate enough to measure the change in chassis deflection. The DC Sports titanium pieces we added did make a difference we could see in terms of more front tire shoulder wear during extreme cornering. Part of why it works so well is that the non-hinged single piece design doesn't have an added degree of rotational freedom between the mounts and the actual bar that transfers the load. At a weight penalty of only 2.7 pounds in front and 1.6 pounds in back, it wasn't something we'd sweat.
Testing Month
You can imagine how many tires we'd be able to test in one month if we weren't SCC. But to us, getting a true street tire impression isn't just a matter of putting on a bunch of new tires during one long day at the track and banging out performance numbers. It actually has more to do with spending time on the street to learn all the little things you'd never notice while flogging it on track. So we got through just one set, the Maxxis MA-Z1 Victra UHP tire.
To make the test fair, the people at Discount Tire Direct supplied us with two sets of 17x7 Enkei J10 wheels with a +38mm offset, chosen because they can mount the same-size tires as stock. The original 215/45/17 Bridgestone RE92 tires were re-mounted onto one set, while the identically sized Maxxis MA-Z1s were mounted onto the other, so we could baseline the stock tire against the test tire on the same day under the same conditions.
We also came across a pressure-sensitive film made by Sensor Products Inc. and used that to get a contact patch for each tire. The Pressurex Pre-Scale Pressure Indicating Film is basically a sheet of material placed between two touching surfaces. Once there is pressure, the film will leave an impression of the contact. It sounds like an expensive way to get an impression of a contact patch, but Pressurex actually has a lot of applications for automotive use, ranging from brake pads to manifolds. Once an imprint is made, the film can be sent back to Sensor Products for post-processing that can break down pressure distribution so you can see how much pressure is acting on which spot and just how uniform it really is.
Stock Bridgestone RE92
The worn stock RE92s blew us away once we made the suspension changes. We didn't think showroom stock tires could work this well, especially when you look at the decidedly un-sporty tread pattern. But the technology and development time spent on the RE92s is clear. The tire is quiet, decent in steering response, communicates wheel motion well, and has a progressive breakaway limit.
Maxxis MA-Z1 Victra
One look at the Maxxis MA-Z1 makes several things apparent. The shoulder blocks are larger, which should mean more cornering grip, and the center V-tread pattern is set at an aggressive angle, which helps with water evacuation. Tread grooves are deep and cut at 90-degree angles, which hold more water, but have more tread squirm and scaling issues under intense heat.
This is exactly what we felt on the street and the track. Although the MA-Z1s physically generated more grip, they're as loud as some R-compound tires at highway speeds, had mild groove tracking characteristics, didn't communicate well how close to or past the limit of grip we were, and had some steering vagueness in the first couple degrees of turn-in. We think these traits were concessions made by the manufacturer for increased wet performance, which we didn't get the chance to test, except at the car wash. We also noted a shorter sidewall on the Bridgestones, even though both tires were the same size, which added to the steering and suspension edge while the car was on the RE92s.
Our figure-eight and skidpad numbers give an idea of the hairs we're splitting here. While none of the configurations even broke 0.9g or posted eye-popping times, the end result is that the combination of a Whiteline/Tanabe suspension, Maxxis street tires and wide torque band puts our 2006 Project WRX at the top of the list for the best street project car in terms of fun, driveability, durability, practicality, civility and just about anything else that matters in a car you'll be commuting in.
| Stock suspension WRX | Project WRX w/ | Project WRX w/ | |
| w/Bridgestone RE92 | Bridgestone RE92 | Maxxis MA-Z1 | |
| Skidpad (g) | 0.79 | 0.85 | 0.87 |
| Figure 8 time (sec.) | 26.91 | 26.58 | 26.47 |
You've seen it before-they did it in Japan and they did it in the US. But those were one-off cars. Who else but HASport would competently engineer the first readily available K-series engine swap for the new GD or Fit chassis?
Though it's been in Asia for some time as either the Jazz or the Fit, America just got the Fit for the 2007 model year as an attempt to compete with Scion and position beneath the ever-bloating Civic. While you might wish that the Fit weighs as little as it looks (so this would truly be a big engine in a small car), today's emissions and safety regs mean it's just not the case. The Fit weighs about 2450 pounds, right in the ballpark of the old EK chassis.
But it's new, has all that safety tech, looks like a trendy micro-car and, given the power levels tuners are achieving with the K-series engines, could really haul some ass with this swap.
Picking The Chassis
Not a whole lot to choose from here, the Fit is the Fit. There's a Sport model, but it's really a mild cosmetic and suspension change. You'll be starting with a fairly new car with lots of fancy sensors and electronics to sort through. You don't want to try this with a Fit that has the CVT (continuously variable transmission), since you'll need a proper shifter on the floor. Plus, it's cheaper-list price for a basic Fit is $13,850 at the time of writing.
Picking The Engine
The choices are endless since Honda has so many versions of the new K-series engine. For this particular swap, HASport used a K20Z3-the engine from the new 2006 Civic Si. It also used its six-speed tranny with its excellent ratios and factory limited-slip differential, something absolutely necessary for something with this much power and oddball weight distribution. But any 2.4-liter K-series from the Accord or TSX can be used-they'll all fit under the Fit's tall hood.
Keep in mind the good K-series engines are from the RSX-S, TSX and the 2006-up Si. Unfortunately, the other K-series don't have real iVTEC and make considerably less power. They are a good deal cheaper, though, and with new cams from companies like Brian Crower or Skunk2, it's possible to make credible power with these engines. You decide: budget or baller.
The transmission is a little more trouble, but one from the previous generation 2002 to 2005 EP3 Civic Si or 2002 to 2006 Acura RSX or RSX-S is cool. Right now, the TSX and all other K24 transmissions have a different housing so they aren't compatible with the bolt-in HASport kit. The 2006-up Si will also work, but, like the '05-up RSX, it uses a different speed sensor. The earlier one is easy to work with, the newer one is different and gives most gauges trouble.
Engine Removal
First, getting the shop manual from www.helminc.com is highly recommended and it's usually cheaper than from the dealer. Start by removing the bumper fascia, radiator, condenser and fans. Then, remove the lower subframe. Disconnect the lower suspension arms, then the front lower transmission mount, then the rear mount at the back of the subframe. There's no reason to remove the Electric Power Steering (EPS) from the car. Just unbolt the rack from the subframe so it stays on the chassis. Drop out the subframe and then remove the axles.
Next, discharge the A/C system, since at least one of the hard lines will need to come off. Do it the right way and evacuate it with the proper equipment. According to the Fit manual, you can use a hoist to support the engine from the top, but you can also support it from the bottom on a 10-inch or taller cart. Then instead of lowering the engine to the floor, the car can be raised off the engine. Test fitting is much easier this way and is how the swap is illustrated.
Wiring: The Fork In The Road
As with most modern engine swaps, electronics and wiring present the main problem. The Fit engine has uses a drive-by-wire (DBW) electronic throttle body and an SOHC VTEC system, not the DOHC iVTEC found on K-series engines. So modifying the stock ECU to run the new engine isn't even an option. Problem two, the Fit's dash, like most new Hondas, is controlled by CAN-bus communication via the ECU. But since each car has its own CAN protocol, a K-series ECU cannot just be plugged in and expected to run the Fit gauge cluster. The level of integration is so high that there's really no way of getting the Fit dash to work without the original ECU.
This is the fork in the road for the swap. Use a Hondata K-Pro ECU and run the engine, but have no gauges, or use the Fit's ECU and lose the iVTEC. The only way to have your cake and eat it is to do both. As a prototype for this swap only, Hondata and HASport have worked together to piggyback a K-Pro ECU onto the Fit's ECU. The K-Pro controls the engine in terms of fuel, ignition, closed loop operation and cams, while the Fit's ECU talks to the gauges, go pedal, e-throttle and the rest of the car. It requires a custom jumper harness, which the two companies are looking into selling, that lets the two computers coexist in relative harmony. Unfortunately, at this point there is no plan for Hondata to offer the wiring harness as a kit, since it's far from a plug-and-play affair, but customer demand might just change that.
To keep it simple, a K-Pro, an E plug to add some inputs and outputs that aren't in the stock engine harness plugs, and a rack of gauges is all that's required, just as we've seen in previous K24 swaps. You will need a speedo, engine temp, check engine indicator, tach and fuel level, at a minimum. For about $750, Racepak's 250-DS-UDXSR street dash has all the above, plus oil temp and pressure, high beam, odometer, brake and turn signals.
Going this route means a lot of re-wiring. Hondata has K-Series swap wiring listed on www.hondata.com/images/k20awiring.gif. The Fit factory service manual is needed to build a subharness that integrates with the cabin harness. The harness needs a starter signal, then power for the main relay, fuel pump relay, O2 sensor relay and ECU. With a dash like the Racepak, a lot of the connections are available from the ECU. Just add the missing sensors. Lots to do, but possible.
Which way you go determines what you will use as an engine harness. The Hondata way uses the original engine harness. Add another cam sensor and wiring, wires for the VTC cam actuator and stretching it here and there is all that needs to be done. If you're going K-Pro only, use the K20's engine harness. Slight modifications and the cabin subharness are needed as mentioned above.
It's also rare to find a K20 engine with the starter and alternator harness. For some reason, these are on a separate harness that also connects to the battery. If you have it, great, modify it to, um, fit. If not, strip the four alternator wires, starter wire and charging wire from the stock harness and integrate them to the engine harness you have. Don't forget the K-series uses a wideband primary O2 sensor. If you didn't get it with your swap, you'll need to buy one.
If all this sounds too complicated, HASport is working on the solution. It will offer a complete harness made from the K20 and L15 engine harnesses along with all that's needed to connect to the Fit's cabin harness, including the O2 sensor connection (but not the sensor).
Engine Mounting
This is probably one of the hairiest engine shoehorn swaps we've done. Although the drive configuration is similar, the stock L15 Fit engine is narrow, and so the engine bay is narrow, even though it has plenty of height. The K20 and trans, on the other hand, is pretty wide. To make the fit, a number of things need to be moved around and the left-side frame rail needs a circular hole cut into it. Other than that, the HASport kit uses the stock mounts resourcefully, with new brackets. In the future, replacement mounts will be offered for less engine movement or even getting racy with the stock engine.
The first thing to do is move the brake lines along the passenger side and back of the engine bay. They will need to come out of the white locator clips and be gently bent by hand to hug the firewall and move along the wheel well above the frame rail. This, in conjunction with removing the hard A/C lines, opens up the right side of the engine bay completely.
While you're there, do the same type of operation to the ABS modulator. It needs to be much closer to the headlight to make room for the idler pulley of the K-series and a HASport bracket. It will take modifying the stock hold-down brackets to reposition the modulator securely.
Moving to the driver side of the engine bay, clearance needs to be made on the chassis frame rail for the transmission case. Measure 10.5 inches back from the bulkhead and cut a notch 2.5 inches in diameter. A hole-saw is recommended. Double-check the notch by lowering the car on top of the engine and checking the clearance. The notch should only be about 0.25 to 0.375 inches deep. Make sure to reinforce the frame rail after removing the material.
Double-check the notching again, this time with the mount in place. This will give you an idea of how much material to remove from one edge of the notch for clearance. Under acceleration, the engine will move forward and up an inch or more. Make sure there is room for that, because when aluminum from the transmission case comes into contact with the steel of the frame rail, steel wins.
The last place to make some room is out front. The radiator core support needs to be trimmed just a bit to clear the intake manifold. Again, lowering the car to the engine will show the amount to remove. Allow at least an inch of clearance, because the stock mounts let the engine move under hard acceleration.
Now the engine bay of your squeaky-new Fit has been hacked into a work of modern industrial art, there's another problem. The only intake manifold that works with this swap is from the 2002 to 2006 RSX Type-S, EP3 Si or JDM Civic or Integra Type-R. They have the large flat front and the letters RBB or RBC cast into them. The longer Euro R, TSX or 2006-up Si manifolds stick out farther and will hit the radiator. The RBB and RBC manifolds will interfere with the alternators from the Accord, TSX and 2006 to 2007 Civic Si. An alternator from a 2002 to 2005 EP3 Si, any RSX or CR-V can be substituted. In addition, on some heads (mostly K24), you will need to plumb the thermostat bypass passage in the head, just to the side of the number one intake runner, back into the coolant system. HASport makes an adaptor plate for this. Don't just block it off, as this is a coolant passage.
Now clean up the K-series engine and take off all the accessories. If you have an engine with power steering, you'll need to replace it with an idler pulley and bracket from an EP3 Si, since the Fit has EPS. To retain the A/C, use the compressor from the EP3 or RSX, because it has a single wire control for the clutch like the Fit. Most K24s have a three-wire setup, not compatible with the Fit. You'll also need to redo the suction and receiver hoses.
Accessory belt size varies, depending on several factors. For K24s and the K20A3, you can use the EP3 (2002 to 2005 Civic Si) belt. On a K20A2, Z1, Z3 or any of the K20A Type-R engines, the crank pulley is smaller, so a shorter belt than the EP3 is required. No A/C? Start with a belt about 1.5 inches smaller than an EP3 and go from there.
If the engine harness is not on, install it. Install the half-shaft from an EP3 Si or RSX, which have 6MN, S5T30 or SNG30 stamped on them. These are the only Honda axles with the proper length and mounting flange pattern. Bolt the HASport right-hand engine bracket to the block using two of the stock bolts and one of the HASport-supplied bolts. With the engine and transmission on the support stand, lower the car over it. Keep a close watch on the VTEC solenoid on the rear of the engine, the clutch actuator fork, and the slave cylinder on the front of the transmission. You may need to twist the engine while lowering the car to avoid contact. This is a two-man job.
Once the car has been lowered and the engine is within a few inches of where the mounts are, install the left-hand transmission bracket using the HASport hardware. Then place a spacer under the bracket on the outside rear mount hole, so the bracket mounts flush. Leave the bolts finger-tight at this time. Continue to lower the car until you can bolt the transmission bracket to the mount. Use the stock bolt and HASport-supplied nylon lock nut.
The Fit's left-hand upper engine mount will need to be modified for clearance. Grind down the small nub on the top, near the upright stud. Notch the mount on the left inside edge to clear the engine-mounted HASport bracket. Put a couple bolts in the right-hand mount (passenger side) and check for clearance (0.25 inches).
Leaving those bolts loose, attach the HASport top bracket with the supplied two bolts. If the hole on the mount end doesn't match up, try moving the engine around until it does. Torque the two HASport brackets to spec and finger-tighten the factory nut at the top of the Fit's right-side mount. Finger-tighten all three factory mount bolts. If nothing looks bound up, torque the top nut on the Fit mount to spec and then do the same for the three bolts around its base. Go to the right side and torque all those fasteners as specified in the HASport directions.
Drivetrain Hook-Up & Engine Accessories
Attaching the two side mounts will hold the engine for now. The swap needs custom-length driveshafts. HASport and the Driveshaft Shop plan to have these available. Install the driveshafts and then attach the lower subframe. After that, the lower control arms can be bolted to the knuckles.
Bolt the steering rack and gearbox back to the subframe. Finger-tighten the Fit's rear mount to the HASport bracket, using the stock rear mount bolt and HASport-provided nylon lock nut. Install the bracket and mount into the subframe together as a unit. You may need to lift the front of the engine to make room for both parts to be installed and line up properly. Install the rear mount using the factory hardware. Don't tighten yet.
Next, bolt the HASport rear bracket to the engine and transmission. The front hole will use the stock bolt you removed earlier from the transmission. The other two holes will use the HASport-provided hardware. Once all three bolts are in, torque the mount and bracket to HASport installation manual specs.
The Fit's radiator fans will no longer work, but the car needs at least one 12-inch electric pusher fan (two, if you keep A/C) on the front of the radiator. Connect it to the stock harness, so the K-Pro can control it. A lower GSR radiator hose, properly cut, will connect both the top and the bottom of the Fit's radiator.
Attach the alternator, connecting it to the alternator/starter-specific harness. Bolt on the EP3 idler pulley and bracket and, whether or not you're using A/C, install it along with the correct belt and new lines.
If you plan to keep the e-throttle (like the HASport Fit), install the HASport adaptor plate and the throttle body (the TSX unit is the largest at 2.44 inches). Most won't be doing this, so the Fit must be converted to drive-by-cable. The pedal assembly will need to get swapped with something from another Honda or custom-fabricated. It will also take some experimentation to find the right length of throttle cable.
Because HASport had a 2006 Si at its disposal, it used the car's K20Z3 engine and transmission. If, by some enormous amount of luck, you can find one of these gearboxes, you can use the Fit's shifter assembly with shortened 2003-up Accord shifter cables. For the rest of us, only a tranny from an EP3 Si or any RSX will work. For these gearboxes, you also need the original shifter cables and shifter box from the chassis. TSX, Accord and other gearboxes have different casings and the HASport mounts won't line up.
The Fit's shifter box won't work because the way it operates the cables is the reverse of the EP3 Si or any RSX gearbox. That's why you'll need the cables and shifter box that match your tranny. The shifter box will also need to be modified. The center tunnel has a big bump that will need working around. But once installed, simply pass the cables through the floor in the stock location.
Fuel System
Luckily for us, Honda's streamlining process means that both the L15 and the K20 use similar quick-disconnect system fuel lines and connectors. With hardly any adjustment, the Fit's fuel line will snap right onto the K20 returnless system fuel line.
Tuners have found the RSX's fuel pump will support up to about 400 wheel-hp, but the Fit's pump is an unknown. Anyone going turbo or using large injectors may want to replace the stock fuel pump. For a mostly stock K-series, the Fit pump will work fine.
Intake And Exhaust System
For an intake, any of the aftermarket RSX short ram units work well. For true cold air, though, you'll need to make one. The exhaust is a bit more complicated, because the Fit has a flat floor with the gas tank under the front seats. Jackson Racing has come to the rescue and will be manufacturing headers that will clear the EPS, the subframe and then terminate just before the exhaust, making a sharp right turn to go down the side.
The header seen here is the prototype for the Jackson Racing unit and should be nearly identical to a production version. Jackson Racing is also working on an exhaust, including a version that should flow well enough to support forced induction.
Measure Twice, Cut Once
This is a complicated swap. The electronics and wiring make it a real challenge. Bending the brake lines gently and getting some new A/C lines, plus cutting and reinforcing a frame rail, means you need to be a competent mechanic.
Any K-series engine will work, but the best is one from an EP3 Si or an RSX. If the engine is still in the car, here's a check list of what the junkyard needs to pull out: engine, transmission, shifter cables, shifter box, primary O2 sensor, ECU, alternator, engine harness, battery/starter/ charging harness and, if you want A/C, the compressor and suction hose. If the engine doesn't have the RBB or RBC manifold, it'll also need one of those.
Decide up front if you're going to do this with just a K-Pro or hope HASport or Hondata makes the harness that lets you keep the Fit's ECU so it can run the dash and a few other creature features.
| K-Series Engine Codes & Chassis | ||
| Engine | Year | Model |
| K20A | 2001-up | Euro/JDM ITR and CTR, JDM Accord Euro-R |
| K20A2 | 2002-2004 | RSX-S |
| K20A3 | 2002-2005 | USDM Civic Si, |
| 2002-2006 | RSX | |
| K20Z1 | 2005-2006 | RSX-S |
| K20Z2 | 2006-up | Acura CSX (Canada), |
| 2006-up | JDM Civic | |
| 2006-up | Euro Accord | |
| K20Z3 | 2006-up | USDM Civic Si |
| 2007-up | Acura CSX Type-S (Canada) | |
| K23A1 | 2007-up | RSX |
| K24A1 | 2002-2006 | CR-V |
| K24A2 | 2003-up | TSX |
| K24A3 | 2003-2006 | Accord (Japan, Europe & Australia) |
| K24A4 | 2003-2005 | Accord & Element |
| K24A8 | 2006-up | Accord |
The Basics
*Use any K-series engine
*Only RSX (all models) and EP3 transmission
*Requires Hondata K-Pro
*Fit's dash will not work without Fit ECU, requires lots of gauges
*Hondata or HASport may have harnesses for both K-*Pro and modified Fit ECU, which allows Fit dash to function
*Custom axles and specific half-shaft
*Custom header and exhaust (Jackson Racing-supplied)
*RBB or RBC intake manifold required
*EP3 idler pulley assembly
*Minor cutting, welding and fabrication required
