When it comes to the track, overweight cars are as useful as a glass hammer. When you're talking about building a car to nail just one sizzling hot lap time, weight is everything. Unlike your average supermodel, you really can't have a time attack car that's too light. That was why we decided to turn the reasonably light 1995 R-package Miata into a featherweight time attack car.
Extra weight means slower lap times. Heavy cars require more force to accelerate, more tire to hang on in the corners and generate added momentum for brakes to deal with. Heavier cars need heavier wheels, tires, brakes and more power adders, which means more weight. It's a vicious cycle.
Instead of adding more mass to make an already heavy car perform, it's much easier to gut what you have, easing the burden on your existing hardware. With no power steering or windows, Project Time Attack Miata is a start, but the diet we had in mind meant stripping all but the most track-functional parts.
If you plan to compete, it's not as easy as calling the boys over and breaking out a 24-pack and the acetylene torch. Figuring out the class structure and acceptable reductions of the sanctioning body you'll be competing with might make the difference between racing in a class of tube-frame prototypes or full-interior Evos.
Most groups will move you into a faster class when you start removing weight from different parts of your car. Replacing doors with lightweight carbon fiber copies may land you in a faster class, while removing that same weight from your spare and jack may not. Different sanctioning bodies govern time attacks by power-to-weight ratios or points accrued from various modifications.
In NASA's Time Trials Series, Project Miata would fit somewhere in its TTS group for cars with a power-to-weight ratio of 8.1:1 down to 5.5:1. Assuming the car weighs 2300 pounds, we would have to be making over 400 wheel-hp to be kicked up to the unlimited class (TTU).
Unsprung weightFew variables affect acceleration, braking, turning, and part wear as much as unsprung weight. Unsprung weight is the mass of all items not supported by the suspension: wheels, tires, uprights, brake calipers and rotors, wheel bearings, and-if you want to get technical-some of the suspension, axles, control arms and any other part that is partially supported by the chassis on one side and connected to the wheels on the other. Yes, that includes brake lines and brake fluid.
While there are plenty of theories regarding the effects of removing unsprung versus sprung weight, it's generally accepted that eliminating unsprung weight is more effective. Reducing weight under each spring contributes to faster lap times by positively influencing such factors as rotational inertia, gyroscopic motion and how fast each corner of the car can react to road inputs and stay planted.
Rotational InertiaAs much as the physical weight of each unsprung corner matters, rotational inertia of wheels, tires or any rotating mass adds to the difficulty of accelerating and decelerating. Imagine you have a 10-speed bicycle with its rear wheel free-spinning. When its tire is filled with air, it's easier to get it turning or stopped than that same wheel with its tire filled with lead. This rotational inertia, or moment of inertia, is affected by the wheel's overall mass and even more by how far out on the radius that mass is distributed. A five-pound disk has less rotational inertia than a five-pound hoop of the same diameter. Even if you keep the weight the same, rotational inertia exponentially increases as the diameter increases. This concept holds true for anything being rotated about a given axis. As tires are the mass furthest out on a wheel, their weight has the biggest effect on the overall rotational inertia. On track or on the street, people often obsess over having ultra-light wheels without giving a thought to the weight of their tires.
Brake rotors have the next biggest impact on rotational inertia. Even though some big brake upgrades may actually weigh less than cast OE components, larger rotors usually mean more rotational inertia. Two-piece rotors with thin steel or aluminum hats help compensate for the weight and moment of inertia generated by the larger parts, but mass at the radius ultimately matters most. This delicate balance of weight, rotational inertia and brake torque will be addressed in a future installment.
Making wheel and tire choicesThe vehicle formerly known as Project Miata rode on abnormally wide 245/45R15 Hoosier bias ply race tires. As Project Time Attack, it will ride on DOT radials to avoid points penalties during NASA and other time trial competitions. We had to find the right balance between grip, size and weight for the car's current characteristics. Problem is, Miatas came with donut-size wheels and wheel wells only a wee bit bigger. So finding a tire small yet wide enough was a dilemma. For now, the widest DOT tires we can run in the correct diameter are a 225/45R15.In addition to our desire to limit rotational inertia with the smallest wheels possible, plans for larger brakes affected our wheel and tire selection. To clear the brake upgrade we had in mind, the wheels had to be at least 15 inches in diameter. Instead of picking the wheel size, we started by finding all our favorite R-Compound tires that come in 15-inch sizes.
The limited selection made this pretty easy. We went for the Nitto NT-01 tire on account of its tread design, price and our past experience. Key advantages include the huge tread blocks and smooth radiused transitions between tread blocks and grooves that reduce squirm and scaling. Its compound also endures prolonged track temperatures while being hard enough to drive to and from the track without incurring excessive wear. Until the car requires more grip, we're going with a set of 205/50R15 Nitto NT01s.Most Miata track cars use 6.5- or 7-inch width wheels with 13- to 15-inch diameters. Since most of the weight of the wheel is in the hoop, as it is furthest out on the radius, the width of the hoop will contribute most to rotational inertia.Narrow wheels use less material in the hoops, which takes much of the weight out at the farthest radial distance. This comes at the cost of reducing tire width and contact patch. Stuffing wide tires onto narrow wheels isn't the answer either; pooched-out sidewalls would cause rollover issues, sloppy turn-in response and a deformed contact patch.
Finding a 15-inch wheel to fit a 205 tire isn't easy. A seven-inch width wheel is ideal. We knew our tire requirements would soon increase, so we looked for a 15x8 wheel anyway. With such a width, we had to make sure we could mount the wheels without touching the fenders on the outside and, more importantly, the control arms on the inside-fenders are easier to cut than control arms.
E-production class Miata race cars have been using zero-offset wheels for a long time with great success, so we decided to look for a wheel with a +15mm offset, since we will ultimately run tires that are 20mm wider. The increased scrub radius of this more positive offset will put more load on the wheel bearings, but we're hoping the trade-off for extra track will improve lateral grip.
There are few 15x8 wheels on the market, even fewer in the offset we wanted. Work Wheels said it could make what we were looking for. Its history of building custom-sized endurance wheels convinced us we'd be getting a light and durable wheel.
After what seemed like a long wait, we received our Meister S1s, beautiful works of art that weigh almost 16 pounds a pop. A little surprising, but not a deal-breaker. Seeing as we've bent our share of unproven super-light wheels in our off-line lawn-mowing excursions, we're happy to stick with Work's products.
Even with all the measuring and hunting for offset-specific wheels, we still ended up with fender clearance issues. To cover up our artistic Sawzall expressionism, fender flares from a small Japanese boutique called Tuckin '99 were added. Tuckin '99, like many other boutique Japanese motorsports suppliers, built its business around a diehard set of Miata fans and club racers, and isn't really interested in scaling its business over the web. Parts are made in small runs and sold by word of mouth. As SCC is all about JDM, we purchased a set from Adrenaline Racing, in the JDM center of the world, Lake Oswego, Oregon.
Sprung weightTaking out sprung weight is far easier and subject to fewer compromises. It's also easier to remove and relocate this type of weight. Big-budget race teams will make everything as light as possible before adding weight back (in the form of lead bars in the floorboards) to satisfy the minimum regulations-all for the sake of better weight distribution. Since the Miata is already relatively well balanced, we opted against such extreme measures and focused on removing as much weight as we could from the edges to reduce the total moment of inertia.
Every removable body panel was pulled off to access the non-essential crap underneath: bumper supports, windows and crash supports, latches, and wiring for stuff we had long since thrown away. Axis Power Racing (APR) created a set of carbon fiber-wrapped Nomex honeycomb-cored replacement body panels-substantially lighter than the stock pieces-to shed further pounds. APR uses a vacuum infusion process to suck out as much excess resin as possible, minimizing weight. Unlike race car chassis components, these pieces are not baked in an autoclave for added rigidity since the panels we replaced are non-structural elements. The honeycomb adds enough rigidity to make the pieces more than just cosmetic and also allowed us to avoid the autoclave, significantly reducing cost.
The pieces were molded directly from the stock panels, but the hood was modified with a vent placed directly behind the radiator to evacuate hot air from the engine bay. This will be a big factor once we turbocharge the car and install various other heat exchangers in the nose. The front fenders were lined and reinforced with Kevlar to save the panels from internal damage due to road debris being thrown up by the tires. The only panels left stock were the rear quarter panels, which are part of the factory unibody. We sourced a Racing Beat Type 2 fiberglass nose to replace the factory piece as it saves a little weight, but also has added cooling ducts.
At 10 pounds per side, the MkI Miata pop-up headlights have a significant impact on polar moment. A time attack car still needs lights, but we didn't want the weight. Advanced Automotive Concepts has a fixed-mount headlight kit that shaves over 12 pounds. Other unnecessary parts (including the soft top, airbags, interior bits, seats, seat belts, stock battery and dash guts) found the dumpster. The stock side mirrors were replaced with carbon pieces sourced from APR Performance and the rear glass in the hardtop was chucked in favor of a Lexan replacement. Our final weight came down to 2018 pounds with a full tank of gas. Not the lightest Miata we've seen, but necessary weight (such as the cage) makes up the difference. Just in exterior body parts replaced, we've shed 154 pounds.
Now that Project Time Attack has spent some quality time with Jenny Craig, it's time for the 'roids. In our next installment, Project Time Attack will receive what is likely the best power-to-weight ratio of any of the monstrosities to come out of our garage.
| WELCOME TO WEIGHT WATCHERS | |||
| Items Removed | Weight (lbs) | Items Added | Weight (lbs) |
| Air conditioning | 36 | APR hard top | 9 |
| Aftermarket soft top and frame | 39 | APR hood | 9 |
| Passenger seat | 34 | APR doors (x2) | 19 |
| Driver seat | 34 | APR fenders (x2) | 2 |
| Spare tire and jack | 27 | APR trunk lid | 6 |
| Doors | 99 | APR bumper cover | 2 |
| 2 front fenders | 12 | Racing Beat nose | 11 |
| Trunk lid | 14 | Headlights | 8 |
| Rear bumper cover | 8 | APR airbag cover | 0 |
| Front bumper | 10 | APR Performance mirrors | 0.5 |
| Hood | 17 | Work Equip Meister S1 wheels (x4) | 62 |
| Wiper assembly | 5 | Nitto NT-01 205/50/15s tires (x4) | 80 |
| Headlights | 20 | Racetech seat | 22 |
| Airbag assembly | 8.5 | AWR cage | 82 |
| Stereo | 4.5 | KW coilovers | 34 |
| Carpets and interior | 4 | Odyssey PC680 | 15.5 |
| Front tow hooks | 3.5 | Total | 362 |
| Seat belt assembly (x2) | 10.5 | ||
| Intake assembly | 3 | ||
| Dash lightening | 28 | ||
| Stock mirrors | 1.5 | ||
| Dampers and springs (x4) | 45 | ||
| Battery | 21.5 | ||
| Steel wheels and tires | 152 | ||
| Total | 637 | ||
I didn't realize it back when I was still knee-deep in junked Celica parts, but there's a certain satisfaction from building a car that's going to be destroyed by a team of equally psychotic car nuts. Call it SCC team building.
With one week left to get Project Lemons ready for the 13-hour endurance demolition derby, we still had to resolve our drivetrain, suspension and brake issues. Plus get a roll cage worthy of this $500 beater race (see SCC, Feb 2007). So our mad panic continued at an even more frenzied pace. With the car already gutted, fluids changed and coolant hoses replaced, we took the car down to MD Automotive in Westminster, California, for some help with the heavy lifting.
At this point, we weren't quite sure how much more we had to tear into the car, but just on general inspection, we figured on a new clutch, CV joints, and some as-yet-undetermined bug in the brakes. The only way to tell was to put it on a lift and break out the impact wrench. Even though we had blown almost all the allotted $500 on just the car, we figured the judges wouldn't be able to tell if we replaced the clutch or a few other parts with OE items. Besides, we were sure everyone else was up to the same trick. So a new Exedy clutch and rebuilt axles were ordered and installed with the help of Mark Dibella at MD. The value of this lemon surprised us again when we inspected the flywheel and found that it didn't even need resurfacing.
Engine mountsWhile the tranny was out, we also realized the rubber in the front engine mount had ripped all the way through. In the spirit of SCC and the Lemons race, we just pulled the front and rear mounts that take the most engine motion and filled them with automotive window adhesive. With the help of a heat gun, the rubber had set enough to be mounted back in a matter of hours. It's a cheap but effective fix that also took out a lot of slop from the steering feel and made the car easier to throttle-steer on track. Like polyurethane engine mounts, the filled mounts do transfer significantly more vibration through the chassis and steering column, especially at lower revs.
Braking on the cheapNext to cooling, brakes matter most to a race car, even a slow one. With no idea what the conditions would be at Altamont Raceway, we took the safe route and fixed the brakes.
Again, the cheapness of the Celica ST was a welcome boon. The rear brakes were drums and no one makes aftermarket rotors or brake lines for this model. We didn't even bother replacing the shoes, since all the bias is up front. From our desperate calls to sponsors for inconspicuous aftermarket performance parts, the guys at Powerslot provided pads from its corporate partners, Hawk brakes. We got two sets-one for each day- of Hawk HP Plus pads, the best compromise between street and mild track use in terms of rotor wear. Although Hawk offers full race pads (like the Blues), they might have upset the brake balance too severely and possibly sacrificed overall stopping ability, since the front tires would do all the work.
To save costs, we tried to salvage the original rotors by turning them down. But the warping was so severe that by the time we finally got them flat, there wasn't enough material to keep them from warping again come race day. We decided to fit a new set of rotors and kept the old ones as back-ups. The entire system was also flushed out with Motul RBF600 synthetic DOT 4 brake fluid, which we've found to work well under repeated track beating. One squishy brake pedal run around the block told us the master cylinder was dead too, so that was replaced.
Overnight Roll CageThe organizers of the Lemons race were smart enough to separate safety equipment, brakes and tires from the original cost of the car. But while we had leeway to build an 800-point demolition survival cage-we only had one day budgeted to come up with the safest rollover protection we could find.
Unsurprisingly, no one in their right mind was up to taking this job, except one of the craziest, yet most reliable fabricators we know: Alex Pfeiffer of Battle Version. We sent the car to G-Dimension in City of Industry, California, where Pfeiffer and his welder are based, and asked for a six- to eight-point roll bar that tied into the door bars and rear shock tower supports.
Overhead hoops were omitted, since I didn't want to wear a helmet for the six-hour drive to the track. Pfeiffer looked the car over, grabbed the keys and with the demented grin of a mad scientist, shooed us away, declaring: "It'll be ready tomorrow before lunch."
When we returned, we found he only had time for a basic MIG welded four-point roll bar that anchored into the floor by the B-pillars and the rear wheel wells, which for an overnight job is still pretty good. With the impending time constraints and having no idea that the race was more demolition than endurance, we thanked him and ran to McKay's.
McKay EngineeringOur final weekend was spent trying to install a bucket seat and rails, safety harness, fire extinguisher, suspension, wheels and tires. We just didn't have a shop and a welder to press-gang. So we headed off to fellow magazine tech editor Ryan McKay's house, or McKay Engineering, as we fondly referred to it. It's a hole in the wall driveway, with an awning for cover and junk parts strewn everywhere for black widows to nest in. But it had what we needed, a household welder, chop saw and a leaky compressor for a cut-off wheel and grinder.
In our budget-oriented wisdom, we considered drilling a hole in the stock dampers and changing the original damping fluid with motor oil, which might have increased overall damping resistance. But spending the previous week in the car told us the fronts were completely blown, meaning the seals were probably done. So we 'found' a set of Koni Sport shock inserts, which, depending on how you interpreted Lemon rules, didn't add to the $500 tab as we scammed them for free from Koni.
Installation wasn't as easy as just bolting new hardware onto the chassis mounts. Since these were inserts, each spring and shock had to be disassembled, then gutted with a saw-zaw to remove the old internals. In the case of the rear shocks, the original housing had to be further modified to hold and secure the insert. Whatever yellow was left peeking out of the strut housing was spritzed with a shot of black rattle can to hide it from the judges. Just in case.
Even though we couldn't find springs in time, the twin-tube rebound-adjustable-only shocks were enough to transform the car from stripped-out crack-dealermobile to some semblance of a handling machine. The Koni's low-speed compression damping added hugely to controlling roll and pitch, and the rebound adjustment allowed us to tune ride and feedback feel. The rear damping was set higher to help the car rotate (which it did beautifully, intentionally or not) on track.
After digging in the bowels of McKay's backyard for an hour, we finally found the two sets of first-gen Miata wheels for which we had ordered our 205/55R14 Nitto NT-01s. All our online research seemed to show the two cars using the same offset and bolt pattern. But when the wheels were mounted, they didn't clear the calipers. Without longer studs, we weren't willing to fit spacers, so we resorted to grinding away at the cast iron caliper-something we don't recommend. Hoping it was only a reference surface for machining the caliper when it was made, we hastily ground off over 2mm of material from the face and bolted the wheels on. There was still minor contact, but the wheels spun and the calipers would cut the remaining grooves they needed into the softer aluminum wheels. We just had to remember to re-torque the wheels later.
In the meantime, others got to work on covering the hole where the sunroof used to be and fabricating a seat bracket for the Buddy Club Racing bucket confiscated from team member Joey Leh's private collection. With no time to get the right parts, we resorted to riveting hardware-store plexiglass to the outside of the roof and spraying the inside with gray primer to avoid greenhouse temperatures. We were also lucky enough to find and re-install the rear-view mirror and driver-side sun visor from the pile of parts we had torn out earlier.
The final hurdle was the driver seat bracket and it was dark by this time. The hour spent trying to break the OE spot welds on the indestructible stock seat's rails came up fruitless. Plan B was to tack weld the aftermarket seat rails to the floor, but the leftover tar underneath kept catching fire. In the end, we built mounting supports and gussets out of thick-gauge scrap metal, which meant the rails would support the driver's weight, not a steel bracket. We knew this would be an issue, but our hope was that the Takata five-point race harness (which retails for more than the car) would do the life-saving, not the seat.
If we had to do it againThirteen hours of non-stop racing is a good way to establish how good a car you've built. To my surprise, Project Lemons not only survived the ordeal, it thrived-performing more reliably than I would have ever imagined. In retrospect, there was little we could have done to better prepare the car for its wide assortment of drivers. The tires and shocks made the difference and we ended up using the brakes only to change lines or avoid crashes. The car was great. All I could have asked for was a proper seat bracket, which wouldn't bend when you go into the tirewall, and a water bottle with a straw.
When it comes to the track, overweight cars are as useful as a glass hammer. When you're talking about building a car to nail just one sizzling hot lap time, weight is everything. Unlike your average supermodel, you really can't have a time attack car that's too light. That was why we decided to turn the reasonably light 1995 R-package Miata into a featherweight time attack car.
Extra weight means slower lap times. Heavy cars require more force to accelerate, more tire to hang on in the corners and generate added momentum for brakes to deal with. Heavier cars need heavier wheels, tires, brakes and more power adders, which means more weight. It's a vicious cycle.
Instead of adding more mass to make an already heavy car perform, it's much easier to gut what you have, easing the burden on your existing hardware. With no power steering or windows, Project Time Attack Miata is a start, but the diet we had in mind meant stripping all but the most track-functional parts.
If you plan to compete, it's not as easy as calling the boys over and breaking out a 24-pack and the acetylene torch. Figuring out the class structure and acceptable reductions of the sanctioning body you'll be competing with might make the difference between racing in a class of tube-frame prototypes or full-interior Evos.
Most groups will move you into a faster class when you start removing weight from different parts of your car. Replacing doors with lightweight carbon fiber copies may land you in a faster class, while removing that same weight from your spare and jack may not. Different sanctioning bodies govern time attacks by power-to-weight ratios or points accrued from various modifications.
In NASA's Time Trials Series, Project Miata would fit somewhere in its TTS group for cars with a power-to-weight ratio of 8.1:1 down to 5.5:1. Assuming the car weighs 2300 pounds, we would have to be making over 400 wheel-hp to be kicked up to the unlimited class (TTU).
Unsprung weightFew variables affect acceleration, braking, turning, and part wear as much as unsprung weight. Unsprung weight is the mass of all items not supported by the suspension: wheels, tires, uprights, brake calipers and rotors, wheel bearings, and-if you want to get technical-some of the suspension, axles, control arms and any other part that is partially supported by the chassis on one side and connected to the wheels on the other. Yes, that includes brake lines and brake fluid.
While there are plenty of theories regarding the effects of removing unsprung versus sprung weight, it's generally accepted that eliminating unsprung weight is more effective. Reducing weight under each spring contributes to faster lap times by positively influencing such factors as rotational inertia, gyroscopic motion and how fast each corner of the car can react to road inputs and stay planted.
Rotational InertiaAs much as the physical weight of each unsprung corner matters, rotational inertia of wheels, tires or any rotating mass adds to the difficulty of accelerating and decelerating. Imagine you have a 10-speed bicycle with its rear wheel free-spinning. When its tire is filled with air, it's easier to get it turning or stopped than that same wheel with its tire filled with lead. This rotational inertia, or moment of inertia, is affected by the wheel's overall mass and even more by how far out on the radius that mass is distributed. A five-pound disk has less rotational inertia than a five-pound hoop of the same diameter. Even if you keep the weight the same, rotational inertia exponentially increases as the diameter increases. This concept holds true for anything being rotated about a given axis. As tires are the mass furthest out on a wheel, their weight has the biggest effect on the overall rotational inertia. On track or on the street, people often obsess over having ultra-light wheels without giving a thought to the weight of their tires.
Brake rotors have the next biggest impact on rotational inertia. Even though some big brake upgrades may actually weigh less than cast OE components, larger rotors usually mean more rotational inertia. Two-piece rotors with thin steel or aluminum hats help compensate for the weight and moment of inertia generated by the larger parts, but mass at the radius ultimately matters most. This delicate balance of weight, rotational inertia and brake torque will be addressed in a future installment.
Making wheel and tire choicesThe vehicle formerly known as Project Miata rode on abnormally wide 245/45R15 Hoosier bias ply race tires. As Project Time Attack, it will ride on DOT radials to avoid points penalties during NASA and other time trial competitions. We had to find the right balance between grip, size and weight for the car's current characteristics. Problem is, Miatas came with donut-size wheels and wheel wells only a wee bit bigger. So finding a tire small yet wide enough was a dilemma. For now, the widest DOT tires we can run in the correct diameter are a 225/45R15.In addition to our desire to limit rotational inertia with the smallest wheels possible, plans for larger brakes affected our wheel and tire selection. To clear the brake upgrade we had in mind, the wheels had to be at least 15 inches in diameter. Instead of picking the wheel size, we started by finding all our favorite R-Compound tires that come in 15-inch sizes.
The limited selection made this pretty easy. We went for the Nitto NT-01 tire on account of its tread design, price and our past experience. Key advantages include the huge tread blocks and smooth radiused transitions between tread blocks and grooves that reduce squirm and scaling. Its compound also endures prolonged track temperatures while being hard enough to drive to and from the track without incurring excessive wear. Until the car requires more grip, we're going with a set of 205/50R15 Nitto NT01s.Most Miata track cars use 6.5- or 7-inch width wheels with 13- to 15-inch diameters. Since most of the weight of the wheel is in the hoop, as it is furthest out on the radius, the width of the hoop will contribute most to rotational inertia.Narrow wheels use less material in the hoops, which takes much of the weight out at the farthest radial distance. This comes at the cost of reducing tire width and contact patch. Stuffing wide tires onto narrow wheels isn't the answer either; pooched-out sidewalls would cause rollover issues, sloppy turn-in response and a deformed contact patch.
Finding a 15-inch wheel to fit a 205 tire isn't easy. A seven-inch width wheel is ideal. We knew our tire requirements would soon increase, so we looked for a 15x8 wheel anyway. With such a width, we had to make sure we could mount the wheels without touching the fenders on the outside and, more importantly, the control arms on the inside-fenders are easier to cut than control arms.
E-production class Miata race cars have been using zero-offset wheels for a long time with great success, so we decided to look for a wheel with a +15mm offset, since we will ultimately run tires that are 20mm wider. The increased scrub radius of this more positive offset will put more load on the wheel bearings, but we're hoping the trade-off for extra track will improve lateral grip.
There are few 15x8 wheels on the market, even fewer in the offset we wanted. Work Wheels said it could make what we were looking for. Its history of building custom-sized endurance wheels convinced us we'd be getting a light and durable wheel.
After what seemed like a long wait, we received our Meister S1s, beautiful works of art that weigh almost 16 pounds a pop. A little surprising, but not a deal-breaker. Seeing as we've bent our share of unproven super-light wheels in our off-line lawn-mowing excursions, we're happy to stick with Work's products.
Even with all the measuring and hunting for offset-specific wheels, we still ended up with fender clearance issues. To cover up our artistic Sawzall expressionism, fender flares from a small Japanese boutique called Tuckin '99 were added. Tuckin '99, like many other boutique Japanese motorsports suppliers, built its business around a diehard set of Miata fans and club racers, and isn't really interested in scaling its business over the web. Parts are made in small runs and sold by word of mouth. As SCC is all about JDM, we purchased a set from Adrenaline Racing, in the JDM center of the world, Lake Oswego, Oregon.
Sprung weightTaking out sprung weight is far easier and subject to fewer compromises. It's also easier to remove and relocate this type of weight. Big-budget race teams will make everything as light as possible before adding weight back (in the form of lead bars in the floorboards) to satisfy the minimum regulations-all for the sake of better weight distribution. Since the Miata is already relatively well balanced, we opted against such extreme measures and focused on removing as much weight as we could from the edges to reduce the total moment of inertia.
Every removable body panel was pulled off to access the non-essential crap underneath: bumper supports, windows and crash supports, latches, and wiring for stuff we had long since thrown away. Axis Power Racing (APR) created a set of carbon fiber-wrapped Nomex honeycomb-cored replacement body panels-substantially lighter than the stock pieces-to shed further pounds. APR uses a vacuum infusion process to suck out as much excess resin as possible, minimizing weight. Unlike race car chassis components, these pieces are not baked in an autoclave for added rigidity since the panels we replaced are non-structural elements. The honeycomb adds enough rigidity to make the pieces more than just cosmetic and also allowed us to avoid the autoclave, significantly reducing cost.
The pieces were molded directly from the stock panels, but the hood was modified with a vent placed directly behind the radiator to evacuate hot air from the engine bay. This will be a big factor once we turbocharge the car and install various other heat exchangers in the nose. The front fenders were lined and reinforced with Kevlar to save the panels from internal damage due to road debris being thrown up by the tires. The only panels left stock were the rear quarter panels, which are part of the factory unibody. We sourced a Racing Beat Type 2 fiberglass nose to replace the factory piece as it saves a little weight, but also has added cooling ducts.
At 10 pounds per side, the MkI Miata pop-up headlights have a significant impact on polar moment. A time attack car still needs lights, but we didn't want the weight. Advanced Automotive Concepts has a fixed-mount headlight kit that shaves over 12 pounds. Other unnecessary parts (including the soft top, airbags, interior bits, seats, seat belts, stock battery and dash guts) found the dumpster. The stock side mirrors were replaced with carbon pieces sourced from APR Performance and the rear glass in the hardtop was chucked in favor of a Lexan replacement. Our final weight came down to 2018 pounds with a full tank of gas. Not the lightest Miata we've seen, but necessary weight (such as the cage) makes up the difference. Just in exterior body parts replaced, we've shed 154 pounds.
Now that Project Time Attack has spent some quality time with Jenny Craig, it's time for the 'roids. In our next installment, Project Time Attack will receive what is likely the best power-to-weight ratio of any of the monstrosities to come out of our garage.
| WELCOME TO WEIGHT WATCHERS | |||
| Items Removed | Weight (lbs) | Items Added | Weight (lbs) |
| Air conditioning | 36 | APR hard top | 9 |
| Aftermarket soft top and frame | 39 | APR hood | 9 |
| Passenger seat | 34 | APR doors (x2) | 19 |
| Driver seat | 34 | APR fenders (x2) | 2 |
| Spare tire and jack | 27 | APR trunk lid | 6 |
| Doors | 99 | APR bumper cover | 2 |
| 2 front fenders | 12 | Racing Beat nose | 11 |
| Trunk lid | 14 | Headlights | 8 |
| Rear bumper cover | 8 | APR airbag cover | 0 |
| Front bumper | 10 | APR Performance mirrors | 0.5 |
| Hood | 17 | Work Equip Meister S1 wheels (x4) | 62 |
| Wiper assembly | 5 | Nitto NT-01 205/50/15s tires (x4) | 80 |
| Headlights | 20 | Racetech seat | 22 |
| Airbag assembly | 8.5 | AWR cage | 82 |
| Stereo | 4.5 | KW coilovers | 34 |
| Carpets and interior | 4 | Odyssey PC680 | 15.5 |
| Front tow hooks | 3.5 | Total | 362 |
| Seat belt assembly (x2) | 10.5 | ||
| Intake assembly | 3 | ||
| Dash lightening | 28 | ||
| Stock mirrors | 1.5 | ||
| Dampers and springs (x4) | 45 | ||
| Battery | 21.5 | ||
| Steel wheels and tires | 152 | ||
| Total | 637 | ||
I didn't realize it back when I was still knee-deep in junked Celica parts, but there's a certain satisfaction from building a car that's going to be destroyed by a team of equally psychotic car nuts. Call it SCC team building.
With one week left to get Project Lemons ready for the 13-hour endurance demolition derby, we still had to resolve our drivetrain, suspension and brake issues. Plus get a roll cage worthy of this $500 beater race (see SCC, Feb 2007). So our mad panic continued at an even more frenzied pace. With the car already gutted, fluids changed and coolant hoses replaced, we took the car down to MD Automotive in Westminster, California, for some help with the heavy lifting.
At this point, we weren't quite sure how much more we had to tear into the car, but just on general inspection, we figured on a new clutch, CV joints, and some as-yet-undetermined bug in the brakes. The only way to tell was to put it on a lift and break out the impact wrench. Even though we had blown almost all the allotted $500 on just the car, we figured the judges wouldn't be able to tell if we replaced the clutch or a few other parts with OE items. Besides, we were sure everyone else was up to the same trick. So a new Exedy clutch and rebuilt axles were ordered and installed with the help of Mark Dibella at MD. The value of this lemon surprised us again when we inspected the flywheel and found that it didn't even need resurfacing.
Engine mountsWhile the tranny was out, we also realized the rubber in the front engine mount had ripped all the way through. In the spirit of SCC and the Lemons race, we just pulled the front and rear mounts that take the most engine motion and filled them with automotive window adhesive. With the help of a heat gun, the rubber had set enough to be mounted back in a matter of hours. It's a cheap but effective fix that also took out a lot of slop from the steering feel and made the car easier to throttle-steer on track. Like polyurethane engine mounts, the filled mounts do transfer significantly more vibration through the chassis and steering column, especially at lower revs.
Braking on the cheapNext to cooling, brakes matter most to a race car, even a slow one. With no idea what the conditions would be at Altamont Raceway, we took the safe route and fixed the brakes.
Again, the cheapness of the Celica ST was a welcome boon. The rear brakes were drums and no one makes aftermarket rotors or brake lines for this model. We didn't even bother replacing the shoes, since all the bias is up front. From our desperate calls to sponsors for inconspicuous aftermarket performance parts, the guys at Powerslot provided pads from its corporate partners, Hawk brakes. We got two sets-one for each day- of Hawk HP Plus pads, the best compromise between street and mild track use in terms of rotor wear. Although Hawk offers full race pads (like the Blues), they might have upset the brake balance too severely and possibly sacrificed overall stopping ability, since the front tires would do all the work.
To save costs, we tried to salvage the original rotors by turning them down. But the warping was so severe that by the time we finally got them flat, there wasn't enough material to keep them from warping again come race day. We decided to fit a new set of rotors and kept the old ones as back-ups. The entire system was also flushed out with Motul RBF600 synthetic DOT 4 brake fluid, which we've found to work well under repeated track beating. One squishy brake pedal run around the block told us the master cylinder was dead too, so that was replaced.
Overnight Roll CageThe organizers of the Lemons race were smart enough to separate safety equipment, brakes and tires from the original cost of the car. But while we had leeway to build an 800-point demolition survival cage-we only had one day budgeted to come up with the safest rollover protection we could find.
Unsurprisingly, no one in their right mind was up to taking this job, except one of the craziest, yet most reliable fabricators we know: Alex Pfeiffer of Battle Version. We sent the car to G-Dimension in City of Industry, California, where Pfeiffer and his welder are based, and asked for a six- to eight-point roll bar that tied into the door bars and rear shock tower supports.
Overhead hoops were omitted, since I didn't want to wear a helmet for the six-hour drive to the track. Pfeiffer looked the car over, grabbed the keys and with the demented grin of a mad scientist, shooed us away, declaring: "It'll be ready tomorrow before lunch."
When we returned, we found he only had time for a basic MIG welded four-point roll bar that anchored into the floor by the B-pillars and the rear wheel wells, which for an overnight job is still pretty good. With the impending time constraints and having no idea that the race was more demolition than endurance, we thanked him and ran to McKay's.
McKay EngineeringOur final weekend was spent trying to install a bucket seat and rails, safety harness, fire extinguisher, suspension, wheels and tires. We just didn't have a shop and a welder to press-gang. So we headed off to fellow magazine tech editor Ryan McKay's house, or McKay Engineering, as we fondly referred to it. It's a hole in the wall driveway, with an awning for cover and junk parts strewn everywhere for black widows to nest in. But it had what we needed, a household welder, chop saw and a leaky compressor for a cut-off wheel and grinder.
In our budget-oriented wisdom, we considered drilling a hole in the stock dampers and changing the original damping fluid with motor oil, which might have increased overall damping resistance. But spending the previous week in the car told us the fronts were completely blown, meaning the seals were probably done. So we 'found' a set of Koni Sport shock inserts, which, depending on how you interpreted Lemon rules, didn't add to the $500 tab as we scammed them for free from Koni.
Installation wasn't as easy as just bolting new hardware onto the chassis mounts. Since these were inserts, each spring and shock had to be disassembled, then gutted with a saw-zaw to remove the old internals. In the case of the rear shocks, the original housing had to be further modified to hold and secure the insert. Whatever yellow was left peeking out of the strut housing was spritzed with a shot of black rattle can to hide it from the judges. Just in case.
Even though we couldn't find springs in time, the twin-tube rebound-adjustable-only shocks were enough to transform the car from stripped-out crack-dealermobile to some semblance of a handling machine. The Koni's low-speed compression damping added hugely to controlling roll and pitch, and the rebound adjustment allowed us to tune ride and feedback feel. The rear damping was set higher to help the car rotate (which it did beautifully, intentionally or not) on track.
After digging in the bowels of McKay's backyard for an hour, we finally found the two sets of first-gen Miata wheels for which we had ordered our 205/55R14 Nitto NT-01s. All our online research seemed to show the two cars using the same offset and bolt pattern. But when the wheels were mounted, they didn't clear the calipers. Without longer studs, we weren't willing to fit spacers, so we resorted to grinding away at the cast iron caliper-something we don't recommend. Hoping it was only a reference surface for machining the caliper when it was made, we hastily ground off over 2mm of material from the face and bolted the wheels on. There was still minor contact, but the wheels spun and the calipers would cut the remaining grooves they needed into the softer aluminum wheels. We just had to remember to re-torque the wheels later.
In the meantime, others got to work on covering the hole where the sunroof used to be and fabricating a seat bracket for the Buddy Club Racing bucket confiscated from team member Joey Leh's private collection. With no time to get the right parts, we resorted to riveting hardware-store plexiglass to the outside of the roof and spraying the inside with gray primer to avoid greenhouse temperatures. We were also lucky enough to find and re-install the rear-view mirror and driver-side sun visor from the pile of parts we had torn out earlier.
The final hurdle was the driver seat bracket and it was dark by this time. The hour spent trying to break the OE spot welds on the indestructible stock seat's rails came up fruitless. Plan B was to tack weld the aftermarket seat rails to the floor, but the leftover tar underneath kept catching fire. In the end, we built mounting supports and gussets out of thick-gauge scrap metal, which meant the rails would support the driver's weight, not a steel bracket. We knew this would be an issue, but our hope was that the Takata five-point race harness (which retails for more than the car) would do the life-saving, not the seat.
If we had to do it againThirteen hours of non-stop racing is a good way to establish how good a car you've built. To my surprise, Project Lemons not only survived the ordeal, it thrived-performing more reliably than I would have ever imagined. In retrospect, there was little we could have done to better prepare the car for its wide assortment of drivers. The tires and shocks made the difference and we ended up using the brakes only to change lines or avoid crashes. The car was great. All I could have asked for was a proper seat bracket, which wouldn't bend when you go into the tirewall, and a water bottle with a straw.
When it comes to the track, overweight cars are as useful as a glass hammer. When you're talking about building a car to nail just one sizzling hot lap time, weight is everything. Unlike your average supermodel, you really can't have a time attack car that's too light. That was why we decided to turn the reasonably light 1995 R-package Miata into a featherweight time attack car.
Extra weight means slower lap times. Heavy cars require more force to accelerate, more tire to hang on in the corners and generate added momentum for brakes to deal with. Heavier cars need heavier wheels, tires, brakes and more power adders, which means more weight. It's a vicious cycle.
Instead of adding more mass to make an already heavy car perform, it's much easier to gut what you have, easing the burden on your existing hardware. With no power steering or windows, Project Time Attack Miata is a start, but the diet we had in mind meant stripping all but the most track-functional parts.
If you plan to compete, it's not as easy as calling the boys over and breaking out a 24-pack and the acetylene torch. Figuring out the class structure and acceptable reductions of the sanctioning body you'll be competing with might make the difference between racing in a class of tube-frame prototypes or full-interior Evos.
Most groups will move you into a faster class when you start removing weight from different parts of your car. Replacing doors with lightweight carbon fiber copies may land you in a faster class, while removing that same weight from your spare and jack may not. Different sanctioning bodies govern time attacks by power-to-weight ratios or points accrued from various modifications.
In NASA's Time Trials Series, Project Miata would fit somewhere in its TTS group for cars with a power-to-weight ratio of 8.1:1 down to 5.5:1. Assuming the car weighs 2300 pounds, we would have to be making over 400 wheel-hp to be kicked up to the unlimited class (TTU).
Unsprung weightFew variables affect acceleration, braking, turning, and part wear as much as unsprung weight. Unsprung weight is the mass of all items not supported by the suspension: wheels, tires, uprights, brake calipers and rotors, wheel bearings, and-if you want to get technical-some of the suspension, axles, control arms and any other part that is partially supported by the chassis on one side and connected to the wheels on the other. Yes, that includes brake lines and brake fluid.
While there are plenty of theories regarding the effects of removing unsprung versus sprung weight, it's generally accepted that eliminating unsprung weight is more effective. Reducing weight under each spring contributes to faster lap times by positively influencing such factors as rotational inertia, gyroscopic motion and how fast each corner of the car can react to road inputs and stay planted.
Rotational InertiaAs much as the physical weight of each unsprung corner matters, rotational inertia of wheels, tires or any rotating mass adds to the difficulty of accelerating and decelerating. Imagine you have a 10-speed bicycle with its rear wheel free-spinning. When its tire is filled with air, it's easier to get it turning or stopped than that same wheel with its tire filled with lead. This rotational inertia, or moment of inertia, is affected by the wheel's overall mass and even more by how far out on the radius that mass is distributed. A five-pound disk has less rotational inertia than a five-pound hoop of the same diameter. Even if you keep the weight the same, rotational inertia exponentially increases as the diameter increases. This concept holds true for anything being rotated about a given axis. As tires are the mass furthest out on a wheel, their weight has the biggest effect on the overall rotational inertia. On track or on the street, people often obsess over having ultra-light wheels without giving a thought to the weight of their tires.
Brake rotors have the next biggest impact on rotational inertia. Even though some big brake upgrades may actually weigh less than cast OE components, larger rotors usually mean more rotational inertia. Two-piece rotors with thin steel or aluminum hats help compensate for the weight and moment of inertia generated by the larger parts, but mass at the radius ultimately matters most. This delicate balance of weight, rotational inertia and brake torque will be addressed in a future installment.
Making wheel and tire choicesThe vehicle formerly known as Project Miata rode on abnormally wide 245/45R15 Hoosier bias ply race tires. As Project Time Attack, it will ride on DOT radials to avoid points penalties during NASA and other time trial competitions. We had to find the right balance between grip, size and weight for the car's current characteristics. Problem is, Miatas came with donut-size wheels and wheel wells only a wee bit bigger. So finding a tire small yet wide enough was a dilemma. For now, the widest DOT tires we can run in the correct diameter are a 225/45R15.In addition to our desire to limit rotational inertia with the smallest wheels possible, plans for larger brakes affected our wheel and tire selection. To clear the brake upgrade we had in mind, the wheels had to be at least 15 inches in diameter. Instead of picking the wheel size, we started by finding all our favorite R-Compound tires that come in 15-inch sizes.
The limited selection made this pretty easy. We went for the Nitto NT-01 tire on account of its tread design, price and our past experience. Key advantages include the huge tread blocks and smooth radiused transitions between tread blocks and grooves that reduce squirm and scaling. Its compound also endures prolonged track temperatures while being hard enough to drive to and from the track without incurring excessive wear. Until the car requires more grip, we're going with a set of 205/50R15 Nitto NT01s.Most Miata track cars use 6.5- or 7-inch width wheels with 13- to 15-inch diameters. Since most of the weight of the wheel is in the hoop, as it is furthest out on the radius, the width of the hoop will contribute most to rotational inertia.Narrow wheels use less material in the hoops, which takes much of the weight out at the farthest radial distance. This comes at the cost of reducing tire width and contact patch. Stuffing wide tires onto narrow wheels isn't the answer either; pooched-out sidewalls would cause rollover issues, sloppy turn-in response and a deformed contact patch.
Finding a 15-inch wheel to fit a 205 tire isn't easy. A seven-inch width wheel is ideal. We knew our tire requirements would soon increase, so we looked for a 15x8 wheel anyway. With such a width, we had to make sure we could mount the wheels without touching the fenders on the outside and, more importantly, the control arms on the inside-fenders are easier to cut than control arms.
E-production class Miata race cars have been using zero-offset wheels for a long time with great success, so we decided to look for a wheel with a +15mm offset, since we will ultimately run tires that are 20mm wider. The increased scrub radius of this more positive offset will put more load on the wheel bearings, but we're hoping the trade-off for extra track will improve lateral grip.
There are few 15x8 wheels on the market, even fewer in the offset we wanted. Work Wheels said it could make what we were looking for. Its history of building custom-sized endurance wheels convinced us we'd be getting a light and durable wheel.
After what seemed like a long wait, we received our Meister S1s, beautiful works of art that weigh almost 16 pounds a pop. A little surprising, but not a deal-breaker. Seeing as we've bent our share of unproven super-light wheels in our off-line lawn-mowing excursions, we're happy to stick with Work's products.
Even with all the measuring and hunting for offset-specific wheels, we still ended up with fender clearance issues. To cover up our artistic Sawzall expressionism, fender flares from a small Japanese boutique called Tuckin '99 were added. Tuckin '99, like many other boutique Japanese motorsports suppliers, built its business around a diehard set of Miata fans and club racers, and isn't really interested in scaling its business over the web. Parts are made in small runs and sold by word of mouth. As SCC is all about JDM, we purchased a set from Adrenaline Racing, in the JDM center of the world, Lake Oswego, Oregon.
Sprung weightTaking out sprung weight is far easier and subject to fewer compromises. It's also easier to remove and relocate this type of weight. Big-budget race teams will make everything as light as possible before adding weight back (in the form of lead bars in the floorboards) to satisfy the minimum regulations-all for the sake of better weight distribution. Since the Miata is already relatively well balanced, we opted against such extreme measures and focused on removing as much weight as we could from the edges to reduce the total moment of inertia.
Every removable body panel was pulled off to access the non-essential crap underneath: bumper supports, windows and crash supports, latches, and wiring for stuff we had long since thrown away. Axis Power Racing (APR) created a set of carbon fiber-wrapped Nomex honeycomb-cored replacement body panels-substantially lighter than the stock pieces-to shed further pounds. APR uses a vacuum infusion process to suck out as much excess resin as possible, minimizing weight. Unlike race car chassis components, these pieces are not baked in an autoclave for added rigidity since the panels we replaced are non-structural elements. The honeycomb adds enough rigidity to make the pieces more than just cosmetic and also allowed us to avoid the autoclave, significantly reducing cost.
The pieces were molded directly from the stock panels, but the hood was modified with a vent placed directly behind the radiator to evacuate hot air from the engine bay. This will be a big factor once we turbocharge the car and install various other heat exchangers in the nose. The front fenders were lined and reinforced with Kevlar to save the panels from internal damage due to road debris being thrown up by the tires. The only panels left stock were the rear quarter panels, which are part of the factory unibody. We sourced a Racing Beat Type 2 fiberglass nose to replace the factory piece as it saves a little weight, but also has added cooling ducts.
At 10 pounds per side, the MkI Miata pop-up headlights have a significant impact on polar moment. A time attack car still needs lights, but we didn't want the weight. Advanced Automotive Concepts has a fixed-mount headlight kit that shaves over 12 pounds. Other unnecessary parts (including the soft top, airbags, interior bits, seats, seat belts, stock battery and dash guts) found the dumpster. The stock side mirrors were replaced with carbon pieces sourced from APR Performance and the rear glass in the hardtop was chucked in favor of a Lexan replacement. Our final weight came down to 2018 pounds with a full tank of gas. Not the lightest Miata we've seen, but necessary weight (such as the cage) makes up the difference. Just in exterior body parts replaced, we've shed 154 pounds.
Now that Project Time Attack has spent some quality time with Jenny Craig, it's time for the 'roids. In our next installment, Project Time Attack will receive what is likely the best power-to-weight ratio of any of the monstrosities to come out of our garage.
| WELCOME TO WEIGHT WATCHERS | |||
| Items Removed | Weight (lbs) | Items Added | Weight (lbs) |
| Air conditioning | 36 | APR hard top | 9 |
| Aftermarket soft top and frame | 39 | APR hood | 9 |
| Passenger seat | 34 | APR doors (x2) | 19 |
| Driver seat | 34 | APR fenders (x2) | 2 |
| Spare tire and jack | 27 | APR trunk lid | 6 |
| Doors | 99 | APR bumper cover | 2 |
| 2 front fenders | 12 | Racing Beat nose | 11 |
| Trunk lid | 14 | Headlights | 8 |
| Rear bumper cover | 8 | APR airbag cover | 0 |
| Front bumper | 10 | APR Performance mirrors | 0.5 |
| Hood | 17 | Work Equip Meister S1 wheels (x4) | 62 |
| Wiper assembly | 5 | Nitto NT-01 205/50/15s tires (x4) | 80 |
| Headlights | 20 | Racetech seat | 22 |
| Airbag assembly | 8.5 | AWR cage | 82 |
| Stereo | 4.5 | KW coilovers | 34 |
| Carpets and interior | 4 | Odyssey PC680 | 15.5 |
| Front tow hooks | 3.5 | Total | 362 |
| Seat belt assembly (x2) | 10.5 | ||
| Intake assembly | 3 | ||
| Dash lightening | 28 | ||
| Stock mirrors | 1.5 | ||
| Dampers and springs (x4) | 45 | ||
| Battery | 21.5 | ||
| Steel wheels and tires | 152 | ||
| Total | 637 | ||
I didn't realize it back when I was still knee-deep in junked Celica parts, but there's a certain satisfaction from building a car that's going to be destroyed by a team of equally psychotic car nuts. Call it SCC team building.
With one week left to get Project Lemons ready for the 13-hour endurance demolition derby, we still had to resolve our drivetrain, suspension and brake issues. Plus get a roll cage worthy of this $500 beater race (see SCC, Feb 2007). So our mad panic continued at an even more frenzied pace. With the car already gutted, fluids changed and coolant hoses replaced, we took the car down to MD Automotive in Westminster, California, for some help with the heavy lifting.
At this point, we weren't quite sure how much more we had to tear into the car, but just on general inspection, we figured on a new clutch, CV joints, and some as-yet-undetermined bug in the brakes. The only way to tell was to put it on a lift and break out the impact wrench. Even though we had blown almost all the allotted $500 on just the car, we figured the judges wouldn't be able to tell if we replaced the clutch or a few other parts with OE items. Besides, we were sure everyone else was up to the same trick. So a new Exedy clutch and rebuilt axles were ordered and installed with the help of Mark Dibella at MD. The value of this lemon surprised us again when we inspected the flywheel and found that it didn't even need resurfacing.
Engine mountsWhile the tranny was out, we also realized the rubber in the front engine mount had ripped all the way through. In the spirit of SCC and the Lemons race, we just pulled the front and rear mounts that take the most engine motion and filled them with automotive window adhesive. With the help of a heat gun, the rubber had set enough to be mounted back in a matter of hours. It's a cheap but effective fix that also took out a lot of slop from the steering feel and made the car easier to throttle-steer on track. Like polyurethane engine mounts, the filled mounts do transfer significantly more vibration through the chassis and steering column, especially at lower revs.
Braking on the cheapNext to cooling, brakes matter most to a race car, even a slow one. With no idea what the conditions would be at Altamont Raceway, we took the safe route and fixed the brakes.
Again, the cheapness of the Celica ST was a welcome boon. The rear brakes were drums and no one makes aftermarket rotors or brake lines for this model. We didn't even bother replacing the shoes, since all the bias is up front. From our desperate calls to sponsors for inconspicuous aftermarket performance parts, the guys at Powerslot provided pads from its corporate partners, Hawk brakes. We got two sets-one for each day- of Hawk HP Plus pads, the best compromise between street and mild track use in terms of rotor wear. Although Hawk offers full race pads (like the Blues), they might have upset the brake balance too severely and possibly sacrificed overall stopping ability, since the front tires would do all the work.
To save costs, we tried to salvage the original rotors by turning them down. But the warping was so severe that by the time we finally got them flat, there wasn't enough material to keep them from warping again come race day. We decided to fit a new set of rotors and kept the old ones as back-ups. The entire system was also flushed out with Motul RBF600 synthetic DOT 4 brake fluid, which we've found to work well under repeated track beating. One squishy brake pedal run around the block told us the master cylinder was dead too, so that was replaced.
Overnight Roll CageThe organizers of the Lemons race were smart enough to separate safety equipment, brakes and tires from the original cost of the car. But while we had leeway to build an 800-point demolition survival cage-we only had one day budgeted to come up with the safest rollover protection we could find.
Unsurprisingly, no one in their right mind was up to taking this job, except one of the craziest, yet most reliable fabricators we know: Alex Pfeiffer of Battle Version. We sent the car to G-Dimension in City of Industry, California, where Pfeiffer and his welder are based, and asked for a six- to eight-point roll bar that tied into the door bars and rear shock tower supports.
Overhead hoops were omitted, since I didn't want to wear a helmet for the six-hour drive to the track. Pfeiffer looked the car over, grabbed the keys and with the demented grin of a mad scientist, shooed us away, declaring: "It'll be ready tomorrow before lunch."
When we returned, we found he only had time for a basic MIG welded four-point roll bar that anchored into the floor by the B-pillars and the rear wheel wells, which for an overnight job is still pretty good. With the impending time constraints and having no idea that the race was more demolition than endurance, we thanked him and ran to McKay's.
McKay EngineeringOur final weekend was spent trying to install a bucket seat and rails, safety harness, fire extinguisher, suspension, wheels and tires. We just didn't have a shop and a welder to press-gang. So we headed off to fellow magazine tech editor Ryan McKay's house, or McKay Engineering, as we fondly referred to it. It's a hole in the wall driveway, with an awning for cover and junk parts strewn everywhere for black widows to nest in. But it had what we needed, a household welder, chop saw and a leaky compressor for a cut-off wheel and grinder.
In our budget-oriented wisdom, we considered drilling a hole in the stock dampers and changing the original damping fluid with motor oil, which might have increased overall damping resistance. But spending the previous week in the car told us the fronts were completely blown, meaning the seals were probably done. So we 'found' a set of Koni Sport shock inserts, which, depending on how you interpreted Lemon rules, didn't add to the $500 tab as we scammed them for free from Koni.
Installation wasn't as easy as just bolting new hardware onto the chassis mounts. Since these were inserts, each spring and shock had to be disassembled, then gutted with a saw-zaw to remove the old internals. In the case of the rear shocks, the original housing had to be further modified to hold and secure the insert. Whatever yellow was left peeking out of the strut housing was spritzed with a shot of black rattle can to hide it from the judges. Just in case.
Even though we couldn't find springs in time, the twin-tube rebound-adjustable-only shocks were enough to transform the car from stripped-out crack-dealermobile to some semblance of a handling machine. The Koni's low-speed compression damping added hugely to controlling roll and pitch, and the rebound adjustment allowed us to tune ride and feedback feel. The rear damping was set higher to help the car rotate (which it did beautifully, intentionally or not) on track.
After digging in the bowels of McKay's backyard for an hour, we finally found the two sets of first-gen Miata wheels for which we had ordered our 205/55R14 Nitto NT-01s. All our online research seemed to show the two cars using the same offset and bolt pattern. But when the wheels were mounted, they didn't clear the calipers. Without longer studs, we weren't willing to fit spacers, so we resorted to grinding away at the cast iron caliper-something we don't recommend. Hoping it was only a reference surface for machining the caliper when it was made, we hastily ground off over 2mm of material from the face and bolted the wheels on. There was still minor contact, but the wheels spun and the calipers would cut the remaining grooves they needed into the softer aluminum wheels. We just had to remember to re-torque the wheels later.
In the meantime, others got to work on covering the hole where the sunroof used to be and fabricating a seat bracket for the Buddy Club Racing bucket confiscated from team member Joey Leh's private collection. With no time to get the right parts, we resorted to riveting hardware-store plexiglass to the outside of the roof and spraying the inside with gray primer to avoid greenhouse temperatures. We were also lucky enough to find and re-install the rear-view mirror and driver-side sun visor from the pile of parts we had torn out earlier.
The final hurdle was the driver seat bracket and it was dark by this time. The hour spent trying to break the OE spot welds on the indestructible stock seat's rails came up fruitless. Plan B was to tack weld the aftermarket seat rails to the floor, but the leftover tar underneath kept catching fire. In the end, we built mounting supports and gussets out of thick-gauge scrap metal, which meant the rails would support the driver's weight, not a steel bracket. We knew this would be an issue, but our hope was that the Takata five-point race harness (which retails for more than the car) would do the life-saving, not the seat.
If we had to do it againThirteen hours of non-stop racing is a good way to establish how good a car you've built. To my surprise, Project Lemons not only survived the ordeal, it thrived-performing more reliably than I would have ever imagined. In retrospect, there was little we could have done to better prepare the car for its wide assortment of drivers. The tires and shocks made the difference and we ended up using the brakes only to change lines or avoid crashes. The car was great. All I could have asked for was a proper seat bracket, which wouldn't bend when you go into the tirewall, and a water bottle with a straw.
When it comes to the track, overweight cars are as useful as a glass hammer. When you're talking about building a car to nail just one sizzling hot lap time, weight is everything. Unlike your average supermodel, you really can't have a time attack car that's too light. That was why we decided to turn the reasonably light 1995 R-package Miata into a featherweight time attack car.
Extra weight means slower lap times. Heavy cars require more force to accelerate, more tire to hang on in the corners and generate added momentum for brakes to deal with. Heavier cars need heavier wheels, tires, brakes and more power adders, which means more weight. It's a vicious cycle.
Instead of adding more mass to make an already heavy car perform, it's much easier to gut what you have, easing the burden on your existing hardware. With no power steering or windows, Project Time Attack Miata is a start, but the diet we had in mind meant stripping all but the most track-functional parts.
If you plan to compete, it's not as easy as calling the boys over and breaking out a 24-pack and the acetylene torch. Figuring out the class structure and acceptable reductions of the sanctioning body you'll be competing with might make the difference between racing in a class of tube-frame prototypes or full-interior Evos.
Most groups will move you into a faster class when you start removing weight from different parts of your car. Replacing doors with lightweight carbon fiber copies may land you in a faster class, while removing that same weight from your spare and jack may not. Different sanctioning bodies govern time attacks by power-to-weight ratios or points accrued from various modifications.
In NASA's Time Trials Series, Project Miata would fit somewhere in its TTS group for cars with a power-to-weight ratio of 8.1:1 down to 5.5:1. Assuming the car weighs 2300 pounds, we would have to be making over 400 wheel-hp to be kicked up to the unlimited class (TTU).
Unsprung weightFew variables affect acceleration, braking, turning, and part wear as much as unsprung weight. Unsprung weight is the mass of all items not supported by the suspension: wheels, tires, uprights, brake calipers and rotors, wheel bearings, and-if you want to get technical-some of the suspension, axles, control arms and any other part that is partially supported by the chassis on one side and connected to the wheels on the other. Yes, that includes brake lines and brake fluid.
While there are plenty of theories regarding the effects of removing unsprung versus sprung weight, it's generally accepted that eliminating unsprung weight is more effective. Reducing weight under each spring contributes to faster lap times by positively influencing such factors as rotational inertia, gyroscopic motion and how fast each corner of the car can react to road inputs and stay planted.
Rotational InertiaAs much as the physical weight of each unsprung corner matters, rotational inertia of wheels, tires or any rotating mass adds to the difficulty of accelerating and decelerating. Imagine you have a 10-speed bicycle with its rear wheel free-spinning. When its tire is filled with air, it's easier to get it turning or stopped than that same wheel with its tire filled with lead. This rotational inertia, or moment of inertia, is affected by the wheel's overall mass and even more by how far out on the radius that mass is distributed. A five-pound disk has less rotational inertia than a five-pound hoop of the same diameter. Even if you keep the weight the same, rotational inertia exponentially increases as the diameter increases. This concept holds true for anything being rotated about a given axis. As tires are the mass furthest out on a wheel, their weight has the biggest effect on the overall rotational inertia. On track or on the street, people often obsess over having ultra-light wheels without giving a thought to the weight of their tires.
Brake rotors have the next biggest impact on rotational inertia. Even though some big brake upgrades may actually weigh less than cast OE components, larger rotors usually mean more rotational inertia. Two-piece rotors with thin steel or aluminum hats help compensate for the weight and moment of inertia generated by the larger parts, but mass at the radius ultimately matters most. This delicate balance of weight, rotational inertia and brake torque will be addressed in a future installment.
Making wheel and tire choicesThe vehicle formerly known as Project Miata rode on abnormally wide 245/45R15 Hoosier bias ply race tires. As Project Time Attack, it will ride on DOT radials to avoid points penalties during NASA and other time trial competitions. We had to find the right balance between grip, size and weight for the car's current characteristics. Problem is, Miatas came with donut-size wheels and wheel wells only a wee bit bigger. So finding a tire small yet wide enough was a dilemma. For now, the widest DOT tires we can run in the correct diameter are a 225/45R15.In addition to our desire to limit rotational inertia with the smallest wheels possible, plans for larger brakes affected our wheel and tire selection. To clear the brake upgrade we had in mind, the wheels had to be at least 15 inches in diameter. Instead of picking the wheel size, we started by finding all our favorite R-Compound tires that come in 15-inch sizes.
The limited selection made this pretty easy. We went for the Nitto NT-01 tire on account of its tread design, price and our past experience. Key advantages include the huge tread blocks and smooth radiused transitions between tread blocks and grooves that reduce squirm and scaling. Its compound also endures prolonged track temperatures while being hard enough to drive to and from the track without incurring excessive wear. Until the car requires more grip, we're going with a set of 205/50R15 Nitto NT01s.Most Miata track cars use 6.5- or 7-inch width wheels with 13- to 15-inch diameters. Since most of the weight of the wheel is in the hoop, as it is furthest out on the radius, the width of the hoop will contribute most to rotational inertia.Narrow wheels use less material in the hoops, which takes much of the weight out at the farthest radial distance. This comes at the cost of reducing tire width and contact patch. Stuffing wide tires onto narrow wheels isn't the answer either; pooched-out sidewalls would cause rollover issues, sloppy turn-in response and a deformed contact patch.
Finding a 15-inch wheel to fit a 205 tire isn't easy. A seven-inch width wheel is ideal. We knew our tire requirements would soon increase, so we looked for a 15x8 wheel anyway. With such a width, we had to make sure we could mount the wheels without touching the fenders on the outside and, more importantly, the control arms on the inside-fenders are easier to cut than control arms.
E-production class Miata race cars have been using zero-offset wheels for a long time with great success, so we decided to look for a wheel with a +15mm offset, since we will ultimately run tires that are 20mm wider. The increased scrub radius of this more positive offset will put more load on the wheel bearings, but we're hoping the trade-off for extra track will improve lateral grip.
There are few 15x8 wheels on the market, even fewer in the offset we wanted. Work Wheels said it could make what we were looking for. Its history of building custom-sized endurance wheels convinced us we'd be getting a light and durable wheel.
After what seemed like a long wait, we received our Meister S1s, beautiful works of art that weigh almost 16 pounds a pop. A little surprising, but not a deal-breaker. Seeing as we've bent our share of unproven super-light wheels in our off-line lawn-mowing excursions, we're happy to stick with Work's products.
Even with all the measuring and hunting for offset-specific wheels, we still ended up with fender clearance issues. To cover up our artistic Sawzall expressionism, fender flares from a small Japanese boutique called Tuckin '99 were added. Tuckin '99, like many other boutique Japanese motorsports suppliers, built its business around a diehard set of Miata fans and club racers, and isn't really interested in scaling its business over the web. Parts are made in small runs and sold by word of mouth. As SCC is all about JDM, we purchased a set from Adrenaline Racing, in the JDM center of the world, Lake Oswego, Oregon.
Sprung weightTaking out sprung weight is far easier and subject to fewer compromises. It's also easier to remove and relocate this type of weight. Big-budget race teams will make everything as light as possible before adding weight back (in the form of lead bars in the floorboards) to satisfy the minimum regulations-all for the sake of better weight distribution. Since the Miata is already relatively well balanced, we opted against such extreme measures and focused on removing as much weight as we could from the edges to reduce the total moment of inertia.
Every removable body panel was pulled off to access the non-essential crap underneath: bumper supports, windows and crash supports, latches, and wiring for stuff we had long since thrown away. Axis Power Racing (APR) created a set of carbon fiber-wrapped Nomex honeycomb-cored replacement body panels-substantially lighter than the stock pieces-to shed further pounds. APR uses a vacuum infusion process to suck out as much excess resin as possible, minimizing weight. Unlike race car chassis components, these pieces are not baked in an autoclave for added rigidity since the panels we replaced are non-structural elements. The honeycomb adds enough rigidity to make the pieces more than just cosmetic and also allowed us to avoid the autoclave, significantly reducing cost.
The pieces were molded directly from the stock panels, but the hood was modified with a vent placed directly behind the radiator to evacuate hot air from the engine bay. This will be a big factor once we turbocharge the car and install various other heat exchangers in the nose. The front fenders were lined and reinforced with Kevlar to save the panels from internal damage due to road debris being thrown up by the tires. The only panels left stock were the rear quarter panels, which are part of the factory unibody. We sourced a Racing Beat Type 2 fiberglass nose to replace the factory piece as it saves a little weight, but also has added cooling ducts.
At 10 pounds per side, the MkI Miata pop-up headlights have a significant impact on polar moment. A time attack car still needs lights, but we didn't want the weight. Advanced Automotive Concepts has a fixed-mount headlight kit that shaves over 12 pounds. Other unnecessary parts (including the soft top, airbags, interior bits, seats, seat belts, stock battery and dash guts) found the dumpster. The stock side mirrors were replaced with carbon pieces sourced from APR Performance and the rear glass in the hardtop was chucked in favor of a Lexan replacement. Our final weight came down to 2018 pounds with a full tank of gas. Not the lightest Miata we've seen, but necessary weight (such as the cage) makes up the difference. Just in exterior body parts replaced, we've shed 154 pounds.
Now that Project Time Attack has spent some quality time with Jenny Craig, it's time for the 'roids. In our next installment, Project Time Attack will receive what is likely the best power-to-weight ratio of any of the monstrosities to come out of our garage.
| WELCOME TO WEIGHT WATCHERS | |||
| Items Removed | Weight (lbs) | Items Added | Weight (lbs) |
| Air conditioning | 36 | APR hard top | 9 |
| Aftermarket soft top and frame | 39 | APR hood | 9 |
| Passenger seat | 34 | APR doors (x2) | 19 |
| Driver seat | 34 | APR fenders (x2) | 2 |
| Spare tire and jack | 27 | APR trunk lid | 6 |
| Doors | 99 | APR bumper cover | 2 |
| 2 front fenders | 12 | Racing Beat nose | 11 |
| Trunk lid | 14 | Headlights | 8 |
| Rear bumper cover | 8 | APR airbag cover | 0 |
| Front bumper | 10 | APR Performance mirrors | 0.5 |
| Hood | 17 | Work Equip Meister S1 wheels (x4) | 62 |
| Wiper assembly | 5 | Nitto NT-01 205/50/15s tires (x4) | 80 |
| Headlights | 20 | Racetech seat | 22 |
| Airbag assembly | 8.5 | AWR cage | 82 |
| Stereo | 4.5 | KW coilovers | 34 |
| Carpets and interior | 4 | Odyssey PC680 | 15.5 |
| Front tow hooks | 3.5 | Total | 362 |
| Seat belt assembly (x2) | 10.5 | ||
| Intake assembly | 3 | ||
| Dash lightening | 28 | ||
| Stock mirrors | 1.5 | ||
| Dampers and springs (x4) | 45 | ||
| Battery | 21.5 | ||
| Steel wheels and tires | 152 | ||
| Total | 637 | ||
I didn't realize it back when I was still knee-deep in junked Celica parts, but there's a certain satisfaction from building a car that's going to be destroyed by a team of equally psychotic car nuts. Call it SCC team building.
With one week left to get Project Lemons ready for the 13-hour endurance demolition derby, we still had to resolve our drivetrain, suspension and brake issues. Plus get a roll cage worthy of this $500 beater race (see SCC, Feb 2007). So our mad panic continued at an even more frenzied pace. With the car already gutted, fluids changed and coolant hoses replaced, we took the car down to MD Automotive in Westminster, California, for some help with the heavy lifting.
At this point, we weren't quite sure how much more we had to tear into the car, but just on general inspection, we figured on a new clutch, CV joints, and some as-yet-undetermined bug in the brakes. The only way to tell was to put it on a lift and break out the impact wrench. Even though we had blown almost all the allotted $500 on just the car, we figured the judges wouldn't be able to tell if we replaced the clutch or a few other parts with OE items. Besides, we were sure everyone else was up to the same trick. So a new Exedy clutch and rebuilt axles were ordered and installed with the help of Mark Dibella at MD. The value of this lemon surprised us again when we inspected the flywheel and found that it didn't even need resurfacing.
Engine mountsWhile the tranny was out, we also realized the rubber in the front engine mount had ripped all the way through. In the spirit of SCC and the Lemons race, we just pulled the front and rear mounts that take the most engine motion and filled them with automotive window adhesive. With the help of a heat gun, the rubber had set enough to be mounted back in a matter of hours. It's a cheap but effective fix that also took out a lot of slop from the steering feel and made the car easier to throttle-steer on track. Like polyurethane engine mounts, the filled mounts do transfer significantly more vibration through the chassis and steering column, especially at lower revs.
Braking on the cheapNext to cooling, brakes matter most to a race car, even a slow one. With no idea what the conditions would be at Altamont Raceway, we took the safe route and fixed the brakes.
Again, the cheapness of the Celica ST was a welcome boon. The rear brakes were drums and no one makes aftermarket rotors or brake lines for this model. We didn't even bother replacing the shoes, since all the bias is up front. From our desperate calls to sponsors for inconspicuous aftermarket performance parts, the guys at Powerslot provided pads from its corporate partners, Hawk brakes. We got two sets-one for each day- of Hawk HP Plus pads, the best compromise between street and mild track use in terms of rotor wear. Although Hawk offers full race pads (like the Blues), they might have upset the brake balance too severely and possibly sacrificed overall stopping ability, since the front tires would do all the work.
To save costs, we tried to salvage the original rotors by turning them down. But the warping was so severe that by the time we finally got them flat, there wasn't enough material to keep them from warping again come race day. We decided to fit a new set of rotors and kept the old ones as back-ups. The entire system was also flushed out with Motul RBF600 synthetic DOT 4 brake fluid, which we've found to work well under repeated track beating. One squishy brake pedal run around the block told us the master cylinder was dead too, so that was replaced.
Overnight Roll CageThe organizers of the Lemons race were smart enough to separate safety equipment, brakes and tires from the original cost of the car. But while we had leeway to build an 800-point demolition survival cage-we only had one day budgeted to come up with the safest rollover protection we could find.
Unsurprisingly, no one in their right mind was up to taking this job, except one of the craziest, yet most reliable fabricators we know: Alex Pfeiffer of Battle Version. We sent the car to G-Dimension in City of Industry, California, where Pfeiffer and his welder are based, and asked for a six- to eight-point roll bar that tied into the door bars and rear shock tower supports.
Overhead hoops were omitted, since I didn't want to wear a helmet for the six-hour drive to the track. Pfeiffer looked the car over, grabbed the keys and with the demented grin of a mad scientist, shooed us away, declaring: "It'll be ready tomorrow before lunch."
When we returned, we found he only had time for a basic MIG welded four-point roll bar that anchored into the floor by the B-pillars and the rear wheel wells, which for an overnight job is still pretty good. With the impending time constraints and having no idea that the race was more demolition than endurance, we thanked him and ran to McKay's.
McKay EngineeringOur final weekend was spent trying to install a bucket seat and rails, safety harness, fire extinguisher, suspension, wheels and tires. We just didn't have a shop and a welder to press-gang. So we headed off to fellow magazine tech editor Ryan McKay's house, or McKay Engineering, as we fondly referred to it. It's a hole in the wall driveway, with an awning for cover and junk parts strewn everywhere for black widows to nest in. But it had what we needed, a household welder, chop saw and a leaky compressor for a cut-off wheel and grinder.
In our budget-oriented wisdom, we considered drilling a hole in the stock dampers and changing the original damping fluid with motor oil, which might have increased overall damping resistance. But spending the previous week in the car told us the fronts were completely blown, meaning the seals were probably done. So we 'found' a set of Koni Sport shock inserts, which, depending on how you interpreted Lemon rules, didn't add to the $500 tab as we scammed them for free from Koni.
Installation wasn't as easy as just bolting new hardware onto the chassis mounts. Since these were inserts, each spring and shock had to be disassembled, then gutted with a saw-zaw to remove the old internals. In the case of the rear shocks, the original housing had to be further modified to hold and secure the insert. Whatever yellow was left peeking out of the strut housing was spritzed with a shot of black rattle can to hide it from the judges. Just in case.
Even though we couldn't find springs in time, the twin-tube rebound-adjustable-only shocks were enough to transform the car from stripped-out crack-dealermobile to some semblance of a handling machine. The Koni's low-speed compression damping added hugely to controlling roll and pitch, and the rebound adjustment allowed us to tune ride and feedback feel. The rear damping was set higher to help the car rotate (which it did beautifully, intentionally or not) on track.
After digging in the bowels of McKay's backyard for an hour, we finally found the two sets of first-gen Miata wheels for which we had ordered our 205/55R14 Nitto NT-01s. All our online research seemed to show the two cars using the same offset and bolt pattern. But when the wheels were mounted, they didn't clear the calipers. Without longer studs, we weren't willing to fit spacers, so we resorted to grinding away at the cast iron caliper-something we don't recommend. Hoping it was only a reference surface for machining the caliper when it was made, we hastily ground off over 2mm of material from the face and bolted the wheels on. There was still minor contact, but the wheels spun and the calipers would cut the remaining grooves they needed into the softer aluminum wheels. We just had to remember to re-torque the wheels later.
In the meantime, others got to work on covering the hole where the sunroof used to be and fabricating a seat bracket for the Buddy Club Racing bucket confiscated from team member Joey Leh's private collection. With no time to get the right parts, we resorted to riveting hardware-store plexiglass to the outside of the roof and spraying the inside with gray primer to avoid greenhouse temperatures. We were also lucky enough to find and re-install the rear-view mirror and driver-side sun visor from the pile of parts we had torn out earlier.
The final hurdle was the driver seat bracket and it was dark by this time. The hour spent trying to break the OE spot welds on the indestructible stock seat's rails came up fruitless. Plan B was to tack weld the aftermarket seat rails to the floor, but the leftover tar underneath kept catching fire. In the end, we built mounting supports and gussets out of thick-gauge scrap metal, which meant the rails would support the driver's weight, not a steel bracket. We knew this would be an issue, but our hope was that the Takata five-point race harness (which retails for more than the car) would do the life-saving, not the seat.
If we had to do it againThirteen hours of non-stop racing is a good way to establish how good a car you've built. To my surprise, Project Lemons not only survived the ordeal, it thrived-performing more reliably than I would have ever imagined. In retrospect, there was little we could have done to better prepare the car for its wide assortment of drivers. The tires and shocks made the difference and we ended up using the brakes only to change lines or avoid crashes. The car was great. All I could have asked for was a proper seat bracket, which wouldn't bend when you go into the tirewall, and a water bottle with a straw.
