| Commanding The Apexes - Project Supra Part 6: Suspension
Although primarily a street car, Project Supra is being built to be a worthy time-attacker for a select few weekends out of the year. As it rolls now, the Toyota has been powered up to just a few ticks under 400 whp with the addition of a front-mount intercooler and more advanced engine tuning that we'll talk about in the next installment. It's got plenty of grunt for the majority of the straights. The Brembo brakes have been phenomenal, thanks in part to the extra grip provided by the iForged wheels and Bridgestone tire combo featured in the last installment. One of the most important fundamentals for a car's performance-whether for pleasure or for dropping a few seconds off your lap time-is the suspension.
Choosing a suspension upgrade wasn't difficult. We wanted something for the Supra that would work well both on- and off-track. With what is available for the Supra today, ride height adjustment as well as damper controls were obvious prerequisites. It would give us the best of both worlds-the ability to stiffen and lower the suspension for a given track and when we're done bring it back to its street setup for a comfortable drive home. TEIN coil-overs not only offer these features, it's Electronic Damping Force Controller (EDFC) allows the driver to adjust the damping force by the touch a button on the fly.
TEIN suspension kits offered for the Supra's JZ80 chassis vary from replacement coil springs to full race suspension systems. Each of the coil-over system offered serves a particular purpose. The most basic system, and the only one that is not EDFC-compatible for the Supra, is the Driving Master Basic Damper, a coil-over setup that offers ride height adjustment only. TEIN's Cruising Master Type CS system was designed for the sophisticated, business-like driver desiring total drive comfort on the street. Drivers seeking ride-height adjustments with some damper control on a relatively soft suspension may opt for this setup.
The Control Master Type Flex system is EDFC-compatible and is designed to provide a good compromise between ride comfort and performance. The company incorporated certain height and preload adjustments for different road conditions for maximum street performance. The Flex system is TEIN's compromise between street and competition.
TEIN's Circuit Master coil-over systems are competition-bred systems. The Type RA system is designed for circuit racing and street use for experienced drivers. TEIN reports this system uses its newly designed mono-tube structure allowing for maximum road holding and stability in all situations, and was developed from their involvement in World Rally, N1 and endurance racing. The Type RA system is stiffer than the Flex system by over 110 lb/in2 per corner. The Type RE is similar to the RA with an added full-length adjustment system, allowing separate settings of the height and spring preload. But the spring stiffness is the same as the RA.
For Project Supra we chose to go with the Control Master Type Flex system. We felt with the majority of miles this car would see on the street versus the track it was a good choice. Should we decide to track the car a lot more we may graduate to the RE system. But for now the Flex offers the best compromise. TEIN's own Philip Chase and Ippei Sugano performed the install at its headquarters in Downey, Calif., which went smoothly. As with most suspension upgrades, make sure after installing coil-overs the car receives a proper alignment job.
The EDFC controller is mounted next to the hood-release latch. I felt if it were mounted on top of the steering hub I'd stare at it constantly. Where it's mounted is out of the way, yet well within reach. The controller features three pre-selected stiffness levels to the front and rear that you can choose from, or you can go up in single-digit increments using the arrow buttons.
During the initial test drive I could instantly feel the stiffness increase over the stock Supra suspension, but it wasn't too stiff. The EDFC has a range of 16 different settings, with 00 being full stiff and 16 being full soft. At the 00 setting the car is a little more jarring but still livable on the street.
Throwing it around a few right-hand-turn, clover leaf freeway on-ramps made the left front tire hit the inner wheelwell when transferring weight forward through throttle steer or semi-hard trailbraking, even on the stiffest setting. At first I thought this was due in part from the wider 255mm front tires. After an alignment was performed for negative 2.5-degrees camber up front it still continued to rub. It was obviously hitting the top of the wheelwell. Needless to say, stiffer anti-roll bars were in order.
Toyota Racing Development offers an assortment of upgrades for the JZ80 Supra, including tubular anti-roll bars, which are designed to offer a flatter, more stable cornering stance. The bars are powder coated for corrosion resistance and work with stock or modified suspensions. The installation is very simple as long as you've got a jack, a couple of jack stands and a basic set of hand tools. Give yourself a couple of hours to do both front and rear.
Shortly after the installation I had the opportunity to test whether the tires would still be rubbing the wheelwells. With what we could do on the street, we couldn't get them to rub on the stiffest damper setting but on the softer settings it still would. At this point, we knew these sway bars helped immensely but the only way we could safely determine whether or not the Supra would need some modification to the fenders and/or wheelwells was on the track.
Speed Ventures is a driving school dedicated to teaching students the fundamentals of driving while allowing the lead-foot racers to bring out their heavy machinery. The prices and track time are some of the best we've seen. This particular time-trial event at California Speedway, configured for the full road course, which included a chicane-less front straight nearly a mile long, was only $280. Part of that was due to the event being on a weekday. By 2:30 p.m. it was an open track with two and half hours to go--by this time we had had enough ourselves.
Prior to the track day we fitted our Supra with a fresh set of Toyo RA1 R-compound tires sized 245/35-18 front and 275/30-18 rear, for extra grip. We tried fitting the rears with Toyo's next size up-305/35-18-with no luck clearing the fenders. The idea was to get the car cornering with maximum g-force to see if the body roll or nose diving under hard cornering, braking or trail-braking would be limited enough not to rub the tires on the inner fenders.
The track day gave us great impressions of the car's new setup. Unfortunately, even with the ride height adjusted to just one-half inch below stock, the car still slightly rubbed in the front fender wells under certain right and left turns on the track, even at full damper stiffness. After discussing this with TEIN, we may have the shocks re-valved and the springs changed for a little added stiffness.
On track, the EDFC is fantastic. Without wasting time coming into the pits one can fine tune the suspension for a little more understeer or oversteer on the fly. TEIN offers EDFC-compatible coil-over suspension kits for a variety of vehicle makes including Acura, BMW, Ford, Honda, Hyundai, Infiniti, Lexus, Mazda, Mitsubishi, Nissan, Subaru and Toyota.
We're pleased with the way our Project Supra is developing, but keep in mind we've barely scratched the surface. We've got most of the fundamentals in order with the suspension, brakes, wheels and tires but it's time to play with getting some more power.
Next month, with the addition of a front mount intercooler, we'll tap the stock, near-100k mile turbos for all they're worth. After that we'll really start pumping some air and fuel into the motor. Stay tuned.
Author's note: Special thanks to Doug at Big O Tires of San Bernardino, Calif., for mounting the Toyo tires on such short notice. Doug also gave the Supra a race alignment with about negative 2.5 degrees camber in front and about negative 2 degrees at the rear. The car turned out a little looser than expected so we'll try a little less negative camber in the rear and see if it improves overall rear grip. Although definitely not with an optimal setup for drag racing or brake tests, the car has seen 0 to 60 mph in 4.8 seconds and a quarter-mile time of 12.8 seconds at 114 mph on its first and only try with boost set at 17 psi (390 whp), and 60-0 mph in 107 feet in the brake test run. These uncorrected tests were done during the Hotchkis Media Challenge down the back straight at the Buttonwillow road course, using a Stalker radar gun.