1994 Toyota Supra Turbo - Powerhouse Supra

Pushing The Definition Of Street Performance

From the July, 2001 issue of Turbo & High-Tech Performance

By Evan Griffey

Photography by Henry Z. Dekuyper

The term street car can be defined in a myriad of ways. From modified cars that are truly daily transportation to hell-bent bruisers that can be driven on the street but, in actuality, see the road as often as Santa Claus comes to town. Where do you draw the line for a street car? What can you sacrifice and still have a streetable vehicle? What is streetable? There's plenty of gray area. While the definition of a street car is a personal observation, Powerhouse Racing's latest creation pushes the limits of how one defines a street car. The Supra on these pages is two-faced. While it's engineered to be converted from strip to street in short order, it's also on a mission to become the first 8-second street Supra.

Powerhouse Racing (PHR) opened its doors in 1996 as a tuner focusing exclusively on the Toyota Supra and, according to owner Jarrett Humphreys, that's the way it is today. The company has taken the "do one thing and do it well" axiom to the extreme by tweaking the potent Supra to the brink of possibilities with the laws of physics. The car on these pages was built in conjunction with MVP Motorsports of Bridgeport, Texas. MVP wanted to build a brutally fast race Supra that, above all, retained its street nature so it contacted PHR in June 2000. The plan was to construct this car to compete during the 2001 season, so PHR moved quickly to plan and execute the project from the ground up.

The project started with an almost bone-stock 1994 Toyota Supra supplied by Dusty Womack, owner of MVP Motorsports. The car was originally a targa roof-equipped Supra, and PHR knew that would not be practical in a street/race car. The targa roof could never be removed once the 12-point roll cage was installed, and it would only reduce chassis rigidity. Therefore, PHR cut the roof completely off the car and installed a non-targa roof from a wrecked Supra. After that, work began on the chassis to strengthen and lighten certain areas. The fenderwells were massaged to accommodate larger wheels and tires in the rear and a set of custom PHR adjustable rear control arms were installed. After this, PHR and Todd Bevis of Bevis Built Race Cars began work on the custom 12-point chrome-moly roll cage to make the car NHRA legal for the anticipated 9.99 and quicker timeslips.

All areas of the stock frame were tied together, and the rear of the car was braced for installation of a parachute. The rear sheetmetal in the trunk was removed to install dual 10-gallon fuel cells and Weldon fuel pumps, along with the necessary Optima batteries and electronics. Once installed, the fuel cells were enclosed in a custom tinwork enclosure, complete with Toyota emblem, to keep a neat appearance and increase safety. A sheetmetal firewall was constructed behind the factory rear seat to further enhance driver protection. The rear bumper incorporates a set of charging terminals to make charging the battery a simple affair. Also at the rear of the car is the battery master cut-off switch.

The interior of the Supra retains the factory headliner and interior leather panels, along with the factory dashboard. The power windows are still operational, along with anything required for street use. The air conditioning and heater were removed, since the car would never see a very hot or very cold day on the street, not to mention the 80-lb weight savings.

The factory stereo components were kept; however, the head unit was removed to add switches in its place while at the track. For street use, the head unit can be installed within five minutes for added driving pleasure, thanks to the removable switch panel. The roll cage was installed through the factory dashboard, with the required dash bar underneath. All points were tied to the structural frame and gussets were added underneath for added strength. The roll cage was outfitted with a Stroud window net; a Stroud parachute is on call at the rear. The parachute and window net are also removable for street use.

Under the hood, tinwork gives the Supra a custom look, not to mention it makes an excellent work surface for engine repair at the track. Removable panels in the tinwork allow access to the brakes, breather system, ignition system and wiring. An electronic panel was added to the roll cage above the driver seat to control basic functions such as electric fans, ignition system, water pump, MoTec engine management system and lights.

The factory front low beam headlights and rear taillights were maintained, along with turn signals for street use. PHR built custom aluminum seat mounts to secure Sparco EVO 2 seats and the required rear seat braces were added to the rear bar. The factory rear seat was kept in place for cosmetic purposes. The factory interior carpet was removed in favor of lightened black carpeting without noise-deadening material. A MoTec ADL digital dashboard is information central for the Toyota. The ADL dashboard is wired into the car in such a manner that the driver can activate the OEM cruise control switch to view different screens with different parameters. The factory steering column and steering wheel were left in place; however, PHR added a custom manual steering rack in order to remove the power steering unit for weight savings. Five-point safety harnesses were installed to keep the driver and passenger safely planted in the seat in the event of an accident. A Hurst shifter was installed on a removable plate for re-installation of the factory six-speed Getrag transmission for street use if manual gear selection is desired.

The transmission selection was a long decision process. In the end, a custom three-speed was constructed to harness the power. The transmission was enclosed in a titanium case (Ouch, that's gotta be big money!) with custom-designed gears. Everything was designed to propel the small-displacement 3.1-liter engine down the track in less than 9 seconds without the aid of nitrous, no easy task for a 3,200-lb car.

1994 Toyota Supra Turbo Three Speed Transmission

Power is output to a custom designed PHR 3.8-inch diameter carbon-fiber driveshaft fitted with Mark William's driveshaft ends. The factory Toyota rear end was kept, along with Toyota axles; changing the differential and axles would mean putting the car in the Outlaw Class, and swapping would affect street drivability. Therefore, PHR opted to stop the driveline modifications at the rear end, keeping the option open for the future. Shocks consist of Konis and Eibach coils and Ground Control coil-overs.

The Supra was equipped with Monocoque Racing wheels-15x10 rear and 15x3.5 front. Rubber consists of Mickey Thompson front tires and Goodyear 28x11.5 slicks, the largest size that fits under the Supra without removing all of the rear sheetmetal. For street use, the car runs 18-inch Racing Hart wheels. The brakes were changed to smaller and lighter non-turbo Supra brakes in the rear and highly modified versions in the front to accommodate the skinny 15x3.5 wheels. Stainless-steel brake lines were added to help maximize stopping power.

Under the hood, PHR's plan was to simply outdo themselves. Considering the company had constructed a 1,000-hp 1998 Supra two years ago, that was a tall order. The PHR crew built a race-spec engine using Carrillo rods, SPS Carr rod bolts and JE pistons. The crankshaft was modified by PHR to increase oiling at higher engine speeds and treated to a balance and hardening process.

The rods and main journals reside on custom bearings and ARP studs hold the assembly together. A custom-modified PHR oil pump was installed, along with a PHR-lightened water pump. The cylinder head was worked to Stage 3 specifications, using 2mm oversize pro alloy valves, dual valve springs and titanium retainers and buckets. Custom PHR camshafts were ground to generate efficient high-rpm operation at 40-plus psi.

Once the long block was complete, PHR then turned its focus to constructing a Stage 3 intake manifold. Using a factory Toyota lower intake flange and runners (enlarged and ported), the Stage 3 is the largest intake designed by PHR, with an internal diameter of 4-inches. The intake manifold is fed through a 75mm throttle body. On the exhaust side, PHR decided to utilize the largest single turbocharger available, the new Turbonetics Y2K (T100). In order to mount this turbocharger to such a small engine, a custom stainless-steel header was fabricated using 1-7/8-inch primary tubing to feed a single 3-inch turbo flange. PHR found it almost impossible to keep the large turbo under the hood line, so it was decided to construct an air inlet capable of feeding the giant hairdryer with a constant supply of cold air. A hole was cut into the new TRD hood and a custom aluminum air inlet was grafted in place. This set-up is reminiscent of Kenny Duttweiler's red Buick. An HKS GT series wastegate was called upon to maintain boost pressure. Once finished, the entire exhaust side of the turbo system was treated to an HPC extreme coating to reduce heat transfer. PHR then constructed 3-inch mandrel-bent intercooler plumbing to complete the system. The intercooler piping was completely chrome plated, courtesy of Tex Plating.

When the project began, a Spearco liquid-to-air intercooler was installed since the engine ran on gasoline. However, as time progressed, it was decided to utilize a gasoline/alcohol mixture that had been prototyped on the PHR race Supra. Therefore, the intercooler was removed and new plumbing was installed that fed the charge air directly to the throttle body. The engine was dropped into the car using PHR solid engine mounts.

Once in the car, a custom 3.5-inch exhaust system was constructed to route the exhaust to the side of the car. An HKS race exhaust can be bolted on when needed for street use. The wastegate gases were routed to exit underneath the car so that the exhaust system can be fitted without removing the wastegate system. A Fluidyne radiator and a Flex-A-Lite electric fan handle cooling chores. To provide enough power to light off the air/fuel mixture at 40 psi on alcohol, a new MoTec CDI ignition was installed along with new factory coil packs.

With the car mechanically in order, body modifications were fitted. The Supra's body sculpting therapy consisted of Stillen side skirts, a Stillen front airdam, TRD modified hood and factory rear wing spoiler. The car was stripped and six coats of PPG Lexus electric metallic blue were sprayed on the Supra's sleek silhouette. All Star Paint and Body in Jacksonville, Texas performed the paint and body work. All vinyl graphics were professionally installed, courtesy of Synthetic Designs of Arlington, Texas. Dyno figures through the automatic transmission are at 18 psi. When the boost is cranked to the anticipated 40-plus psi, Powerhouse estimates output to be around 1,200 hp.

We caught up with the car as Powerhouse was entering the high-boost tuning portion of the project and we will run a performance update when we get additional dyno and/or track numbers. Currently the Supra is slated to debut at the World Import Challenge in Houston, Texas June 8-10.

Where would you classify this Supra? Is it a street car? The car's interchangeable parachute, interchangeable stereo system, retention of power windows and integrated roll cage are nice touches-not to mention a full interior. The muscular Toyota is street registered. But how practical are its gasoline/alcohol fuel strategy and external battery charging terminals, as well as 40 psi of boost? We love that last characteristic; in fact, we'd like to drive the car for a week to help with our own internal dictionary's definition of a street car. Please, guys?