The current generation Supra Twin Turbo has a well deserved reputation as killer hotrod material.  If we head-lined a 708-horse hotrod Turbo Suprawith 601 at the rear wheels you'd believe us, right? But actually, this story's not about a Turbo Supra. It's about Lufkin, Texas, tuner Powerhouse's hotrodding package for the naturally-aspirated Supra. They offer a kit which performs the neat trick of transforming the naturally aspirated-and much less-expensive-2JZ-GE-powered Supra from a mild-mannered 160 stock rear-wheel horsepower into a breathed-on super-freak with 600 horsepower at the rear wheels-which, for the mathematically challenged, computes out to 708 at the crankshaft.

Of course, turbocharging the naturally aspirated version of a car that is sold turbocharged straight from the factory begs a simple question: Why? The economics of the Powerhouse Supra turbo conversion is simple. The turbo version of the Supra costs up to ten grand more than a naturally aspirated (N.A.) car, depending on age and condition. And when you've paid more for the turbo car, you've got exactly 250 horses at the wheels. On the other hand, if you buy the naturally-aspirated Supra-saving yourself $4,000-10,000 and then spend $5,000-8,000 for the Powerhouse turbo conversion, you've now got as much as 600 horsepower at the wheels! Maximum boost varies from 8-12 psi in Powerhouse's Stage 1 kit on up to 20-psi in the Powerhouse Stage IV package. Obviously, a turbo conversion is not everyone's cup of tea, but if you've got a 2JZ-GE Supra you love, or you find a good deal on one, and you need more power, the Powerhouse solution makes excellent sense.

Interestingly, in some ways the naturally aspirated 2JZ-GE car is actually superior tuning material to the turbo 2JZ-GTE. The non-turbo has fewer computerized anti-hotrodding counter-measures to defeat in order to gin serious horsepower. Additionally, the Powerhouse conversion is available for the 1996 and 1997 Supras with Level II On-Board Diagnostics (OBD)-II). These OBD-II engines are the trickiest turbo conversions, and good hotrodding results (for off-road use only, of course) require that all O.E. sensors remain in place. They also require the least possible interference with the stock electronics. So auxiliary fuel computers are virtually mandatory, and other intercepting electronics may be required, with changes as simple as adding a resistor to the wiring harness, or as complicated as adding an intercepting digital computer.

In typical Toyota fashion, the Supra 3.0 liter in-line six is capable of withstanding large power increases without any aftermarket internal engine upgrades. One up-and-coming California tuner put it this way: "You open a Honda, you find a lightweight jewel of an engine where the components' strength is calculated to the last decimal place. The block's aluminum. Maybe you find an 11 mm stud some-where. You look in a Nissan, the corresponding stud's typically a little bigger-say 12 mm. But check out a Toyota: You'll probably find a 16. In a cast iron block, of course."

You'd think these guys at Toyota were building earth-moving equipment, when it comes to creating strong engines. Manual transmissions break before Toyota engines, even at extreme power levels. The 3S-GTF engine found in the turbo MR2 has been hotrodded to 980 horsepower for Pike's Peak racing-and this engine is not some breathed-on monster totally unrelated to the street MR2 engine, it's the same block and crank and head and most other parts. The 2JZ-GTE engine as found in the street Turbo Supra is essentially a 500 rear wheel horse engine de-tuned to half that for the street. Toyota not only builds exceptionally strong mechanical components, they build "fail-safe" computer software designed to protect the engine from abuse and extreme levels of power. On the 2JZ-GTE, we're talking multiple classes of air-fuel and timing tables, computer wastegate control with "low" and "high" boost modes, and sophisticated algorithms to retard spark and boost depending on air-temperature, coolant temp, knock sensor readout, and other engine status data. Tadashi Nagata, whose G-Force Engineering converts Toyota computers to full programmability with the Techtom ROMboard, is able to safely achieve substantial power increases with reprogramming alone for knowledgeable enthusiasts who will always run premium fuel and keep the engine in a high state of tune and maintenance.

The 2JZ-GE engine is similar in many respects to the factory turbo, even down to the vestigial engine block fittings for turbo oiling, oil return, and coolant plumbing. Both engines use p ressure-cast pistons, although the Turbo has more sophisticated piston-oil-cooling and wrist-pin lubrication.  Obviously the 2JZ-GE uses much higher compression pistons; Powerhouse reduces compression with a special thicker 3 mm steel head gasket. The very newest Turbo Supras have beefier rods than other 2JZ cars.

Bottom line, when Powerhouse looked beyond the Turbo Supra to pump up its less glamourous but also less-expensive naturally-aspirated sibling, you know they started with high-strength raw material.

The 2JZ-GE Supra turbo kit is itemized in the Powerhouse price list as a series of stages where increasing money buys increasing power. In reality, you talk to Powerhouse owner Jarrert Humphreys. And Jarrert consults with you to assemble the right package of custom parts from the Powerhouse bag of tricks to match your intended application and financial resources.

All stages require a custom cast-iron turbo exhaust manifold-a piece developed in cooperation with Toyomoto as a derivative of the Toyomoto Lexus 300-series turbo package. Depending on which turbo you choose, the turbo flange is machined differently. You'll pick one of several different turbo options, from a stock-type CT-26 to a Turbonetics T04. The first three stages include turbine-in and -out, and cornpressor plumbing to mate with stock components. Also included is a stock twin-turbo Supra intercooler (or a massive Spearco center-mount unit measuring 26" X 13" X 3.5"). You'll also get an anti-surge by-pass valve (two choices), high-flow air filter and air intake, and a 3mm Powerhouse steel head gasket used to lower compression from above 10:1 down to 8.48:1. Fuel system upgrades start with a Haltech additional injector controller managing two additional 440 cc/mm injectors, with higher levels of power utilizing larger primary injectors, bigger in-tank pumps, more and larger additional injectors, variable-rate-of-gain fuel pressure regulator; and so on.

The Stage IV kit featured in this story uses a massive Turbonetics T-72 turbo with a specially modified Powerhouse exhaust manifold. The Stage IV pack-age provides a custom Powerhouse aluminum intake manifold. It features a much larger 6 x 4-inch plenum, a 12-injector fuel system, with fuel management coordinated with an auxiliary HKS AIC-III additional injector controller to supplement the stock computer controls.

One of the problems with extremely high-output turbocharging is that you need very high flow compressor sections-which implies large, high inertia compressor wheels (and turbine wheels, in some cases), where you trade off low-speed boost for very efficient high-end boost and air flow. Twin turbos, ceramic turbos, variable area turbine nozzles, and twin sequential turbos are all effective in fighting lag. But in many ways, nitrous and turbos were made for each other. Nitrous produces a sudden rush of power and torque that is independent of engine speed, and it makes the most noticeable difference down low where the increase in torque is a huge percent-age in relation to pre-nitrous conditions. This is exactly where turbos (being exponentially-increasing air flow devices) are sometime unable to make much boost. Given the relatively low exhaust energy at low engine speed, there can he a latency period while the compressor wheel gets up to speed where it can make boost and feedback more exhaust for more power and so on.

A sudden jolt of nitrous produces quick heat and exhaust energy, producing instant power and also spooling up the turbine right now. Within limits, the more boost a turbo makes, the more boost it can make, so once you re in boost mode, it's typically possible to faze out nitrous in a way that is essentially not noticeable while boost skyrockets. The 60-horse nitrous shot used in the Powerhouse Stage IV kit kills any adverse low-end effects of switching to a very large, high-output turbocharger.

Powerhouse optionally installs on any stage turbo kit a special version of HKS's Vein Pressure Converter (VPC) to allow removal of the restrictive stock air flow meter. The VPC converts engine speed and manifold absolute pressure (MAP) sensor voltages into virtual (simulated) Mass Air Flow (MAF) data for the stock computer. The VPC also provides limited programmability of idle mixture, transitional enrichment, and across-the-board gain of plus or minus 12 percent via dials on the front panel. Powerhouse uses a special version of VPC internal code similar in structure to that of the previous-generation Supra VPC code, plus special active wiring with altered resistance that's needed to make the HKS unit work on the 2JZ-GE turbo conversion. Powerhouse vastly upgrades the Stage IV car's fuel supply system with #8 braided steel supply lines, and #6 return lines, plus a massive Paxton 1100-horse-capable fuel pump that probably has nearly enough raw power to function as a backup power source! The Stage IV pressure regulator is also a Paxton unit.

Drivetrain

Jarret describes the heavy-duty clutch upgrade on the Powerhouse turbo conversion as "optional." Clearly it's mandatory with the Stage IV car, which uses a Clutchmasters performance clutch with a three-blade segmented carbon single-disc with a sintered-bronze cast-iron pressure plate employing 4000 pounds of clamping force. "It's essentially an on-off switch," says Jarret-which is pretty much what you want on a car with serious drag-racing capabilities. The stock 5-speed transmission withstood 40,000 miles of Powerhouse torture at 600 horsepower before a series of launches with drag slicks finally forced rebuild time. With essentially no upgrade transmission parts available, the stock 5-speed was returned to blueprint condition. Jarret estimates it should be good for a minimum 40K miles. Powerhouse briefly considered upgrading to the Turbo Supra 6-speed tranny. "The Turbo Supra transmission looks tougher on paper" says Jarret, "but we've seen just as many failures with the six-speed." As far as the rest of the power train is concerned, the 2JZ-GE rear end is a heavy-duty unit, and the drive shaft stock.

Powerhouse currently runs stock wheels and tires on the Supra. "We had 18's on it for a while, but the car wears out tires so fast, we went back to stock for economic reasons." A bolt-in Auto Power roll cage provides race legality, as well as adding to the stiffness of the chassis.

Sources

Powerhouse

102 White House Dr.

Lufkln, TX 75901

(409) 637-6937

(409) 637-6938 fax

Clutchmasters

1330 OlasselI, Unit N

Orange, CA 92867

(714) 288-8811

(714) 288-9093 fax