Mechtech Twin-Turbo Sc400

As seen in Turbo Magazine
Text & Photos By Lawson Mollica

Back in 1993, a leading consumer magazine rated the Lexus SC400 one of the best cars ever-at any price. The only reported drawbacks were its lack of overall power and its somewhat sparse rear-seating capacity. For Bill Craig, owner of this sleeper '94 Lexus SC400, these drawbacks really didn't matter. "I didn't care about rear seat room," says Bill, "and it has been my goal since purchasing the vehicle to turbo or supercharge it to get the performance." When the time came, Bill contacted TRD USA and the local Lexus dealership and both suggested that he look into quenching his thirst for power with a twin-turbo set-up that was being developed by MechTech in Escondido, California. Having received such high recommendations, Bill made a call to MechTech owner Jim McFarland and the rest, as they say, is history.

SC Roots

The Lexus SC400 is the brainchild of Calty Design and was born in the heart of Southern California's cutting-edge car culture of Newport Beach in 1991. Even in stock trim the SC400 is in the upper echelon of luxo-cruisers-packing a healthy helping of horses to back up its suave, sophisticated side. In 1994, the SC400s fourcam, 32-valve V8 pumped out a respectable 255 flywheel horsepower ('99 models with VVT-i now boast 290 ponies at the flywheel). The suspension set-up is a four-wheel independent wishbone configuration that employs coils and shocks for dampening that has been fine-tuned throughout the SC400's existence. Sixteen-inch five spoke aluminum alloy wheels are standard also, as are the V-rated performance tires that wrap them.

Heart Transplant

Before the Lexus was taken to MechTech, Bill had already begun to open up the SC400s breathing capacity. The Lexus was taken to Explorasport in Corona, California where an RS Akimoto intake was installed in place of the factory airbox and the throttle body was ported and polished to increase flow capacity. The intake manifold was also removed to receive the port and polish procedure and the factory exhaust was replaced with a high-efficiency set-up.

Bill knew that the "cruise-ready" 3.92 factory rearend gear ratio would not suffice at stoplight confrontations, so to add some spunk off the line he had Explorasport owner Glenn Maurer upgrade the gearing ratio to 4.27. After making its way down the coastline from Washington state, the Lexus arrived at MechTech for its transplant and twin model 110 Aerodyne VATN variable-vane turbos were squeezed underneath the block. The hot sides mate to a MechTech exhaust designed specifically for this application and the cool sides feed air into one huge front-mount air-to-air intercooler. The appeal of the Aerodyne turbos in this type of vehicle is that they do not eliminate the stock driving characteristics of a vehicle if pedal pressure is kept light. However, if you stomp on it they spool quickly to deliver a knockout punch. Boost is controlled by an electronic quick-change boost control unit with high- and low-boost settings. Low boost is kept at four psi and high boost tops out at 6.5 psi. Additional fuel is delivered via two pumps that flow at a rate of 220 lph. The auxiliary fuel pump is activated by a boost-indexed fuel pressure regulator and engages once the regulator reads one psi of boost.

The guys at MechTech mounted fuel and boost pressure gauges inside the glove box to monitor engine vitals and a lighted toggle switch was integrated into the pod to adjust between high- and low-boost settings. Aside from the pre-turbo mods and the turbo system, everything else was kept stock to retain a completely stealth look. If it wasn't for the huge front-mount intercooler, there would be no signs of forced induction when looking in the engine bay.

The Results

When MechTech owner Jim McFarland first told us that the Lexus recorded a baseline run of 179.8 horsepower to the wheels we were surprised to say the least. Jim has dyno'd three different SC400 coupes; two stockers and Bill's mildly-modified (at the time) sleeper, and has netted similar results with each one. In fact, the other two cars recorded around 155- to 160wheel horsepower. We called Lexus and were essentially told that it is difficult to get full power readings for an SC400 on a dyno because of the vehicle's sensors. They told us that, among other things, high-heat conditions and the traction control sensors will dialback engine performance by adjusting ignition and fuel timing.

Although Jim agrees that these influences may affect readings to a degree, he believes that the power loss ultimately can be traced to the design of the transmission. If you have ever driven an SC400 one of the things you will notice is that it is hard to determine when the vehicle shifts. Due to the transmission gear design there is no vibration, which in turn fosters silkysmooth acceleration. While this is a nice touch for a luxury cruiser, it makes extracting power a little tricky.

Regardless of the cause of the baseline dyno readings, the one indisputable fact is that MechTech's twinturbo set-up netted very impressive gains when compared to the vehicle's baseline runs on the same dynamometer. Peak horsepower now checks in at 276.6 with torque figures pegging -319.0 at the wheels. Those are peak gains of 96.8 horsepower and a whopping 126.1 lbs-ft of torque-and possibly more on the street where the car's brain seems to be happiest. Additionally, one look at the power curve reveals a much more aggressive shape when compared to the linear power curve of the stock engine.

Speaking of on the road, we had a chance to drive the SC400 and can say first hand that when you step on the go-pedal, this baby is ready to move. The turbos spool quickly and full boost is realized when the revs hit about 3500. At the high-boost setting with the throttle buried, it feels like you got kicked in the tailpipes by Paul Bunyon.

Ego Boost

"I initially told Jim I wished to create a 'sleeper,' not intending to race it (but instead) just support my ego around town," says Bill. Since the weather can get nasty in the Pacific Northwest region, the car remains parked and only sees the road on sunny days. At press time, the Lexus was getting ready to be shipped back to Washington, so Bill had yet to sample the results of his SC400's heart transplant. When we first spoke with Bill, he told us that he would wait to see what the increased power will do to the car before upgrading the brakes, suspension, wheels and tires. Whether or not he continues to modify his vehicle or keep the current underhood surprises totally stealth, one thing is for sure-the next stoplight contender this SC400 encounters is in for a surprise.

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