Project MR2 Spyder - Part 4

The unconventional rear mount intercooler uses a bottom scoop to direct cool air up through the cooler and into the engine. Production models will have a stainless or fiberglass air scoop.

The unconventional rear mount intercooler uses a bottom scoop to direct cool air up throug

The XS MR2 kit is almost entirely a bolt-on affair, except for some welding required for the drainback bung on the oil pan. Fortunately, this is a fairly simple bit of welding that nearly anyone can get done locally.

Engine management
With fragile high compression pistons in the 1ZZ, careful attention must be paid to engine management. Although the fuel system (fuel pump and injectors) are an optional part of the turbo kit that jacks up the price, we highly recommend going with the XS fuel package to ensure trouble-free operation. The stock injectors are replaced with 525cc/min units to insure adequate headspace for turbocharged operation. Likewise, the fuel pump is ditched for a high-capacity Walbro 255lph unit. If more boost is desired later, as in the case of an owner installing forged lower compression pistons, this fuel system can support upwards of 400 wheel-hp.

ACT's heavy duty pressure plate and performance street disc were put into Project MRS, since the stock clutch would only last two launches with the new-found torque.

ACT's heavy duty pressure plate and performance street disc were put into Project MRS, sin

The stock ECU is replaced with an A'PEXi Power FC standalone engine management system. Although A'PEXi's Power FC for the MR2 was meant only for the Japanese-market Spyder, the harness and algorithms are identical and will plug in directly - even though it comes with a base map only suitable for JDM cars. This base map won't matter, since the ECU must be retuned for the turbo and larger injectors anyway. The Power FC for the MR2 is one of A'PEXi's most developed applications - it can mimic factory ECU functions even down to automatically switching ignition maps based on knock sensor activity, saving the engine from low octane detonation. Using the Power FC also saves us the headache of modifying the fuel system with return lines.

It's no secret that Eric Hsu is one of the best tuners in the country. He's spent a lot of dyno, track and keyboard time to assure the tuning of the XS turbo kit is optimal from both a performance and reliability standpoint. In normal street driving, the MR2 exhibits exceptional lag-free driveability, which is helped somewhat by the lack of blowoff valve. The engine feel is everything a good turbo system should be, with linear boost response and the sensation of a larger displacement, exactly what we had targeted. XS hit the nail on the head by creating something that feels like what Toyota should have created in the first place.

TRD's lightweight chromoly flywheel was put in to help with engine response and more precise clutch and throttle control.

TRD's lightweight chromoly flywheel was put in to help with engine response and more preci

Back on the dyno, the 1ZZ delivered 216 wheel-hp and 198lb-ft of torque, an amazing increase of 100 more hp, especially considering the low 7.5psi boost pressure. To get that much more power out of the 1ZZ in naturally-aspirated form would mean a seriously expensive engine build and a very definite lack of driveability in street operation.

Anticipating the huge jump in torque our boosted motor will make, we replaced the stock clutch with an ACT heavy duty pressure plate and performance street disc combination. This street performance clutch only mildly increases pedal pressure while offering a 30 per cent gain in clamping force, which adds up to about 230lb-ft of torque. Engagement is smooth and predictable since the disc retains a sprung hub and a marcel spring. It also uses a semi-metallic friction material that will take loads of abuse and still operate at the high temperatures created when slipping the clutch on acceleration runs.

A'PEXi's JDM Power FC software is among the most advanced offered by A'PEXi and allowed XS to tune the MR2 to run as sweetly as a standard model.

A'PEXi's JDM Power FC software is among the most advanced offered by A'PEXi and allowed XS

While we were in there, we replaced our stock heavy iron flywheel with a lightweight TRD version made of higher strength chromoly steel. The stronger alloy allows TRD to take several pounds of material while maintaining the same strength and reducing inertia for better throttle and boost response.

Our infusion of power has transformed Project MR2 in other ways as well. Every five minutes, someone on staff now comes by to try and steal the keys. With our power to weight ratio now sitting at a bit under 10.5:1, we're in serious world class performance car territory. And the car can give thoroughbreds like the Lotus Elise a run for their money with no sacrifice in civility or tractability. Our XS-tuned system has proven reliable in withstanding our track torture as well. But best of all, since we talked XS into doing it, you can simply step up and buy a better, more finished kit than we have. Next time, we'll throw on some sticky rubber, trackable pads and pray for victory. Stay tuned.

By Mike Kojima

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