The Toyota Supra Twin Turbo was a fantastic car out of the box. The handling, power delivery, braking and overall balance were bettered only by vehicles with price tags that can even break matrimonies of the affluent. It's still a very popular car today-not one day goes by in this car where I don't get either the obvious stares, "nice car" comments, or even the classic "let's see what you've got" glare at the stoplight from a soon-to-be-embarrassed motorist.
These cars are also popular for the seemingly endless performance upgrades that can be performed. But before we explore the land of stupid power, we'll remain focused on extracting more reliable performance from the stock twin turbochargers using California's horsepower-killing 91 octane.
To bring you up to speed, last time we saw more than 311 whp from a simple intake and turbo-back exhaust upgrade. For a retail price tag of about $1,200 and change, that near 50-whp gain was excellent bang-for-the-buck. The main reason for the gains is the small stock wastegates have little control over boost once the exhaust is freed, hence the car saw boost levels ranging from about 14 psi to a 17 psi spike. Without increasing boost whatsoever, we wanted to see how much better the car would do with the addition of a couple of components and some custom tuning.
Advance Engine Management's (AEM) adjustable cam gears were next. CNC-machined from 6061-T6 billet aluminum, these gears were reportedly the first adjustable cam gears to hit the sport compact car market. The gears allow the vehicle's cam profile to be tweaked in one-degree increments measured by their laser-etched markings. According to AEM, each precision-cut tooth, as well as AEM's hard anodization process, ensures no premature wearing on the belt surface.
AEM's Jason Siebels was our installer once again. "The main thing to note when installing the cam gears is to line up the zero marks on the gears with the raised marks on the rear of the cam backing plate, while the crank is lined up on the TDC (Top Dead Center) mark," says Siebels.
Since he's spent hundreds of hours tuning Supras, we went with his suggestion of retarding the exhaust cam three degrees and advancing the intake cam two degrees. Picking up where we left off in Part 2 (just one day prior to this test day) peak horsepower and torque didn't go up much with these cam gears but if you know how to read a dyno graph correctly, you'll notice a greater area under the curve. Noticeable gains of 5 to nearly 20 lb-ft of torque were realized from 2000 to 3700 rpm. Up top, the power curve was flattened out nicely with 8 to 10 more horsepower from 6400 to redline.
The stock Supra's air mass sensor is a known restriction in the 2JZ-GTE's intake tract. AEM has developed a Speed Density Coversion kit for the MKIV Supra that eliminates the air mass sensor all together, but is intended only for vehicles using AEM's EMS (engine management system). The speed density kit for the Supra is guaranteed by AEM to be a proper fit and it features zirconia-based powdercoating for reduced heat soak. The kit also comes with a lifetime warranty and C.A.R.B. exemption-important for Calif. residents.
The AEM EMS features full custom tuning via its user-friendly software that uses three-dimensional graphing and tables. Compared to many other other stand-alone engine management systems, the AEM EMS is in a class of its own.
For the Supra, this unit is a direct replacement, which means no wiring or hardware necessary, just plug-and-play. The system runs on Windows-based software so it can be tuned from the driver's seat. Onboard datalogging, sequential fuel injection, nitrous, boost and knock control and forced induction compatibility are just some more of its features. Unlike some of the other EMS systems that can take hours and endless dyno runs to fine tune fuel maps, this unit features automatic fuel mapping, cutting your wide-open throttle and part-throttle tuning by several hours. Virtually any fine-tuning you'd like to have done to your Supra can be accomplished with the AEM.
Want traction control? Specific boost levels for a given gear so you don't roast the tires at low speeds? How about having this system control your launches, or wheel slip around a full-throttle turn? The AEM EMS system can do it. If you want, the stock twin turbos can be run in a parallel, "true twin" setup as opposed to sequential. AEM says Calif. residents should know that the AEM EMS system is legal in California for off-road use only and should never be used on a public highway.
The EMS system reads off the factory sensors but we went ahead and included AEM's UEGO (universal exhaust gas and oxygen) wideband sensor for optimal air-fuel control with the EMS. Siebels welded a bung to the previously featured Stillen downpipe and screwed in the sensor so that it would be reading right after the turbo.