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.
On the dyno, the AEM EMS and Speed Density intake combo took the car to a different level, even without adding a pound of boost. At 340 whp, the gains were realized throughout the entire rev band, with the greatest gains up top. The graph was substantially smoothed and the car was running better altogether, still on 91 pump. The air-fuel ratio reading from the UEGO was data-logged through the EMS software and gave a reading of about 12.5:1 in the upper rev range.
On the road, the car feels considerably faster than it was prior to the EMS, intake and cam gear conversion. Between 2200 to 3500 rpm, while still being pushed forward only by the first turbo, the Supra gained between 10 to 20 whp. At 2900 rpm, the 20 whp gain equates to no less than a 36 lb-ft gain in torque! Once the second turbo hits, it's a whole different ball game; the area under the curve tells the entire story. At about 5200 rpm, the second turbo's spool-up thrusts me into my seat harder than before, which explains why there's more than a 45 whp gain there (at that rpm it's also a 45 lb-ft of torque gain, before you ask).
Up top the gains were also magnificent. To compare, in Part 2 the Supra's final pull with an intake kit and full turbo-back exhaust ranged between 278 whp to 311 whp from 5500 to 7000 rpm. With the addition of the AEM components, the horsepower graph was remarkably increased as well as flattened, registering between 330 whp to 340 whp in the same rev range. It's these gains that tell a much bigger story than simply comparing peak horsepower values.
While a 12.5:1 air-fuel ratio doesn't alarm many tuners as being too lean for a street car, I still like to stay on the richer side of things. I had Siebels add a little more fuel in the upper rev range, bringing the ratio to 11.7:1. At this air-fuel ratio, the power came to 326 whp, but the shape of the power curve was still the same-flat up top. However, since this car will be street-driven primarily on pump gas for now, I felt this was a safer mixture to run.
Next time we'll make more power and accomplish it without changing boost pressure or the air-fuel ratio. Stay tuned.
On track-getting a feel for the carAs mentioned in the introduction, the goal of Project Supra isn't solely focused on power and drag racing. Toyota built a sports car with phenomenal handling and equally superior braking, two performance aspects that can only be fully experienced at the track.
Redline Track Events was started by fellow track junkies, Nikolas Malechikos and Chris Willard, with just a few things in mind: fun, safety and affordability. And although safety tops the organizers' priority list, make no mistake about it-Redline Track Events offers one of the best values around by keeping the entry list and price to a minimum and your track time to a maximum.
The particular track day we selected to test to participate in took place at the Streets of Willows, a track that offers a great balance between speed, safety and difficulty, which is important to consider when getting a feel for a particular car for the very first time. The Bridgestone S-03 tires and bone stock braking system weren't changed so as to keep a stock-like setup, save for 320 wheel ponies we had with the new AEM stuff.
Since the car is still using the factory intercooler and lap-after-lap driving would inevitably increase intake (and therefore combustion) temperatures, we selected to fill the car up with Sunoco's 112-octane race gas to avoid any unsparked detonation the otherwise 91 pump piss would be going through.
Like all other fuels, the 112 octane rating was achieved using the R+M/2 method. However, this fuel in particular has one of the higher Motor Octane ratings-the more important octane rating for wide-open-throttle performance-when compared to other race fuels at this octane level, with 110. Due to the elimination of the cats in the last installment, we were able to run leaded gas, which offers greater resistance against detonation. Unfortunately, leaded fuel also harms oxygen sensors over time, so be prepared for premature wear if you plan to run this stuff often.
If unleaded racing fuel is what you desire, Sunoco also carries 100- and 104-octane unleaded fuels, which don't affect oxygen sensor or catalytic converters. We purchased this fuel from Downs Commercial Fueling in Corona, Calif., but you can visit www.racegas.com for more Sunoco distributor info
On track, the Supra in its stock form is nothing short of magnificent. Although soft enough for the street, the stock suspension was a terrific match with the braking and engine power. Additionally, it seemed to work well and be extremely predictable in conjunction with the Bridgestone tires around the corners. Even with the stock-sized tires, the car seemed to grip comfortably enough at wide-open throttle from third gear on, allowing confident pressure to be applied to the throttle through each high-speed apex. In second gear, it was a different story; you don't want to be at wide-open throttle unless you're pointing straight.
The large factory brakes performed surprising well and didn't experience fade throughout the entire day, but the braking system wasn't really pushed to 100 percent, either. Thanks to the impressive tire grip, we didn't experience much ABS intervention, due in part by widening the front size to a 245/45-17 (from a stock 235/40-17). All in all, it was a fantastic and enjoyable day running with some of the other cars there, including Z06s, NSXs and WRXs. There was so much track time, we even called it a day a couple of hours early.
Although the relatively stock setup was impressive, we plan to return with more grip, handling and braking on track next time. Stay tuned.