With some help from HKS, Scott Dahlquist does the Stage 6 Shuffle in Toyota's returning Supra. Photos by the Author
I was calmly motoring through weekend traffic when my attention was suddenly arrested by a flash of silver closing in fast from the on-ramp. It was a Supra, its inline-6 megaphoned through a huge chrome sewer pipe and its fat tires wrapped around trick racing wheels. What really caught my eye, though, was the manufacturer's license plate on the back-the factory still owned this car, which meant it might be a clandestine Toyota R+D test mule. Then it hit me: The Supra disappeared from our shores for a while-was its resurrected body being primed for a serious performance upgrade?
Apparently not. A few quick phone calls produced some real answers on the silver bullet's identity, specifically one to aftermarket specialist HKS. They acknowledged that the silver Supra I saw mauling traffic on Highway 101 was in fact a Toyota R+D project; some of the factory's more enlightened tinkerers had asked HKS to modify the car as a study, but there was nothing more to report on it. Doubtful I'd get my hands on that one. Then my contact went on to mention that HKS had just built a similar Supra Turbo mule for themselves-a project that took all the goodies of the R+D example and went one more step beyond it. Would I maybe like to drive that car? I was out the door for HKS's headquarters in Torrance before the phone hit the cradle.
The Big Dipper HKS's Supra seems externally similar to the R+D car, but the feathered Pirelli P-Zeroes and scattered rock chips below the beltline give this Darth Vader Black example a distinctly utilitarian look. Under the hood, everything appears normal: HKS has kept the stock block and head, but nearly doubled the engine's horsepower by going from 8.5 to 17.5 pounds of boost. A new EVC (electronic valve-body controller) and VPC (variable-pressure computer) monitor and balance manifold pressure, engine speed, wastegate position, and other factors to keep the airflow moving at optimum velocity under all conditions. The HKS treatment also includes a less-restrictive intake-metering system, a new airbox, and significantly larger intercooler piping.
So far this is all neat stuff, but nothing particularly revolutionary: HKS lists everything above as part of its Stage 5 mail-order kit, which conspires to raise the stock Supra Turbo's horsepower from 320 to 415. Toyota R+D's car uses just such a setup.
But while that was deemed enough for Toyota's purposes, HKS wanted their own prototype to go further. Noticing a slight flutter in the sequential actuation of the stock car's twin turbos, the aftermarketer decided to seek out 70 more horses-and a purely linear boost curve-by moving on to Stage 6: Replacement of the small twin turbos with a single huge Garret T0S4. Tweaked for 18.5 pounds of boost, the new turbo mandates higher-flow fuel injectors and a mandrill-bent exhaust manifold to tie everything up to the Stage 5 system's existing 4-inch exhaust. The stock intercooler also gets sent to the trash and is replaced with a new one four times its size.
Hands and Feet in the Car
What can I say? The ol' on-ramp test proves very exciting indeed with the Stage 6 engine! The single Garrett takes a bit longer to spool up than the stock car's smaller sequential turbos, but when it does reach full boost, hold on! With 469 bhp to play with, this car simply explodes onto straightaways. Even with a rolling start the tires are easy to smoke in first and second gear, and at anything over 2500 revs there's enough power on tap to outgun any volume-built car on the road.
Even more intriguing, the effects of all this newfound grunt aren't readily apparent in everyday use. The engine ticks over calmly at idle and our test car handles everyday traffic jams like any other Toyota. In fact, you really don't notice any change at all until the light flashes green and you dump the easily modulated clutch-then the HKS gets off the line faster, harder, and stronger than any stock ride in town. As soon as the boost turns positive, the g-force slams you back in the Recaros so hard that it's a fight against physics just to upshift again before redline.
When the asphalt tightens up, you also come to realize that the awesome cornering power of the stock Supra is more than up to the increased output of HKS's engine. Squeezing on the throttle in mid-corner produces a blast of smooth, predictable thrust that can be used to hold lovely, power-induced slides with ease. If the car gets a little too far out of shape, just ease back on the gas and the tail steps right into place. This was no doubt one of the questions that Toyota R+D wanted to answer with their own mule-whether the stock Supra chassis could handle another 100 horses. It obviously can, as HKS's 160-horse boost has proven. Adding this kind of power to an existing machine usually just magnifies its quirks, but unlike most cars, the Supra seems to get better and better.
Scott Must be This Tall... On smaller roads, the exhaust note of the Stage 6 car is even sharper and more racer-like than that of its Stage 5 sibling. Find a deep, winding canyon and the tailpipe reverb will send thunderstruck critters scurrying to their hideouts. This is about as close as a boy-racer can get to The Real Thing: a loud exhaust and power to burn at the merest touch of the toe. The only thing missing is a full-face helmet, a set of HKS's awesome Brembos, and an entry form for your local SCCA World Challenge race.
Actually, these guys think they can find another 120 horses for the pure-race Stage 7 engine. Wherever your interests lie, this car is one serious thrill ride.
Hands and Feet in the Car 