A GT4094R is not that great of a match for a Supra.

What's the rest of your engine build/configuration look like? What fuel will you be running?

 

I'm stock JDM GTE at the moment but noticed a good deal on these parts new so just beginning to research and collect parts.

 

What's the rest of your engine build/configuration look like? What fuel will you be running?[/QUOTE]

I'm stock JDM GTE at the moment but noticed a good deal on these parts new so just beginning to research and collect parts.[/QUOTE]

On race gas a GTX 35R should be sufficient with plenty of midrange response. Or the Precision 6266 Gen 2. Both .82 A/R

Also upgrading from the stock JDM cams will help reach your goals too

 

I would be using 94 Octane pump gas

 

Hey man.

I'm in Ontario too using a gt4088R
on 94 octane i put down 605 HP/520 TQ @ 23psi.

This was done with an inadequate Intercooler(since then it has been replaced by a better one, sure i gained some ponies) and a restrictive 3" exhaust setup - will be going to 4" next season

Im confident with those two right there i will be around 650 range, so i think with yours you should be close what you're looking for depending on the mods you have of course(fuel cams, etc).


"A GT4094R is not that great of a match for a Supra. "

Really? its not that much larger than my gt4088r and its a blast to drive(street wise)?

 

What cams? What exhaust manifold?

 

GT4094 is old tech, GTX3582R gen 2 will flow exactly the same and spool better, 3584RS if you want more power with almost the same response. Plenty of precision turbos that fit this bill as well.

 

650whp on 94 octane pump premium will take a hogged out head, big cams, and a big ass turbo that will not likely be as responsive as you'd prefer. 71mm+ typically. GT4094R's are a bit too small on the hotside to run happily at high RPM on a Supra. The GTX4088R does way better with less lag as does the GTX4294R if you need more HP. The GT4094R would likely do great and be reliable on a tubular manifold and E85 but it'll be lazy for the HP produced vs other turbo options, but it'll choke at high HP/boost/revs vs a GT4294R and the 4294 likely wouldn't have that much more lag at all. A 4094R is a better match for a 2.2-2.4L 4 cyl looking for 94R levels of HP.

For road racing you really need to consider the limitations of your tire & suspension configuration because 650whp is a shitload for a track oriented RWD car.
$ to $, if you don't have a badass cooling, suspension, brake, and tire package I'd spend the money there first before HP. A properly prepared BPU car with lots of grip and lots of brake will smoke most other Supras on a road course.

Assuming you've got full custom Penske's and a quality BBK on all four corners and you've stuffed as much of the stickiest tires possible fat ass tires under the car (315's or 335's out back and 285+ up front) and you're planning on an engine management system with a *good* traction control system that can run off the ABS sensors, then we're maybe ready for 650whp on a track.

For the manifold I'd skip the tubular options for hard track use and instead go for a SPA turbo cast manifold, set up for a V-band wastegate.
Joutterbridge nailed it on turbo selection - I'd go for a 6266 Gen 2 or GTX3582R Gen 2. You'll get a lot more out of responsive HP under the curve on most road courses vs peak power above 4500rpm.
I'd go to a VVTi head, GSC S1 cams, 4in DP/MP, and a top shelf ECU that has good traction control features and top shelf injectors to match. You will make mid-500's on pump gas easily with the possibility of more HP depending on how the Gen II options do and the turbine housing size you choose. 700+ would be available on E85 or race gas with outstanding response to match.

To that end, I'd strongly recommend against going above 500whp if you don't have all of the footwork/brakes/tires etc sorted out to the max. If you're tired of the stock twins and need some more HP, that is easily done with the SPA manifold and either of the turbos mentioned without sacrificing response. On a road course, that kind of configuration properly tuned at ~500whp will annihilate a 650-750whp combo with more lag and no traction control on virtually every track in North America.

 

Wreckless, why VVTI head?

 

"What cams? What exhaust manifold?"

I have a SP(original) divided manifold, 46 mm precision WG, with TOMEI Poncaf cams, built motor 9:1 compression. Id like to think with 4" intercooler and 4 inch exhaust 630+/- ISh on 94 octane. I also am using the smallest Exhuast housing too. HP starts to fall off around 7250 RPM.

Sorry i overlooked the track purpose you're intending it for . Wreckless is probably right with that.

 

Too lazy..

 

If my understanding is correct, more usable low-end torque to get you out of corners faster and faster turbo spool on a VVTi head.

 

Interesting, I wonder why though?