1993-’98 Supra Twin Turbo Frequently Asked Questions
First off let me answer the 3 most common questions we get from people:
1. The Non-turbo to Turbo conversion question: I want a Twin Turbo Supra but can’t afford one. Can I just buy a Non-Turbo Supra and easily convert it to a Twin Turbo version?
Answer: No. There are MANY differences between the Non-turbo and Twin Turbo Supras, not just the fact that one has turbos. Other differences include pistons, the head casting itself, camshafts, ignition system, fuel system, transmission, rear-end, springs, shocks, brake rotors/pads/calipers, wheels/tires, ECU, wiring harness, and MUCH more. Simply slapping a turbo on a Non-turbo Supra without the proper ‘supporting modifications’ will quickly result in a blown motor considering the Non-turbo Supra has a much higher compression ratio than a Twin Turbo Supra, not to mention weaker fuel and ignition systems (among other things.) If you just want the look of a Supra, buy a Non-turbo. If you want to make 400+ rear wheel horsepower RELIABLY with very few modifications and have a true supercar in terms of handling and braking, save your money and buy the Twin Turbo version to start with. Also, doing a full driveline conversion by putting a Twin Turbo motor/transmission/rear end in a Non-Turbo Supra will result in probably spending way more money than it would cost to simply buy a Twin Turbo Supra. Also keep in mind the fact that when you go to sell the Non-turbo you won’t be able to sell for much more than a standard Non-turbo Supra because of the fact that banks loan MUCH less on non-turbo Supras than Twin Turbo Supras.
2. The Automatic to 6-speed conversion Question: Can I easily convert an Automatic Twin Turbo Supra to a 6-speed tranmission? How much will it cost? Are the other alternatives?
Answer: Yes you can convert it to a 6-speed, but considering the necessary parts (not including installation/labor) to do the swap will cost between $4000-$10,000 depending if you buy used or new parts, it is usually not worth it considering that we normally sell 6-speed Supras for only about $5000 more than a comparable Automatic. Parts need for the swap include the transmission, clutch, clutch fluid resovoir/lines/cylinders, clutch pedal, shifter, 6-speed console piece, 6-speed ECU, 6-speed wiring harness, a custom tranmission tunnel, and much more…
However, we offer a TH400 transmission swap with automatic OR manual valve body. With a manual valve body, you HAVE to shift gears up and down just like a normal manual transmission, but the great part about it is that there is no clutch pedal. This mean several important things: more aggressive and consistant launches from a stop, no missed shifts/gears, and best of all the car will hold boost between shifts instead of dropping/blowing-off the boost like normal 6-speed Supras do. The TH400 transmission we offer comes standard with a 1000 horsepower rating, SFI approved bellhousing scattershield blanket, B&M Quicksilver shifter, 6-speed console piece and leather shift boot, custom driveshaft/mount/adapter plate, B&M transmission cooler with fan, and much more! You can also add a trans-brake for even harder launches. Please drop us a line for more info on this wonderful swap!
3. What are the first few modifications that I should do to my Supra for more reliable horsepower?:
Supra Turbos respond very well to the following list of basic performance upgrades, otherwise known as ‘BPU’. These five upgrades are considered by most people to be the best ‘bang-for-the-buck’ upgrades you can do to your Supra:
- Cat-back exhaust system – this is all of the exhaust piping from the downpipe back, and includes the muffler and tip. Some brands have a ‘silencer’ (which is basically a 1-chamber muffler) sitting about half way back. Most of the major brand name exhausts are fine, and there are many styles and sounds out there. The bigger the piping diameter the better for peak power, less lag, better spool, etc.
- 3″ Downpipe – this pipe connects the turbo collector piping/EGCV pipe (which is a 2 into 1 pipe coming from the turbos’ turbine housings) to the cat-back exhaust system. It contains 2 catalytic convertors from the factory which are VERY restrictive. Downpipes are available with or without high-flow catalytic convertors. Running without the ‘cats’ will obviously give max HP and spool, but is not emissions legal.
- Boost controller – either a manual bleeder, ball-and-spring, or eletronic version will work. You do not want to use electronic boost controllers w/ fuzzy logic (e.g.. profec a and hks evc) with sequential turbos. Most people run either a GReddy PRofec B, HKS EVC, Apexi AVC-R, or one of the Blitz controllers.
- Fuel cut removal – GReddy BCC (boost or fuel cut contoller – same thing) tuned to 4.3V is the BEST mod to prevent fuel cut at 14.7psi of boost. HKS’s FCD skews the signal at all times, and the FFCD (free fuel cut defenser, which is simply capping off the hose coming from the turbo pressure sensor) is not recommeded because it TOTALLY blocks off the signal from the turbo pressure sensor which affects other engine functions as well.
- Air filter / intake pipe – preferrably an intake kit that isolates the air filter from the rest of the engine bay and high underhood temperatures, such as the MAXX-AIR box with K&N Extreme filter (best system, best heat isolation, best filtration, 2nd best flowing filter) or the Blitz Stainless Steel Mesh air intake with block-off plate (worst filtration, best flow, decent heat isolation.)
With these basic parts installed, your Supra should have around 360-415 rear wheel horsepower (rwhp) depending on transmission, ect. You will also want to install a boost gauge to see how much boost you are running. Obviously running more boost is going to decrease the life of your turbos more than low boost, so you will want to watch this. The #2 turbo quickly comes online from a slow spin to peak boost (starting around 3800rpm’s,) which can eventually lead to the shaft between the turbine and compressor wheel becoming warped which rubs the bearing causing failure. This causes the turbo not to boost or boost very erratically, make a howling sound (aka death whine), and spit out or burn oil. Most people think the best compromise for reliability and power is no more than 15-17 psi on a daily basis, although some have had success and longevity with higher boost. A conservative number would be to run 15 psi low boost with occasional runs to 17 psi if you get an EBV that is easily adjustable on the fly. I have heard of people hitting 29psi max boost on the stock twins with the hose from the turbo to the actuator pulled…I accidentally hit 28psi on a long straight away in my first 6-speed with a manual boost controller one night when I lived at sea level with air temps around 25 degrees; spinning through 3rd gear is pretty insane for stock turbos The heavily boosted #2 turbo died several days later!