Many have wondered what the limits of the MKIII supra are. After years of playing with it and tearing a few down and doing research I decided to write a summary of things I encountered. What you read is my thoughts and in no way written in stone. The 7mgte engine is a tough motor that can deliver if prepared for duty. What I will discuss is the path I took to making a reliable high horsepower MKIII.
CRITICAL ELEMENTS
Always use a reputable shop.
This is often misunderstood. My suggestion is to use a shop that specializes in the motor you have. In this case the 7mgte engine. American shops often don’t realize the tight tolerances that the Japanese engines have. So they slack on the little but big details. Look around the shop build a friend ship with the guys there and you might find yourself getting little things done for free. Trust me you’ll need little favors.
THE BUILDUP
The 400rwhp motor
The stock motor can take 400rwhp pretty easy but the age of the motor might be the problem. Don’t try to run 400rwhp on a stock motor with 200,000 miles on it. You’re just asking for trouble. However with the right mods and a fresh build up you can run the power all day long. That’s assuming you tune it to that and don’t try that seat of the pants stuff.
The 500rwhp motor
When you approach the 500rwhp mark you must and I repeat must go inside the engine. Pistons (.40) and rings are the tools to make 500rwhp reliable on this power level. Have the shop use a torque plate and get those cylinders perfectly straight while boring it. The head needs no modifications and of course the turbo will need to be upgraded. A nice balance job will be in order also if you want to feel great about it.
The 600rwhp motor
Things break here if you don’t be careful. I suggest getting forged rods and pistons. The valves and springs would also benefit from a Ferrea valve train enhancement. That means 1mm oversize valves, dual springs, titanium retainer clips and locks. At this point you need to balance it without a doubt. 2mm head gasket is a good idea also as it will lower your compression a bit. Also bearings don’t like this level. Get the Clevite 77 and do yourself a favor. Like all the rest you will need a supporting cast of parts more on that later.
The 700rwhp motor
With this step everything you have on the following stages plus the right turbo. Here is what I suggest at this level. Beef up the transmission or at least freshen it up. Go with a RPS stage 3 or any carbon carbon clutch. At this level you will need a lot of supporting power makers. Also note there is no mention of cams. Stock is fine! I searched all over and the stockers did the job. Spend your money elsewhere
SUPPORTING CAST
The lightweights
There are a few things that don’t make power but they definitely help when you intend to run serious numbers. Lightweight pulleys except crank pulley, electric fans, lightweight drive shaft, and lightweight flywheel. By doing these little things you free up a lot of power that is loss. The port and polish job.
The fuel system
My rule of thumb is always have more fuel then you need. This always good except when you are breaking the newly built motor up. A great fuel system will always have a adjustable fuel pressure regulator and strong pumps. My favorites like most are the walbros. Two if you decide to make 550rwhp plus. I have always used the 255lph pumps. They flow for days and are proven. With the lines you have a choice of 6an dual feeds or a single 8an feed line. Either will work fine. Don’t skip on this mod you’ll pay if you do. As for fuel injectors 550 are good to 500rwhp or so. After that shoot for the 720cc style injectors or larger.
The Electronics
You can go two routes here. The Lexus afm route or the VPC route. I choose the Vpc route because I like a crispy idle and the vpc frees up the intake with a adjustment spots.
The Lexus afm route can make power but prepared you learn how to tune. Eric Varah actually made 622rwhp all through a Lexus Afm and tuning. So power can be made this way but you will need to tune a little more with the Safc and fuel cut issues. On the other hand the vpc doesn’t have the fuel cut issue. For adjustments I chose the Safc for that, as the HKS GCC doesn’t have the tune ability that the Safc does.
The Intercooler
All I can say is get a Greddy three row for a MKIV or get a custom one made from spearco. At the 500rwhp mark I think the cooling effect of the Spearco kit for our cars is reaching it limits. Better to efficient then not efficient enough.
Turbo kits
My favorite part is the kit. I own the SP kit and the HKS cast kit. They both flow great but the SP kits blow everyone else away. Looks good flows good delivers. Little expensive if you’re not up to it but well worth the cash if you get it. Don’t skip on this mod. Depending on the power you want the MKIII responds great to smaller turbo’s but it really wakes up when you reach for the t61. Not the 60-1 but the T-61. People for some reason confuse the two. This turbo will flow 550 plus rwhp in a MKIII all day long.
Now for the guy really wanting to reach out and deliver a blow the t-66, sp67, bl67 and larger will work fine. Only thing is you start losing the great spool for the street and become a lag monster. I personally would not go past a t-72 for the street and that’s to big. For the Dyno queen the sky is the limits so go for the sp74 and all those track turbo’s. Avoid the t70 series and t64 series turbo’s they have surge problems. Although I hear now they have been cured with anti surge housing. Bottom line my feeling are that the t61 and t66, sp67, bl67 etc are the best bang for the street. They deliver 600rwhp and are again proven.
The Bottom Line
SPEED cost money! How fast do you want to go? Leaving things out almost always results in failure. Trust me I’ve seen it millions of time. Guys uses an old oil pump then develops rod knock. Guy runs 20 psi on a motor with 200,000 miles then ask what happened. Common sense plays a lot. This is one expensive game and there WILL be failures. Ask any big name out there things break. How you handle it is up to you but don’t expect the car to deliver if you don’t use good judgment. With that said build the car up the right way the first time if you don’t have the cash just save. Hard to do but worth it in the end.
