The Basic of the 7M

Disclaimer

Please remember: I am not responsible for the results (good or bad) of any actions you take, even if I suggest them on this page (or other pages). The result of any modification will depend on many factors including the unique condition of your car. Also, everything you do has some inherent risk. Please see the "Oops!" section.

What to do first?

I get a lot of email asking what mods people should add to their MKIII Supras and I've written many similar responses. So, you've just bought a (nearly) stock 3rd generation Supra turbo and you want to know what you can do to it!

Well, for starters, make sure all the regular maintenance is in order. The Supra is a Toyota, and as such it will run forever if you take care of it... Fix anything that is wrong mechanically first. If the car has an oil leak, fix it. If the car needs a set of valve seals, replace them. Anything that could cause problems should be dealt with before you begin modifying your car.

Second?

Well, my advise is to do some more research (you found this, so you've at least started). If you are new to turbocharged cars, or to working on cars in general, get the basics. You need to know how a piston engine works, and how a turbocharger works.

You will also need tools. Invest in good tools. It is tempting to buy inexpensive Chinese made tools at stores like Harbor Freight, but you will find that they are not much cheaper than brands like Craftsman. The Craftsman tools are made much better, with tighter tolerances and better materials. The more expensive tools will pay for themselves the first time you don't round a bolt head over, or need a tool replaced.

If you have that down, look for information about the head gasket on the 7M engine (google "head gasket 7m supra"). They are prone to failure around 70K miles due to low head bolt torque. Of course, at this point, most cars are way beyond that. In any case, you probably want to do a head bolt re-torque, and torque the head bolts to around 70-75 ft/lb instead of the factory 52 ft/lb. This is a fairly common practice and a good first step before increasing the boost.

Note: There is a small chance re-torquing the head bolts could cause a blown head gasket. It is small but it still exists.

Third?

Now, you're ready to start for real. The car is in order and now you want to up the power. The first mod is a duesy (mostly just to give you a fix for a little while). Go to the hardware store and buy some washers that will fit on a 3/8" bolt. Buy about 6 of them. Price should not exceed $0.50 total. Now, google for "Supra shim waste gate" and you will find several articles on this simple mod.

You're basically going to put 1, 2 or 3 washers between the turbo and the waste gate actuator (the articles will have pictures to show you what I'm talking about). This will cause the turbo to produce slightly higher boost. Instead of 6 to 7 psi, you will now have 8 to 10 psi depending on a lot of factors. The car should feel a little more energetic now.

Don't forget to remove the washers when you get some other form of boost controller!

Oops!

While this is a very simple low risk mod, it is now time to talk about what MAY happen to your car. The MKIII supra is a very tough animal and very forgiving. It is a great car to learn on. However, if your car is all original and 150K+ miles old, things may start to go wrong. It is possible that the turbo will start to leak oil into the exhaust and then later go out (you will see white puffs of smoke at idle). This isn't likely, but possible.

If it does happen, it is not the end of the world. There are various places that rebuild turbos. Depending on how damaged the turbo is, most rebuilds are less than $400, some less than $300 including shipping. The faster you catch the problem, the cheaper it will be to fix. I drove my car with the turbo going out until if completely failed. I had to buy a NEW turbo because I had ruined the center cartridge on mine.

When you get your turbo back, it will be good as new. Of course, you could also have the turbo modified at this point. Why not? You already went to the trouble of removing it from the car. More on this below in step 3.

There are other things that could go wrong during this process also. You may kill your clutch, or auto tranny. Both are just a fact of life when significantly increasing the power on an engine (if you go through step three, you will have nearly twice the factory fly wheel horse power, but at the wheels). Also, a blown head gasket is a possibility. If you have re-torqued your head bolts, and your head gasket was in good condition, it probably won't happen. If it does, you will have to pull the head and install a new gasket. This is a major undertaking, but also provides an opportunity for other mods, such as porting the head, or larger valves, different CAMs, or other head changes.

The real mods!

Assuming everything is going right, here is what I normally recommend as a progression of mods. Remember each mod slightly increases your risk of breaking something.

Step 1:

• Intercooler (sparco, HKS, custom) and maybe hardpipes.
• 3" down pipe and 3" exhaust with (or without for off road use) a high flow cat.
• Electronic boost controller.

I choose an electronic boost controller for a reason. You could build or buy a much cheaper manual boost controller, but they are not very reliable and they actually hurt your spool up (how fast the turbo reaches the desired boost). Remember if the boost controller lets boost rise uncontrolled, you WILL blow your engine, blow your head gasket or damage your turbo. Good boost control is one of the most important thing to keeping a turbo engine alive.

With this set of mods, you should be able to run just under 13 psi. If you try to run more, you will notice the car cuts out as boost passes 13 psi. This is because the computer has a built in protection system that shuts the car off if the turbo produces more than desired boost (a fail safe). We will disable this later, but for now, it provides a good safety net.

Also, I've only listed the major items above. You will probably also want to get a boost gage (unless you have an electronic boost controller with a built in gage) and an EGT gage. Both provide some safety checks as you make changes. A good cone filter isn't a bad option either.

If you are having trouble getting the boost to rise to 13psi, it is possible you have a bad bypass valve (blow off valve). The Toyota valves tend to leak at higher than factory boost. You can either buy a fancy blow off valve, such as the HKS SSQV, or google for "Supra Porsche BOV" which will give you a cheaper alternative. You should probably change it at this point in any case. Also, don't let the lack of prestige dissuade you from buying the Bosche/Porsche valve. It is good enough for Porsche to use on a 300+ hp, $85K+ car. It is a good unit. I don't recommend the Saab unit. It will "hoot" which is really annoying.

The car should now feel MUCH faster. Enjoy it for a while before you do anything else.

Step 2:

Well, the first step is pretty straight forward. The second step isn't so deterministic. There are a lot of options. To go to higher boost you really need some form of fuel computer. There are TONS of options from things as old and simple as HKS F-CONS to the modern Greddy E-manage. Do lots of research and ask around to figure out what they all do and what will do what you want.

Besides some form of fuel computer, you will need to eliminate the boost cut. Greddy (the BCC) and HKS (the FCD) both sell devices that remove boost cuts. The Lexus AFM + 550cc/min injector swap is an option to move the boost cut up, but you should probably have the electronics in any case.

You will also want to fix the poor factory fuel pump at this point. The stock injectors are 440cc/min. On the supra, a good rule of thumb is cc/min for a single injector is about your MAX rear wheel horse power potential. So the injectors are good to the low 400 rwhp range which is plenty for everything this pages describes. 550cc injectors would give your car an extra safety margin, but are not required.

The fuel pump is not big enough however. It stinks. There are two decent options. The first is to buy a Walbro GS341 (the MKIII supra kit that comes with it if possible). They are cheap (around $100). The other option is to find a MKIV Supra TT pump. However, they aren't quite as good, and are hard to find used (new they cost a fortune).

With these items you should now safely be able to raise the boost a little more. However, the factory turbo doesn't work very well above 13 psi so you won't get much more power at this point, but the car is ready for the next, and final mod I suggest on this page (although, by this point, you will probably have learned enough to have your own ideas of where to go next).

Step 3:

Now for what I consider the best bang for the bucks mod out there. Have your stock CT26 turbo modified to use a 60-1 garret compressor wheel and have the exhaust clipped 8 to 12 degrees. This combination will make the turbo awesome at 15psi to 20psi. You should consider paying a shop with a wide band O2 system to tune the car.

Depending on a lot of factors, the car should produce well into the 300 rwhp range on a 5 speed with about the same torque. My car (an auto), with this level of mods produce 283 rwhp but with 410 ft/lb of torque with the factory fuel pump on only 13.5 psi boost (the turbo is more efficient so you get more power/torque at a given boost level). If I had changed the pump, I could have produced another 40 horse power easy, probably more.

Modifying the turbo usually runs between $500 and $750 depending on the condition of your turbo.

On another note, if at some point your turbo needs to be rebuilt, you can have it modified, even if you don't have the other mods listed here. The only difference will be that you can't raise the boost. You'll have a modified turbo and have to run stock pressure (or a little higher) until you get the other mods. Economically, it makes since to have the turbo modified when you remove it for a rebuild, instead of later.