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, Wed, 29 Oct 2003 17:39:36
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I've modified my '89 T16s, (SPG), with the upgrades you metion and feel that the best way to start is as follows:
1. Buy a K&N air filter which replaces unnecessary pipe work. (It also helps a lot to try and fit the ducting pipe supplied with the air filter, so that it scoops air from underneath the engine bay straight onto the filter). Fitting this filter increases the air flow to the tubo thus keeping it that much cooler and that much safer.
2. Increase the turbo boost pressure by adjusting the waste gate actuator rod located underneath the turbo. See instructions on this website or in the haynes manual. BUT be careful, too much and the APC will cut in everytime you floor it! Try to find a balance between more power and engine safeguards.
3. Get your local exhaust centre to take out the middle box section and weld a straight section in its place. Also rear twin pipes diposes exhaust gases much quicker. This improvement really increases forward momentum when changing gear, increases top speed and sounds understatedly purposeful!! Otherwise replace the whole exhaust with a 3" to 3.5" bore.
4. You can actually increase the fuel pressure from 2.8 to 3.0 by simply knocking a circular dent in the top of the original fuel pressure regulator using a correct sized socket. (Large enough to just go around the outside of the inlet pipe). Although this sounds extremely malicious it does work and isn't as drastic as you might think. HOWEVER, be warned that this is irreversible. A rising rate fuel pressure regulator is a better option, but how much power increase or engine responsivness you feel at this stage of tuning is very debatable. (Personally I felt none until I started more advanced levels of tuning).
5. Adjusting the APC valve is highly effective AND potentially highly risky. Depending on year and model, the APC valve is situated in different locations. (See this website or the haynes manual for directions!). There are 3 screws that make up the APC, turn the one in the middle, (which is also the largest), clockwise to tighten and thus increase the point at which it cuts in to protect your engine. BE VERY CAREFUL WITH THIS PROCEDURE, many an owner has turned that screw too far and ended up with an extensive range of spare parts that don't fit together anymore!!!! Adjust an eighth of a turn at a time until you find the point at which your turbo needle goes far enough into the red for you.
What you will then begin to see when you floor the throttle is the turbo needle leap into the set point in the red zone and the ECU reeling it back into the orange/red. Where it settles depends on a huge amount of factors usually revolving around base factory settings and condition of the ECU circuit boards. Now this brings you onto the next stage of tuning-
6. A tuned ECU basically pushes the boundry where it hauls the turbo needle back. Now, instead of being between orange and red it allows that needle to sit in the middle to the end of the red zone, unfalteringly.
Before you spend money on a tuned ECU try points 1-5. Here you will see the greatest benefit of power until you then start spending a lot of cash, on new a turbo, flywheel, dumpvalve, AID, etc, etc.
When tuning there is so much conflicting advice but in my experience if you USE COMMON SENSE and IF YOU THINK YOU HAVE GONE TOO FAR, (especially with point 5.), YOU PROBABLY HAVE.
Also make sure that any and every pipe, no matter how small or insignifigant, is securely fastened as the greater pressure you will now be developing in the engine will find any weak points to escape. This includes the dump valve which you may have to upgrade soon after tuning.
Your '88 turbo unfortunately has the smaller pinion bearing in the gearbox. (You may want to check this statement as american models may differ to the european ones). This is by no means a great problem as long as you don't tune the engine over 220BHP. The aforementioned points 1-5 will increase to around 205 - 215BHP. (And you can always upgrade the pinion bearing).
At this stage of tuning do not bother wasting money on upgraded injectors. What you have for this stage of tuning is more than sufficient.
Gwion
posted by 213.78.9...
, Wed, 29 Oct 2003 17:39:36
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