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My '87 900T (the Beastie) will now sustain 80% redzone boost when I need it, thanks to about $1K worth of SPG9 mods. I'm not done yet, either! My excursions into the redzone are not repeated or continuous, as in racing; for that sort of demand, I know I would have to make further modifications. But here's what I did so far, and I think it's a good starting point:
New Stage 2 APC box -- the heart of turbo boost control. I call it the "Army mod" because it lets your engine "be all that it can be." I honestly believe that this mod is the foundation for anything else you do with your engine, and is worth every cent invested. Some people have tweaked their APCs and there is plenty of info available on how to do that -- a very inexpensive alternative. But the SPG9 Stage 2 APC is wonderful. With this mod alone you'll see the boost venture into the red, but the knock sensor will probably limit you due to fuel leaning at those boost pressures. So...
New oversized injectors and the SPG9 Rising Rate Fuel Pressure Regulator are next. These will give you sufficient fuel flow you need when you need it at those higher boost pressures, without adversely affecting your mileage when you're not boosting around. The Beastie gets better highway mileage now and the new injectors are quieter than the stock ones I replaced. After doing this mod, I could sustain mid-range to low redzone boost. The problem causing knock-sensor twitch at high boost was ignition timing, so...
Next, go with the SPG9 Advanced Ignition Diaphram, or AID. This device allows more boost retard, thus more initial advance on your ignition. After this mod, and with a little tuning, I can now sustain that 4/5 redzone boost during a wide-open throttle accel run. No knock twitch at all. The car is most definitely quicker and more responsive in every regard.
I did not do intake or exhaust mods, change my throttle body, cam, heads, gut my catalytic converter, go to an oversized or fan-cooled intercooler, or add octane boosters, which are all topics we've discussed recently on this board. I don't want to go to a new tranny, either.
I bought a new hooter (turbo bypass) valve and have a new wastegate controller on order from SPG9, and I will do those mods as soon as I receive the wastegate controller. I'm toying with the idea of a high performance exhaust and also with some means to improve the efficiency of my intercooler, but for now those stock parts are adequate to my purposes, and I'm not really on a quest for the World's Baddest Saab or the 250+ horsepower regime.
Anyway, I can testify that the SPG9 approach works. The guys I've talked to on the phone there are friendly and helpful. If you have the time and money, this is a good option. I'm not saying it's the only way to accomplish your goal, and there are lots of Saabers who, I'm sure, will share their methods and results with you. Good luck with whatever you choose, and please post the results of your mods if you decide to do them. We all enjoy reading about these things!
TO THE REDZONE, AND BEYOND!
- = M = -
'87 900T 158K
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