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Search "tweak your apc" on the performance board or go to turboteameurope.com to learn how to manipulate the stock turbo control unit. You will need more fuel to support the higher boost pressures and control pre-ignition. A 3.0bar fuel pressure regulator off of a non-turbo c900 will help somewhat, and can be found in junkyards for cheap. This combo will get you at or near 200 crank hp. For more, you will need more boost, more fuel support, and ignition fortification. Your boost should be within reach by modifying your stock apc box using the various techniques you will read about (email me if you want opinions on bypassing the "F" pot as described on the tte page). Fuel can be supplied by using 30 lb/hr mustang (ford motorsport, accel, etc.) injectors. Post questions you have about this on the performance board when you get to this point, you may need to modify your air mass meter to get your car to idle and not throw a CEL (check engine light). For ignition, most go with the MSD 6AL-BTM as this powerful ignition includes a timing retard control that is set proportional to boost level. For info on this, visit twinsaabs.com and read Kevin K's writeup. You can get an MSD at summitracing.com or other speed shops. 250 crank hp should be within reach with this equipment installed and tuned properly.
Keep in mind-
C900 transmissions, especially 88 and older are made of glass. They will not hesitate to shoot pieces everywhere (or at least stop working) if you piss them off (I.E. careless power use, too much power, old age, time of day, location, phases of the moon, etc.). You could upgrade to an 89+ tranny, or pinion bearing from one, and that would hold for longer. 250bhp should be ok as long as you are kind to the tranny.
C900 headgaskets fail under stock boost levels, this is something to keep an eye out for. Make sure there is no coolant in your oil.
C900 turbos are designed to produce around 11psi for short periods of time. 250bhp requires somewhere in the 20psi range. Your stock turbo will not last long at this level, and will be very inefficient. It will not flow well at these boost levels and generate a lot of heat, both of which kill hp. SPG9 (spg9.com), Swedish Dynamics (saabperformanceparts.com) and Turbonetics (turbochargers.com ?) all offer good upgrades.
Other necessary items:
2.5in or larger cat-back free-flow exhaust
K&N air filter (debateable, but flows better than stock)
Upgraded bypass valve (the stock one leaks at high boost)
Larger intercooler or water injection. Many have had success with front mounting a 9000 intercooler. Water injection (search "aquamist" on the performance board) is available through Brad at kcsaab.com.
You can learn a lot just by reading these boards. You will want to spend some time on the performance board reading threads that are pertinent to your car and level of modification. You will also learn that typing in all caps is interpreted as shouting and you probably don't want to do that.
Good Luck,
Andy
91 Red SPG
Some mods
Boulder CO
posted by 216.241....
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