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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
Not an expert, just my opinion.

Decide what your goals are for the car. Shoot for the moon HP, improved power with divability, colectability, track car...

Turbos can eat an insain amount of money and achive insain power levels. However, there are some natural levels of development.

Stage I: Lets call this a tuned motor. By just changing out the muffer to the lowest back pressure unit you can stand, verifying you get .8 to .85 bar boost, setting the CO to 3% and /or getting it set up on a dyno by somone that knows there stuff to optimize the ignition and Air Fuel ratios makes for a nice car with much less lag that is about 330+hp fast. (Add an R&P, suspention kit, and some track time and fue with more HP will come close to catching you.)

Stage II: "The sweet spot" A package with a good intercooler, well matched and effecent turbo, updated blow off valve, and .9bar boost is kind of the sweet spot for a 930. It dose not overly tax basic design or thermal limits to any great extent. It should be good for about 360-380hp and makes the car a rocket. The
K27-7200 turbo works very well here and comes in hard.

Stage III: Now you are entering the 400hp club. This requires a turbo that can support more HP (K29 or HF), a fuelling strategy, and management of other areas that are starting to approach there limits. Attention should be paid to things like the clutch, oil cooling, cylinder head sealing when playing at this level.

Ports and cams. At some point when the motor gets to come out for somthing like a reseal or a clutch, it may be an opertunity to improve you motors effecency (VE) by improveing how well it breaths. The stock cams and ports are actually very acceptable and can take you quite a way. However, the intake ports are on the small side to help with air fuel mixing on CIS for improved effissions. Also there are cams grinds that do help the motor breath easer for some added improvement.

Gearing: Many have found that by changing out the Ring & Pinion for a lower gear ratio, it can wake up a 930. Boost is reached faster in first and the motor stays in the fat part of the HP curve more. A stage one or stage two car with will a lower R&O or better yet, closer ratio gears feels and is much faster.

Headers: You have the Euro Style heat exchangers already. Do not let anyone tell you they need to be changed. They are dead reliable and do not crack or drag. Most exaust gains are in the muffler. There is not much differance in volunm between your system and most of the shorty systems if you count there long wast-gate tube and changing them is not going to make a big differance in lag or HP levels for the expence involved. (May that have spent the $2k will dissagree.)

Boost: Try not go to far with adding boost. Going from .8 bar to 1 bar can add about 10% power at the very most and only if the motor dose not have restrictions some where else. Going from .9 bar to 1 bar might get you 10-15 hp depending on other components. Going to 1 bar on a 930 is like running 11+/1 compession on a normally asperated car. Further is is like doing so with the intake air being heated to boot. Running 1 bar with 7/1 compression ratio is very near the limit of what pump gas can support. Running lower boost on a well tuned car with the right AFR's should get you almost the same HP.

Don't forget handling. There is a lot of fun to be had there also.

Enjoy the ride.

Old 03-16-2009, 11:52 AM
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