Turbo 3.0 Modification for HP
 

Based on some preliminary measurements, I may have to replace my pistons and cylinders on my 3.0 turbo during this rebuild project. Since I have to pay the bucks anyway, I was thinking of bumping up the compression to 7.5 or 8.0 (based on comments from Wayne's engine rebuilding book) for more bottom end power. I have also looked through a lot of posts trying to figure out whether it would be worth it, or if it is possible, to go with 98mm cylinders and make a 3.2. Any advice would be appreciated as the rebuild saga continues. Thanks

Well if you already have to replace pistons, bumping C/R slightly is a good idea.

Bumping up displacement to 3.2 is somewhat expensive way of gaining power as P&C's cost a lot and whatever you gain by in horsepower is easily achieved by turning up the boost 0.05 bar or so.

My advice for cost effective 3.0 930 engine is: JE pistons, 7.5:1 C/R, SC cams and K27 turbocharger.
After that it starts to get expensive.

I agree with Goran on the bump in compression. By itself, don't look for a big improvement in performance on the low end - you'll notice a little better response when you let the clutch out.

The same holds true for increased displacement, but this might be a good opportunity for you to combine two things to improve low end. EBS has a good deal on both P&C's using the full finned 3.2L cylinders and JE pistons (good combination). By bumping the compression AND increasing the displacement, you'll notice better response.

Check out the K27HF turbo as it is a better platform that a stock K27.

I would also suggest that you talk to a cam grinder such as John Dougherty who frequents this forum. Explain exactly what you want to accomplish and have him recommend the correct cam. When building a car (especially a turbo) the cam is extremely important and can make or break your project/rebuild when doing cusom work (like increasing compression/displacement). You might find out that a custom grind is a great way to acheive your goal. Remember, the cam is the heart of the engine and should be the last thing to order, based on the improvements you end up with...