Over the last couple of months swapping back the old cylinder head from the blown 3.0L motor has been of primary concern (see european car 06/02). After evosport pulled the 3.0's cylinder head, we discovered it was simply a broken copper head gasket-the cylinder head and block are fine. Noticing how clean the pistons were even after 6,000 turbocharged miles, I decided to have the cylinder head swapped to the old one, because with the current one on the 3.2L the car has been going through oil at a rate of one quart every 400 miles on the street (and much worse on the track)-this is not good.
Looking through the spark plug holes on the current motor, it was evident oil was present on the top of each piston. I had the cylinder head rebuilt once before, and while the head was off I could see the centralized oil deposits on the pistons, indicating most likely a leak from the top end. Not surprisingly, the car was still consuming oil at the same rate after the rebuilt head was installed-it was time to put the old one back in. Fortunately, the Bavarian Engine-built block is still great, helped by the Techron I've been pouring through the intake from time to time to clean out the combustion chambers and piston tops-as discussed in Part 19-to help avoid detonation.
The car will visit evosport once again for the swap. Once the original cylinder head is reinstalled, I foresee a lower octane requirement for high-boost runs, since there won't be oil deposits present to heat up and predetonate the fuel.
Since the turbo will have to come off during the cylinder-head swap, one of two possibilities will happen: Either the fins of the current Mitsubishi turbine will be clipped a few degrees for better flow (the Garrett compressor side untouched) or the entire unit will be replaced with another. This actual unit is fine, but the EGTs are a little high for my taste, especially on the track. The exhaust sees as much as 1,250F on the street and as high as 1,390F after several laps on the track, but these temperatures are measured right after the turbo-the temperature coming out of the actual exhaust manifold is probably getting up to over 1,500F. Much of this has to do with the log design of the Active Autowerke exhaust manifold. Unfortunately, there isn't room for an equal-length, tubular design at the moment either.
If I go the new turbo route, it won't be necessarily to make more power-more than 400 at the wheels is plenty for me. Instead, I'd like to see over 400 whp with less boost, see a quicker turbo response, and hopefully see slightly lower exhaust gas temperatures. If this is accomplished, it will be well worth it. Since the exhaust manifold will be off as well, I may even get it thermal coated to further lower the underhood temperature.