I haven't opened up the 3-liter motor that croaked on me back in late January, but I'm guessing by the compression ratio and leak-down tests that it was the head gasket, specifically the part in between cylinders 5 and 6. It wasn't an emergency, because I had already made plans for a new, low-compression motor with forged internals months before.
Bavarian Engine Exchange is a well-established business dedicated to the re-manufacturing of BMW engines in the U.S. and offering them at affordable prices. The company backs up its products with a two-year, unlimited mileage warranty.
My initial plan was to keep the stock 3-liter displacement. That way, I would only be pushed up one class at time-trial events for having the turbo. But after realizing much of my fun would be experienced off the track, I opted for the torque-rich 3.2-liter found in OBD-II M3s. I don't care what time-trial group I have to compete in anymore-Project M3's too much fun to drive to worry about that kind of stuff.
Another reason I opted to go with a 3.2-liter was Karl Hugh of Active Autowerke, the brains behind Project M3's turbo system. He'd already programmed chips specifically for these "built-up" 3.2-liter turbocharged motors, and I didn't feel a need to reinvent the wheel, especially with AA being clear across the country.
With so many AA-turbocharged, built 3.2-liter M3s running around in Miami with hardly any issues, I wanted the same for Project M3. These low-compression motors have already been proven, and Karl discussed the companies he'd had success with in building up these 400+hp motors-JE Pistons and Pauter Machine Company.
Pistons and Piston RingsJE Pistons, probably the most well-known forged piston manufacturer in America, supplies top engine builders for such racing series as NASCAR, NHRA, IHRA and IRL. If these guys can build pistons for 6000-hp dragsters, I reasoned that JE's forged pistons should easily handle Project M3's comparatively wimpy power.
The company uses CNC machines for manufacturing and purpose-designed forgings, enabling it to maintain exact specifications and close tolerances. Finite Element Analysis (FEA), Ultra Crown and Digital Three Dimension Piston Crown Machining processes are used in designing and testing of the pistons. The company reports it's the only high-performance piston manufacturer to earn the QS-9000 quality standard.
I decided to use JE pistons over the stock BMW units because BMW's stock pistons are cast, leaving them more vulnerable to failure under extreme, high-horsepower conditions compared to forged pistons. How else do you think those juiced-up Skylines, Supras, Porsches and other turbocharged cars are making so much power on stock bottom ends? A major factor is forged pistons.
Forged pistons can withstand the higher pressures and heat in high-performance motors more effectively and drastically reduce the possible catastrophic consequences of detonation and excessive heat in the combustion chambers. Forged pistons are for engine longevity, peace of mind when pushing your internals to the limit.
Project M3 received a set of custom low-compression pistons from JE to lower the compression to about 8.5:1 (stock is 10.5:1). The stock compression limits turbo boost to about 9 psi on good gas. But even on Project M3 I wanted to go the safer route, even if I were to run at only 9 psi (I know this probably won't be the case).
AA supplies a thicker copper head gasket to lower compression (as seen in Part 8), but achieving that CR with low-compression pistons is the better way to proceed. This allowed me to revert back to a stock 1.8mm head gasket, which was supplied by BMP Design. The JE pistons are 330 grams apiece compared to 440 grams for the stock cast pistons.
When having a motor beefed up, it's important to eliminate the weak links with quality products. It's also critical that the cylinder and combustion chamber pressures are maintained-and this is why JE Pistons uses Total Seal piston rings.