Forged High Compression Oversize Piston Set, Mahle - E9X M3

Mahle Motorsports S65 pistons are forged for strength, light weight, and low drag to be a more specialized application than stock BMW pistons. Factory BMW pistons are cast aluminum, which is fine for the intended power output and durability. But increase the performance, especially on turbocharged engines, and the cast aluminum becomes a weak link at some point. The strength of cast parts is susceptible to heat, detonation/knock, and other timing or fuel issues. These types of combustion forces can make it brittle or even deform the piston shape or size. Forged pistons are inherently a stronger material and more robust in these extreme conditions.

This is a piston with higher compression for more performance and a larger bore for engine rebuilds. The factory uses a 92.19mm for a 1st oversize rebuild and these are 92.50mm to use as a 2nd overbore or to maximize cylinder volume.

Full specs -
Bore: 92.50mm
Stroke: 75.2mm
Rod length: 140.7mm
Compression height: 27.3mm
Pin diameter: 21mm
Piston crown volume: 12.2cc
Weight: 372g
Compression ratio: 12.3:1

As a high compression design, it's vital that valve-to-piston contact is evaluated during engine assembly.

Mahle Motorsports pistons are better engineered than mass-market OEM pistons. Quality and machining is much more tightly controlled, ensuring superior performance. Mahle uses a Grafal coating on piston skirts that reduces drag, friction, scuffing, and cylinder bore wear and a phosphate coating on other surfaces.

All pistons include a ring set, wrist pins, and circlips.

Made in the USA.