Mahle MS BMW S65 B40 4.0L 92.50mm x 27.3mm CH 2.1cc 372g 10.2CR Pistons (Set of 8)

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 turbo- or supercharged 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 that is a lower compression for boosted applications but 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: 2.1cc
Weight: 372g
Compression ratio: 10.2:1

This part also goes by the following cross reference.

Cross Reference Part Number: mhl197843342