Forged High Compression Oversized Piston Set (12.5 CR), Mahle - E36 M3, MZ3

Mahle Motorsports S52 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 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 high compression spec for tuned built engines. These would be 2nd (or 3rd) oversize bore to get more volume from the S52 block. BMW's 2nd oversize piston set is 86.565mm and these are slightly larger at 86.6mm.

Full specs -
Bore: 86.60mm
Stroke: 89.6mm
Rod length: 135.0mm
Compression height: 31.0mm
Pin diameter: 22mm
Piston crown volume: -5.0cc
Weight: 342g
Compression ratio: 12.5:1

Because of the higher compression and new crown shape to these pistons, it's absolutely vital to check valve-to-piston clearance during 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.