Mahle OEM vs. Mahle Motorsports

[wintersurf]

Rebuilding a 2.4 S engine to basic stock configuration for street use only.
Considering replacing the P&C with Mahle.

Mahle OEM 8.5cr with a cast piston. Cost 4000
Mahle Motorsports 9.0cr with forged piston. Cost 5500

I know I will enjoy a slight performance boost with the higher CR of the Motorsports pistons. But, is it worth the extra $1500 for the Motorsports set?

Anyone been in my shoes? What did you do ?

[Henry Schmidt]

A stock 2.4S was closer to 8:1 than 8.5:1
The increase in performance is from 8:1 to 9:1 is appreciable.
The "S" cylinders you have should be Biral (aluminum fins/cast iron liner.)
You can easily have them bored from 84mm to 85 mm and use a 9:1 CP piston to create a very nice package. The cost to do this should be around $2,500
If you want to get fancy, you can have the Biral cylinders Nikasil coated for an addition friction reduction and cylinder life. The other benefit to this option is aesthetics. New Mahle cylinders look like 2.7 cylinders, so from a strictly concours perspective, reconditioning the Biral is visually correct.
We've used this exact formula maybe 30 times.

[wintersurf]

Thanks Henry for your input. Great idea.
Are there any issues with clearances between C & P ?
I read one posting of piston slap with the JE in a Mahle cylinder. Different expansion rates.
But it sounds like you have not had an issue with that …
Would you use the JE piston? And if so what type of clearances w/ P&C.? .0015 ?

[Henry Schmidt]

Originally Posted by wintersurf

Thanks Henry for your input. Great idea.
Are there any issues with clearances between C & P ?
I read one posting of piston slap with the JE in a Mahle cylinder. Different expansion rates.
But it sounds like you have not had an issue with that …
Would you use the JE piston? And if so what type of clearances w/ P&C.? .0015 ?

It's impossible for me to comment on a random comment about issues with piston clearance.
My experience with both JE and CP is that the modern materials used function perfectly when proper setup is used.
Many years ago, JE had piston design issues but those issues were resolved 15 or 20 years ago. Sometimes old stories linger.
It's also common for inexperienced builders to blame build results on aftermarket parts suppliers.
If your plan is to bore Biral barrels tell the piston manufacture your plan. Expansion rates for Biral vs Nikasil cylinders are different as are the ring packs.

[wintersurf]

Thanks Henry for your wisdom!