Alusil Pistons

[Bergerac]

Someone on the PCGB forum used Mahle Motorsport pistons for their Alusil rebuild within the last couple of years I think. I'll admit I was sceptical and posted that, but it seems it's all good. So showed how much I knew.

I've got Mahle Motorsport pistons in my alusil build, no problems so far. Not the cheapest option though

Did you custom order them?

Mine were custom order, they have some 8V options off the shelf but only in oversize. My buildsheet wont help, theyre for a 3L 16V and they were built off the measurements for my block & CR target. It really is an easy process to complete thier custom order form, they have enough designs on file to fill any gaps you have.

https://www.us.mahle.com/en/motorsports ... ston-sets/

Screenshot 2026-07-08 200549.png (118.63 KiB) Viewed 73 times

[gruhsy]

Ah

Thanks

Definitely a special order being 100mm

I've got Mahle Motorsport pistons in my alusil build, no problems so far. Not the cheapest option though

Did you custom order them?

Mine were custom order, they have some 8V options off the shelf but only in oversize. My buildsheet wont help, theyre for a 3L 16V and they were built off the measurements for my block & CR target. It really is an easy process to complete thier custom order form, they have enough designs on file to fill any gaps you have.

https://www.us.mahle.com/en/motorsports ... ston-sets/

Screenshot 2026-07-08 200549.png

[blade7]

It still seems a mystery whether the original Porsche pistons are forged or cast, due to the very low expansion rate?

[944m3]

It still seems a mystery whether the original Porsche pistons are forged or cast, due to the very low expansion rate?

My understanding from internet reading is that they are hypereutectic, which are between regular cast and forged.

I sometimes wonder if too much is made out of forged pistons. Meaning a regular cast or hypereutectic piston, which are cheaper, would do just fine.

[PSU_Crash]

It still seems a mystery whether the original Porsche pistons are forged or cast, due to the very low expansion rate?

My understanding from internet reading is that they are hypereutectic, which are between regular cast and forged.

I sometimes wonder if too much is made out of forged pistons. Meaning a regular cast or hypereutectic piston, which are cheaper, would do just fine.

I have experienced a hyper-u piston catastrophic failure on my friends boosted 80s beast. We both ran a very similar build and nearly identical tune in our cars at the time. My wisecos were definitely trashed when we tore down, but they didn't break while endouring moderate to severe detonation!
Forged is my go to on any boosted setup. It adds a little margin for error in the tune, in my opinion. On a good tune either piston will likely be fine. NA I wouldn't hesitate to use a hyper-u.
This was also the last engine I ran a standalone on and tuned purely on the street. Dyno tune is the only way to get it right. Lesson learned.