Question: would running low compression FRM compliant Mahle (or other?) pistons be the happy medium between the cost of sleeving a block and the reported unreliability of a 3mm HG? What are the pros and cons of this path?

hypothetically for 14-18 psi on an SOS s/c, 91 octane.

 

I can't see any cons I have never heard of a sleeve failure in an F20/22 I wouldn't even say it's a "medium" I think it's probably better for most people than sleeving the block there are many advantages to FRM over iron.

 

But do Mahle make them?

I know Woessner do:

http://www.woessner-kolben.de/english/

 

Mahle makes the pistons for the H22... I've wondered about them for a while. They are the same Bore, but I was told (I don't know for sure if it is correct) that the crown of the -7cc (Dish) version need to be milled down 1mm...

The person who told me this could be wrong, though. I've got the thickest SCE Copper gasket (2.XXmm) and I wanted to try and see if they would work. I just don't have time right now to do any of it.

Would anybody know what the height of the stock S2000 piston (from the wrist pin) is Versus the height of the Mahle variants?

 

Where does it say on the site that they are FRM compliant? I would buy their "00-03 S2000 Turbo Pistons" if I know that they were safe for FRM and came with rings that were also!

 

Chris Barry has used Mahle H22 pistons along with a K24 crank and custom rods to build a 2.4L F series engine. However there is a whole lot of machining required.

We discussed the H22 pistons for a low compression engine but it is not practical.

However, Woessner seem to do a piston for the S2000 with a CR of 8.5. I have enquired about it.

 

It doesn't, that what I have asked them to confirm.

 

WOW that would be great if they are FRM compliant. One question though, since I'm an AP2 would these pistons work for me? I know the bore on AP1 and AP2 is the same and the stroke is 84mm and 90.7mm respectively but is the difference in stroke made up in rod length/crank dimensions or in piston height? Obviously if the piston height between the AP1 and AP2 is different I'll have to look elsewhere

 

The stroke difference is mostly made up by the shorter rod but AP1 and AP2 pistons are different.

 

There's some conflicting information in the application sheet and between the former and the online shop regarding the f22C application.

http://www.woessner-kolben.de/english/

The spec sheet lists the kit # k9245DA as a low compression "stroker" kit. They list a 90.7mm stroke for it, which is AP2 stroke. So they marked it as a stroker kit of the f20. However, they put a rod length of 153mm, which happens to be the F20 rod length. So 153mm rod + 90.7mm stroke = not possible.

http://wossneronline.com/forged_pistons/in...&products_id=20

Now at their online store they list the following specs for the same part number: