Help - Identifying 3.2 Carrera Pistons

[tom1394racing]

I have a large inventory of used pistons that I need to identify so that I can offer them for sale. I have been able to identify most of them but I am having trouble telling the difference between the Euro and USA Mahle 3.2 Carrera pistons.

I have a confirmed set of 3.2 Euro Carrera P's and C's with the the Mahle pistons stamped "95P36+" on the bottom side of the piston. I also have a large number of 95mm Mahle pistons with the number "95P36++" stamped on the bottom. The domes on both groups of pistons look identical. Are these both Euro pistons with the 10.3:1 CR? Did Mahle make the pistons for the USA version and if so, what was the piston number?

I also have KS pistons with the number "95175" stamped on the bottom. Does anyone have any idea whether these are Euro or USA??

[RSstop]

Tom,
The Mahle catalog doesn't offer much help. Both USA and Euro 3.2 L use 95P36.
You may have to accurately measure dome height to distinguish the difference. The dome should be higher by 1.3 mm in two places. I cannot tell by the catalog where to measure.
10.3 CR Piston numbers 503 55 00, 95P36
9.5 CR Piston numbers 503 56 00, 95P36
The + and ++ are diameter classes.
Maybe some else has more information?
Lyn

[tom1394racing]

I would guess the dome peak would be a good bet for the best place to measure. I'll check my set of confirmed Euros against my other 3.2 pistons to see if I can detect a consistent difference.

[tom1394racing]

Sure enough, Lyn is correct!!

I measured up about 2 dozen pistons this morning. I found the confirmed Euro 10.3's to be, on average, 1.3 mm higher at the dome peak as compare to the USA 9.5 pistons.

Visually, I can't tell the difference.

Thanks Lyn!!

[ChrisBennet]

Tom,
Could you post the actual measurements?
thanks,
-Chris

[tom1394racing]

I measured from the the bottom base of the piston beneath the pin hole to the top of the dome using hand help digital calipers.

The Euro's gave an average of 64.66 mm with a max of 65.08 and a min of 64.45.

The USA's had an average of 63.41 mm with a max of 63.81 and a min of 63.26.

The variation is as much the crude measuring technique as it is variation in the pistons.

I used a cutoff of 64.00 mm to sort between the Euro's and USA's.

[ChrisBennet]

Thanks Tom!
-Chris

[mikedsilva]

Great thread, and giving it a bump.
I'm building a Euro spec 3.2 Carrera with the claimed "10.3:1" compression ratio.

I use "" as we all know what Porsche claimed, and what they are in reality are different.

I used to think, and perhaps others too, that the designation 95P36++ meant it was a "10.3" piston, but I have 2 sets of 3.2 pistons and sure enough, the Euro ones are approx 1mm higher in certain spots.
It is VERY deceptive though.. when you look at the "9.5" piston in your hand, the shape of the dome looks to be greater than the "10.3"... never trust your eyes!

To take it one step further, I decided to cc the piston in a cylinder, then work out the dome volume.

According to my measurements (i'm no nasa engineer) the "9.5" dome was 31.15cc and the "10.3" dome was 35.49 cc.

Using an online calc, and assuming a 1mm deck height, I get 9:1 and 9.56:1 respetively.

I should probably do the "10.3" piston again as I was hoping to be closer to 9.8.. usually the Porsche claims are about 0.5 of a compression point from actuality, from my observations. Just leaving this here so the next time I do a search cos I forgot, I can find my info!

[john walker's workshop]

The machining for the wrist pin bore cuts into the lower overhang on 3.2s. Doesn't on 3.0.

[pampadori]

I took a picture of the 8.5:1 and 9.3:1 3.0L CIS pistons when i did my budget rebuild back in 2017. I got the 9.3 set from Tom. you can really see the difference when you have them together.


I think the ++ was either to specify the diameter (there was a range of pistons and cylinders that were all "95mm" but some where on the smaller end and others on the larger end) or the weight range. They had + and ++ and - i seem to recall.

[jsoderbe]

Hi, after reading this thread we decided to measure my pistons. I get the total hight to 66 mm! Please see attached pic.

What do I have?

Regards, Johan

[Jeff Alton]

Mike,

Those who actually measure the CR like you did, find that the factry overstated the stock CR. Your numbers are similar to what we have seen years ago measuring stock Euro and NA pistons.

Cheers