Mahle question???

[Arctic Rat]

Hi
When I bought my 911 it came with an assortment of spare parts, including the original 2.0l in boxes. Today I was going thru the box of P&C's and I have a question about my findings.

The P&C's are clearly marked Mahle so no question there, but 5 of the C's are 90ZN2 W5 and 1 C is marked 90ZN2 W6 ?

Is there any difference between these two part#'s I need to worry about?

All the piston are the same part# 90P27 W2.

I was told by the PO the engine was set up to be a 2.5lt. The PO did not like the peakiness of the engines power and replaced it with a 2.2 E engine.

I hoping to put the 2.5 back together.

Thanks

Joe

[tom1394racing]

Pistons are 2.7 RS - CR 8.5:1

Cylinders are standard Mahle Nikasil

[Arctic Rat]

Thanks Tom.

Does the W5 or W6 at the end of the part # mean anything?

[ajwans]

It might be the weight group. Normally you would use a matched set but perhaps there's
some other reason for the odd one out.

andy

edit: sorry, thought you were talking about the pistons. Don't know why the cylinders might
be marked differently.

[Ernesto 911]

I just bought a new sealed Mahle set from Andial, and 5 cylinders are marked W5 and one is marked W6 like yours.
I was told that the height group numbers (marked inside a triangle) need to be the same.
Pete at Andial said not to be concerned as long as those match.

It may be just a different casting number reference to make up a matched set.

Regards
Ernie

[Arctic Rat]

Ernie,
Thanks! Were else can one person gain the experience of so many, but here on pelican.

Thanks everyone

[911pcars]

You can assume it's correct or confirm by measuring or have the specs measured. I would measure.

You can measure cylinder heights with a vernier caliper and verify the piston/piston pin weights are within spec when balancing the crank, rods, etc.

Sherwood

[zioo]

I found it interesting that the simple question of what the difference in the W5 and W6 part number was not answered by anyone. No one stated that they did not know. Contained in most of their answers was the fact that they did not know exactly why a different part number was used. However there was speculation. There was one solution as to weather or not it makes any difference and that answer suggested full measurements of weights and sizes of the odd piston against the others. The rest of those responses were guesses. I could guess too. One would be that it is for the 5th cylinder. Another guess would be that one piston ate it at some time in the past and an order for a new set came with a new part number that distinguishes it from Porsche original Mahle Pistons and this is and OEM piston cylinder kit with a diverse number to show that it did not come from the Porsche factory. All this is guess work until someone who knows the answer, provides it. - Zioo

[356RS]

The W5 is the cylinder height of 85.400 - 85.425 for the 2.4 engine with Biral Cylinders
The W6 is the cylinder height of 85.425 - 85.450 also for the 2.4 engine.

The 2.7RS used a color dot on the bottom of the cylinders for the height group.
Red= 85.400 - 85.425 and blue= 85.425 - 85.450.

IMHO the W5 & W6 on the 90mm RS cylinders are the old height group ID's and are not used or accurate anymore. I have opened up new sets of the 2.7RS lately and found W5's and W6's mixed in with the set. When I measure the height groups, there are all the same, usually 85.400 - 85.425. And can't seem to find any color dots on them anymore.

[AlfonsoR]

Excellent info Mark!!