Stock Piston Differences: Where do I find this info?

[E turd]

I am buying an m52 with single vanos m50 pistons in it. Supposedly the m50 pistons bump up the CR, but without the dimensions of the already installed m50 pistons, I can't do the math required to be able to select the appropriate thickness head gasket.


Anyone know where I can find out the differences between the m50 and m52 pistons such that the CR changes?


TIA

[PiercedE30]

M50TU or M50NV? The NV pistons have a wrist pin about 5mm lower than the TU.

[Wh33lhop]

M50TU or M50NV? The NV pistons have a wrist pin about 5mm lower than the TU.

5mm difference? That would make for a pretty large CR bump. If he doesn't know, I think we can figure out which ones if someone knows the measurements. One of the CRs would probably be less ludicrous.

[Aptyp]

rod makes up for that 5mm difference

[Wh33lhop]

rod makes up for that 5mm difference

Well no shit, but the wrist pin's stationary in this situation. ;)

[E turd]

Sorry about that guys. The m50 has single vanos. I think the guy said it will be around 11.25:1 CR, but he can't say for sure and I need to know so I can run whatever HG thickness that will allow for safe use of 91 octane.

[E turd]

Bump for views

[E turd]

One more time.....any takers? Please?

[Mitch M]

http://www.motorenteile.mahle.com/eLIZA/mahle/query/engine/byParams?cocoon-action-1c2f747d4e3b622a22234e4c75643221418e6880:EngineQueryResult:queryNextPage

[E turd]

YOU ARE THE MAN!!!! Thanks a ton!


And to anyone who might find this thread useful down the road:

From what I could gather, the wrist pin location on the m52 pistons is higher than the location on the single vanos m50 pistons. Thus, using the m52 rods, the m50 pistons will rise approx .73mm higher than the stock m52 units.

Of course, I'm not a mathematician, so please double check the math before you do anything else. I used the following part numbers for reference on the Mahle site:

PN: 11251703456
M50B25 single vanos piston (there were a few options, all with slightly different bores on the realoem page, but I think the wrist pin location should be the same regardless)

PN: 11251432086
M52b28 piston (same thing about options/bores on the realoem page)


The Mahle specs for the pistons show the distance from the top of the piston to the center of the wrist pin to be 31.82mm for the m52b28 and 32.55mm for the m50b25.


I guess now it's time to try to plug some numbers into a CR calculator. Wish me luck and thanks again to all who helped!