Piston Ring Design

[redneckvtek]

Hello

I am looking to build a M20 with stock "I" pistons at the +0.50 size. This is what I have been provided by the customer so this is what I am going to use.

I am having trouble sourcing the correct piston rings. They are currently NLA from BMW, and all suppliers that I can find who indicate stock are "ECS Tuning" companies, or are located in eastern Europe. I do not want to risk my customers money on either of those endeavors.

Specifically, I am searching for PN 11251713195, and would like to locate qty 7 to ensure I get good fitment for this engine build.


The purpose of this question is to ask if anyone has specific knowledge about using different rings for M20 engine builds.
For example, the rings for the M20B27 +0.50 are still available from BMW. I don't have a +0.50 set of M20B27 pistons for measuring, does anyone know or have first hand knowledge of the difference between "E" and "I" rings?
These would be PN 11251713181 and need to be ordered from the fatherland at significant cost.

M50 +0.50 rings are available as well, also in the fatherland, as PN 11251437054.

I do have a set of M54 pistons, so I plan to measure these and compare with M20 size, but M54 only come in +0.25 due to the liners in the AL block.

Are there good aftermarket options that work with OE pistons? I am unsure about the specific legality of this in certain racing series, but certainly this is not the first time a racer in those series has encountered this. I suspect its not enforced due to the challenge in determining ring design in assembled engines.

Thanks,
Chris

[AWDBOB]

IE shows stock for +0.50 rings, but they don't specify brand. May be worth giving them a call

https://www.iemotorsport.com/product/piston-ring-set-m20/?gQT=2

If you can't find rings, you can still get the Mahle +0.50 pistons that come with rings and are only $105ea

11251714810

[redneckvtek]

IE shows stock for +0.50 rings, but they don't specify brand. May be worth giving them a call

https://www.iemotorsport.com/product/piston-ring-set-m20/?gQT=2

If you can't find rings, you can still get the Mahle +0.50 pistons that come with rings and are only $105ea

11251714810

Last time I did business with IE I purchased their rocker arms for a customer's engine, and the rocker arm pads immediately disintegrated and destroyed the engine. Have you used their rings before? Based on my previous experience I have serious concerns.

Damn, I sound like a grouchy old man bitching about suppliers being sketchy or dishonest. Fool me once, as they say.


I wonder if something like this will work on OE pistons. Is it as simple as measuring the grooves in the pistons and ensuring the dimensions/tolerances match the OE rings?

https://www.summitracing.com/parts/WIS-8450XX

[digger]

i have used Spareto a couple times and had good results. at the lest it gives you the manufacturer p/n to help with your search

https://spareto.com/oe/11251713195

those wiseco wont work, most sets use thinner rings than what OEM did in the 1980s. even if you find the correct axial thickness 1.5/1.75/3 you need the correct radial width which would be a whole lot of stuffing around potentially

[hasa]

I'd search rings by dimensions of OEM rings are not available. Plenty of other brands have 84.50mm pistons.

And there are piston ring manufacturers like Total Seal in U.S. Plenty of choises.

[TobyB]

+1
Last I looked, Total Seal made rings for the M20-
and while I'm not 100% sold on their sales pitch* I have run their
rings in several engines and they're fair value for money.

t
*their rings give very good static leakdown numbers,
but I'm not convinced that translates to all that many
extra horsepowers at the crank. It certainly doesn't hurt.

[redneckvtek]

Schmiedmann responded to my inquiry that Mahle brand 11251713195 were available at a very reasonable cost (lower than FCP excluding international shipping), so I placed an order.

I did measure M50 pistons and the ring lands are narrower than M20 piston ring lands, so I don't think M50 rings will work for future reference.

M20 measurements for reference:
1.6mm top ring
1.8mm second ring
3.0mm oil ring

M50 Measurements:
1.5mm top ring
1.5mm second ring
2mm oil ring