Quote:
Originally Posted by herrubermensch
Old thread, I know, but we consider ourselves one of the top alusil bore reconditioning shops (out of a whopping three or four in the nation). At Partee Racing, the alusil engines we build are BMW S62s, S65s and S85s. We have spent quite a bit of money and time developing our specific recipe for boring, honing and re-exposing the silicone of alusil bores.
The re-exposure process is done with a manual hone and requires specific friction levels (as measured by the amps pulled by the machine while honing) for a specific amount of time to achieve the necessary surface roughness parameters (Ra, Rpk, Rvk, Mr1 and Mr2) as confirmed on a cylinder by cylinder basis with a profilometer. One of our former colleagues (now a consultant to us) is the former head of Dinan's engine shop during the time when it supplied the Rolex 24 Hour winning S62 engines.
Interestingly, BMW recently restarted production of new S62 blocks, and one that we ordered arrived with some damage that precluded its use. So we have used that block as a test mule to compare it with our own work. The cylinder surface roughness parameters were acceptable, but nowhere near ideal nor what we achieve through our process. As an aside, note, we discovered that BMW does NOT use torque plates when it bores and hones alusil cylinders, meaning that those cylinders are materially distorted out of round once cylinder heads are bolted into place. Not out of spec, but enough to be material to a high performance engine in our opinion. As a result, we re-bore, re-hone, and re-expose even brand new blocks from BMW. And we use torque plates on both banks simultaneously!
I love this stuff and am happy to discuss it with anyone who so desires. peters@parteeracing.com is my email.
--Peter |
Finally find someone that knows Alusil, will reach out to you Peter. Have a S63B44 build for a forged motor for X5M.. Why the heck does BMW sell 89.25mm pistons if someone cant bore Alusil? ha
joe