Quote:
Originally Posted by Doc Brown
I never heard that before on simple engines but I know a lot about how multi cylinder race engines are treated. I know that the legendary Judd V8 is broken in in a very special way as I had the chance to talk the tech chief. Any time before its started oil and water are warmed up or it goes west, but that's another story...
|
It's kind of the same story though.
All to do with tolerances, operating temps, and thermal expansion. Generally speaking bigger parts require bigger tolerances to allow for greater variations. In a race engine with tighter tolerances you need to remove some of the variables.. thus specific start up/warm up procedures.
From my research, it seems to be the same with most of the 2T reading about heat cycles. Usually bigger bores (think jet skis/snow sleds, etc), moving from a cast piston to a forged. Forged by nature expands more and needs more tolerance. Add to that the bathtub curve and infant mortality, and odds are that when you make significant mechanical changes, that if it's going to fail it's going to do so sooner rather than later. If you're going to have a big piston nip up due to thermal expansion you're best chance of avoiding is a slow warm up, and in the event that it does nip it's best on a low load slow idle than wide open down the track.
Factories probably tend to stick to a certain procedure for consistency and fault finding. The less variables you are dealing with the better.