Quote:
Originally Posted by swartzentruber
An finally, I'm also not sure why the conclusion that lower octane is related to the failures necessary equates to BMW screwup. I have a somewhat strong suspicion that many of the CA failures might have also been tuned, so it could very well be the case that BMW got the ECU programming right for 91 octane, but the aftermarket tunes have not.
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It certainly is an interesting situation.
RG has asserted over and over that you cannot run 12:1 compression with 91 octane fuel unless your knock sensing technology is state of the art and he's right. Further, it seems extremely unlikely to me that BMW's knock sensing technology is the source of these engine failures. In fact, I'd be surprised if the BMW technology couldn't handle lower than 91 octane. Why would they limit it? If I were designing the SW, I would require that if the system couldn't ensure there wouldn't be damage, it wouldn't even allow the engine to run. That should be pretty easy, especially since the throttle is controlled by the computer. It would be easy to simply not allow a load on the engine if the SW believed damage would occur.
I believe it's also true that tuners really have no idea how their tunes might affect detonation/knock/preignition in various kinds of
corner cases. If it works on their dynos in LA during 80 degree weather, it must work well in every scenario, right? I personally think you'd have to be crazy to get your car tuned IF you were also worried about the potential of losing your engine. The tuner is going outside the factory derived settings and without *any* solid engineering to determine whether exceeding these factory settings has a long term detriment.
But I think this data is also suggesting that rod bearing engine failures are not singley correlated with tight bearing clearances. For one thing, the failure rate is way, way too low. For another, there shouldn't be giant disparities between states, although I admit we may still just have noisy data.
I think one of the most important things to continue to do is to try to find and track additional engine failures. That's how we can all contribute. The more data we have their, the more likely we'll be able to draw firm conclusions.
Pat