Quote:
Originally Posted by catpat8000
So it seems to me that the ECU cannot compensate for any possible situation. There must be a limit to its ability and perhaps SFP is saying he heard that the limit is fuel with anti-knock of 90 under certain ambient conditions.
That is what I am questioning because I find it hard to believe that the ECU couldn't compensate for 90 Aki.
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A few days ago I came across a post by Mike Benvo that referenced a couple of things that have since come up.
Firstly Mike noted that there was a limit to the amount of pull that the ECU could make in response to detonation and that 90-91 aki was the ballpark lowest level that the ECU was programmed for. Noting that the ECU doesn't know or care what octane fuel is being used, it simply reacts to the data provided by the ionic current sensing system...and that environmental conditions would also have a significant effect.
Secondly, Mike was specifically asked why not just map the range down to cover 87 aki and the reply was it would be technically too difficult (it was explained better than that but that was the essence of it).
Further confirmation is provided by BMW who specifically warn against using fuel below 91 aki as it could lead to engine damage...and the common sense point that if the S65 could indeed handle 87 aki octane fuel without consequence then this would be a positive selling point.
Again note that I am not touting this as "the cause" of high bearing wear and engine failures just that it is most likely a factor in some cases.
For posters who question the very idea that any M3 owners would use 87 aki fuel then there is this:
"So i'm filling up my tank yesterday, and I see another guy with an M3 also filling up at the pump next to me. I couldnt help but notice he was putting 87 octane in his car (I always use 91). So I asked him why he uses 87. He said that he "used to use 91 and since he switched he cant tell any difference in performance, and it is top tier gas"
http://www.m3post.com/forums/showthr...hlight=pinging