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Discussion Starter #1
Hi again everyone:
My computer system at work is down so I decided to entertain myself playing mechanic with my 1998 230 SLK. Yesterday I saw a youtube video of a gentleman talking about what type of gas to use. He claimed that using 87 or 89 was a mistake. To prove this he ran his car with different gas grades and checked his cylinder advance timing to make his point. I admit to using lieer grade fuel, brand name though, since I really don’t push my car and can’t feel any difference. However, when checking my timing advance at idle, it’s around -11.5. Don’t know what that means but comparing it to the video, it seems awful. Any ideas what it should be? Thanks.
 

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Administrator 2009 SLK 55 AMG/Founding Member 2006
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Premium Member 1999 SLK 5.4 M113
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-11.5 is good. A nicely tuned engine should idle comfortable between 10 and 15 degrees advance. not knowing how advanced the ECU is, my guess is that it will only variate between a couple of idle advance options - depending on temperature and other factors (maybe). I believe that the only way timing advance changes is when the knock sensors detect pre-detonation, which could come from lower octane fuels, but also by too-advanced timing.

Right now I'm Running Megasquirt on my SLK. It idles good in the 14* advance, and I'm running less advance in other rpms (28 max) so that I can run with a poorer grade fuel that we get out here in the middle of Kansas.
 

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BTW, car has had spark plugs and coils changed within last 1,000 miles. Car wasn’t used too much, maybe turned on once a month for about 2 years. That’s why I decided on changing the plugs and the coils. It runs without a problem now except for a 455 evaporative emission system leak which I’m trying to correct.
 
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