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On 16 Oct 98, at 7:40, Erkson, Toby wrote: > Jim, I gotta disagree with you on this detonation topic. It can happen at > higher RPM -- I've experienced it around 2600-3000rpm while trying to make > it up a hill. That sounds pretty high to me, but combustion science isn't my field, so I only have the reading that I have done, plus my own experience, to go on. I have only experienced this at low RPM, and that was a long time ago, before I even knew what it was or what to do about it. > Higher compression engines, like my engine, that are at operating temp or > higher I assume that here you mean "normal operating temp or overheating" > can have preignition and detonation events occur, particularly > while the engine is under load (driving up a hill or that damn mountain in > Arizona y'all are gabbing about) and too much gas is being delivered > (heavy throttle). Actually lots of gas/air, but too little gas. One of the benefits of a rich mixture is the cooling effect of the extra gas. > You will notice that backing off on the throttle stops > this condition. Retarding the spark advance will help as well but you may > experience a loss in acceleration and power. I can't help wondering if what you are experiencing is a slightly different thing: preignition. This may be nitpicking, but preignition is the ignition of the mixture by something hot in the combustion chamber. It is not the same as detonation (ping, knock, etc) and I don't think higher octane gas will help it. I am not particular sure about this, but I think the symptoms, and the engine damage that can result, are similar. I have a friend that I can check this out with. Jim - ******************************* Jim Adney, jadney@vwtype3.org Madison, Wisconsin, USA ******************************* ------------------------------------------------------------------- Unsubscribe? mailto:type3-request@vwtype3.org, Subject: unsubscribe