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On 7 May 2002, at 23:44, Simon Glen wrote: > I continue advancing the timing and testing until she just begins to pink and > performance falls off. Then, I retard the timing by 1 to 2 degrees. This > I expect is the optimum timing for the fuel used. I try to stick to the > same brand and octane fuel. This sounds fine except that I understand that it is possible for an engine to ping (knock, detonate, etc.) so lightly that it can't be heard. The rule of thumb for VW tuners has always been to avoid going over 30-32 deg of max advance (not counting the economy vacuum advance incorporated in mech/vac advance distributors.) I'd suggest checking that you were within this limit when you're done with your testing. Part of the problem is that knock can depend not only on the engine and the gas, but also on the air temp and barometric pressure, so you could get caught by outside changes that you did not expect to make a difference. Thus you need to build in a little leeway. Your final retard of 1-2 degrees may be all the leeway you need. - Jim Adney jadney@vwtype3.org Madison, WI 53711-3054 USA ------------------------------------------------------------------- List info at http://www.vwtype3.org/list or mailto:help@vwtype3.org