Dennis, Thanks for the clear reply on the reasons for the Vanagon timing specs. I do set the timing "by the book" by disconnecting the temp sensor while the engine is running, etc. However when checking with a timing light I'd noticed that both my cars "from the factory" were set slightly more advanced than the 5 deg BTDC timing mark. "Correcting" back to nominal made the low end response suffer - even though it was only a 2 deg or so change. This made me wonder how close the pulley mark is compared to the TDC sensor and digital test rig that VW uses. (I've also compared two timing lights - same result.) Since the spec is 3-7 deg BTDC and such a small change makes a noticeable difference in engine response, I think it makes sense to adjust to the upper limit. I find negligible difference in idle speed with such a small change. The car is still within spec, but drives much better. Of course it would be best to check CO and verify - and with tightening EPA testing I expect to be looking for a reasonable CO meter soon. I see a lot of posts about repeated smog tests before people get their cars to pass, and trying to find the problem by shooting in the dark and paying for a retest doesn't make much sense. I'd rather pay the money up front for the test equipment, and KNOW my cars will pass the first time. Tom Austin, TX '87, '91, '97, etc. >Advancing the timing this way causes two problems. You increase the >possibility of engine knock and you also increase the production of NOx. VW >sets the timing to reduce the "Peak Flame Temperature" and uses the 3-way cat >to control this most harmful emission. <snip> >Hope this helps, >Dennis. |
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