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On 28 Apr 2004 at 17:43, Mark Seaton wrote: > From: "Jim Adney" <jadney@vwtype3.org> > > Another test that I'd suggest would be to put a Tee in the vacuum line and > then > > run an extra line up to a gauge next to you while driving. This way you > could > > note how much vacuum you actually get in various driving situations. You > should > > be able to make a chart of vac vs. vac. advance and then tell us how much > vac > > advance you're actually getting under various situations. > I'd like to try that but I'm not sure how I'd log it all- particularly the > mechanical advance which I'd need to work out the vac advance. I'll have to > have a longer think about this! With a Tee and a gauge in the line, just suck on the hose while you watch the timing change as the engine idles. Set the timing to TDC statically. Record the advance, vacuum, and RPM at several points up to max vacuum advance. Now, with no vacuum advance, use the throttle to duplicate the same RPM readings and record the amount of mechanical advance at the same RPMs as your previous data. Subtract the 2 advance amounts to give you the amount which is solely due to the vacuum advance. (If you're lucky, the extra vac advance won't give you enough RPM increase to bring on the mechanical advance.) Now you have a vacuum advance chart, like that in the Bosch lit or the Bentley manual. With that chart in hand, you can now do various kinds of driving, and, while consulting the gauge, tell how much vac advance you must be getting under each of those conditions. Yes, it would be a bit of work and somewhat involved, but it sounds just interesting enough that I suspect that you'd enjoy doing it. -- Jim Adney jadney@vwtype3.org Madison, WI 53711-3054 USA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ List info at http://www.vwtype3.org/list | mailto:gregm@vwtype3.org