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<TITLE>Opinions wanted ( analysis of the effects of spark advance variation on vacuum)</TITLE>
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<P><FONT SIZE=2>Friends, Programmers, Hacks, Lurkers-</FONT>
<BR><FONT SIZE=2>.</FONT>
<BR><FONT SIZE=2>I would like your feedback/ opinions on a little experiment I did.</FONT>
<BR><FONT SIZE=2>The experiment was studying the effects of spark advance (closed throttle) on idle vacuum.</FONT>
<BR><FONT SIZE=2>.</FONT>
<BR><FONT SIZE=2>Please take a look at it here:</FONT>
<BR><FONT SIZE=2><A HREF="http://cmillard.freeservers.com/Z28/PCM/Ignition/idle%20spark%20tuning.htm" TARGET="_blank">http://cmillard.freeservers.com/Z28/PCM/Ignition/idle%20spark%20tuning.htm</A></FONT>
<BR><FONT SIZE=2>.</FONT>
<BR><FONT SIZE=2>My theory was based on for the same given RPM (900 rpm) the spark advance which yielded the highest vacuum would give the best fuel economy. The MAP sensor reads opposite vacuum (higher vacuum is lower MAP, and vise versa), so I was shooting for minimum MAP. I plan to apply this to idle at first, then the entire timing map, if enough data can be collected.</FONT></P>
<P><FONT SIZE=2>.</FONT>
<BR><FONT SIZE=2>This is based on Bruce's tuning tips I read about two years ago on ECMGuy's page, which just started to click in my short circuited brain (zap!)</FONT></P>
<P><FONT SIZE=2>.</FONT>
<BR><FONT SIZE=2>The test vehicle uses a '8051 (as Daawagon and Dave H. called it). The 16188051 is factory in my 1995 Camaro Z28 running 11.4:1 compression with a LT4 HotCam (219/228 .525/.525 112)</FONT></P>
<P><FONT SIZE=2>.</FONT>
<BR><FONT SIZE=2>I did several excel pivot table charts based on data from about 12 flashes with closed throttle spark advance varying between 12 and 34 degrees. Here's what I found:</FONT></P>
<P><FONT SIZE=2>.</FONT>
<BR><FONT SIZE=2>The higher the spark advance the higher the vacuum ( to a point, up to 36 degrees advance ) Optimum spark at idle was 34 degrees, factory was 20 degrees- whoa.</FONT></P>
<P><FONT SIZE=2>.</FONT>
<BR><FONT SIZE=2>The higher the spark advance the lower the injector pulsewidths (matchs vacuum), again to a point. This again would help to suggest better gas mileage.</FONT></P>
<P><FONT SIZE=2>. </FONT>
<BR><FONT SIZE=2>Sorry for the rant, it's Friday.</FONT>
<BR><FONT SIZE=2>.</FONT>
<BR><FONT SIZE=2>Your feedback is appreciated, </FONT>
<BR><FONT SIZE=2>-Christian</FONT>
<BR><FONT SIZE=2>(disclaimer: working on 2 hours sleep)</FONT>
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<P><FONT SIZE=2><A HREF="http://cmillard.freeservers.com" TARGET="_blank">http://cmillard.freeservers.com</A></FONT>
<BR><FONT SIZE=2>(Feel free to snarf the folders of my site for amusement)</FONT>
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<P><FONT SIZE=2>Christian Millard</FONT>
<BR><FONT SIZE=2>Application Developer</FONT>
<BR><FONT SIZE=2>Crutchfield Corp</FONT>
<BR><FONT SIZE=2>www.crutchfield.com</FONT>
<BR><FONT SIZE=2> </FONT>
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