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<DIV><SPAN class=366165514-21092001><FONT face=Arial color=#0000ff size=2>are
you also attempting to lean? </FONT></SPAN></DIV>
<DIV><SPAN class=366165514-21092001></SPAN> </DIV>
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<DIV class=OutlookMessageHeader dir=ltr align=left><FONT face=Tahoma
size=2>-----Original Message-----<BR><B>From:</B> owner-gmecm@diy-efi.org
[mailto:owner-gmecm@diy-efi.org]<B>On Behalf Of
</B>cmillard@crutchfield.com<BR><B>Sent:</B> Friday, September 21, 2001 7:05
AM<BR><B>To:</B> gmecm@diy-efi.org<BR><B>Cc:</B> Chipsbyal@aol.com;
ewright@silverback.gorilla.net; douglas.t.wood@lmco.com;
jll@edge.net<BR><B>Subject:</B> Opinions wanted ( analysis of the effects of
spark advance variation on vacuum)<BR><BR></FONT></DIV>
<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> </P>
<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> </P>
<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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