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<TITLE>RE: Opinions wanted ( analysis of the effects of spark advance variation on vacuum)</TITLE>
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<P><FONT SIZE=2>Hi Bruce, </FONT>
<BR><FONT SIZE=2>I only changed the Closed throttle spark settings (not very scientific of me - I'll do better next time.)</FONT>
<BR><FONT SIZE=2>I let the PCM control fueling via O2s, IAC, etc, left VE alone, so I did not have as much of a control group as I should have. </FONT></P>
<P><FONT SIZE=2>My methodology (last nights tuning). I flashed the pcm, let car run 5 minutes, recorded 5 minutes worth of data, turned off, reflashed, started again, etc... The temp was consistant 166F-173F. I did not drive the car in between flashes last night, as I ran out of time (Girlfriend needed company :-)</FONT></P>
<P><FONT SIZE=2>I will repeat the experiment in open loop, disable the IAC (although the IAC vacuum adjustments feel like they should be taken into account.) </FONT></P>
<P><FONT SIZE=2>Cruising is the next step, baby steps I try to tell myself...</FONT>
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<P><FONT SIZE=2>Hmm.. Plug gap.. I have a virgin set I can install at factory spec.. I'm running 1 step colder due to 11.4:1 compression, I will go to stock temperature if anyone feels that is a factor, I would like to avoid detonation, and I know the colder plug always helped from my blown days..</FONT></P>
<P><FONT SIZE=2>Gotta run to a meeting (darn work..hehe)</FONT>
<BR><FONT SIZE=2>Keep 'em coming (Thank You!),</FONT>
<BR><FONT SIZE=2>-Christian</FONT>
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<P><FONT SIZE=2>-----Original Message-----</FONT>
<BR><FONT SIZE=2>From: Bruce [<A HREF="mailto:nacelp@bright.net">mailto:nacelp@bright.net</A>] </FONT>
<BR><FONT SIZE=2>Sent: Thursday, September 21, 2000 11:17 AM</FONT>
<BR><FONT SIZE=2>To: gmecm@diy-efi.org</FONT>
<BR><FONT SIZE=2>Cc: Chipsbyal@aol.com; ewright@silverback.gorilla.net; douglas.t.wood@lmco.com; jll@edge.net</FONT>
<BR><FONT SIZE=2>Subject: Re: Opinions wanted ( analysis of the effects of spark advance variation on vacuum)</FONT>
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<P><FONT SIZE=2>Opinions wanted ( analysis of the effects of spark advance variation on</FONT>
<BR><FONT SIZE=2>vacuum)</FONT>
<BR><FONT SIZE=2>Did you disable the IAC, set the VE table so that for a given amount of timing the fuel baseline was the same?. Over what period of time was all this done?. How long was the engine run for temps to stabilize. Looking at the BLs, seems like the pcm was affecting the outcomes, by being closed loop.</FONT></P>
<P><FONT SIZE=2>I'd suggest repeating things with the above considerations. Nice to see someone putting in the effort to really tune something and share the results.</FONT></P>
<P><FONT SIZE=2>I've found that making cruise corrections takes the ecm 15-20 mins for each correction to really take effect.</FONT>
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<P><FONT SIZE=2>While timing is a big concern, remember it's really about recovering heat energy. ie having the optimum timing of when the reaction will be pushing the piston back down. So plug gap will have a rather large effect also (in response to you using a .040" plug gap). Bruce</FONT></P>
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