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Old 07-14-2009, 08:08 PM   #1
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Unhappy 96+ MSPNP Idle Problem

My first post! Anyway, I've installed the MSPNP, IAT, and LC-1 Wideband O2. I'm configured to run with MAF removed. Everything is communicating as it should and it starts and runs fine, the first time. My AFRs are right where I want them to be 14.3 idle 14.8 cruise and 12.0 WOT @ 7psi (using MegaLogViewer and VE Analyzer) except for when I shut the car off and start it again. I always save my msq file and make sure I burn my last changes to the ECU.

Whenever I start the car after shutting it off for a while it has a hard time coming to a steady idle. It'll be rediculously lean (15.5:1 - 18:1) and the idle will jump around for a while, but if I drive the car a few hundred feet and let it come down to idle it idles just fine after that. Anyone else have this kind of situation? Any other suggestions?
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Old 07-15-2009, 11:06 AM   #2
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It sounds like a heat soak problem. You might want to try compensating with more ASE on hot starts.
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Old 07-17-2009, 10:02 AM   #3
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Quote:
Originally Posted by Matt Cramer View Post
It sounds like a heat soak problem. You might want to try compensating with more ASE on hot starts.
What would you guys recommend? When the coolant temp is over 160 it's only at 10% enrichment, should I bump it higher?
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Old 07-17-2009, 11:17 AM   #4
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Sure, try it and see if that helps.
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Old 07-17-2009, 06:41 PM   #5
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Yeah, this does sound like heatsoak. I'm not sure that ASE alone would solve the problem though.
Check out these two threads:
https://www.miataturbo.net/forum/t34473/
https://www.miataturbo.net/forum/t36594/
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Old 07-18-2009, 11:14 AM   #6
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Okay, well I tried to enrich the mixture and that was a total fail. Can anyone make some suggestions on how I should setup the ASE and/or Coolant/IAT Correction? I'm a little foggy on how they work and what they do.
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Old 07-18-2009, 01:06 PM   #7
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Well first make sure this is actually the problem. Compare your IAT before you shut the car down to the IAT right after you restart it. See if the IAT right after you restart is something outrageously high. Then when you go drive it, you should expect something more reasonable and the car idles more like normal. If what I described is what happens, then congrats, you have IAT heatsoak.

If you've actually got your LC-1 hooked up to your MS, then you can use EGO correction to mitigate much of the problem... just set your EGO target at idle to whatever you want it to be and give it enough authority (like 20% or something?). However, if the IAT temps are so far out of whack that you would need some outrageous authority, then you can make up for it with IAT related air density.

I don't have my MSQ on hand, but IIRC I do something like 125% fuel at 120*F IAT and linearly extrapolate that to 100% at 95*F or something. I didn't bother trying to get it absolutely dialed in since I let EGO correction take care of the rest.
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Old 07-18-2009, 07:38 PM   #8
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That worked like a charm, thanks Holy Driver. I'm just trying to fine comb it now.
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Old 07-18-2009, 08:02 PM   #9
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Good to hear. Are you using EGO correction alone, IAT related air density alone, or a combination of both?
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Old 07-18-2009, 08:08 PM   #10
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Both, but due to the current VE table it ended up running about 1.0 richer than the target AFR but the analyzer corrected it and now it's good. Thanks a lot!! Now to hit the dyno and see what she puts down, Monday 9AM!
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