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Old 04-24-2016, 07:14 PM   #1
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Default AFR worth worrying about...?

Some full disclosure... I tune a lot of motorcycles, so I'm not completely ignorant to the principles, however, this is my first toy car, and I couldn't be more clueless in regard to Miata tuning. So much so, that while doing extensive search on the forums, the lingo is way over my head, so sadly it's not been much help.

The car is a 40k mile cherry 04 MSM I bought off a retired gent. I added FM intake, exhaust, boost controller, and intercooler. At that point, I was done looking for performance, but the OE computer fueled really irregular, so I went with the Mega Squirt from Rev. and RX8 injectors. (side note: he was a pleasure to deal with, offering very timely support). I did a lot of local research, and all the great feedback led to one tuner, so I took the car there last week. Now.....
  • It's still hard to start cold. Is this the nature of an aftermarket computer?
  • AFRs look nice and safe under spirited driving, but run 15-15.5/1 under light cruising loads. Is that optimal? Is it even safe?
  • The tuner said for some reason the AEM gauge isn't sending signal to the computer for trim. That was a plug and play connection. Perhaps I have to enable it via the laptop? I'm also guessing that may cure some of my lean AFR readings?
Other than the hard cold start, the car runs and pulls well. I just want to make sure I'm taking care of it and have it optimized, as it's a weekend mountain toy for me and the wife, and hopefully will be for years to come... Thanks to any of you willing to overlook my ignorance and offer solid advise.

Greg
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Old 04-24-2016, 10:09 PM   #2
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Quote:
Originally Posted by MNNTHBX View Post
  • It's still hard to start cold. Is this the nature of an aftermarket computer?
  • AFRs look nice and safe under spirited driving, but run 15-15.5/1 under light cruising loads. Is that optimal? Is it even safe?
  • The tuner said for some reason the AEM gauge isn't sending signal to the computer for trim. That was a plug and play connection. Perhaps I have to enable it via the laptop? I'm also guessing that may cure some of my lean AFR readings?

Bad cold starts is just bad tuning. It can be fixed.

15-15.5 is fine under cruising loads

If you're referring to the gauge being attached to the ECU fixing lean AFR readings, no. Completely unrelated. The fact that the AFR isn't being read at all by the computer is due to a wiring issue between the AEM gauge and the megasquirt. It should be a white wire for 0-5V signal going to the megasquirt.
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Old 04-24-2016, 10:42 PM   #3
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Thanks for the input. After revisiting all the instruction, it appears I did have to enable the AEM gauge via an ini file. The AFR gauge on tuner studio now works, so I assume I have that handled... I thought the computer would auto trim within reason...?

It does show my timing advance at 14 degrees. Does that sound right?

Also, the car idles at 800, unless of course I roll the windows down, hit the brights, etc., which pulls 200 rpm out of it. Can I raise the idle RPM just a bit? When clutching for a stop light, etc. it dips low for a second, which is a bit unnerving...

Again, I really appreciate you working with my ignorance here... It's valuable stuff to me.
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Old 04-24-2016, 10:46 PM   #4
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Quote:
Originally Posted by MNNTHBX View Post
Thanks for the input. After revisiting all the instruction, it appears I did have to enable the AEM gauge via an ini file. The AFR gauge on tuner studio now works, so I assume I have that handled... I thought the computer would auto trim within reason...?

It does show my timing advance at 14 degrees. Does that sound right?

Also, the car idles at 800, unless of course I roll the windows down, hit the brights, etc., which pulls 200 rpm out of it. Can I raise the idle RPM just a bit? When clutching for a stop light, etc. it dips low for a second, which is a bit unnerving...

Again, I really appreciate you working with my ignorance here... It's valuable stuff to me.
Timing Advance is a whole table. Unless you mean for cranking only, then yes, 14 is fine.

Autotrim = EGO in the sense of something that is always active, but usually only makes like 5% changes.
Autotrim = VEAL, makes permanent changes to the tune, where as EGO is more just for getting out any final little bumps and fluctuations AFTER you're tuned.

To raise the idle you have to change your Target Idle Curve. Though there is a voltage correction table you should be able to tweak to try and fix the rpm drop during periods of high current draw.
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Old 04-25-2016, 12:10 AM   #5
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Find a new tuner too.
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