IACV Tuning

Civic/Integra/etc with a K swap

IACV Tuning

Postby mattj » Sun Jul 01, 2018 11:22 pm

Hi again,
I had my K24 tuned recently and we couldn't improve the extremely low cold idle RPM without an IACV, so I added this on:
https://kmiata.com/products/idle-air-co ... mote-block

Trouble is, with this on, warm idle is about 1800 and doesn't budge. I have the TPS calibrated at 0% (actually 0.450V) and the IACV enabled on the monitors tab. If I restrict the IACV airflow by pinching the hose 95%, I can get a reasonable idle speed. This is all with the throttle blade screw almost completely closed. I've already confirmed I have no vacuum leaks (engine stalls quickly with hand over TB).

The RPM does increase if the IACV is unplugged from the engine harness, so it does appear to be doing something. Hoses leading into and out of the IACV are 3/8"; one ahead of the throttle blade but before the air filter, the other going to the 1/8NPT port at the rear of the Skunk2 intake.

The ECU has a '03 Accord (RAD?), and the harness is from an Element. The IACV is a Standard products brand which seemed to get good ratings on Amazon.

Any ideas on this? I feel like I'm missing something.
mattj
 
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Re: IACV Tuning

Postby KTuner » Mon Jul 02, 2018 5:18 pm

Unfortunately with an aftermarket plate it may be letting more air through than was called for with the factory setup. The fact that you can restrict airflow and maintain a lower RPM also suggests that. So in reality too much air is getting by on its own for the IACV to limit RPMs. What happens if you block the screw bypass completely and just allow the IACV to do the work?

With IACV disabled you would need to use fuel and ignition to maintain an RPM, which there are controls for using the PRB codebase.
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Re: IACV Tuning

Postby mattj » Mon Jul 02, 2018 5:49 pm

Thanks for the reply. If I close off the throttle plate completely, it will maintain 1500 RPM or so while warm. That being said, when using an IACV, should the butterfly be completely closed? Other platforms I have used usually want the butterfly to be slightly open so the IACV is partially working and not supply all of the engine's idle air.

Does it make sense to use the ignition/fuel to maintain idle along with the IACV? Or is it one or the other? To me it makes more sense to calibrate the TPS at 0% and not rely on ign/fuel when using the IACV in an effort to simplify things.

I'll add a flow restriction inside the hose and see where that puts me. 3/8" hose may simply be way too much air.
mattj
 
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Re: IACV Tuning

Postby KTuner » Mon Jul 02, 2018 9:52 pm

Yes, but generally idle is controllable doing such and you're suggesting that's not the case for you. I indicated everything points to you getting too much air.

By default the ignition adjustments for idle are taking place to aid the IACV. You can alter those for more control.
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Re: IACV Tuning

Postby mattj » Mon Jul 09, 2018 7:46 pm

I have the issue figured out. I thought I should post the fix to hopefully help others down the road.

Long story short, I had the car dyno tuned and there was a number of odd issues after that. IACV problems, idle misfires, off idle stumbles, no closed loop operation, etc etc. Just a bunch of odd problems. I ended up coping the fuel/ignition/cam maps into another file I used previously and bingo, runs like a dream. Near perfect both cold and hot operation. Both files used the same compensation settings that I could tell. I really can't explain it, but it worked - I wish I had a definitive reason though!
mattj
 
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Re: IACV Tuning

Postby KTuner » Mon Jul 09, 2018 8:51 pm

Send both files by email and I'll take a peek!
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