IAC control?
 

Anyone figure out good values for closed loop IAC control? I've been playing with my MS maps and have no problem with startup as well as verifying that fuel and spark are working, but it seems that my idle issues are from MS trying to control idle via the PWM control of the IAC. I probably will fiddle with this thru the week, but I may just have to hand back IAC control to the stock ecu. :cry:

What transistor are you using for idle control? Tip120??

I did some testing with the TIP120 trany's for PWM IAC control on a '90 Miata and found good settings for it. I'll add them to our Miata article.


Done. Check the bottom of the article now--

http://www.diyautotune.com/tech_arti...azda_miata.htm



FYI-- the TIP120 works pretty well, but on the Miata valve the range of idle speed control is somewhat limited. I've started using a different trany but it's SMT so it's not easy to retrofit on a standard board. To be honest though, the TIP120 works well enough to warm the car up just fine, I think the high idle was around 1300rpm.

Jerry, those settings are from a 1990 aren't they?

The 1.8's have a slightly different IAC which works on a much lower frequency. I tried to run my 99 engine/IAC from the old 1.6 ECU and the ECU fried the IAC because of the different frequencies.

My Idle Valve Freqyency setting is at 32 and if I set it any higher the whole intake buzzes like crazy (which is what the old IAC used to do before it died completely on the old ECU).

It is probably worth mentioning something about which engine those settings are for.

Steve

Yep-- from a 1990. Good callout, I just updated the article with that info. I'm looking to get a 94-95 car pretty soon and I'll test the settings needed with that valve and post those as well.

since we both are 1.6, you could try my settings if you want, they're not closed loop, but they work fine.

i hope adam isnt having this many problems with mine that i would feel bad. + he might jack up the price quick everyone think positive waves his wya and the MS will magically be perfect with no problems :rofl:

Using the TIP120 as per your site. I tried your settings (thanks BTW) to no avail. It's definitely the IAC issue as I did two other things, I set the IAC control to off and the car idled high, but no wavering and no stalling. Then I tried closed loop which interestingly enough worked better than the warmup only setting but still getting an oscillating idle. I may try to tune the closed loop settings.

If I use your settings the idle oscillates a lot and then quickly stalls if I do not hold down the gas. Granted the easiest thing is to just return idle control to the stock ECU, but I'd rather go complete standalone.

Try closing the gap on the high and low DC settings, instead of 40 and 12 try 37 and 15. See if that works any better...

There may be some variance from car to car in the exact threshold, and if so a safe range should be able to be found that should work on all cars with the same valve, there shouldn't be that much variance.