SM4 IAC tuning

[yrkesman]

I have been playing few days, with the SM4 IAC controll. The car I have is escort cosworth and it has the standard idle control valve. I have been using the Bosch 2 wire option, but I'm not sure if that is the correct one for my setup? I've noticed that with it, the valve won't close more than ~31-32%, is this normal? Could someone explain how the IAC should be setup? What's the correct method to tune "slow adapt rate", "slow adapt rate (no F/B)" and "IAC dynamic comp"? I have tried various slow adapt rates and dynamic comp values, but the idle still does hunt sometimes. I'm beginning to wonder if the problem is really my iac valve. I use idle ign delta RPM, with -200rpm@0deg, 0rpm@10deg, 400rpm@20deg.

[MRMRacing]

If you select 2-Wire Bosch in SM4 software it offsets the output 30 % compared to linear. So if you select 2-wire the SM4 min value O/P is 30 % duty, but you can not see this except if you have a scope. The IAC valve % will not display this. So if the software displays around 30 % you may have the IAC min position value to high. IAC valve in software can be from 0 % to 100 % but it is the O/P signal thats offsets invisible.

[yrkesman]

If you select 2-Wire Bosch in SM4 software it offsets the output 30 % compared to linear. So if you select 2-wire the SM4 min value O/P is 30 % duty, but you can not see this except if you have a scope. The IAC valve % will not display this. So if the software displays around 30 % you may have the IAC min position value to high. IAC valve in software can be from 0 % to 100 % but it is the O/P signal thats offsets invisible.
Okay, thanks. My minimum opening is set to 0. How about those adapt rates?

[MRMRacing]

And still stuck at 32% IAC valve pos? Have you set IA tps & load settings properly so it is activated? Adaption No feedback is how fast back to calculated IAC position based on settings like IAC closed RPM & IAC Prop.range and more. The feed back is also based on actual rpm,

[yrkesman]

And still stuck at 32% IAC valve pos? Have you set IA tps & load settings properly so it is activated? Adaption No feedback is how fast back to calculated IAC position based on settings like IAC closed RPM & IAC Prop.range and more. The feed back is also based on actual rpm,
No, the valve position goes to zero, but like you said, there's the offset (which I didn't know earlier). I'll check those options again, if there is something wrong. If that doesn't help, I'll try my friends iac valve.

thanks for your help.

ps. Do you have any IAC base settings for cosworth yb engine that I could try?

regards,
Jani

[MRMRacing]

Select the linear insted of 2-wire Bosch.
I would suggest
Slow adapt rate to 1400.
Slow adapte no feed back to 950
Dynamic comp to 40

Also strongly suggest use of three wire IAV valve, then you can control it in both directions and not have to count an the spring to return the valve. I have archived much better idle with 3-wire instead of the 2-wire.

[gti]

I am working on a VW Golf VR6 which has the Bosch 2 wire ISC.
I changed the settings as per Robert advised.
It is now idling much better, from cold to warm.
Thanks!

[yrkesman]

It seems that swapping to 1.09 chip solved my idle problems. I'm not 100% sure that it wasn't some wrong setup value, but I'm quite happy now how it works with the 1.09 chip. Car also starts now pretty much as good as standard car with the 1.09 chip and the mrm base map values :)