Volvo turbo cold start idle surge

[VolvoTurboWagon]

Hello,

I'm new here so please excuse any errors or if I've posted in the wrong section.

I have a '91 Volvo 240 wagon that has been turbo'd running microsquirt. It actually has a pretty good tune on it I think running 10 pounds of boost. Not a race car but will get out of it's own way.

Anyways, I have been unable to get the cold start idle sorted out. Usually it will fire up fine, rev to 2600-2800 rpm and then either die or almost die then rev back up. It will do this for a minute or two and gradually rev lower and lower until the idle settles around 1200. When the car is warm I can start it, it will rev to 1000, then fall to 800-900 and sit there steady.

Below is a data log from this morning's drive into work showing the cold start idle.
http://docs.google.com/file/d/0B66rDzn6 ... cslist_api

I'm at my work machine for the moment so if the link is unviewable let me know and I can fix it on my home machine.

Thanks!

[nathanhardy]

post a msq

I learned recently that bosch valves need some duty to stay shut if you taper down to zero duty it will open I think its designed that way so as if it fails you can still drive the stock car! try tuning it up to the 30+% range keep going past 40 if it doesn't drop by then I'm wrong on your setup.. are you using open loop? also have you played with crank duty? maybe the taper needs to be lower so it comes down faster

[nathanhardy]

could also be timing from what I hear if it;s to high the motor can get stuck in those higher timing cells due to the rpm and just wont drop out, there is a fairly resent post on that

[VolvoTurboWagon]

Okay attached is the current tune.

[Matt Cramer]

The closed loop idle seems to be chasing its tail here; can you get it to idle well in open loop?

[VolvoTurboWagon]

I'll flip it over to open loop and see what it does. Anything else I should change?

[VolvoTurboWagon]

Just to update.

Flipped over to open loop and I was able to get it to cold start immediately into a smooth idle. After driving it if I put it in park the idle will rise to 1400 or so but I just shut it off as I've gotten to where ever I was going. So far I haven't felt like messing with it more to try to get it to not do that. I've just been happy to be able to start it and have it idle like a normal car.