m20b25 icv Q

[BrandonG]

i just did a sawp and engine was from an auto and ther was no icv so do i need to worry about this im just gunna cap all the vacume ports not used ?? i got it started with all the ports open and idle was high but i was thinkin it was a vac leak as i couldnot leave it running since ther was no intake pipe or exaust hooked up yets

[whodwho]

You can cap the ports for now and adjust the idle by throttle stop but will need to readjust the TPS. ICV are so cheap now I would just get one and put it together right. ;)

[BrandonG]

i have an icv from my eta i just wanted to delete everything im trying to clean up the bay :) im gunna cap it and try it for now , im runnin an aluminium 3" intake saturday and installing longtubes monday after class.. i am starting to love these bmws more than my vw XD

[MR 325]

All M20B25 engines have an idle control valve. Automatic or stick makes no difference.

Put one on.

[nando]

have fun on cold starts with no ICV. it's going to be a couple minutes before you can lift your foot off the gas without it dying, or you'll have a 1200rpm hot idle..

[DmcL]

All M20B25 engines have an idle control valve. Automatic or stick makes no difference.

Put one on.

what he said.

additionally you can run without an ICV and set the idle with the TB stop screw but as mentioned u will have to hold the throttle before warm or set the idle high so it will idle when cold but then will be to high when warm. i was running without an ICV for a while just to see if it made any difference in performance, seemed to sharpen on/off throttle response a little but not much else, also revs dropped quicker between gears.

what i did was i fit a locking choke cable and ran it to the TB so that i could start the car on the gas pedal and get the idle where i wanted it while cold and then lock the choke cable to stop the TB from closing back to the "warm" idle position i had set with the TB stop screw. once engine warmed up a bit i just unlocked the choke cable and the TB went back to resting on the stop screw.

as for choke cable to TB fixing/mounting i rigged up something from bike brake cable parts and misc random bits and peices i had laying around:

http://www.youtube.com/watch?v=GhQUIGigufk

[nando]

removing the ICV isn't going to make even a tiny difference in performance. it's basically a bypass valve, it's not in the flow path at all. it's also 100% closed most of the time, unless you're in overrun or at idle.

the only thing removing the ICV will do is make your car more of a pain in the ass to drive. I did without one for about 3 months during the summer, and it was very annoying. I can't imagine what starting/driving the car would be like in sub-freezing temps..

[DmcL]

no, not any difference in power but the ICV itself makes the engine feel more laggy driving harder and even in general a bit. without the ICV on lift off the engine started to decel instantly, likewise with opening the throttle from decel and when changing gear quickly the revs dropped quicker which made for smoother, seemingly easier shifts, maybe something to do with the revs and the selector in the box moving or something?

its a total PITA without some alternate way to increase idle for cold start but with that choke cable setup on mine it ran/started up like a champ warm or cold.

[nando]

I think that may have been in your mind a bit. it opens and closes instantly when the commanded duty cycle changes - bench tested mine to find the real open/closed duties at ~90hz. There's no lag, except that it's supposed to open a bit on overrun, because when you shut off the injectors, vaccuum increases, and the car will slow down faster if the valve is closed because engine braking torque will be higher. By opening it you can stay in overrun longer (with the injectors off) and save more fuel.

[DmcL]

wasnt a huge difference but there was a difference.. also on overrun as u said, engine braking felt better also.

bench testing might show the speed of the ICV to react but wont show how long it takes motronic to signal the ICV to react ontop of that.

[nando]

I'm sure the signal is very fast. All it has to do is change the commanded PWM duty.

[DmcL]

yea it seems quick but not as quick as the TB butterfly opening/closing lol

[nando]

I bet it's faster, since all it needs to see is a switch signal from the TPS.

[DmcL]

i dunno.. all i know is response on/off throttle feels more crisp as does gear change.

[BrandonG]

lol ill figure this outs :P i just wanted to run 3" aluminum intake

but i still have old icv and boot for it