AACV - Large/Main adjustment screw turns, how many?

[nelsonmxmarc]

Pulled my AACV in the midst of my rebuild and decided to give it a thorough cleaning. However, when i pulled the hardened silicone shell from the large adjustment screw, i forgot to count the number of turns needed to replace it.

---Does anyone know the correct, or ball-park amount?---


I'm only concerned because there has been a substantial amount of work done to the car - if it doesn't start properly with the nistune daughter board, i'm going to be looking at idling issues via the AACV and would like to rule that out now.. (I counted the number of turn in's for the idle air adjusment FYI)







And some fun pics FAIL!



Thanks guys

[love_boost]

didnt know there was 2 screwws :S
i think mine is turned in all the way and backed off 3-4 turns. but i cant remeber, i think its different for each car.

[nelsonmxmarc]

That big brass one is hidden under an eighth inch of epoxy/hardened silicone sealent.. Most people dont bother to remove it but i wanted to do a complete clean, and you'd understand why had you seen the crap that came out of it. Just concerned it's going to run rough @ idle until i tweak it and seal it up again..

[Skym]

Big brass looking screw looks like a spring preload screw. BOV's, etc have a similar preload screw. Sorry, wouldn't have a clue what it's set to, if it's related to that. Being glued, I would assume they don't want you to touch it. Set too soft, valve probably would bleed air, just like a BOV. Too tight and valve won't open or late open. If just a cap, use tape to seal thread, add some silicon on outside to reseal it.

With small screw, just set AAC valve to make engine idle higher, then bring idle down later on when engine is up to operating temperature and settles on 650rpm when base idle rpm is set correctly. As far as I know turning screw on AAC valve counter clockwise raises idle rpm and clockwise drops idle rpm.

You'll need to reset base idle via Nistune tuning software (under display and then consult active test) or via turning screw / diagnostic pot fully anticlockwise on side of ECU and from memory, before you do that, unplug AAC valve plug (stops ECU playing with idle rpm). Then adjust AAC screw clockwise until idle rpm drops below 600rpm and then turn AAC screw counter clockwise bring idle rpm back up to 650rpm, which matches idle rpm on ECU.

Essentailly what your doing is making the AAC valve idle rpm (650rpm) match the ECU idle rpm (650rpm). So if ECU decides to adjust idle rpm upwards, engine is exactly at that idle rpm. I guess you could call it calibrating the base idle rpm.

[nelsonmxmarc]

Thanks Skym,
base idle will be set through Nistune, however i only wanted to calibrate ecu idle / AAC idle once this bolt was set in the correct position.. Like you said, it is most likely NOT meant to be tweaked being that it was sealed in place, however it was due for a serious cleaning, couldn't resist

As i look at the AAC valve, the only plausible explanation i have for this large brass screw/spring combo, is that it runs in line with the AAC valve solenoid, operated by the ECU. When the car is turned on, the ECU Should calibrate this solenoid should open/close to let in the proper air @ idle. So in theory, no matter how much tension or how little tension i put, it should calibrate to a certain extent. Basically, i need to find a happy medium for the two, so that it can open and close to its maximum potential..
Perhaps a bit confusing..

At any rate, the idle air screw (smaller one) has been set to its inital position. I believe i had a few vac leaks, however, so it will likely be quite off as well..

If anyone has exact turn #'s, i'd greatly appreciate it, however, i plan to run the car and tinker with it anyways to see what kind of results i can yield @ idle.. Perhaps it will mysteriously cure peoples idle hunting issues ? I'll let everyone know once the car is running - unfortunately, by mid march.

[Skym]

I wish you best of luck in sorting out that AAC valve.

If somone could post a photo of their AAC valve and by just looking at depth (how many screws of hole you can see and position of hole in middle of screw) should give you a rough idea how many turns and rough position.

[nelsonmxmarc]

Thanks bud!

If somone could post a photo of their AAC valve and by just looking at depth

Been searching my arse off!!
I know there's one lingering on SAU, as that's where i picked up on the dissassembly of the unit.. There was also a before and after image of the one he cleaned, but it's turning out to be quite elusive lol.

Have been keeping busy with my rebuild though - emphasis on RE, as it's finally going back together... Ahhhh spring's a comin'!

[BrianV8]

don't think there is a set number of turns otherwise they wouldn't be adjustable. Every car is different. Adjust it to make it work for your application

[nelsonmxmarc]

Thanks Brian,
Going to look into it more once the car is running, however a baseline setting would be useful as opposed to having it turned in 2 - 3 turns when the oem could be as much as 7-8.. Could be the difference in a terribly idling car vs being completely fine.. But we shall see come spring.

[BrianV8]

yeah i've had high idle issues with my motors. Don't know why, 2 different AACV's so i just screw it all the way in to get the idle as low as possible and call her good. I"ve worked on many proper idling skylines too and yeah just let the car idle and slowly adjust it until it runs how you want it.