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Scorpio · Posted: Thu Jan 29, 2009 1:10 pm Post subject: AAV replacement for EFI

Min left his in
Leadfoot used a stepper motor sytem
Macb used a solenoid valve

Is the AAV sufficient as an idle air valve? dont really want to complicate my already complicated megasquirt install if i dont need to

Thoughts, options?
_________________
1979 NA
MS1..EFI..
GARRETT T25 TURBO
BILSTEIN SHOCKS
GT BASED CUSTOM BODYKIT

Brisbane , Australia
Think mean think fast
all youll see is
my Porsches Arse!!!

Min · Posted: Thu Jan 29, 2009 1:55 pm Post subject:

I'm not happy with my AAV, I intend to switch it out for a on/off 'fast idle valve'

flosho · Posted: Thu Jan 29, 2009 2:05 pm Post subject:

I don't have any cold idle valve..

Starts a little rough in sub 40 temps, but other then that its fine.

I've been looking for a FIdle valve that is simple to plumb in...
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[This Space For Rent]

Scorpio · Posted: Thu Jan 29, 2009 2:20 pm Post subject:

so basically the IAC or AAV or solenoid valve steps out of the equation once the engine is warm? So its purpose is only to provide extra Idle air on a cold start?

so how would a solenoid style "ON/OFF" valve be controlled ?

and wouldnt it give a "sudden" spike in the A/F ratio curve?
_________________
1979 NA
MS1..EFI..
GARRETT T25 TURBO
BILSTEIN SHOCKS
GT BASED CUSTOM BODYKIT

Brisbane , Australia
Think mean think fast
all youll see is
my Porsches Arse!!!

Min · Posted: Thu Jan 29, 2009 4:16 pm Post subject:

leadfoot · Posted: Thu Jan 29, 2009 8:15 pm Post subject:

Actually I think it was the opposite mate.
I used the solenoid and mac used the stepper motor.

The solenoid was always on. The air bypass screw on the throttle is screw in closed so the solenoid controls all air bypassing the throttle.

The middle or idle RPM was dependent on coolant temp i.e cold , normal and hot temps and programed on a temperature basis.
There were two speeds, slow and fast... these could be set for RPM, load and temperature and also overrided in respect to time. i.e fast idle cold start for 30 seconds to 50 deg
There was also an extra air opening setting for added air in extreme temperatures.
The PWM duty could be changed via frequency of the valve and there is also a dead zone were the valve become inactive.
Need to check the MS manual for available settings you can program... essentially they can do far more options than a stepper.
Stu
_________________
1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress...

Martijnus · Joined: 29 Dec 2006 Posts: 2019 Location: Netherlands

I'm using a PWM valve (2 wire).

I didn't want to use my AAV because since my whole engine is controlled by a computer, I thought the fast idle should be computerized too

AAV can be used though... Didn't want to use a stepper motor, haven't seen any yet and it takes a lot of MS's capabilities (so other options can't be used).

Can't tell you how well it works, the problem I have is that I need to distribute the air to each cylinder because I'm using ITB's... I connected the PWM valve to my vacuum accumulator to provide the cyls with the air...but that is STUPID...do NOT do that

what happened in my case is that my vacuum lines (3mm ID) are too small to suck enough air through. The volume my 4 lines can displace is just 14% of what the PWM valve itself can displace.

Another effect was that my MAP didn't go below 90kpa causing my brake booster (and ignition and FPR) to function badly (in case of the brake booster, it doesn't work..).

Made a new vacuum accumulator, which consists of two chambers, 1 chamber for vacuum, one chamber for idle supply. Using thicker lines to feed the air to the engine (to the stock injector holes).

Hope that works

I'm quite sure though that using a on/off solenoid will be adequate to raise the idle speed.
If you use a stepper motor/pwm valve, you introduce another variable that is tunable... so now I have to adjust my WUE and my PWM%, while with a on/off valve, you've 'locked' the air factor, and you only have to compensate fuelwise.
_________________
"Rule: Turbo's make torque, and torque makes fun." (C. Bell)

924 "50-jahre", 1981.
MSII/extra, LPG, ITB's, 5lug.
To be turbo'ed in a while.
Killed her at the Nurburgring, Porscheless at the moment

flosho · Posted: Sat Jan 31, 2009 5:08 am Post subject:

Martijnus, do you have a part # or pictures or both of the FIdle valve you used?
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[This Space For Rent]

Martijnus · Joined: 29 Dec 2006 Posts: 2019 Location: Netherlands

Raceboy · Joined: 01 Mar 2004 Posts: 2327 Location: Estonia, Europe

I have used many IAC valves and stock AAV is next to useless with EFI.

I've had best results with BMW/Porsche 993 3wire PWM valve and Opel 2wire PWM valve (same ise found on Porsche 944 S and 964, though with different part numbers, obviously for pricing). I used those with VEMS, they require hi-current FET output. Some of them can be used with stepper outputs (the ones that don't consume more than 1A on normal operation).

On daily driver I wouldn't have a car without it because it makes idle very precise to target with switching high-beams, aircon, blower/rad fan etc. And of course making cold idle and warmup exactly like normal driving.
_________________
'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold

'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche

Joes924Racer · Posted: Sat Jan 31, 2009 8:26 pm Post subject:

Ive been looking at the mega squirt 2 web site and reading about it
seems like something id like to have.
_________________
1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.

Scorpio · Posted: Sat Jan 31, 2009 10:55 pm Post subject:

Raceboy · Joined: 01 Mar 2004 Posts: 2327 Location: Estonia, Europe

It means that when engine is cold and needs more fuel, it needs more air also. If you switch on AC, engine rpm drop because of the additional load, as do with heater blower, rad fan etc. correctly configured IAC valve will compensate for these occasions automatically pretty much without noticing the rpm fluctuation.
_________________
'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold

'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche

Min · Posted: Sun Feb 01, 2009 3:09 am Post subject:

RC · Joined: 25 Mar 2007 Posts: 2637 Location: Australia

A GOOD stock AAV could be used for a cheap/easy/lazy option with some fiddling of the throttle bypass screw and possibly a restrictor. However it was barely adequate with CIS and even new valves dont completely close, let alone 30 yo used ones.

Next easiest/cheapest option is a simple solenoid valve, on/off, since it practically never gets below 0*C here. Heaps of various ones available. Perhaps look at emissions systems at the local wreckers or something similar to this one.
http://www.jaycar.com.au/productView.asp?ID=SS0905&CATID=&keywords=solenoid+valve&SPECIAL=&form=KEYWORD&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=
It is only 1/4" but should be sufficient, only has to allow some air to bypass the throttle plate when cold. Play around with switch point for best warm up, say >40* but <75*.

If you really want the engine to start/warmup/run like a new modern car and take advantage of MS capabilities you should consider a PWM or preferably a stepper motor IACV. Either will give much greater versatility and performance. Most PWM valves are relatively large and must be mounted close to TB. Stepper IACVs usually mount in the TB, so should be considered together, especially if you havent yet got one. Some external system like the carved 2" cube of aluminium to accept an IACV as promoted on MS site could be adapted. Of course these options cost slightly more and involve additional time setting up and tuning.

http://www.megamanual.com/v22manual/mwire.htm#idle

http://www.megamanual.com/ms2/IAC.htm