924Board.org

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

Anyone know why the 931 piece looks so incredibly over-engineered?

The valve I'm using with my EFI is either on/off. This can make the idle _really_ high when it's warming up. And when the valve clicks closed, it idles _really_ low until it warms up a bit more. So I'm looking into using the CIS AAV, which has a gradual movement of the disc based on temp (and electrical current).

I'm wondering if I can just use a simple 924/944 AAV in a boosted engine. I can't figure out why the 931 part is so chunky?

Alternatively, anyone have an extra 931 AAV to get rid of?

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1980 931S
15psi boost, MS-II, EDIS, 951 IC, custom intake, Ford 5.0L throttle body, Forge BOV, WB o2, G31 w/LSD, 964 wheels, 968 rear sway, Bilsteins, 200# Welt. springs. A laptop, and a partridge in a pear tree.
1991 964 C4 Cabriolet

Smoothie · Posted: Fri Mar 23, 2007 7:10 am Post subject:

All I can guess is that the 931 AAV is designed to handle both vacuum and pressure while the 924NA's was designed with only vacuum in mind. I'd give the 924NA version a try personally. Then if it pops open under boost (it would most likely go at the electrical connector end), drill and tap for a strategically placed screw or two to hold that end on.
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"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

Mike924 · Joined: 12 Aug 2004 Posts: 2601 Location: IoW UK

Have you thought of using the later VW type of idle valve, Nick?

There're a quite simple progressive-type design which could be adapted to your EFI system...?

The problem I have with the CIS AAV is that the open-closed range seems pathetically small. I my view, you want something with about three times as much range on it.
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1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

I need something that is temperature operated. I would have to do more soldering and circuit board & wiring changes than I would like if I switched to an electrically operated progressive solenoid.

I give the n/a CIS valve a whirl first.
_________________
1980 931S
15psi boost, MS-II, EDIS, 951 IC, custom intake, Ford 5.0L throttle body, Forge BOV, WB o2, G31 w/LSD, 964 wheels, 968 rear sway, Bilsteins, 200# Welt. springs. A laptop, and a partridge in a pear tree.
1991 964 C4 Cabriolet