toofast928

What do you use for idle up valve during cold start? The L Jet AAV or just a idle bypass valve, open for start, close at preset coolant temp.

Lizard928

Whatever you want!

You can use the AAV, or use a PWM valve, or a 4 wire IAC. The list goes on.

toofast928

What do you use Colin?

Ducman82

i use the 3 wire bosch unit. PWM warm up.

Lizard928

I use a 2 or 3 wire PWM valve.
The 928 S4 one works, or the VW one from a ton of golfs work. Even the 3 wire ones only require 2 wires. Then use the F-idle output to control.

If you need one I have a couple spars on the shelf. $40 shipped.

toofast928

Thanks for the input. I decided not to use the warm up valve and to go with the simple on/off bypass valve. The AC idle up valve from L Jet. Two reasons-

- The Bosch warm up valve needs 12 ignition voltage in order for it to close. If the ignition is on but the engine is not running, the valve is in the process of closing. So its possible I may sit in the car, listen to the radio, warm up valve does its thing and closes. When I start the engine their is no air bypass.

- The second and most important reason not to use this valve, it leaks vacuum when closed. When closed at engine warm up the valve does not seal 100%. Additional air "leaks" past the throttle plate.

Ducman82

The valve closes with ignition on only if it needs to close. It will open and or close depending on engine temp. As far a air leaking, mine would leak so little it's not worth thinking about. It seals pretty good. Unless it's some crazy hyper sensitive boosted application it would work fine. It is a stock part after all

toofast928

My engine isn't exactly stock.

Without the valve installed, measured 2 Hg rise in engine idle vacuum using Pico Scope with pressure transducer.

Lizard928

The AC idle up valve will not supply enough air for really cold starts. It's too small.....