IAC Valve

[craigkenyon]

I am just starting the design ideas for a intake manifold. I saw the following TB from Eldebrock. It has no provision for a IAC. What would be the downsides?
http://www.edelbrock.com/sportcompact_n ... vict.shtml
Craig

[Paul_VR6]

No idle valve gives you a low cold idle rpm and a higher hot idle rpm, and depending on where you set it, you can stall coming to a stop.

However you can drill a hole in the manifold, install a fitting and fit something like a Bosch 2 wire PWM valve in almost anything relatively easily.

[craigkenyon]

OK, how about this idea, set the idle properly for fully warmed up operation and use a choke cable as a hand throttle to manually set the cold idle speed? I would get to use my choke knob that exists for something and the actions would be similar to what I currently do. I don't need to automatically bump idle as there is no A/C load. What do think?

[R100RT]

That works okay. I've done that on my motorbike, as the throttle body had provision on it for a small cam plate and throttle increase cable attachment on it, for just such a purpose. I find it is relatively easy to start with "choke" on (which is just a throttle increase of course) and as it warms up I reduce until right back at base idle minutes later.

[Bernard Fife]

craigkenyon,

You don't necessarily have to have an IAC - I didn't on my 406 Corvette until MS-II came out (so from 2002 to 2005 when I was running MS-I). You might have to let the engine warm up for a few minutes before putting it in gear (especially with an automatic). It also depends on how cold it gets where you are (it rarely goes below freezing where I am).

So if this was mine, I would try without it, then add one only if you find you need it.

Instead of a 'choke' cable acting on the throttle, it might be easier to run a vacuum hose to a valve near the driver - so you can operate it manually. After all, the IAC valve itself is just a controlled vacuum leak, and MegaSquirt is only concern about the MAP, not how it gets into the manifold. You might want to source the air from the engine compartment (ideally downstream of the air cleaner) to provide clean air and reduce the 'whistling).

Lance.

[Jack]

Instead of a 'choke' cable acting on the throttle, it might be easier to run a vacuum hose to a valve near the driver - so you can operate it manually. After all, the IAC valve itself is just a controlled vacuum leak, and MegaSquirt is only concern about the MAP, not how it gets into the manifold. You might want to source the air from the engine compartment (ideally downstream of the air cleaner) to provide clean air and reduce the 'whistling).

Lance.

Nice Lance. My IAC is acting up, but until I can pull it apart and clean/fix/rebuild it, Teeing off a vacuum line is an easy fix.

Thanks,

Jack