Techsalvager

I was reading a book about tuning and notice a section about idle air valve and superchargers and how some recommend letting the IAC take air from a atmo source instead of the pressurized intake system.

With megasquirt will the idle valve ever truly close with proper settings. I was thinking about trying this but unless I can make sure it fully closes when not in use for idle than it would also become a big air leak.

Braineack

iTrader: (62)

IIRC ours will leak under boost.

D.dutton9512

Did you not install a 1 way check valve on the line from the IAC? One is included in the JRSC kits and prevent exactly that. I don't see why this wouldn't work for turbo guys as well.

Techsalvager

are you venting the IAC to atmo and using a check valve to prevent air under boost to leak though the iac?

Braineack

iTrader: (62)

(zack morris's phone)

That is the question

Ben

iTrader: (33)

If you program it correctly, yet it will close, no different than unplugging it. That is not to say that it can't leak (which would be a mechanical fault and would occur with any type of engine management), but if both sides of the valve are plumbed into the intake, the leak would be incidental.

Braineack

iTrader: (62)

When my valve is "closed" (i.e. min. duty cycle), I can still idle at like 600RPM, that would suggest it would leak if plumbed to ATM.

Ben

iTrader: (33)

What changes when the valve is unplugged?

Also the idle valve isn't the only place where air can get in. Check out the throttle blade itself too. It doesn't close 100%. There's also the throttle bypass screw. Half the race cars I see don't have IAC, but they all still start/run/drive.

Braineack

iTrader: (62)

true.

D.dutton9512

No, the hose comes from the valve, with a 1 way check valve in place, and then into the intake, not atmo. This way even if it does leak the check valve will stop it from being a boost leak.

Braineack

iTrader: (62)

I don't understand the point of the check valve in this instance.

If the air valve leaks when closed, and you're boosting boost will enter both the hose for the idle valve and the TB and all is normal.

If the air valve leaks when closed, but it's getting air from VTA, when you're boosting, boost will exhaust from the idle valve and all is bad.

D.dutton9512

The hose from the valve connects to the intake before the supercharger. So if it leaks when boosting it will act as a boost leak. With the MS1 this is a really good thing because funky things happen to idle when you set the closed(dc) to 0.

Techsalvager

I was firguring there is more air to had from having it open to ATMO so it can react quicker to the air right there versus the air in the intake system.

94mx5red

iTrader: (14)

*sigh* Mine is VTA.

Braineack

iTrader: (62)

but that's an if.

falcon

iTrader: (13)

I haven't had idle control on my Miatas for almost 2 years n started out with it leaking when I had the ms, and now with the haltech I don't runone because it can only control open loop idle so I didn't bother hooking it up. I don't have stalling issues and I have a supercharger.