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Old 06-03-2011, 06:48 PM   #1
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Default idle air valve

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.
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Old 06-03-2011, 07:01 PM   #2
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IIRC ours will leak under boost.
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Old 06-03-2011, 08:11 PM   #3
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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.
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Old 06-16-2011, 06:54 PM   #4
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Quote:
Originally Posted by D.dutton9512 View Post
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.
are you venting the IAC to atmo and using a check valve to prevent air under boost to leak though the iac?
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Old 06-16-2011, 08:19 PM   #5
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(zack morris's phone)

That is the question
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Old 06-17-2011, 11:33 AM   #6
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Quote:
Originally Posted by Techsalvager View Post
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.
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.
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Old 06-17-2011, 11:35 AM   #7
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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.
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Old 06-17-2011, 11:40 AM   #8
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Quote:
Originally Posted by Braineack View Post
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.
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.
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Old 06-17-2011, 11:48 AM   #9
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true.
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Old 06-17-2011, 04:17 PM   #10
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Quote:
Originally Posted by Techsalvager View Post
are you venting the IAC to atmo and using a check valve to prevent air under boost to leak though the iac?
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.
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Old 06-17-2011, 04:53 PM   #11
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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.
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Old 06-17-2011, 07:57 PM   #12
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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.
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Old 06-17-2011, 08:20 PM   #13
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Quote:
Originally Posted by Ben View Post
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.
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.
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Old 06-17-2011, 08:35 PM   #14
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Quote:
Originally Posted by Braineack View Post
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.
*sigh* Mine is VTA.
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Old 06-17-2011, 09:00 PM   #15
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but that's an if.
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Old 06-17-2011, 11:00 PM   #16
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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.
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