I think my IABs are always open

[gloryaccordy]

I took my TB off this weekend to do my rear motor mount and just out of curiousity I looked in to check my IABs out...are they supposed to be open when the car is off??? And how do I check to see if their open from the outside?

[NAiL05]

Yea since there is no vacuum generated it stays open.

[92acclude]

Mine on my H22 are like that, didn't affect power on the dyno. I wouldn't worry about it.

[owequitit]

They should stay shut for a little while after you turn the car off. Once the car is off though, the vacuum in the IAB system isn't a perfect sealed one, so they will open after a period of time.

[wed3k]

try opening it with your finger when the car is on, i couldnt do it :o

[accordaffair]

Yes they are open without vacuum. Car off equals no vacuum.

[cp[mike]]

They should stay shut for a little while after you turn the car off. Once the car is off though, the vacuum in the IAB system isn't a perfect sealed one, so they will open after a period of time.

:clicks car off:

....ssssssssPSSHHHHH *pop*





i dont have IAB

[palinix]

:clicks car off:

....ssssssssPSSHHHHH *pop*





i dont have IAB

This is the exact same sound I hear when I turn the off the car. What exactly causes it?

[Spartan1987]

Yeah I have heard it too.
It's probably the pressure changing due to the engine being off.
Kind of like sealing up something, maybe?
Doesn't really matter though, it's supposed to do it.
If your car doesn't I wouldn't worry about it.

[owequitit]

It is the air rushing through the idle passage. Since the TB is closed, the outside atmosphere flows in through the open idle passage. But since the volume of the IM is so large compared to the amount of air flowing through the passage, it takes a few seconds for the pressure to equalize and for air to stop flowing.

One of the noises that the stock intake masks I assume. I am not sure exactly how it does it, but it seems to be related to the rubber seals, and the fact that the passage is so long and convoluted, it is muffled long before you hear it.

This same thing is what causes the humming or sucking sound with an intake.

[gloryaccordy]

It is the air rushing through the idle passage. Since the TB is closed, the outside atmosphere flows in through the open idle passage. But since the volume of the IM is so large compared to the amount of air flowing through the passage, it takes a few seconds for the pressure to equalize and for air to stop flowing.

One of the noises that the stock intake masks I assume. I am not sure exactly how it does it, but it seems to be related to the rubber seals, and the fact that the passage is so long and convoluted, it is muffled long before you hear it.

This same thing is what causes the humming or sucking sound with an intake.

Ahhhh so the throttle completely closes off at idle and there's a passage to keep the motor running? Interesting. Does this passage close off when the throttle is open? If not I could see how that would make the whistling sound associated with an intake at part open throttle. My car's whistle is loud...

[cp[mike]]

This is the exact same sound I hear when I turn the off the car. What exactly causes it?

owequitit answered your question, but in my post i quoted something he said, so my post was in reference to what he said... the hissing the intake repressurizing, and the pop is the IAB plates snapping shut. you wont hear this on cars without IABs, youll hear just the hiss.


anyway yes, theres always a small passage open. ever wonder how the idle screw and fast idle valve worked? if the TB plate closed with no other way for air to get in, the motor would be choked and stall...

[gloryaccordy]

I thought the throttle stayed "a little" open...good to know though, you learn something everyday.

[SuddenCb7]

Yeah man on my h23 intake mainfold you can watch the iab open and close when you rev the engine. You also shouldnt be able to open them by hand if you can then the vacuum diaphram doesnt have enough vacuum.

[mondojackal]

This same thing is what causes the humming or sucking sound with an intake.

werd..mine hisses...people get wide-eyed when i crank my car..they are all like "what is THAT??"