View Poll Results: Does your FAST intake make a hissing/sucking sound (especially at cold idle)?
Yes, a hissing sound is normal with a FAST intake
37
80.43%
No, my intake does not make any strange sounds
9
19.57%
Voters: 46. You may not vote on this poll
If you have a Fast intake, please read
Thread Starter
11 Second Club
iTrader: (18)
Joined: Mar 2008
Posts: 8,358
Likes: 27
From: Northwest AR
Mine makes a lot of noise on first start but once warm the sucking sound gets quieter.
It's also a little different with my current throttle body versus the Fast 90mm brand tb I had before. Leads me the believe the sound is mostly a whistle from the smaller aftermarket IAC opening.
Smoothing the rough edges of that might help reduce the noise.
It's also a little different with my current throttle body versus the Fast 90mm brand tb I had before. Leads me the believe the sound is mostly a whistle from the smaller aftermarket IAC opening.
Smoothing the rough edges of that might help reduce the noise.
Moderator
Joined: Aug 2010
Posts: 7,323
Likes: 529
From: Ann Arbor, MI
Confirmed - the noise is coming from the IAC; turning in the TB stop to lower the IAC value from around 70 to just 30 at idle eliminated the noise.
I'll take ThunderStruck's suggestion to try smoothing out the IAC paths in the TB.
Thanks guys.
I'll take ThunderStruck's suggestion to try smoothing out the IAC paths in the TB.
Thanks guys.
TECH Junkie
Joined: May 2012
Posts: 3,045
Likes: 713
From: Poplarville, MS
As mrvedit said crack open the throttle blade more to drop your IRC count down to around 30. Too much air is having to pass through the IAC passages to maintain an idle and this is causing the hissing sound. In the older model GM service manuals there is a procedure of this adjustment. I’m sure it is still in the manuals for the newer model cars also.
Last edited by bbond105; Aug 23, 2015 at 05:14 PM.
add me to the list, I have a fast 92/92 combo and it has done that since install. I now have a chris 1313 ac version and it did not make it louder, its still the same. but does seem to go away after a while, or could just be im not paying that much attention to it after I start the car up.
The sucking noise is only from the TB when the IAC is at full open while cold. As the engine warms, less air is needed. This is normal and shouldn't be noticeable when warm.
The fast does echo any valvetrain noise much more than a factory intake.
The fast does echo any valvetrain noise much more than a factory intake.
Moderator
Joined: Aug 2010
Posts: 7,323
Likes: 529
From: Ann Arbor, MI
I probably notice it more because my 419ci stroker with 19* overlap cam needs a lot of air just to idle. Even with the throttle stop adjusted to 30 IAC when warm, it is at 200 on a cold start and the noise is very noticeable.
At least I know that the problem is the TB and not the intake now.
Thanks again.
At least I know that the problem is the TB and not the intake now.
Thanks again.
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This is the correct answer. My LSXrt intake, while being huge and noisy has led to more than one person asking me what supercharger I'm running. Nope, no supercharger...just a noisy intake when IAC is wide open. It does get quieter when the IAC counts get down to the 120 range or so, but never silent. I would advise anyone running a good sized cam to NOT lower your IAC counts to 20. You will have a bad time.
I should add that the IAC opens to max counts when you get on the throttle. Will add to it. Maybe a little smoothing around the ports to the IAC and PVC clean air port to remove the whistle effect.
My FAST 90 sounded like a Hoover. I switched to a Accufab 4150 and it's much quieter.
Just a normal sound of an engine (in my case a healthy 383) ingesting enough air through a small hole to idle.
Just a normal sound of an engine (in my case a healthy 383) ingesting enough air through a small hole to idle.
On The Tree
Joined: Nov 2008
Posts: 123
Likes: 2
This is the correct answer. My LSXrt intake, while being huge and noisy has led to more than one person asking me what supercharger I'm running. Nope, no supercharger...just a noisy intake when IAC is wide open. It does get quieter when the IAC counts get down to the 120 range or so, but never silent. I would advise anyone running a good sized cam to NOT lower your IAC counts to 20. You will have a bad time.
