thunderstruck507

iTrader: (18)

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.

Darth_V8r

iTrader: (4)

This is my experience so far 1-week into running it

mrvedit

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.

scotty2000ss

iTrader: (2)

I have the hissing noise. Now that I have the chrs1313 it's even LOUDER. See YouTube link.

bbond105

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.

Firebirdmuscle

iTrader: (16)

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.

Exidous

iTrader: (11)

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.

mrvedit

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.

Rise of the Phoenix

iTrader: (27)

Mine does this, and I have the stock LS6 intake. Doesn't sound like anything to be concerned about.

HISS

iTrader: (52)

My 102's have sounded like a vacuum cleaner. Normal.

Pharcyde50

iTrader: (11)

Mine is noisy. Especially on cold starts and the iac is opened up.

1970camaroRS

iTrader: (8)

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.

Exidous

iTrader: (11)

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.

FormulaZR

iTrader: (7)

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.

robznob11

does your lsxrt flex under throttle?

Steven White

YES the throttle body mount and the front of the intake flexes when I crack the throttle.