BrightBlue00GT

What the heck does this rectangular canister do coming off the IAC?

devongarver

isnt it just a one way valve? like a check valve?

cliffyk

It's a Helmholtz resonator, to prevent standing waves at certain intake pulse frequencies from messing up the IAC air flow. You can bet Ford would not have spent money making it if it wasn't needed...

devongarver

I hate to disagree with you cliff, but I dont think thats what it is...or atleast I dont understand the placement if it is that. H-resonators are USUALLY tee'd into the intake track, not paralleled to it. Additionally, they are completely useless on engines as far as performance, H-resonators are there for one purpose and one purpose only, to quiet the intake noise so they can pass federal regualtions.

Also, recently when I replaced the IAC I also was looking at that little box, and I removed it to see what it was. I blew in it from each end, and it only let air through one direction. So i assumed it was just a bypass valve for the IAC.

Can you elaborate more as to why you think its an H-Resonator?

cliffyk

Good points all,

H-boxes are indeed very often tee'd into intakes, and are properly defined a closed end cavities--I am guilty of using the term too loosely (though I am not alone in that).

With regard to the performance aspects of H-boxes on intakes, they can impact performance, on the NA ('90 through '97) Miatas (Miatiae?) removing it caused the 3500-3800 rpm range to fall flat on it's face.

It's been a couple years since I had mine off (and keep in mind I'm old), I don't remember whether I checked it by applying pressure or not--I will do that later today.

Sxynerd

I can blow through in both directions on mine. It has a sponge type element inside. I am going to move it along down the line today to see if there are any ill effects.

Brute03

well if it's supposed to be a silencer, mine is broken. i get a lot of swooshing and sucking noises when the IAC opens up

Sxynerd

Do you have the element inside it?

cliffyk

I just checked mine ('03 GT made in March 2003), it's a hollow box--no stuffing, no check valve, just a resonator box--you can see a flashlight beam stuck in one end, from the other...

The car was dead stock, except for the welded in Flowmaster 40s, with 30k miles when I got it in December 2006, I am pretty sure the IAC box was never messed with...

devongarver

man, i swear i remember blowing through it both directions and only one way worked...Im gonna go take it off and check when i get home from work tonight. Maybe Im just remembering wrong..