Hyper-X

After taking a few minutes today to find out what is causing this constant harmonic "tone" from my intake system and it kind of sounds like a loud 1Khz tone. I finally was able to find out a few definite things.


1. The source of the problem has absolutely nothing to do with the electric steering or air pump for the cat.

2. The sound does not originate from the OEM intake tube that connects the filter to the throttle body.

3. The sound is audible near idle speeds (~900rpms to 1500rpms)

4. The sound is amplified by the intake components like the tube, air filter, stock air box, etc. by sound reflections.
This is much like how a speaker sounds louder (and fuller) in a box than by itself in mid air.


Okay, so you want to know where it's coming from? (drum roll please)




It's coming from those 2 holes. If you cover one of those with your finger, the sound goes away completely. I'm not sure of this since I'm very new to the S2000, but could the sound be the result of the port size/shape combined with the air speed that passes through it somehow (creating an effect similar to how a whistle works)?

Here's my newbie question. What in the world are these two holes? My first guess is that this is the idle bypass which attenuates the idle speeds? I noticed an electrical device attached to the same side of the 2 ports. Am I on the right track or am I completely off?

Any clues will be welcomed. I know trying to find a solution to this may be a hopeless thing to do but I have to know what's causing this.

rstark

Good question. Although I don't know what these holes are for, you would probably get better and faster reponses if you posted this in the "Under the Hood" forum.

SECRET AP1

i believe one hole is for the idle air bypass and the other one leads to the idle air control valve. not 100% on those though.

Hyper-X

I've let my friend who's a mechanic at Pflueger know about it and he was puzzled too.

When another S2k rolls into the shop, he's going to use it as a comparison to see if it is indeed normal. He did listen to it and he even said "damn, that's too friggin loud to be normal."

My initial theories are:

1. Throttle Body
2. Poorly positioned TB gasket
3. Irregular intake manifold machining (for the idle bypass)
4. Stuck/defective idle valves
5. A hidden mongoose in the intake tract going "POOOOOOOOOOOOOOOOOOOOO!"
6. A well-hidden tornado product designed to help me save gas.

xviper

YOU'VE GOT IT!
Plug those two holes with your finger and I'll bet your idle goes to crap or the engine dies. With the throttle plate closed, where do you suppose the engine gets its air from to idle?
I hope you had fun chasing down this humming noise. I'm afraid I'm not that obsessive.

Silvers808

^^ were u bored today? thats a old thread lol!

xviper

I realize that now but someone linked to this thread from another current one dealing with the same topic.

Silvers808

ah that makes sense =)

Roku_F20C

It was me..and I am just gonna clean out the tb to see if the sound goes back down to a lower db level

smccurry

LOL! I was wondering what was going on. The original poster (Hyper-X) has installed the V2 AEM so this problem should no longer apply to him. I only realized the date of the thread after reading the whole thing again.