Had my Airbox removed together with the tube between the TB and filter to get to the radiator for some work. They placed everything back on again.

I started engine and could hear a howl coming from under the hood. I opened hood and the airbox lid and the howl got even worse to a point where it could shatter glass. I removed the air filter and identified the howl was coming from the rubber tube aperture

I did some testing to try and identify the source.
Closing half the aperture with my hand = No howl
Rev to around 3K rpm = No howl
Disconnect the tube from TB (running on an open TB) = No howl
Inspected and cleaned the tube and placed back on = Howl came back again.
Twisted the Tube sideways, upwards and all angles = Howl remained
Checked all Pipes around the area and all seemed in place where they should be


Some months ago (November), I used to drive my car without lid and never had this howl. So something must went wrong.
In my small garage the howl was so amplified and irritating that I had to get the car outside to work on and do the testing.

Any Ideas please

 

curious. I know that the S2000 intake makes a whistling/howling noise naturally. are you certain you put everything back together correctly? the howl, as I understand, actually comes from secondary air injection module, or the intake throttle body.

 

I am not certain as it wasn't me who did the work and i wasn't even present.

When I disconnected the secondary air injection module (J shape rubber tube) from the throttle body, the howl gone.

 

It sounds to me like the seal between the tube and TB has a small leak or isn't a tight fit, and that air is being sucked through this tiny gap causing a howling noise. When nothing is connected to this end of the tube, the howl goes away.

 

I did tighten the "JUBILEE CLIPS" but to no avail.
If this is the case, In my understanding when i blocked half of the airflow with my hand, it should increase the air passing from this tiny gap/leak making the howl worse.
As for your last sentence, it is correct.

 

I know the howl you are talking about...But it is only present when I have the lid (currently) removed on my OEM air box...It was only noticable after replacing the filter with a k and n filter and removing the top....When I put the top back on the box it is barely even noticable...But I leave it off because I like the growl emitted when accelerating.

 

I used to have the lid off before for the same reasons (growl) . I used to hear a "blip" sound when shifting gears or releasing throttle, But never had this iressistable howl, My filter is OEM and the same one i had before the change.
I will compare it next to another car same year and with lid off. I might try to do a movie clip with audio too.

 

I think I had a similar howl but mine only appeared with slight throttle around 3k rpm. The dealer got rid of it acording to the tech by cleaning the trottle body. It has since come back though. Sounds like the tube is not making a good seal at the tb. to me too.
Good luck.

 

Make sure you plugged all hoses back. Secondary air pump, vacuum...