Small hose near intake??
 

Hi,

I've been DIY boosting my car for the past week or so, and when I was fitting the cold side ducting I realised that there was a small hose to the bottom left of the throttle body that was sucking in air with nothing attached to it.

I have tried to find out what it is, and whether it needs atmospheric pressure or boost.

I've pinched a picture from youtube to try to help me explain what is it, but the hose with a red ring around it is the one I'm after.

http://puu.sh/odBC3/99ccfc5730.jpg

I'm in the dark, any advice would be highly appreciated, thanks!

idle valve hose

I'm seriously concerned about someone boosting their car without even knowing what the idle valve hose is

Tough crowd

That's the idle air hose. One end goes to the air intake pipe, the other end to the idle air control valve which sits right under the throttle body. If one end of the hose is loose, there should be a free spot for it nearby.

There's now aftermarket hoses attached to the compressor, and nothing on the end of the metal tube poking out.

will it need boost or atmospheric pressure?

The inlet on the IAC valve should be connected to whatever stuff is in the intake pipe before the throttle body. In your case, that would be boost air. Also needs to be downstream of the MAF/AFM if you still have that.

If you still have the MAF it has to be plumbed into the intake. If you've converted to a MAP sensor then it will run fine, but boost will leak out of the valve. Ideally you want it plumbed in, but I've run mine with a check valve and a little breather filter on it. The added restriction of the filter and check valve made tuning idle more difficult but ultimately it worked.