boost / hiss noise (RS2 spec coupe)

[avants2turbo]

@quattro20V - send me PM again - sorry - still backlogged there a bit... I cannot remember your setup.

Paul,

today i got the chance to have a gander at the vacume hoses around the ECU, the hissing noise does not sound like its coming from anywhere near the ECU! I did do the suck test on the vacume pipe on the ecu and in not 100% sure but pretty sure it was holding a vacume, the noise seems to be coming from higher up, if your sat in the passanger seat of the car it sounds like its coming from the rear left hand corner of the glovebox, so i had a look and theres a brass "looking" valve of some description that seems to have a vacume outlet/inlet with no pipe on it? it had several other pipes coming out of it, but i couldnt see a stray pipe to plug into it, what is this valve, and what should be plugged into it, i susspect that what ever and where ever this pipe is, thats whats making the hissing noise (the valve thing kinda looked a bit like a N75 valve)

[stevieyid]

Keith im sure there was a pipe coming from there that Newsh plugged!

[avants2turbo]

Keith im sure there was a pipe coming from there that Newsh plugged!

Any idea where that pipe is? Couldnt see any unplugged vac pipes, im sure thats whats making the hissing noise

[stevieyid]

Hmm i think it was connected to the valve and pluggedbut did not know what it was for. Maybe it has come off somehow but im sure there was a line coming off it that was plugged.

[S2central.net]

Check the vac pipes that go to the aircon recirc valve... its at bottom left corner of glovebox... I have accidentally dis'd one or two of those in the past - it can be snagged when swapping ECU if you are unlucky. There is also a vacuum reservoir between the recirc valve and IM via a 1-way valve... this is under passgr wing so check that too.

Also check the ECU boost pipe goes to water trap on passenger a-pillar and this is an airtight path all way to the IM.

[newsh]

The pipe was not coming from the valve, it would not reach it, it was coming from higher up IIRC, nearer the ecu, thats probably why it was plugged into the ecu by mistake.

[newsh]

I reckon its worth having the glove box out, only a few screws..

[S2central.net]

I reckon ye are right !

[avants2turbo]

I reckon ye are right !

Ill whip the glove box off tomorrow and have a butchers, Paul, how much boost should i be seeing with the n stream? Peak and redline?

I did have a gander at the a few other parts today, i replaced the broken throttle quadrant with my 034 metal one and adjusted the cable as i wasnt sure that the tb was fully open when the pedal was fully depressed, also replaced the rubber connector between the metal boost pipe and tb with a brand new audi one + checked the hose clips were tight and replaced a couple, it does feel a little quicker, and am seeing 1.3 bar but it seems to drop off quit quickly to about 1 bar (seeing between -0.6/-0.8 bar vac on idle)

[S2central.net]

Max on RS2 N-Stream is 1.5-1.6bar and ~1.3bar on the redline.

If unsure about TPS then check its resistance at WOT - plenty posts on that of course.... but you need to get to bottom of this air leak noise as that is the most likely candidate.

I'll seek out the ABY vacuum tree as well to help you test each pipe.

[S2central.net]

Here goes... http://s2central.net/images/Vacuum_and_PCV/

[S2central.net]

Actually there is a mistake on the ABY tree - the check valve shown to connect to front reservoir has another pipe that goes to the recirc valve. I only discovered that long after doing the diagram so apologies for not updating it... Will try to resolve it this week if time permits.

Paul

[avants2turbo]

Paul, the max boost i see is 1.3bar, could the wastegate spring be an issue, what i mean is, on my last s2 the wastegate cap was drilled/removed, and the 6mm allen screw was screwed in, this one has still got the cap on it, so im guessing that it hasnt been adjusted, or the spring replaced, should it have been replaced/adjusted with the the upgraded turbo etc?

[S2central.net]

No that boost is with factory wg spring

Gotta find source of the hiss - tis an air leak for sure

[avants2turbo]

small update, just driven 30 odd miles a21-m25-bit of town driving, in 1st, 2nd its pushing 1.3bar but tails off very quickly to about 0.8 4th gear boosts to about 1bar and tails off to about 0.8 by about 5krpm, 5th gear goes to about 1.1 bar and slowly increases to about 1.2/1.3 bar as the revs increase... Weird

I try and get the glovebox out and find that pipe thats come adrift