Boost leak where to next?

[dennis1987]

I have had the inlet system on my URS4 in bits today looking for my boost leak but all of the major pipes are all okay, the inlet manifold to intercooler is good, the pipe from the intercooler to the solid pipe under the engine is good, the pipe from the solid pipe to the turbo is good, i have hade a look at all of the smaller pipes and they seem good, i dont know what else it could be. the symptoms are very strange but point to a boost leak

1) if i accelerate hard in third sometimes the car boosts up to 2.2 bar (indicated on the computer) and stays there and then snaps off at about 5500 rpm and drops to about 1.4 bar, other times the car just boosts 1.6 and no more no less

2) hoof it in second boost builds to 2.2 then falls of to 1.4 at around 5500rpm, upshift to third and boost stays at 1.4/1.3 until about 4000rpm then jumps up to 2.2 then drops again to 1.4 at 5500rpm then the same again on the upshift to 4th

the car has a a re-map that takes it to 280bhp not sure what the boost is set at on the map but i think its similar to the homefried ecu's

any help would be appretiated

cheers
dean

[dennis1987]

oh and when i took the pipe off that connects the intercooler to the solid pipe under the engine alot of oil came out and was present in the pipe, so im assuming that the intercooler has alot in it aswell because it wa dripping when the pipe was off, there was also oil in the throttle body, dont know if this could be part of the problem

[twenty valve]

the boost pressures you're talking about are WAY above what you should be getting

a standard engine with a homefry chip should peak around 1.4 bar, tailing off toward 1 bar at redline.

ALSO: oil in the inlet system is perfectly acceptable, providing it's not excessive. Take the intercooler off, turn it on its side and see what you can drain out

[AndyP]

The S4 boost gauge measures absolute pressure, so take off 1 bar to get boost pressure.

[dennis1987]

and dont know if it is normal on URS4 but when i come off the throttle i can hear the flutter noise coming from the turbo, although it sounds cool i know it isnt good the the turbo, it isnt very loud but it is noticable

[twenty valve]

when you come off the throttle the dump valve has to get rid of the pressure hence the flutter sound.

[dennis1987]

when you come off the throttle the dump valve has to get rid of the pressure hence the flutter sound.

surely that should just be one big dump noise and not a flutter, im sure the flutter is turbo stall

[Acidburn]

sounds like the diverter valve needs looking at.

[dennis1987]

bit of a newbie question pete but which one is the diverter valve pete?

[martinjs]

Take off your DV and check it for leaks. The main boost pipes are more robust than S2 items so dont fail as often but make sure you check the bottom i/c pipe thoroughly ie under all the metal reinforcing rings, a small split can be hard to notice, and change all the small vac pipes coming off the back of the inlet manifold (i was losing 0.1bar there).

How long have you had it? Have you checked for codes?

[dennis1987]

the boost leak hasnt been there that long only about two weeks this is the first proper chance i have had to look at it and this weekend

[prj]

1. Your bypass valve is shot, replace it with a 710N unit. Ask for bypass valve for Audi TT or Audi S3, it will cost maybe 40 EUR or so.
2. Pressurize intake and check for leaks.

Do not operate the car on boost with the shot valve. There is almost always some oil in the intake system, and if you operate your car like this, the oil will fly right into the MAF.

And then you are looking at an expensive replacement...

[martinjs]

Has it always made the 'flutter' noise?

[dennis1987]

Has it always made the 'flutter' noise?

yeah

[dennis1987]

1. Your bypass valve is shot, replace it with a 710N unit. Ask for bypass valve for Audi TT or Audi S3, it will cost maybe 40 EUR or so.
2. Pressurize intake and check for leaks.

Do not operate the car on boost with the shot valve. There is almost always some oil in the intake system, and if you operate your car like this, the oil will fly right into the MAF.

And then you are looking at an expensive replacement...

what does the bypass valve do exactly? i might be able to rob the s2's one while it is off the road