New Mk4 GTI Owner - need some help

[dubster99]

Why do you say that jason? Its got to be something with the boost system not exhaust

[theBRUCEofWAYNE]

I just asked my guy your exhaust concern TheOt, he said it's not the exhaust because it's a separate system and could not effect it.


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[h100vw]

I just asked my guy your exhaust concern TheOt, he said it's not the exhaust because it's a separate system and could not effect it.


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A free flowing exhaust would not cause dropped boost pressure. It's something else, boost leak, failed N75, Wastegate sticking.

Gavin

[theBRUCEofWAYNE]

Hey boys. Just got my car back. The culprit was this pipe below. Was only getting 8psi. Now getting 12psi. Big difference. Still possible leak near the pcv t-junction piping. The cracked tube he found looks fine from the top view. But from underneath, it's cactus!
Guess my pressure test method was a fail. My guy uses a thin-nozzled pistol trigger, so he can force more air through the pipe work in large bursts.

Hope that helps. Good luck!


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[TheOt]

I think it's my 3inch down pipe because my boost only started to drop after it was installed. I took it back to the exhaust place and they couldn't find a boost leak but they wouldn't have pressure tested it. I did ring a few places up about it and they said the the exhaust is to big for the turbo not enough back pressure. Maybe I need to find some test for leaks. Cheers for your info and help

[h100vw]

I think it's my 3inch down pipe because my boost only started to drop after it was installed. I took it back to the exhaust place and they couldn't find a boost leak but they wouldn't have pressure tested it. I did ring a few places up about it and they said the the exhaust is to big for the turbo not enough back pressure. Maybe I need to find some test for leaks. Cheers for your info and help

There's nothing wrong with the downpipe and exhaust. It couldn't reduce boost at all.

There's something else wrong with it. Google turbos boost and back pressure. Then decide for yourself.

Gavin

[GeeMatt]

3" Downpipe on std GTi here. No noticeable issues with boost ! (No gauge tho) Goes good, makes broom broom noises

Needs Custom Code ECU tune !

[TheOt]

I have done some reading on turbo boost and back pressure and in theory I shouldn't have this problem. Need pressure before the turbo but almost none after the turbo. Please correct me if I'm wrong. Either I have a boost leak (I'm going to have a good look for a leak today) or the spring in my actuator is very weak and the pressure of the exhaust flow is ordinary the wastage open a bit.

What do you all think?

[TheOt]

I have the ko3 turbo

[theBRUCEofWAYNE]

I have done some reading on turbo boost and back pressure and in theory I shouldn't have this problem. Need pressure before the turbo but almost none after the turbo. Please correct me if I'm wrong. Either I have a boost leak (I'm going to have a good look for a leak today) or the spring in my actuator is very weak and the pressure of the exhaust flow is ordinary the wastage open a bit.

What do you all think?

My personal view. Never underestimate the quality of your hoses and pipework. If they are black, and original tubes, get them replaced. I was running 3-4 psi less for the last 6 years thinking it was normal to be running at 9psi. But then I found out my ecu was chipped all along *what a goose* (thanks Gavin). I still have another leak but I should be able to achieve 15psi (1 bar) when I replace all my piping.

*hint when you pressure test. You should see the rubber hoses expand and stretch. eg. The large hoses attached to the charge pipe (at the back) and your throttle body pipe.


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