supergeorgy

Hello I have a 2002 audi tt quattro and I am having a problem hitting full boost I have tried changing the N75 valve, checked for boost leaks, and also had a brand new OEM borgwarner turbo installed professionally by a shop with new gaskets and bolts and although the new turbo did help with the way the car feels the car is still refusing to hit full boost. Any suggestions on what it could be would be greatly appreciated since this car has given me nothing but headaches aha

lyleswk

Assume you replaced the diverter valve.

supergeorgy

Yes I have I have replaced it with a forge 008 DV running a higher spring rate but rather it's a higher spring rate or a normal one or even putting back on the stock one the same problem happens and it just refuses to hit full boost it feels very sluggish. I had a 2004 tt quattro that ran all my mods and even in stock form it didn't feel this sluggish in terms of boost.

Christian Garofalo

Have you done a pressure test for the intercooler piping? Is the vac line to the DV plugged in and not leaking? Do you have access to VCDS, could scan for any codes that may be causing something electrically to make it not fully boost. Is the MAF Sensor plugged in? Could there be a leak also in the EVAP/ PCV SAI ETC?
Most importantly, do you have a boost gauge hooked up? that way you could find out exactly how much boost you are getting.

J. Patterson

Did you pressure test for boost leaks? I have found more than I can count over the years when I had boost issues.

My bung is made from PVC piping parts but same idea.

supergeorgy

I have not specifically tested the pressure on the intercooler piping the only way I have tested for boost leaks is with a homemade boost leaks tester which consists on a plumbing end cap with an attachment drilled into it and sealed so that my compressor can be hooked into it. I do have access to a scan tool that plugs into the obd2 of the car and I have checked and it has no codes. The vac line to the DV is hooked in and no leaks are present that I have found And yes the maf sensor is plugged in and there doesn't seem to be a problem with the sensor and for EVAP, PCV and SAI there isn't any leaks. I will go ahead and double check everything again today and let you know what I have found and unfortunately no I do not have a boost gauge installed. Is there anyway that I can better pressure test the system maybe something I've missed and can I test the intercooler piping specifically since you said that could be the issue

supergeorgy

I have done this exact same boost test but I also disconnected the pipe to the intake manifold at the bottom and tried sealing it as best as I could since people say not doing that will let pressure blow by the throttle bottle should I retest again without disconnecting the intake manifold?

Christian Garofalo

Well, what i would really do is, go to an auto parts store and get a real cheap boost gauge and hook it up, that will show you accurately how your boost curve is, if it had a leak then you'd see it peak and then start dropping quickly. You don't even have to install it, just run it through the hood and through the door just to test. Also, Harbor freight sells them too if you want really cheap lol. Let me know how it goes

Christian Garofalo

also, when you get on boost, does it feel like the power peaks then drops off? also, do you know if you are getting black smoke out the back?

Christian Garofalo

Oh and one more thing, it could be in limp mode, the most common is 5 PSi and it wont go over