ok long story short i have had my car 98 a4 1.8tqm tuned by apr,91octane chip, call them and they said iam suposto be boosting 20spike hold 17. i have NO boost leaks (tested 6 times now), replaced the diverter valve, tested the n75, and now iam narrowing it down to the wastegate. what iam thinking is that mine is loose and or its not closing all the way to build any more then 10psi at 5k revs. i bypassed the n75 by pinching off the line coming form the n75 to the wastgate actuator,(this i would think make the turbo make as much boost as possible without bleeding if off) took it out for a drive (carful drive)and only got 10psi at 5k revs again... so question, is there a way to get to the adjustment nuts/lockin nuts on the wastegate shaft without taking the turbo off the car????? this way i could close the gap on the wastegate so i can build more boost..
thanks tyler
also i have the diverter valve with the highest spring rate so it would hold at least 18psi

 

have you scanned for codes?

 

the software was made to use the n75... dont bypass it..

check your maf if it needs to be cleaned or replaced

 

If you cut off the supply of pressure to the wg actuator completely and still not hitting more then 10psi then the wg is most likely cracked open all the time.

 

So the rea question is, are you still hitting somewhere between 17 and 20 psi before 4k? The turbo is small as hell and cant hold that psi very long, it falls on its face at 5k. If you arent seeing that much psi, the nut on the wastegate arm could be loose, you could have a cracked housing or even just a simple leak between the turbo and manifold which is common.

 

this is what iam thinking, so is my wg shot then? or is there a way to adjust it? even if i have to take the turbo out i want to adjust it. just wanna know before i do that if it is adjustable??

and cincyTT iam hitting a SPIKE of 10psi at 5k revs. before 5k iam at 4psi....its freakin retarded. iam so pissed its like my car is stock..but yet i spent 500 bucks on ecu and diverter valves and all that crap

 

Just to throw out a random but somewhat related question...how much boost does a stock 1.8T run?

 

i think its 8

 

Time to start investigating. You have some sort of exhaust leak due to what you are saying. Check the wastegate arm and if it seems ok, start the car when cool and feel around the manifold and turbo connection for leaks.

 

will do this on monday. and do another boost leak test..ah iam running outta ideas. i think my wastegate is just screwed. so soon the turbo will be coming off the car to look at it...