car being a bunghole

[wildbill]

so with a pc 16 im getting wicked overboost. ive pressure tested to 15 psi, changed everything but the maf, but running it doesnt show symptoms instability. im running marren 315cc injectors, 3bar from ecs, evo ms fmic, 2.5 apr catback, 034 high flow cat, forge 007 dv, replaced most vaccum lines. also it pulls 18 in mercury at idle cold, goes to 20 in warm, wonderng if theres a hidden vac leak. possible maf? or shitty file? ive seen youtube videos of low rpm WOT on a passat and it pulls up to 18psi and holds, mine hits, drops to 15, then bounces til 3600 rpm or so...im at a loss

[wildbill]

bump

[wildbill]

someone has to have an idea...good or bad

[JEmm]

Bad n75? Boost leak? Those are really my best guesses.

[wildbill]

checked fore leaks, new n75 from ecs, non race

[JEmm]

checked fore leaks, new n75 from ecs, non race

is the file new or have you had it for awhile and just recently getting problems?

[wildbill]

put it in in march, but when from a bad turbo, boost leaks, wrong fpr...etc, got it all fixed about a month ago, but am painting the car so only get to drive it a few miles at a time as it doesnt have doors a trunk or bumpers :) it is erratic until 3500 up and down between 15 to 18 all day, and im ready to throw a grenade in my car as it is the worst b5 in history....ever

[walky_talky20]

If you unplug the electrical connector from the N75, it should limit boost to spring pressure by giving full pressure from the compressor housing to the wastegate actuator at all times. Stock spring pressure should be less than 5 psi. A quick unplug and check it out. If it boosts above that, there is a problem with the wastegate/actuator or the pressure line in/out of the N75. If it limits correcly, your overboost problem would likely be caused by a faulty N75, tune, or MAP sensor. Pretty easy test anyway.

[wildbill]

tune is off the shelf giac, already done that n75 test with it holding perfectly at 5 lbs, and dont have a map, its a 97

[walky_talky20]

Sounds like a bad N75, then. I've seen this (overboost) failure before on an N75. Seems like the internal spring gets weak and the solenoid moves too easily, blocking more boost signal than it ought to (from getting to the actuator). I saw the failure on a stage 3 S4. During tuning the boost was way too high, even hitting fuel cut sometimes. Popped in a new N75 and boost was back under control. Seems like his lower-boost tune was stressing it a bit much having to control dual K04's. He had it fail again 6 months later, that time with an underboost problem.

[wildbill]

as i stated, its new with like 1000 miles on it

[99blueb5]

what kind of plugs and gap are you running

[wildbill]

.28 ngk all day

[walky_talky20]

Hmm. 5psi seems too high for a stock wastegate. I'm pretty sure it should be closer to 3psi when running off the spring. If its at 5, there may be too much preload on the gate which can cause boost to spike too high.

Did you check for leaks in the pressure line between the compressor housing and the actuator?

[wildbill]

replaced them, put my old n75 in with no result