not hitting requested boost.

[CELison]

Lately I have not been able to get up to requested boost. I see about 18-19 psi in 2nd and 20 psi in the upper gears. I should be seeing 22-23 psi. Boost also comes on slower than it should. Pressure tested, no leaks. Dvs held vacuum fine, so I'm thinking its a bad n75. I Usually don't have my s4 at school, but my old man took out a family of deer so I gave him my mighty 12v 2.8 until his is fixed. Of course now that I'm 200 miles from home its acting up. I have a buddy here with an s4 but his n75 is bad, so I can't swap it out. ECUX refuses to log with my ecu and I don't know anyone here with vcds. But does this sound like an n75 issue? Boost doesn't fluctuate, it just holds too low of pressure. And if anyone is in the state college pa area and wants to lend me their n75 for an hour that would be awesome.

TIA

[NOTORIOUS VR]

sounds plausible.. I started to have similar issues yesterday... I'm also thinking it's the N75

[CELison]

Yea idk what else it would be. I just want my boost back

[MileMan402]

Hmm that sucks. I'm actually from state college but at school in Bethlehem sorry.

[CELison]

Hmm that sucks. I'm actually from state college but at school in Bethlehem sorry.

I live 500 feet from Bethlehem (palmer township) but in school in state college

[MileMan402]

I live 500 feet from Bethlehem (palmer township) but in school in state college

Haha small world.

[rtl5009]

pm'd

[DanS4]

Lately I have not been able to get up to requested boost. I see about 18-19 psi in 2nd and 20 psi in the upper gears. I should be seeing 22-23 psi. Boost also comes on slower than it should. Pressure tested, no leaks. Dvs held vacuum fine, so I'm thinking its a bad n75. I Usually don't have my s4 at school, but my old man took out a family of deer so I gave him my mighty 12v 2.8 until his is fixed. Of course now that I'm 200 miles from home its acting up. I have a buddy here with an s4 but his n75 is bad, so I can't swap it out. ECUX refuses to log with my ecu and I don't know anyone here with vcds. But does this sound like an n75 issue? Boost doesn't fluctuate, it just holds too low of pressure. And if anyone is in the state college pa area and wants to lend me their n75 for an hour that would be awesome.

TIA

log. check the sticky

[VR6Bomber]

I have a spare n75 and vagcom but am in central nj

[jerodmetcalf]

I had similar issues and here is the cause of mine: http://www.audizine.com/forum/showth...=turbo+failure

[CELison]

I had similar issues and here is the cause of mine: http://www.audizine.com/forum/showth...=turbo+failure

I found the issue of the boost coming on slow (ic coupler was crimped) so I doubt this is my problem. Boost comes on fine now, and the car still feels strong, its just 1 or 2 psi short of what it should be boosting

[CELison]

log. check the sticky

ecux will not work with my car and that is currently all I have access to. 3 different people and 3 different laptops including josh from jfonz could not get it to connect.

edit: Didn't see the new sticky. Ignore^^

[jibberjive]

ecux will not work with my car and that is currently all I have access to. 3 different people and 3 different laptops including josh from jfonz could not get it to connect.

If I was a betting man, I'd be willing to wager that you didn't read the sticky Why is ECUx all you currently have access to, no internet connection to download MELogger?

[CELison]

If I was a betting man, I'd be willing to wager that you didn't read the sticky Why is ECUx all you currently have access to, no internet connection to download MELogger?

you would have won that bet. I didn't notice that there was a new sticky. I'll be downloading it in the morning.
Thanks and good write up

[CELison]

Still having this issue. Haven't been driving the car much so I put it on the back burner. But today I threw a pressure control negative deviation code. Car has no leaks and runs strong besides being about 2 psi under what it should be. I'm thinking n75? it still has the factory clamps so I am guessing it has never been replaced.

[aysix]

Home depot made pressure tester will probably help

[CELison]

I have one. No leaks like I said

[Don Supreme]

I have one. No leaks like I said

Put an ohm meter on the n75 pins and report back what it read.

[CELison]

Put an ohm meter on the n75 pins and report back what it read.

I'm swapping n75s with a buddy in the AM. If that doesn't do it I will look into wastegate issues.

[Don Supreme]

I'm swapping n75s with a buddy in the AM. If that doesn't do it I will look into wastegate issues.

perfect!

[Trigger Happy]

Put an ohm meter on the n75 pins and report back what it read.

I have a feeling my n75 is bad. What should the pins read? I've been trying to figure out a sure fire way to tell if it's my n75 or not.

[Don Supreme]

27-29+.. (ohm) higher the worse.

[zadeluca]

Has anyone thought about pressure drop/loss? Or maybe your gauge is just inaccurate or not receiving the correct?

I mean, if you haven't been logging boost, all you have to go on is what you can read on your boost gauge? That isn't the most accurate way to determine how much boost you are hitting.

And the idea of pressure drop, the N75 receives its boost source directly from the compressor on the turbo. Where is your boost gauge tapped into? If it is the intake manifold, that should account for your lower readings. The air has to travel all the way through all the IC piping and FMIC first.

Thoughts anyone?


EDIT: nevermind. i just realized that the ECU uses the charge pressure measured by the MAP sensor to determine how to control the N75. the N75 never actually measures anything from its boost source, it just follows orders from the ECU.

which brings me to ask, if the N75 were misbehaving, shouldnt the ECU modify the signal sent to it in order to behave properly? you really need to run some logs to see whats going on :)

[CELison]

put in a new n75 this morning and problem solved. holds 22~24 psi. If the n75 isn't functioning like it should the ecu will not be able to correct it. If it could there would be no point of replacing it. The car will usually throw a code for positive/negative deviation implying there is a boost leak/vac leak/wastegate/n75 issue.

[Don Supreme]

Excellent!

[Trigger Happy]

Nice Jesse. Mines shot too, thanks don for the tip.

[CELison]

Nice Jesse. Mines shot too, thanks don for the tip.

fix that shit. It feels good to have your boost back. And when you put on those coils I know someone who will buy your springs.

[PovGRide742]

Had the same issue last year when I was on GIAC-X with K03s... was boosting about 2psi low. Replaced the N75 and it fixed it. Just started boosting about 2psi low during this past week. Had a hiss for a while (since before I got tuned) that never prevented me from hitting requested boost. Figured I'd trace it down. Spent HOURS today between tracing the leak (fuel injector o-ring into intake manifold) and keeping the leak away (swapped o-rings, reinstalled injectors, rail-to-injector o-ring started leaking, replaced, reinstall injectors, another injector started leaking at intake manifold). I now have absolutly zero hiss when boost leak testing at 20psi. STILL boosting about 2psi low.

After reading this, although hesitant as I just replaced my N75 last year, starting to think, yet again, I need a new N75. Maybe I'll look into that 034 one and have Josh re-tune my PID.

[Jetta03GLI]

Im having the same issues as -2psi than normal... i usually spike 14 psi, than settle at 12psi and holds strong.. starting yesterday.. i sometimes hit 10psi and holds right theres.. sometimes hit 12 and back to 10 and holds there as well... also seems like the boost isnt coming on as fast.. i really hope its just my n75 as well... would hooking up a mbc w/ the n75 still pluged in.. temparly let me know if my n75 was bad or not?? like if i set the boost for 15psi? and it holds? that would be a bad n75

[Jetta03GLI]

Forgot to mention there's no cel coming on.. Hoping it's just a faulty n75.

[Jetta03GLI]

Tonight I was hitting as low as 6-8 psi. But steady 10 psi.. Even sometimes 12-14. I'm really thinking its my n75?? If it was a boost leak. I wouldn't be having odd boost sequence? It wouldn't hold boost

[CELison]

pressure test first. If it checks out then its a good possibility your n75 took a shit

[Jetta03GLI]

I gotta find someone that can check for me. Until my pressure test kit gets here.. Thanks for the input