View Full Version : boosting 3 psi.

12-14-2007, 05:31 PM
i drive an audi a4 1.8t fwd.

anyone know why it's only boosting 3 psi?
sometimes it spikes about 5-10psi.
most of the time it just boost 3psi.

any help appreciated. thanks.

12-14-2007, 05:40 PM
could be a vacuum leak or bad solenoid. any strange noise coming from the turbo? mileage?

12-14-2007, 05:59 PM
haven't heard anything so far, just been hearing like knocking noises like theres rocks in my engine or something i dont know. i have 138,000. i don't have a vacc leak, i got a boost gauge and its reading 20vac. :(

12-14-2007, 06:04 PM
Are you leaking any oil from in/around the turbo? The turbos on my S4 just went out (they made the whining noise) but regardless, they only made 2-3psi. Maybe your turbo's going out.

12-14-2007, 07:18 PM
boost leak, bad turbo, check for oil. stock turbo all 138 k miles??? maybe time to replace

12-15-2007, 12:22 AM
unhook your n75 valve and if nothing changes its your n75 valve, i had the same problem but it turned out to be my wiring to the n75

12-15-2007, 09:26 AM
unhook your n75 valve and if nothing changes its your n75 valve, i had the same problem but it turned out to be my wiring to the n75

yea this should keep your wastegate closed, or just unplug the vac line going to the wastegate.

i did a write up, personally i think your cat it clogged. but i always say that.


this will help

12-15-2007, 11:06 AM
alright, ill try it out, thank you guys!

12-17-2007, 08:57 PM
so then can anyone give me a write up on the easiest way to unplug my wastegate to see if my wastegate is dead.
i would apprecaite it aloot. thanks!

12-17-2007, 10:21 PM
You just un-clamp the vac hose on your wastegate. Pretty straight forward. Be careful though!

12-17-2007, 10:51 PM
is there something i should be alert about???

12-17-2007, 11:35 PM
If you disconnect your wastegate then there is really nothing protecting you from overboosting.

01-01-2008, 05:21 AM
alright, so then i disconnected my wastegate, now i am boosting about 15-16 psi. is it safe to just leave it disconnected? or do i just replace the wastegate or something? i'm completely lost. :)

the speed is vicious! although its eating gas like a piece of AAAAAAAAA

01-01-2008, 05:43 AM
unless youre chipped... plug it back in! the stock ecu doesnt like that kind of boost with stock fuel mapping. Sounds like your N75 is shot. easy cheap fix... before you do that though. check if its not just your wires that plug into the n75

Its right next to the pancake valve on our cars. its metal has plastic nipples and a rectangular rounded edges plug. When i installed my n75h i pulled the wire out of the plug contact so it didnt work. Resoldered the wire into place and now its amazing. Give that a try, if not then its your valve. which isnt expensive.

01-01-2008, 05:54 PM
xD, its really bad?

i think im gonna go buy a new n75 valve, if its not bad then im just gonna leave it disconnected. what are the risk im gonna have to deal with by leaving the wastegate disconnected?

thanks for the help everyone.

01-02-2008, 10:12 AM
if i wanted to test the wires going to the N75 valve. how much power should they be receiving? 12v all the time or what

01-02-2008, 10:35 AM
Could you just not purchase an mbc to replace the n75? Then you can adjust to boost around 9psi. Assuming the n75 is the problem. Then if he decides to chip in future, all he will need is new dv and chip.

*note, if the person's whom thread this belongs to takes this info in kind, get the bleeder type manual boost control. just what I was told

01-02-2008, 10:37 AM
i have a similar problem. now my question is when i unplugged the N75 valve hose to the wastegate, i was boosting the 18psi that i should with my Chipped ECU. my question is is the problem the N75 valve, or the wastegate. the reason i ask is because my wastegate does rattle when i let off the gas. should i be replacing the N75?

01-02-2008, 11:57 AM
i heard you could use a mbc in replace of a n75, the bleeder type is a the better way, i read it somewhere i forgot though. what are the consequences of leaving my wastegate closed and boosting 15 pounds? i think i might get a dv / chip in the near future, most likely if i decide to keep my car, something clicks under my hood, i don't know what it is, maybe a bad wastegate?