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View Full Version : Car boosting over 20psi with stock ECU!?!?



v1nyd
02-27-2009, 01:56 PM
Car: 1999.5 Audi A4 1.8TQM

So I sold my N75 race valve/turbo/software and inlet pipe and installed all the stock parts back in, car started up fine and no CEL's...I took it for a test drive and quarter throttle the car was boosting up to 15lbs on stock software I noticed quickly because the car had crazy power out of no where for driving it soft. So then I floored it to see what would happen and the boost gauge shot over 20psi and then the car choked and I let off and it drove fine under boost. I figured it choked because the stock software realized it was over boosting and cut of the fuel supply but I don't know why this is happening...is my N75 bad? It was fine 6 months ago when I took it out. And will a MBC fix this problem if I just manual turn my boost down? and will this solution work with a faulty N75?

Somebody have any useful input [confused]

TIA

EDIT: New Question!: so if I bypass the N75 valve but leave it plugged in and run the hose from the barbed turbo line directly to the wg instead of to the N75 then back to the wg, will this make the wg run 5psi stock?

.Mad Hatter.
02-27-2009, 02:02 PM
you and i need to switch problems

zrowcool
02-27-2009, 02:18 PM
vac line to wastegat came off would be my guess

t1demont1
02-27-2009, 02:28 PM
check all lines to n75. one may cracked.

mike-2ptzero
02-27-2009, 02:31 PM
Like everyone else said, check your vac lines to the N75 and check to see if you installed the N75 correct. For some reason the pressure is not getting to the wg actuator and this means the wg is not opening to control boost.

pipe7284
02-27-2009, 02:40 PM
Yeah, what they said!!!

t1demont1
02-27-2009, 02:58 PM
Yeah, what they said!!!

copy cat!

v1nyd
02-27-2009, 03:15 PM
That was the first thing I checked, all the hoses to the N75 but everything seemed to be on tight just to make sure, the curved hose off the N75 goes to the barbed line coming out of the turbo and the straight hose from the N75 goes into the wg correct? (just making sure I didn't get the two mixed up)

v1nyd
02-27-2009, 03:25 PM
Do you guys think if I bypass the N75 valve but leave it plugged in and run the hose from the barbed turbo line directly to the wg instead of to the N75 then back to the wg, will this make the wg run 5psi stock?

mike-2ptzero
02-27-2009, 03:31 PM
Do you guys think if I bypass the N75 valve but leave it plugged in and run the hose from the barbed turbo line directly to the wg instead of to the N75 then back to the wg, will this make the wg run 5psi stock?


Yes.

v1nyd
02-27-2009, 03:32 PM
sexy. I'm going to go and try to do that in the dark lol

v1nyd
02-27-2009, 03:33 PM
Yes.

also is there any side effects to by passing the N75? like any cons to me running my car like that if this works for me

v1nyd
02-27-2009, 04:22 PM
also is there any side effects to by passing the N75? like any cons to me running my car like that if this works for me

well it worked...just sucked doing it in the dark with a flashlight that ran out of batterys...then of course it started to RAIN in the middle of this.

so anyway still wanted to know if there were any cons to doing this?

B5A4Kevin
03-02-2009, 04:01 PM
low boost. thats about it i think.

M_souren
03-02-2009, 05:10 PM
not to thread jack but how would a bad vac line cause a spike in boost? I believe this theory, im just wondering why it would happen.

mike-2ptzero
03-02-2009, 05:28 PM
not to thread jack but how would a bad vac line cause a spike in boost? I believe this theory, im just wondering why it would happen.

Because there would be less pressure in the vac(pressure line) then there really should be. This means the turbo is making more boost then what is being sent to the N75 or the WG.

M_souren
03-02-2009, 05:45 PM
ohhhh ok, gracias mi amigo. time to unplug my n75 vac line so i can hit 20psi on a stock a4 :D loljk

v1nyd
03-02-2009, 06:21 PM
ohhhh ok, gracias mi amigo. time to unplug my n75 vac line so i can hit 20psi on a stock a4 :D loljk

lol you'll hit 20psi for about a second then it'll shoot up past 25 and you'll experience fuel cut before you even get half way through the gear

v1nyd
03-02-2009, 06:23 PM
low boost. thats about it i think.

so if I add a manual boost controller in between that line and set it at like 7psi that would be a way to not have to replace a faulty N75 ?