Think i have a boost issue

[R 20vt J]

My car seems to be only boosting at 12psi (peak) holding at 10, sometimes 12.
When idling the car is sitting at -30 (as low as it can on the boost gauge)

The boost should be peaking at around 22 psi as it is running a stage to map!
I have also been told when idling it should be at around -20.

My maf is reading at .369 lbs, Should it be reading more .399?

Could it be my n75 valve as it has been replaced but was replaced with a different lettered one (Seat said it was the exact same)?

Could anyone point me in the correct direcion?

Thanks, Ross.

 

[Bolland]

I've a similar problem, idling my boost gauge is at -30 ( the lowest) Then i put my foot down and its up to 20-22, then back down to -30

 

[CupraR-34]

what size of down pipe your running mate?

 

[R 20vt J]

3" downpipe and decat. then 2.5" cat back! Could this be causing the problem?

 

[CupraR-34]

ye your overboosting, star preformance told me to say away from 3" down pipe and get a 2.5" becouse of the problems you are now suffering

 

[M87NER]

im sure mine went down to -30 on the gauge when i had issue with my brakes, had to bleed them,

 

[R 20vt J]

But is there not a lot of people on here running 3" downpipe and decat with no issues?

 

[Myki da Pyki]

Your supposed to have negative boost on idle as the engines not creating boost.

Sounds to me like the N75 is plumbed in the wrong way, change the pipes over on the N75 then see how it goes.

 

[PhilW]

If you had something like -10 then i would say you had a vac leak, but -30 means you probably havent got a vac leak.


You need to log it to see whats goin on.

 

[R 20vt J]

What should i log? I have vag com but have only used it to find codes never actually ran a log. Think my bro can do it so will get him to do it after his work.

 

[R 20vt J]

heres a pic of my n75 valve? Does it look the correct way round?

 

[Myki da Pyki]

tbh its been so long since ive seen an N75 that i couldnt tell by looking at it. But from what you've said sounds like its plumbed in wrong mate

 

[R 20vt J]

Anyone? I took off the n75 valve and tried my old one and the car ran just the same.

I am pretty sure that it is plumbed the correct way! The only thing left for it to be is my 3" dp and decat. Should i get it changed to 2.5"?

 

[PhilW]

Any fault codes?

I very much dound its a bigger DP, but it could be your decat if you havent had it mapped out.

What mods do you have?

 

[Myki da Pyki]

If its on wrong it wont bring up any fault codes. Try plumbing it in diferent an see what happens, it wont do any damage cos it'l only boost fully if plumbed in right

 

[R 20vt J]

My decat is mapped out.

Wel i thought it was, i just went and got 2 codes... p0102 maf or vaf a circuit low input

p0420 catalyst efficiency below threshold (bank 1)

This is the first time i have had these 2 codes since having this problem. I cleared them and took thecar out a 10 min drive and cheked again and had 0 fault codes.

My current mods are: BMC CDA indction kit, Split r dv, Uni fmic with uprated piping, 3" dp and decat, 2.5" supersprint cat back and Forge TIP.

 

[R 20vt J]

The part of the valve which goes into the tip s a lot bigger than the other side so i would guess it is the correct way round but i will try it just now anyway

 

[R 20vt J]

Just tried it plumbed in a different way but it ran worse. Peaked at 10psi and held aroun 8-9psi.

Its driving me mad, I just don't know what it could be.

 

[R 20vt J]

Could it be that my turbo aint working to well and thats why it isn't creating a lot of boost?

 

[PhilW]

Log it.