s4 not hitting requested boost

[gheron]

alright... Dave from EPL let me know the car is not hitting requested boost.. current file requests 26 psi the car is hitting 20.9 according to PPD logs so we can call it 21, not sure what the issue is, dont have a pressure tester so i have not done a pressure test yet but made sure all hose clamps where nice and tight, vacuum reading is at a solid -21 so there is no vacuum leak... thought it may be the N75 but the boost does not fluctuate it holds 20.9 psi all the way to the top... any insight? anyone with a pressure tester that can help me out one evening?

any help would be appriciated,
Jonathan

Edit: car runs great other wise no hesitation, no CEL nothing that seems out of the ordinary.

[PRY4SNO]

Re: s4 not hitting requested boost

Probably way off here but any chance it's your MAP sensor?

[gheron]

Re: s4 not hitting requested boost

map sensor is brand new, part of the PPD, map on PPD and ECU read the same

[Natty54]

Re: s4 not hitting requested boost

Can borrow my tester. I made it for a 996 turbo. But should work I think, its a 3" and it has a tire valve. Another thing you will need is a spray bottle of soap and water. Some of the smallest leaks will cause issues.

Can also make one up with a quick trip to home depot : http://www.awe-tuning.com/media/pdf/...ure_tester.pdf

[bobkatkat]

Re: s4 not hitting requested boost

I would check your DVs first as would be the easiest test. Then pressure test.

[gheron]

Re: s4 not hitting requested boost

sorry may be a silly question, how would i go about testing the 710's?

[Natty54]

Re: s4 not hitting requested boost

sorry may be a silly question, how would i go about testing the 710's?

http://www.vaglinks.com/Docs/Misc/VA...rter_Valve.pdf

[Mantis]

Re: s4 not hitting requested boost

I bet your Tial S605 wastegate's are set to open at 19, that would limit your max boost to a solid 20.5 to 21.5. Double check that the N75 is in the correct orientation. You can try disconnecting the N75 to double check WG pressure

[gheron]

Re: s4 not hitting requested boost

when my fail safe was kicking in for the meth kit the car was only seeing about 15 psi, but ill disconnect the n75 for my drive back home and see what it reads, ill test the DV's as well and report back.

[turbomeyers]

Re: s4 not hitting requested boost

I would check your DVs first as would be the easiest test. Then pressure test.

this .... just replace them with forge units to ensure never to worry about them again

[Mantis]

Re: s4 not hitting requested boost

710n's will be more than good, plenty of 770 cars running them. Doesn't sound like a faulty N75 to me, you should look elsewhere

[gheron]

Re: s4 not hitting requested boost

Dv's hold vacume fine, wastegates crack at a little higher than 15 psi, tested the n75 resitance and I'm getting a 33.6 ohm reading, I thought I read that anything over 29 is "bad" can any one confirm?

[Mantis]

Re: s4 not hitting requested boost

I have two confirmed good that I just measured, one at 29.5 one at 30.3

[gheron]

Re: s4 not hitting requested boost

Ryan, are they the ones on the cars or you have a couple laying around? if its the latter mind if i swing by and do a quick swap just to test?

[Mantis]

Re: s4 not hitting requested boost

I have them in hand

pm me