Correct me if I'm wrong but doesn't absolute pressure or atmospheric pressure change by the elevation>?? Here in Utah at about 4200 feet above sea level we have less atmospheric pressure than in Cali or somewhere else close to sea level....therefore the math changes, right??

 

It's not that much of a change, maybe 1 psi. Sea level, is 29.93 In. of Mercury Squared for 14.7psi. That's standard pressure, higher altitude only changes the Mercury by a few tenths, thereby reducing or increasing psi by 100ths of a psi,. and whatever the barometer is doing will also have an effect on it, but still a VERY small one. I carry a digital barometer with me when I fly in order to get very precise altitude readings, and at 5k feet flying over Fl, on a "standard day" (29.93 at seal level), it only drops to 29.85, which is 14.661 psi., so there's not much change.

 

...although a n75 valve is for a stage 3 setup for sure. if you want to run more than 19 psi.

And stock is like 9psi or 10psi.
...The GIAC stage 1 chip I was running 17psi.

 

Every B5 S4 came with an N75 valve. It has nothing to do with stage 3.

Mike "2k s4" doesn't come around anymore since his s4 was totalled so trying to correct him on a year old thread probably won't do much good.

 

I dont know if im posting in the right place, im new to this site.
Just wanted to know if any of you would know what the problem is or could help me with it.
My car is acting like it is having a boost/fuel cut problem. THe car shakes alot and the stock exhaust sounds like i have a 2step setup, but only does it when im wot and it tries to boost. It does this when it goes above 5psi and i tri to make it hold their, but it only stays till the check engine flashes and the nit drops down to 5psi. I have a APR Ecu reflash and it boost up to 17 and settles around 15psi about. I just recently changed my intake TBB and it was running fine for almost a week. then it started doing this. Its very annoying especialy when u want to pass some one on the road and ur car basicly cuts the hp on you and u got a semi coming right at you! LoL
thanks in advance for you that put in an effort to try and help!

 

sounds like you have an ignition coil bad, had the same problem and turn out that #5 coil was bad after checking it with a scanner, after I replaced the coil the engine was pulling strong again all the way to redline

 

Change your plugs too. If the coil was bad, wouldn't it run like crap all the time? I've had plugs go bad and it causes the spark to blow out and the car will buck. There may be a way to test the resistance in the coils and if one or more are out of range then change them too.

 

i hope they got it fixed.... that was a year ago.. fyi..

 

I may be trading my 02 cbr 954rr for a 2000 audi tt is there anything I need to worry about with these cars.... like constant problems..... are the turbos good or do they go bad fast plz let me know thank you...

 

well i just got an 01 s4 and i used an app on my iphone to measure psi. It says my boost is at 14.5 psi when i floor it? the guy i bought it from says car is completely stock. how can i tell if it has a tune? it doesnt feel all that fast either tho. Car is an automatic.