I would have to disagree with this because of personal experiences. I know for sure that my cars fuel cut is at 7.5, others may have other experiences.

I have never seen any "offical" source on the matter. Has anyone else? NZ, what is your source for the information? I had always hear that s4's were 7.5 and s5's were 8.6

 

Err.. my car is an S4... before I had my FCD it hit fuel cut at 8.x psi.

Others have performed tests on the ECU and found that fuel cut hits at a certain voltage signal which corresponded to 8.6 psi.

 

Mine cuts at 8-9psi (bit hard to read exactly) and I've heard many, many people say the same. The info in the instructions for the TeamFC3S DIY FCD back that up.

 

According to my boost guage, I'm fuel cutting at 7.5 psi. I was beginning to think my boost guage was off but then i noticed that my boost hesitated at 5.5 psi for a little before creeping to 7.5. So, i know my guage is right.

 

Pinning down the exact fuel cut boost pressure is a bit tricky because the ECU will tolerate overboosting at some rpms for a certain length of time. Also, manufacturing tolerances in the various components (eg boost pressure sensor) will affect things a bit. Conventional wisdom is that the S4 and S5 have different cut points though - hence different fuel cut defensers are made for the two different series ...

 

i don't want to sound like a know it all, but i thought that the difference between the two was changes made in the wiring harness. to the point that s4 and s5 sensors couldn't be interchanged cause the wires were switched around. i could have been fed some BS by someone, so please, correct me if i'm wrong.

 

What is that supposed to prove?

And if you say "5.5psi is stock max boost", you're wrong...

 

mines an s5 and i've just hooked up an mbc and fcd in the last couple of days. i figured it would be best to put the mbc on first and adjust it without the fcd on. reason being that if i set the mbc wrong with the fcd on there would be nothing to stop the turbo boosting too high. good job i did this because it turned out the minimum setting on the mbc was about 12 psi and the wastegate wasn't opening at all before the fuel cut kicked in. i hit fuel cut at .7 bar - about 10 psi, sometimes a little higher but never lower. i've now got the mbc set at 10 psi with the fcd on but it does spike to 11 sometimes. should have ported the wastegate while i had the turbo off

 

Isn't that what the WG is trying to achieve? The WG opens at 5.5 and continues opening to keep it at 5.5 until it reaches full open, in which case boost creep starts. The time between when it starts to open and when it's full open is the hesitation I was referring to.