4CE FED NOGARO

Can anyone tell me what is the stock boost level of the B8 Audi S4? Is it different in comfort vs dynamic?

rktskicar

~ 12 psi max. If you have a VAG (VCDS), you can measure it (block 436).

Bruce

NWS4Guy

This, plus remember it's NOT a turbo, so those are apples to oranges. Also, stock boost bleeds off from about 5200RPM north. APR tune will remove that so it builds to redline.

rktskicar

boost is boost. The peak SC boost is fixed by the pulleys and SC. The turbo boost is not, so can make more psi down low than up above if needed. block 436 (absolute manifold pressure) is for the B8 S4 for boost, was block 115 (requested and actual boost) on the B5 S4.

Bruce

primetime

I have vagcom logged 13.4psi and Richib has seen as high as well...

rktskicar

true enough. the OP is asking about stock boost levels though.

Bruce

GR8-LIFE

I doubt comf vs dynamic changes it. What I noticed about dynamic mode, aside from the red line shifting, is when steadily crusing in certain gears the RPMS are just a bit higher. I tested this out by driving in cruise at 60 mph and when I changed form dynamic to auto and the rpms dropped like 400 - then went back up 400 when i switched back to dynamic. It would be nice if they had a boost gage. That way, you know the boost and also if there is a boost problem. You will feel a boost issue when its obvious but not a subtle change so a gage makes things easier. With a gage you will also see when the real hot weather slightly affects the performace (even though it is intercooled). I really wont be modding this car much but A gage of some sort will be my next purchase.

helix139

You must have the S-Tronic and it must drop down from 7th to 6th in dynamic. Otherwise RPMs at any speed in a given gear will always be constant unless your clutch is slipping

GR8-LIFE

yes, I have the s-tronic. The gear drop makes sense. Perhaps it goes into the higher gears at higher speeds in dynamic. I will have to test this out

CJ_S4

I bet we are making peak boost before 5200 rpm...The torque plateau begins around 3000 rpm, which I suspect would require peak boost or something close to it. My guess would be that it builds peak boost very low in the rpm band and just bleeds excess until the 5200rpm number then it really starts venting boost (for some reason). This would allow the ECU to better control boost levels with the bypass valve rather than being dependent on engine rpm. Like you mentioned the APR tune keeps the boost in longer.

Just a hypothesis...