Boost level, does this look right??

[MNRS6]

Just got a brand new Ross-tech VAG com cable so I decided to log some pulls. Take a look, does this look right? Seems like it should be smoother. I don't thing the tune is stock.

[SzymekCRX]

Looks stock.

Something's not right though. Looks similar to when I had a leak in my intercoolers. It does not hold the boost right and I don't like this surge when You release the throttle.

Possible causes for not holding the boost:

- leak in the intake (all the way from MAFs to the TBody)
- vacuum hoses leak (especially near the N75)

Surge:

- DVs failure
- N249 failure (and hoses around it)

Do a visual check at first under the hood

[MNRS6]

Those all seem like easy things to check. I have a nice 600 mile road trip at the end of January I would like to have these issues cleaned up by then.

Thanks
Jim

[4everRS]

I guess is diverters

[MNRS6]

What is the technical term for the diverter valve and where are they located? I have the eBahn manual and cannot find it.

Thanks!

[kday]

The diverter valves are known by a few names -- bypass valve, recirculation valve, even sometimes (incorrectly) blow-off valve. The Bentley manual calls them "overrun air recirculation control valves".

Does your car make a weird sound when you lift the throttle after accelerating hard? For reference you can search youtube for old Audi Group B rally videos. Those cars didn't run bypass valves, and the pressure surge when the throttle closes abruptly makes a very distinctive sound. (I really enjoyed the few weeks of having a stuck-closed bypass valve on my Ur-S4, which has a similar engine to those old Group B cars.)

edit: couldn't resist watching one again: http://www.youtube.com/watch?v=DGIiarIrUCI, 1:33 and 2:13 for the surge noise.