Steven Lin

<center><img src="http://pictureposter.audiworld.com/953/log.jpg"></center><p>What is the expert opinion about what is going on here?

Why is the actual boost rising before requested boost, in the beginning?

Does the lag look acceptable?

Is the residual boost at the tail end a sign of stuck BPVs?

DAP@EPL

Actual boost sometimes fluctuates a bit with partial throttle even when requested boost stays at the baseline.

And I usually see the residual boost like that after letting off the throttle as well. A stuck BPV would be indicated by an actual boost spike between shifts rather than the drop off shown.

-Dave Pramanik

mpwolf

It looks a little strange, but I haven't been looking at this data for too long. Here's my stock S4 at full throttle:

<img src="http://pictureposter.audiworld.com/26345/block_115.jpg">

pattersom

The spikes can be associate with part throttle actual pressure surges (boost not being requested), but they could also be a broken bypass diaphram.

Easy to check too - see if they hold vacuum. If there are toasted, they won't hold a smidge of vacuum and result in the boost spikes your seeing.

Steven Lin

This was logged while taking city streets to work.

Thanks, everyone. Guess it's normal.

M3iRiSH

Seems fine, I get the same thing...