Hi All,

I went out tonight to do a little logging and I noticed something that I hadn't seen in any of my previous logs.

I did a 3rd gear pull as well as a 2nd+3rd gear pull, both with sport mode off. Boost built up to target boost but then at around 12-13psi, the actual boost surpasses target boost by 1 to 1.5psi until I stepped off the throttle. At one point boost requested was 13.3psi and actual boost spiked to 17.3psi, although this was for just one data cycle. The requested boost ramped smoothly from 0 to 16.6psi @5700rpm.
The actual boost ramped linearly up to 13psi @ ~4700rpm but then overshot to the mentioned 17.3psi for a fraction of a second then backed down to closer to the target boost but held about 1.5psi about target through the end of the pull.

I'm also getting a fraction of surge when I let off the gas as the log shows a sample at target boost of 0 but actual of 22.5. Again this is for a split second.

Not sure if this is normal or falls within sensor +/- . Just found it odd as I hadn't seen that behavior before.

I'm also getting some knock values up to -9 for about a second at the top end.

I'm running a Cobb stage 2 OTS at the moment.


Has anyone run into this before?

Thanks all!

Tom

 

Hey Tom,

Shoot us logs would would be happy to check it out for you and go over any questions you may have!

porsche.experts@cobbtuning.com

Thanks!

-Mitch

 

Thanks Mitch! Will send them over

Best,

 

It's normal for boost to overshoot target a little during spool up, particularly with the VTGs. That's why you always see that little torque jump right at full boost on dynos. Also, you are most likely seeing a pressure spike at the pre- throttle body map from the throttle closing and the momentary spike in pressure before the diverter valves open to recirculate the charge.