MoTeC Global Forum

I'm hoping someone can enlighten me to the workings of the wastegate pressure controls for boost control.

I am looking to solve a few issues with target boost on a GPR-Drag package that is using CO2 and wastegate pressure to control boost. I have read through the help associated with it but still have questions as to boost aim when wastegate pressure is driving.

Currently it has onlt wastegate offset set to -70kpa to account for the wastegate spring. I am seeing a higher boost pressure than target, how does boost aim resolve itself when in open loop? is it just using the wastegate aim or is there more of the boost aim system working to reach target boost?
Since I am seeing more than target boost will a negative wastegate scale allow compensation and enable closed loop and drive boost aim to the requested level?

I am sure there are a small number of cars using this and values from each application may differ greatly, I'm looking for clarification as to how the system operates with and without closed loop so I can make this system more accurate

Regards all.

Hi Kevin,

You will need to have the Boost Control Feed Forward Main table populated, and make sure that the Wastegate Pressure Scale has enough range.

Hi Stephen,

Thanks for your help. The document describing the wastegate control system was great in explaining the way the bost control system should operate.

In testing i have found that the wastegate pressure system is unaffected by target boost in the closed loop arrangement only responds to a change in wastegate offset. Boost level is not approaching target and i am seeing 0 wastgate pid while boost as pressure rises. The boost pid system does seem to respond, however it does not relate to the wastegate pressure.

I can supply logs and package files but would rather keep these private as the ip relating to the rest of the tune is not mine to share.

Regards

Hi,

Send them through to support@motec.com.au

Have sent logs though.

Seems that wastgate offset needs to be much more than with open loop, I wouldnt have thought the offset needed changing.

Regards

Have sent dropbox link for logs to support@motec,

Please let me know if these arent available

Regards

I have them, I'll look through them today.

Update on this since someone might be interested

Boost for launch has bee stable but issues arise from asking more boost or rpm. It seems tailoring feed forward should cover this, i have yet to have an opportunity to test.





Wastegate target appears to be much greater than required until within boost range
Once launch boost is increased it overshoots then oscillates until engine speed is sufficiently stable and boost flattens out.
Feed forward and boost pid disappear from logs once boost is outside range, docs suggest it should command 100% duty in increase or decrease depending on the overshoot. I am unclear on how this behaviour is setup or what strps i have missed.

I can upload files as per previous contact if/when required

Thanks

Hi,

Can you send the files through to support @ motec.com.au with details of your issue.

I must update this thread for anyone who might have issues setting up the closed loop wastegate boost control.

It does work as described, although not how i had originally understood it.
Many thanks to Scott and Stephen for explaining it to me and dealing with my frustration as it didnt follow my reasoning.

Back on the horse and one less system to configure.