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cj.surr

Boost Stage 2 PID Tuning

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I'm having an issue trying to dial in the PID settings for closed loop boost. I get a slight boost spike on spoolup. I think it is because the P-value is adding duty cycle immediately when the boost control transitions from Stage 1 to Stage 2. This correction doesn't make sense because the wastegate is transitioning at this time and any corrections will be delayed. If I lower the P-value sensitivity, I don't get all of the high RPM correction that I need (my setup is prone to creep). 

Are there any recommendations for working around this issue?

It seems to me like there should be a delay before correction when transitioning between Stage 1 and 2. And/Or, separate P-value sensitivities set for Stages 2 and 3.

Thanks

CJ

PID boost.png

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45 minutes ago, cj.surr said:

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It looks like the wastegate duty cycle table needs tweaking first, it doesn't look very tuned?.  The I-term is having to do a lot of correction to maintain steady boost.  Once it's tuned, the PID terms will have less work to do and it should make tuning a lot easier...

 

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I wouldn't say the DC table is perfect, but it's about as close as I can get it. (IWG on a big, fast spooling turbo being fairly inconsistent). The I-value is pulling about 2%, not a lot. Seems like it wanted about 19% DC to hit target, and in my WG table it was 21%.

 

I think the problem is that when transitioning into Stage 2, the DC started at 26% because the P-value is immediately being applied (Table value is 21%). It tapers down towards 20% but since the WG has a delay (at least a few tenths of a sec), the higher DC initially does contribute to overshoot. 

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