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Old 11-10-2015, 11:17 AM   #21
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Originally Posted by Braineack View Post
tune PID by hand like a man.
I can max P I and D or set them all to 0. It behaves practically the same.
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Old 11-10-2015, 11:38 AM   #22
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I can max P I and D or set them all to 0. It behaves practically the same.
That's not tuning. Add a **** ton of I and see if the oscillations go away.
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Old 11-10-2015, 12:06 PM   #23
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I can max P I and D or set them all to 0. It behaves practically the same.
if youre telling the MS basically not to do anything (200 0 0), but it does, then I'd start looking as to why it's doing what it's not supossed to do.
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Old 11-10-2015, 09:13 PM   #24
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So I did what Braineack said. I went and tuned the PID, like a man. Actually I did what aidandj said as well.

I turned up I to 200 and left P and D at 0. It behaved completely differently, no oscillation. It just shot staight to overboost. Long story short I was pretty excited cuz this was the first time I actually saw it do something different. I started lowering I and eventully settled on 20. Anything more then 35 would make it go straight to overboost while anything lower then 10 would oscillate like crazy. With PID or 0/20/0 it would it would now sort of get to the desired 15psi and sort of hold it. Progress.

From there I started increasing P. I found that anything below 8 did nothing and anything above 15 made it oscillate to hell and back, much like it was doing at previously. I settled on 11 because it seemed to keep overshoot under 2 psi.

Frankly I have no idea what D does. I played with it a bit and left it at 15. It seemed to be better but honestly I think its all in my head. Please explain what I should be looking at.

At the end of the day Im left with this:




The target is 15psi and I hit it initially and then taper off. The boost duty has room to help that out significantly. Which gain will help with this?





Current settings.



What was screwing me up was two things. This is my first time tuning a PID and I have no idea what to expect. Every guide has always focused on P first. Without and I, my setup oscillates no matter what the P. The second thing is that from what I have seen, I was expecting much higher gain values, nothing this low.

Either way, Im feeling pretty confident about this whole closed loop thing and think I can get it pretty damn close before my dyno run on thursday.
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Old 11-10-2015, 09:26 PM   #25
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I'll write more later. But 2 things. 1. It makes sense that you had oscillations without I. All P does us try and get you to the target as fast as possible. If you are 100 away it will add 200. Sudenly you are at 150. (These are all made up numbers) what I does is take the error over time into account and smooth out the output.

2. The sensitivity slider is still active in advance mode.

3. Post your logs on msextra. It looks like basic mode is too sensitive.
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Old 11-10-2015, 10:41 PM   #26
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So if I understand correctly, more I from where it is now should help get me hold target with less tapering off.

Is 50 a big number for the lower limit delta or is it normally ballpark?

I'll address the basic sensitivity issue later this week. I'd like to get it close with what I've got. It seems doable now. I'll ask th e ms extra forums for a more permanent fix after I get my dyno pull in.
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Old 11-10-2015, 10:45 PM   #27
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Adjusting sensitivity will cause you to need to retune PID. 50 is fine for the old boost control method.

Yes.

Lower P until you barely get overshoot. Add I until you have no more oscillations. Add p back if you loose initial spool. Adjust I accordingly. Use D to dampen sudden changes.
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Old 11-11-2015, 10:00 AM   #28
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You need more I to hold the target to redline.

then youll have to add P to hit the initial target again.

then more I to combat the extra P.

then add in lots of D if oscillation kicks in.
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Old 11-12-2015, 04:30 PM   #29
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So I had my dyno runs today and I think I found the problem causing most of this.

We first did pulls at low boost, wastegate actuator only. Each run the system would build 15ish psi (on a 7psi actuator!) Then taper off down to 8-10psi. It was the first few runs so we just figured that's how the setup reacted.

We decided to go to high boost (ms controlled at 15psi). Every run was going straight to overboost! I kept decreasing P and increasing I and still overboost. I switched to open loop and still overboost. I lowered the dc of everything below 7k rpm to 0% and still overboost. Switched back to actuator only and was still overboost.

Obviously it was pretty clear that there was a wastegate issue so we disconnected the wastegate actuator and put 7psi shop air to it and it wouldn't budge. Put 15psi and it barely moved (and when it did it was sticking).

So more likely then not I had a dying actuator this whole time which would tend to stick or be hard to open. This probably caused the PID loop to over react which caused the oscillation. Finally after the actuator got hit with repeated 20+ psi of overboost it **** the bed for good. Understandable since this was a 20+ year old part with a 20+ year old rubber diaphragm.

When the new actuator arrives hopefully it will be smooth sailing.
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