Tuning Boost Control With Bias Table

Testing and development of Megasquirt 3

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nathaninwa
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Re: Tuning Boost Control With Bias Table

Post by nathaninwa »

I would make the delta 50 or larger at first. Maybe near 70

The launch table should use your target table, which would then use the according bias table row. Depending on your max boost level, you should tune your bias table like every 10 to 20kpa. I'd start off at wg pressure and tune just above that. Mine starts at near 170 then when I hit 200kpa it's every 20 after that. It does take a bit of time to tune each row all the way up, but it makes for more seamless boost control in the end

So if your in the 170 area, I'd start off at 140, 160, 180, 200 for boost bias

I would also leave your bias table values where they are right now, make the delta 70 and make a pull and see what boost pressure you get. If it runs like 150 then we know that's the dc to make that pressure and you can tweek values from there
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racerron
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Re: Tuning Boost Control With Bias Table

Post by racerron »

I did read it once. there is a lot of info on this thread. I have to read it again. did not digest it the first time.
racerron
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Re: Tuning Boost Control With Bias Table

Post by racerron »

nathaninwa wrote:I would make the delta 50 or larger at first. Maybe near 70

The launch table should use your target table, which would then use the according bias table row. Depending on your max boost level, you should tune your bias table like every 10 to 20kpa. I'd start off at wg pressure and tune just above that. Mine starts at near 170 then when I hit 200kpa it's every 20 after that. It does take a bit of time to tune each row all the way up, but it makes for more seamless boost control in the end

So if your in the 170 area, I'd start off at 140, 160, 180, 200 for boost bias

I would also leave your bias table values where they are right now, make the delta 70 and make a pull and see what boost pressure you get. If it runs like 150 then we know that's the dc to make that pressure and you can tweek values from there
ok. thank you. I will try that maybe tomorrow.
aidandj
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Re: Tuning Boost Control With Bias Table

Post by aidandj »

racerron wrote:so I guess this thread died. great info on this thread.
Track season started. I ran out of time to tune. I will get back at it this winter and update with what worked best for me.
aidandj
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Re: Tuning Boost Control With Bias Table

Post by aidandj »

EDIT: Posted the wrong logs. Updating now

EDIT 2: Realized my gear calculations were wrong. Will update tomorrow morning when I get another chance. Is there a reason why the temperature changes have such a dramatic change on my boost levels? And why closed loop hasn't been counteracting it?

Its cold here again in the morning and I'm back to hitting overboost.

Log shows that the duty cycle never even drops to my bias table.

Settings and logs:

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muythaibxr
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Re: Tuning Boost Control With Bias Table

Post by muythaibxr »

If I had to guess I'd say sensitivity is set too high and/or PID numbers are too high. IF it's not even getting to the bias table values, then PID is tuned to aggressively.
Megasquirt is not for use on pollution controlled vehicles. Any advice I give is for off road use only.
aidandj
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Re: Tuning Boost Control With Bias Table

Post by aidandj »

When you say "too aggressively" which part of PID do you mean? I will try lowering the sensitivity again.
muythaibxr
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Re: Tuning Boost Control With Bias Table

Post by muythaibxr »

I was just saying overall mainly. Just turn down the sensitivity. We may need an air temp/density component to adjust the sensitivity.
Megasquirt is not for use on pollution controlled vehicles. Any advice I give is for off road use only.
aidandj
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Re: Tuning Boost Control With Bias Table

Post by aidandj »

Now that would be cool. This is the perfect season to test that. Freezing mornings. Hot lunches, cool evenings.
Peter Florance
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Re: Tuning Boost Control With Bias Table

Post by Peter Florance »

muythaibxr wrote:I was just saying overall mainly. Just turn down the sensitivity. We may need an air temp/density component to adjust the sensitivity.
I think that would be helpful.
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muythaibxr
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Re: Tuning Boost Control With Bias Table

Post by muythaibxr »

I'll think about it some more and add it to the list.

The biggest problem with this sort of thing is getting anyone to test it.
Megasquirt is not for use on pollution controlled vehicles. Any advice I give is for off road use only.
aidandj
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Re: Tuning Boost Control With Bias Table

Post by aidandj »

I can definitely test.
muythaibxr
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Re: Tuning Boost Control With Bias Table

Post by muythaibxr »

As a proof of concept, can you try changing the sensitivity slider whenever this happens? Try making it more sensitive or less sensitive in these situations and see what happens. As long as you're doing it in such a way that overboost won't cause you any other problems.
Megasquirt is not for use on pollution controlled vehicles. Any advice I give is for off road use only.
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Re: Tuning Boost Control With Bias Table

Post by Peter Florance »

muythaibxr wrote:As a proof of concept, can you try changing the sensitivity slider whenever this happens? Try making it more sensitive or less sensitive in these situations and see what happens. As long as you're doing it in such a way that overboost won't cause you any other problems.
I wonder if this needs to be a modifier to Bias table?
Peter Florance
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60-2 Wheel LS2 Coils, Low Z Inj
Co-Driver 1999 BMW E46 DSP car.
aidandj
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Re: Tuning Boost Control With Bias Table

Post by aidandj »

Peter Florance wrote:
muythaibxr wrote:As a proof of concept, can you try changing the sensitivity slider whenever this happens? Try making it more sensitive or less sensitive in these situations and see what happens. As long as you're doing it in such a way that overboost won't cause you any other problems.
I wonder if this needs to be a modifier to Bias table?
That's what I expected
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Re: Tuning Boost Control With Bias Table

Post by muythaibxr »

It may need both.
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aidandj
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Re: Tuning Boost Control With Bias Table

Post by aidandj »

The new bias table made tuning boost control very easy. And I got to a good point very quickly. Until the temperature changed. I could run a not very aggressive PID and get good solid results because the bias table matched the conditions so well. But once the weather changed, and I needed say 5% less duty to get the results I wanted it became very difficult. I either had PID running so aggressively that i got oscillation. Or not aggressively and I got overboost. I am very open to testing this. Maybe tuning a "cold" bias table and a "hot" bias table, and blending them.
muythaibxr
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Re: Tuning Boost Control With Bias Table

Post by muythaibxr »

Yeah I am thinking of ways around this. Was leaning towards an adjustment curve for the bias table.
Megasquirt is not for use on pollution controlled vehicles. Any advice I give is for off road use only.
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Re: Tuning Boost Control With Bias Table

Post by Peter Florance »

muythaibxr wrote:Yeah I am thinking of ways around this. Was leaning towards an adjustment curve for the bias table.
I'm hoping it will be pretty linear correction
Peter Florance
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aidandj
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Re: Tuning Boost Control With Bias Table

Post by aidandj »

It happened again. During the day I was maxing at like 12ish psi, and then I went out in the evening and it shot straight to overboost (~14psi). Going to get logs tomorrow.

Looking back this is what I should test.

-Lower sensitivity and see if it fixes the problem.
-Lower the bias table to see if it fixes it too.
-Get logs of all of this.
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