Tuning Boost Control With Bias Table

Testing and development of Megasquirt 3

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aidandj
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Re: Tuning Boost Control With Bias Table

Post by aidandj »

If it gets cold enough tomorrow I will do a test this evening and in the morning. Its like 95 here during the day, not sure how much it will cool down.
muythaibxr
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Re: Tuning Boost Control With Bias Table

Post by muythaibxr »

OK. I'll look for logs when you post.

Ken
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 »

Its been way too hot here lately. Still waiting on a cold morning.
racerron
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Re: Tuning Boost Control With Bias Table

Post by racerron »

so I guess this thread died. great info on this thread.
Dennis930
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Re: Tuning Boost Control With Bias Table

Post by Dennis930 »

I have question regarding MS3 1.4.1 boost control. When boost pressure approaches the target KPA minus the delta, does the boost duty go to the specified duty in the bias table for the target boost? Or does it go to a value that represents the current load/RPM duty when boost pressure reaches the delta point? I am just trying to understand what I am seeing in datalogs when tuning.
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racerron
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Re: Tuning Boost Control With Bias Table

Post by racerron »

I believe it goes to the boost control biased duty table
nathaninwa
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Re: Tuning Boost Control With Bias Table

Post by nathaninwa »

You are correct. It uses the current boost target row You should have rpm points lower than what your target will make. Mine starts around 3000 rpm. If you set the delta to like 100 then you get total boost dutys needed. Then when you see a trend you can decrease the delta. Mines at 20 currently and that doesn't give me any overshoot
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Dennis930
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Re: Tuning Boost Control With Bias Table

Post by Dennis930 »

OK, so if my target boost is 217 KPA, my delta is 25, I am seeing my logs when it gets to about 198 KPA it switches to the bias table. That duty value will be the duty at say 3100RPM and 198 KPA and not the target duty for 217 KPA? I am still in closed loop basic and boost does not reach the target. I have the slider adjusted to 160. Do I need to lower the slider to get it to the target?
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Re: Tuning Boost Control With Bias Table

Post by nathaninwa »

Post a log and msq. Until boost is reached you should be in setup mode in which case the slider and pid are inactive. Duty is just most likely to low If your target is 217, you need at this point a 217 bias table row, it will use the values in that row only
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Peter Florance
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Re: Tuning Boost Control With Bias Table

Post by Peter Florance »

You too, Ron. Post a log
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racerron
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Re: Tuning Boost Control With Bias Table

Post by racerron »

im having some problem getting the boost to hit the boost target. most of the passes on the dragstrip were under boosted. one was over boosted. had to abort run and did not log that one.
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Re: Tuning Boost Control With Bias Table

Post by racerron »

log
racerron
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Re: Tuning Boost Control With Bias Table

Post by racerron »

this log the boost hit the target but not until the last part of the run. the boost was oscillating so I moved the slider down and it went away but still did not hit the target.
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Re: Tuning Boost Control With Bias Table

Post by racerron »

this msq I had the bias table set higher and the lower limit delta at 5 kpa. this tune felt like the boost was way over shooting and had to abort the run.
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Re: Tuning Boost Control With Bias Table

Post by racerron »

other than going to the dragstrip is there another way to test boost control target?
nathaninwa
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Re: Tuning Boost Control With Bias Table

Post by nathaninwa »

In setup mode, the slider has no effect on tuning. Its using bias table values only. You are just low on the dc. I would suggest if your targeting 175, to have a 175 row on the bias table as well, then you can stick to just this row for tuning that boost target.

Make your delta larger, say 70 at this point. One log you had a target of 170, with a delta of 20 I bet, and you oscialted pretty bad. That's from dc being to low. With the larger delta, that will allow actual DC being used and not to reenter a 100DC state.

It might be worth making the code in setup mode to use 100%dc for the initial hit, then to only use the bias table. <(note for devolpers)
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nathaninwa
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Re: Tuning Boost Control With Bias Table

Post by nathaninwa »

Just looked at the last MSQ with delta of 5. Until you get boost tuned, forget about making it so tight. Use a value that is the difference between your target and 100KPA. This will use the bias table only and will only ramp boost in slower. Once you hit your target then you can tighten the delta up. I use a value of 20 personally

The delta is the value below your target that the code uses 100% dc to ramp boost in. If target is 175, and your delta is 5, then it will use 100% till 170kpa, then it will use bias table values. If the values are low, and boost drops below 170, then it ramps back up to 100% again. This is the oscialltons your feeling. So raise DC in the bias table some, and raise the delta number till your boost is flatlined

For testing, I have a super top secret back road, and Ill also use freeway onramps. Ill get into third gear, and make a pull from 2K on up. I can get to 80 pretty quicly and that will give me the data I need as trends are showing
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Re: Tuning Boost Control With Bias Table

Post by Peter Florance »

nathaninwa wrote:Just looked at the last MSQ with delta of 5. Until you get boost tuned, forget about making it so tight. Use a value that is the difference between your target and 100KPA. This will use the bias table only and will only ramp boost in slower. Once you hit your target then you can tighten the delta up. I use a value of 20 personally

The delta is the value below your target that the code uses 100% dc to ramp boost in. If target is 175, and your delta is 5, then it will use 100% till 170kpa, then it will use bias table values. If the values are low, and boost drops below 170, then it ramps back up to 100% again. This is the oscialltons your feeling. So raise DC in the bias table some, and raise the delta number till your boost is flatlined

For testing, I have a super top secret back road, and Ill also use freeway onramps. Ill get into third gear, and make a pull from 2K on up. I can get to 80 pretty quicly and that will give me the data I need as trends are showing
That's what I was trying to explain to Ron on our phone call.
Get the Bias table tuned first as described above ^
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racerron
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Re: Tuning Boost Control With Bias Table

Post by racerron »

ok thank guy. I think personally I learn better by reading then talking on the phone (no offense peter).that way I can read over again. I will try the on freeway on ramp pull and work on that bias duty table and you said put the delta at 50kpa. one other question does the launch kpa use the bias table also for a target?
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Re: Tuning Boost Control With Bias Table

Post by Peter Florance »

racerron wrote:ok thank guy. I think personally I learn better by reading then talking on the phone (no offense peter).that way I can read over again. I will try the on freeway on ramp pull and work on that bias duty table and you said put the delta at 50kpa. one other question does the launch kpa use the bias table also for a target?
None taken. It's why I suggested you read this thread in the first place
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