Boost control duty temperature compensation

Testing and development of Megasquirt 3

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3.0 GT
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Boost control duty temperature compensation

Post by 3.0 GT »

I am not sure if this is something that has been discussed before or not, but I could find some value to it. I find that if I fully tune boost control perfectly on one day, either closed loop using the initial value table or open loop just filling in the duty table, it is always different on another day.

For example if the boost control is holding perfect and then tomorrow Its colder and I drive, the boost will spike and boost high. If it is hotter the next day boost will undershoot and the overall psi will be lower.

I know with closed loop it should be able to adjust quickly for that, but I find if the initial value table had a temperature curve on top of it that adjusts the initial duty table values by X amount based on IAT temps. Similar to the air temp compensation curve for fueling, but for boost duty.

Is that something that could be added to make for the most reliable boost settings at various IAT temps? I would love for boost to not spike when cold and not have to ramp up to target from PID reactions when its hot. Thanks for reading.
LSXCutty
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Re: Boost control duty temperature compensation

Post by LSXCutty »

This is another great suggestion. I have had same issues to the point I want used closed loop boost. Just in setup mode.
KeithBoden
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Re: Boost control duty temperature compensation

Post by KeithBoden »

How about this? Based on 1.4 source, untested, but rather straightforward implementation of adjusting the target duty cycle from the table based on a temperature curve. PM me if you want to try it!
Camaro, Mark IV aluminum big block Chevy, 8.8l, Procharger F1-R @ 12psi, MS3Pro
nathaninwa
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Re: Boost control duty temperature compensation

Post by nathaninwa »

That's really cool. My 2jz car suffers from this issue
Volvo 940, 2jzge, MS3Pro, daily
240Z, 2JZ, MS3Pro boost control
3.0 GT
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Re: Boost control duty temperature compensation

Post by 3.0 GT »

That looks neat and I would love to try it, but have since switched to 1.5 and got all the engine states and new changes all configured and running well again. I would hate to have to go back :/

I am also on a 2jz, with a holset he351cw
KeithBoden
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Re: Boost control duty temperature compensation

Post by KeithBoden »

All good! I'll keep this branch of code for you and when the source for 1.5 comes out I'll rebase on it and update this thread!
Camaro, Mark IV aluminum big block Chevy, 8.8l, Procharger F1-R @ 12psi, MS3Pro
tpsretard2
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Re: Boost control duty temperature compensation

Post by tpsretard2 »

My STI also suffers from this problem. the implementation looks good to me..
aidandj
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Re: Boost control duty temperature compensation

Post by aidandj »

I've also seen this issue since switching to the 1.4 boost control method. Ken discussed it a while ago, wonder if they could implement it in the next beta
3.0 GT
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Re: Boost control duty temperature compensation

Post by 3.0 GT »

Yeah, I would love to see this put into the next beta so we could test it... Hopefully.
LSXCutty
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Re: Boost control duty temperature compensation

Post by LSXCutty »

Does anyone else also notice a difference based on gear?
TurboFan
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Re: Boost control duty temperature compensation

Post by TurboFan »

We need this feature.
BMW 525i, stroker 2.8L, MS3-Pro 1.4.1, BIPs 373, 66mm turbo 30 psi
Toma
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Re: Boost control duty temperature compensation

Post by Toma »

This is normal behaviour. Some ecu's use open loop duty, then have a boost target error duty adder. It's almost like closed loop, but nifty implementation.

With your observation, there are 2 things play here.

Actual Inlet air temps.
people insisting on mounting a MAC valve rated at 120F in the engine bay, and especially next to the turbo hot side. lol
suberimakuri
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Re: Boost control duty temperature compensation

Post by suberimakuri »

What a good idea (temperature correction). Would like to see this integrated.
I haven't looked at the boost by gear but that's the second issue if running very tight boost targets. Typically I just build targets based on 3rd or 4th gear.

Boost control gets surprisingly complicated when you want to achieve better results than the spring will give.
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