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Which means "Evil Twin". Lets see your projects where you change boring into fun or create the fun from scratch.
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 Post subject: Re: fuel pump control
PostPosted: Sun Oct 25, 2015 9:38 pm 
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The reason we did the bang-bang control is because we didn't have a fuel mass calculation on the 'old' alpha-N software and the new air model came with a physical pressure regulator so we got rid of PWM control and went to 'pump is on when engine spins' control.

But accurate, learning open-loop control systems are a favorite of mine.

You could probably break it down into tables purely based on fuel pump characterization.

Sum of fuel_req for each cylinder * cycles per second = fuel flow g/sec which should match fuel pump flow rate steady-state.

Fuel pressure could come from a speed/load table, or some other logic (e.g. tied to an idle mode flag or something like that). But the target fuel pressure comes from somewhere.

Pump flow rate should be a function of input voltage (or battery voltage * PWM DC) and pump pressure. You can solve for required voltage based on target voltage and current flow rate, OR current pressure and current flow rate.

The closed-loop pressure part can use a transient error function (additional flow request based on pressure error) and steady-state error function (slow I type control to hold pressure by adding flow rate, which adapts pump flow rate). Adaptive and physical-based controls require less tuning parameters and they are less dependent on the individual characteristics of your system as long as the models are accurate enough.

Theoretically you should be able to enter a few pump characteristics (flow rate vs pressure) and the control algorithm should figure out the variance of the pump and control well without much tuning. If the math is correct.

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 Post subject: Re: fuel pump control
PostPosted: Mon Oct 26, 2015 8:33 am 
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The problem is getting good pump data :?


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 Post subject: Re: fuel pump control
PostPosted: Mon Oct 26, 2015 10:22 am 
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I would probably bench-test the pump similar to a fuel injector. It's easier than bench testing an injector.

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"Any sufficiently advanced technology is indistinguishable from magic" ~Arthur C. Clarke


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 Post subject: Re: fuel pump control
PostPosted: Mon Oct 26, 2015 1:27 pm 
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Agreed on the bench testing.

Kinsler, RC and others do this, but are very pricey. All you need is a good, stable DC voltage supply (ie a battery with a charger on it), your PWM circuit, a pressure regulator and some instrumentation. As far as flow measurement goes, you can do a known quantity (like a gallon) over time to get the flowrate, or invest in a little turbine meter.


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 Post subject: Re: fuel pump control
PostPosted: Mon Oct 26, 2015 4:00 pm 
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cribbj wrote:
Agreed on the bench testing.

Kinsler, RC and others do this, but are very pricey. All you need is a good, stable DC voltage supply (ie a battery with a charger on it), your PWM circuit, a pressure regulator and some instrumentation. As far as flow measurement goes, you can do a known quantity (like a gallon) over time to get the flowrate, or invest in a little turbine meter.


For the pump it's $60 at RC
https://www.rceng.com/Fuel-Pump-Service ... x2428GMZZ4

No way would I go to the trouble of setting up my own bench test for that.

...and while that's certainly the best way, I'm probably not going to to it and will just rough something in because once I add a regulator it's just a heat management issue and I've already ran this pump with no PWM on the last 2 engine with no issues.

Good is running and fun but perfect is never finished ;)


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 Post subject: Re: fuel pump control
PostPosted: Mon Oct 26, 2015 4:50 pm 
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They've dropped the price substantially!!!

Last time I contacted them, they wanted another zero on that figure.

But then, I wanted a pump curve from atmospheric to max pressure, at 6-8 different voltages, so they priced it such that each voltage would have been a separate run/test.

Kinsler were the same way.


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 Post subject: Re: fuel pump control
PostPosted: Mon Oct 26, 2015 9:56 pm 
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cribbj wrote:
They've dropped the price substantially!!!

Last time I contacted them, they wanted another zero on that figure.

But then, I wanted a pump curve from atmospheric to max pressure, at 6-8 different voltages, so they priced it such that each voltage would have been a separate run/test.

Kinsler were the same way.


hmmm....they talk about pressure from o- full but don't mention voltage, you probably just get 13.7V for $60


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 Post subject: Re: fuel pump control
PostPosted: Mon Oct 26, 2015 11:31 pm 
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It's not terribly difficult to flow test using an adjustable regulator, battery with charger, and bucket. It does, however, take a lot of time.

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