Vaspi
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Automotive Ecu is it possible ?

Sun Jul 03, 2016 11:49 am

Is it possible to use a pi as a engine management sysytem? my aim would to use it on small capacity engines that are normally carburettor run for better fuel burn power and emissions. Or am I being silly?
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DougieLawson
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Re: Automotive Ecu is it possible ?

Sun Jul 03, 2016 1:13 pm

You're being silly. Engine management systems have to run in real-time. A RPi running Linux isn't even close to real-time.
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Vaspi
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Re: Automotive Ecu is it possible ?

Sun Jul 03, 2016 2:14 pm

That is a very confusing answer.

As I was under the impression that sensors can be purchased for the pi for robots etc do thease not react to the world in real time? An engine actually has a stroke value depending on rpm to make a complete cycle this takes a certain amount of time (lag in computer terms) as your probably aware how a 4 stroke engine cycle works, and that time halfs with a 2 stroke engine.

Off the head figures there is probably a 14ms window for a 4stroke engine to make calculations for the air fuel mix.

How familiar are you with vehicles? not to be rude could you back up your answer with anything , as I don't want to give up on one mans answer on the Internet unless it's a fact. Just trying to be constructive not rude.

Thanks for replying I appreciate it
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DougieLawson
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Re: Automotive Ecu is it possible ?

Sun Jul 03, 2016 2:47 pm

You're still wrong. ECUs are real-time processors that need to keep step with the timing of the engine. Get out of step and the engine will disintegrate drastically (a bit like the way Sainz's engine went at Austria yesterday).

Most ECUs are built on PLCs or FPGAs with a specially made real-time control program.
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acewiza
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Re: Automotive Ecu is it possible ?

Sun Jul 03, 2016 2:50 pm

I think it's funny how people get ahold of a Pi, play around with it a bit then start imagining how it could potentially do almost anything. Not a bad way to think, but as Clint Eastwood so astutely put it, "a man has got to know his limitations..."

Vaspi
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Re: Automotive Ecu is it possible ?

Sun Jul 03, 2016 3:44 pm

I also think it's possible only intrested in air fuel mix as this would only ever see 150cc project, just want a clean burn. But in the same breath if the pi isn't up to the job can you point me in the right direction. as it somthing I like to work on as a mechanic this is the only part of a vehicle that still just the magic box to me. I know the theory, held and fitted thousands of them.
But to develop one be cool.

Like I mentioned as a mechanic I can find uses for a pi still in vehicles so no real issue finding a vehicle project with a pi. But a low cost ecu could Benifit so many countrys that use carbs regularly still just saving money on fuel be a win for me.

Thanks for the help
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Re: Automotive Ecu is it possible ?

Sun Jul 03, 2016 6:22 pm

Vaspi wrote:I also think it's possible only intrested in air fuel mix as this would only ever see 150cc project, just want a clean burn. But in the same breath if the pi isn't up to the job can you point me in the right direction.
You've now changed what you aim to do to something far more modest and, I think, possible. Early attempts to bring in computers to automotive engines included basically replacing the carb with a computer controlled device that injected the fuel in a similar location, I think that's throttle body fuel injection. Doing that and doing what you originally suggested, which was to emulate a modern ECU, they inject measured fuel into each cylinder at exactly the correct time, they advance and retard the spark of each plug (or set of plugs in a waste spark system) exactly at the right time, etc., this sort of thing is hard real time and is what the pi is ill-suited for.

Some sort of FPGA, which often include ARM processors on their boards or even within the FPGA itself, is often what is used. A middle ground might be something like a Beaglebone Black/Green that include two PRU processors that can be dedicated to real time activities. But starting out by simply converting from carb to throttle body fuel injection would, I think, be within what could be done with a pi without needing to add an FPGA to it, although I am speculating here.

And I'll add the following because safety can't be repeated often enough: Keep in mind that fuel injection means gasoline is pressurised and squirted around, hopefully in the correct places and in the correct amounts. If you've ever had occasion to be around a burning gasoline vehicle, you'll agree that you cannot allow any chance of gasoline catching fire, which means no leaks are allowed, which means no chance that anything pressurised can pop free and get flammable liquids or fumes on hot surfaces.

Vaspi
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Re: Automotive Ecu is it possible ?

Sun Jul 03, 2016 9:48 pm

I never changed my objective , I just don't think I made my question clear enough.

Mechanical side is the easy bit I could make the system no problem , I just cannot make the brain so to speak. I will have to look into the options you gave me , thank you
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dancytron
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Re: Automotive Ecu is it possible ?

Sun Jul 03, 2016 11:00 pm

You can look at how the early pre-OBD-I computer controlled engines on Jeep 4.2 Liter engines worked. It was in production from about 1983 to 1990. It used a 2 barrel Carter carburetor that had a stepper motor that moved a pair of needles that controlled the amount of air coming into the carburetor to control the mixture. It also retarded the ignition timing as needed via the computer. Many people who own them either bypass the computer or convert them to fuel injection. Lots of information here. http://home.sprynet.com/~dale02/list.htm

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