Counter

[Butio1]

hello to you all
I need some help on the next thing:

I have a car with injection. I want make a time elapsed counter (in seconds) that counts the total time that i have pulses in th injector. In that way I can in a distance known know exactly the amount of gasoline i have consommed.
I have search the web searching for circuits that can make that, but .
any help?
thanks
carlos

 

[tunedwolf]

your idea is flawed....

If you accelerate, more fuel is put into the injection system, the injectors are fired for longer, thereby consuming extra fuel. The engine management system takes care of load to a degree, so when you start to go up a hill for instance and extra load is placed on the engine, the management system will add extra fuel to prevent stalling. Then there is the effect of the Turbo to consider also...etc etc

It would make more sense to have a flow meter on the fuel line and plot the result against time.

 

[audioguru]

When you run out of gas the injectors still fire so you might think the engine is using too much gas.

 

[Butio1]

what I need fot now is a time elapsed in seconds with display...
That will be graet as a start
Thanks again
or links for a page taht have it...
regards

 

[kamdy]

I think i you measure the pulse width of the injector pulse it will give a measure to how much fuel is injected in the cylinder

 

[audioguru]

I think i you measure the pulse width of the injector pulse it will give a measure to how much fuel is injected in the cylinder

The car's computer already knows exactly how much fuel is injected. The injector's pulse width is only part of it. The fuel pressure changes with the amount of fuel and how often (RPM).

 

[evandude]

I'm sure the accuracy will be somewhat limited. Fuel-injected cars will have a fuel pressure regulator, but I wouldn't expect it to be an extremely high-precision device (and your fuel pump will have limited pressure/flow as well), so (as audioguru said) you would probably end up with variations in fuel pressure with other factors, and thus your duty cycle alone would not tell you the exact amount of fuel you were using. How closely you could predict it would depend on how good your FPR regulates, and/or whether you try to model its imperfect performance if it is too far from ideal.

Also, in response to someone else's idea, a flow meter on the fuel line is not a great solution either, because with a FPR you have both a feed line and a return line, so you would have to accurately measure BOTH flow rates and find the difference. I think this would end up introducing more error than the other method, not to mention being much more complicated (I don't think a gasoline-safe flow meter that will not interfere with your fuel system's operation is going to be a very common item)

 

[tunedwolf]

I don't think petroleum flow meters are a common component to find off the shelf, but neither is what the poster is trying to achieve going to be simple or straight forward. Any good engineering firm can produce a safe mechanical component to allow the measurement to be taken. Let's face it, if a cheap plastic fuel filter can be used, I see no reason why a machined and properly sealed alloy component can't be. The accuracy of such a component can be tested and controlled at the time of design, and any small adjustments made in software.

 

[Butio1]

fuel

Hi to you all
My idea is measuring that pulse of injector, and measuring the real debit in one second make some sort of fuel comsumption meter. Is the pressure of the fuel rail not constant? And how the regular computers measure besides the injector pulse in order to calculate the fuel comsumption?
I' will keep tring put that idea in pratice...
rgds

 

[Nigel Goodwin]

Hi to you all
My idea is measuring that pulse of injector, and measuring the real debit in one second make some sort of fuel comsumption meter. Is the pressure of the fuel rail not constant? And how the regular computers measure besides the injector pulse in order to calculate the fuel comsumption?
I' will keep tring put that idea in pratice...
rgds

I presume that's how the built-in ones work?, but mine certainly isn't very accurate - it always reports fuel consumption as better than it is - suggesting 55mpg when I'm actually getting about 45mpg. I've also logged all the petrol I've put in the car, along with the mileage reading - one day I'm going to stick it all in a spreadsheet and run the figures.

 

[Butio1]

thanks. lets forget the reason I need the counter .
regardless the fuel, please anyone has a a time elapsed circuit in seconds, that I can try?
thanks very much
carlos

 

[Nigel Goodwin]

Probably the simplest way is to use a PIC?.