Datalogging fuel consumption?

[rockit]

hi, I was planning on making a little screen to show my instantaneous fuel consumption (similar to what lancers have now).

I made the datalogging cable using the how-to. and i was using mitsulogger (i didnt want to fork out for evoscan) however fuel consumption isnt one of the logged values.

is there some way of getting the fuel consumption data? or more likely does anyone know the equation for calculating fuel consumption from the variables that can be logged?

 

[TME_Steve]

You could log the duty cycle of the injectors and then you would have to relate that to speed. You could use pulsewidth but then you would need a counter. Does that help?

 

[Rabit]

Is it possible to log fuel consumption using Evoscan? Would be a useful thing to be able to do.

 

[rockit]

well i thought it was actually one of the ECU parameters, but after having a look at the OBDII (yeah i know vr4s dont use this, but its something close isn't it) it isn't actually a parameter..

anyway i sort of figured when it wasn't one of the logged values that it isn't something the ecu spits out (otherwise it would probably be included in evoscan/mits logger)

but i'm hoping there is an equation that can be used with the parameters that are avaliable

 

[TME_Steve]

Yes an equation could be written and I think evoscan could do it, pretty sure duty cycle is calculated so that would mean you can use multiple parameters to get an output. Instantaneous consumption is in there by default, just that it's wrong....

 

[rockit]

ok so think i might have the equation..
6*PW*injector size .. that gets the fuel flow in cc/min.. can then divide by 1000 to get l/min miltiply by 60 for l/hr

so we have 6*pw*inject. size*60/1000 (l/hr)

and divide by speed gives l/km

divide by 100 to get l/100km as is standard..

so that gives final equation to be

6*pw*inject. size*60/(1000*speed*100)=consumption in l/100km

this assumes the fuel pressure is at the injectors rated pressure..... which may or may not be true.. i don know if fuel pressure is even a loggable value.

 

[Kenneth]

You also need to make sure you are using the injector pulse width figure BEFORE latency has been added on, since there is effectively no flow during that latency period.