> >
> >> If the ScanGauge II gives actual sensor voltages and frequencies, then
> >> it is worth the money. I'm not that interested in all of the other
> >> stuff the unit displays, but it might be worth it for someone who is. >
> >> No problem leaving it plugged into the OBD II port unless you leave the
> >> vehicle parked for long periods, where it will probably drain the
> >> battery more quickly.
> >> --
>
> >> Ray O
> >> (correct punctuation to reply)
>
> > I'd like to know how they are calculating mpg just from ECU data. Makes me
> > wonder how it can tell the mileage difference from say a 41 mpg Corolla,
> > and a 27 mpg Chevy Impala for instance.. "actual real life ratings, I've
> > driven both". The Impala had that mpg indicator built into the car on the
> > headliner display.
> > Seems to me you would have to calibrate the thing according to miles
> > driven, and gallons of gas burned. They seem to let you input gas data. >
> The ECU now controls everything; the speedo, the odo, everything.
> It would be a simple calculation from the data to figure fuel economy.
In addition, the car must have some way to determine how many gallons of fuel (or more likely, how many pounds of fuel) are left in the tank. Otherwise, the car's computer would not be able to estimate how far the car can go until the tank is empty. It can use this and the miles driven to determine average mileage.
Jeff