Fuel consumption data from a scan tool?

[Gasoline Fumes]

I have a Tech 1A scan tool that works in my 1994 Metro. Can I rely on this to give me instantaneous fuel economy feedback by watching the injector pulsewidth at a given speed? I know it won't give me MPG, but I'll be happy as long as I can see if what I'm doing is helping or hurting.

[Old Tele man]

...theoretically, yes.

...practically, no.

...remember, cylinders do NOT all combust exactly the same, so the computer has to continually play a "tweeking" game between cylinders to maintain an AVERAGE optimization, rather than an individual optimization of any specific cylinder. This is because the "feedback" mechanism are the common 02-sensors, ahead of and behind, the catalytic converter...which means averaged feedback about the aggregate exhaust, not specific feedback for any one cylinder.

...nevertheless, you probably CAN gain some knowledge about what's going in the ONE cylinder you're monitoring...plus a lot of mental "integrating" of what you're seeing.

[Gasoline Fumes]

This is a TBI car, so there's only one injector.

[dcb]

the injector duty cycle can be a relative indication of gallons per hour. You can use it for relative mpg by doing the math in your head (mph/duty cycle) and try to get the lowest duty cycle for any given speed.