94 XLT, 2.3l, 5 speed manual

Hi. I had to change the speedometer gear as the 19 tooth gear was too slow. About 15%. I put a 16 tooth gear in. Now the odometer reads about 3% fast. I had to run a GPS speedometer on the old gear. Didn't want a ticket. So all fuel mileage was calculated using the gps. I notice a bit better engine response, especially when the a/c is running. With the old gear, a/c running, starting off in 1st, it would hesitate a fraction of a second, even noticing a lag shifting to 2nd. Now, no hesitation. It seems to accelerate a bit better too, not having to downshift as I did. The second thing I notice is nearly a 10% increase in fuel mileage calculated on actual miles driven, not the odometer.

Does the ECM use data from the speed sensor, that is at the speedometer gear, to adjust engine performance?

Thanks.

 

With a manual trans speed shouldn't matter too much, yes computer does get the speed signal, but it was mostly for automatics and TCC and 3/4 shift solenoid use

Its possible when calculating engine LOAD speed might play a small part, so it could change the spark timing enough to get better MPG

GPS miles traveled doesn't take into account up or down hills or most curves, its basically "as the crow flies" as far as miles traveled, so it would certainly show a lower MPG than actual

 

A GPS will measure in 3 axis. It was consistent in measuring mileage against the odometer.

 

The only change I was expecting was to have a more accurate speedometer. I was pleasantly surprised by the other.

 

I would chalk it up to more accurate speedometer/odometer, but either way its still best results