I used the TP gauge today on the SG2. At idle my van is at 12. One thing I noticed though is that there is 10mpg difference between 14 and 15. I think I'm going to use the TP gauge more often. Also how do you read the load gauge on the SG2? Does the number represent a percentage of the engine load?
I'm not really sure where the load figure is derived from. I suspect it uses multiple input factors such as the oxygen sensor, throttle position, timing, and rpm to derive it, as it is not something directly measured by the computer.
TPS on my Saturn is zero at no throttle. It's been a long time since I put the peddle to the floor, but I think it registers 100 at that point. I'll have to check to see if SG2 reports TPS with the engine off, key turned to "run".
When I moved, I rented a U-Haul (moving truck, for your out-of-Staters). It was a 2007 Ford so my SG2 worked. TPS at rest was 12%. Got 10.3 MPG for the 70 mile haul... 6.8L V8.
TPS is throttle position and varies with the idle setting and the sensor adjustment. They are probably set to maximum to show 100% and the idle is whatever it turns out to be. Load (LOD) is the percent of power being generated from the total available at the present RPM. Seems my gearing in 5th runs in the 40-50% LOD value independant of speed so it seems they have matched the torque/power curve to the drag curve of the vehicle pretty closely.
You'll also notice that when you are at WOT the TPS will only read about 75-77, rather than 100. My mom drives a Town and Country with I believe the same setup (3.3 V6 4 speed auto) and that is what the SG registers. Same thing on my Jeep. I figure its a Dodge ECU/Sensor thing.