Alex Pepper Software
 

I got a chance to try the Alex Pepper Software on my 97. There were 2 things I saw that I didn't understand. TP - throttle position. It reads 11% at idle and 67% when I hold it to he floor. Why not 100%? Am I not getting all that I could?
The second thing was EP - exhaust pressure. It reads 16.7 lbs. The cat and ebpv are gone. Do I need to adjust this reading by barometric pressure? So I've actually got around 2 - 3 pounds of back pressure?

Neat software, and fun to play with too! It was also interesting to look at things I've seen discussed on this forum like duty cycle and Map frequency.

Reading my post I see a mistake. Not TP. I meant APP - accelerator Pedal Position is 11% to 67%. I just tried it again and this is what the software reports.

I'd say the tab or whatever on the sensor needs to be adjusted until teh SW says 100% when floored.

Where did you get the SW, sounds fun!

same stuff i got. have fun

The TP % is because the PCM sees voltage but the software is giving you %. it works on a 5 volt reference. so 0 volts is 0% and 5volts is 100% but the TPS never sees less than around .4-.5 volts and never should see more than 4.7 volts. if it goes under the low or over the high it sets a code. The exhuast back pressure is probably also throwing in 14.7 for atmosphereic pressure.

OK Thanks. I see the relationship. I'm at about .55 volts to 3.35 volts. Is there a max voltage to try adjusting the pedal for before setting a code?

I don't know anything about that software, but you may have a problem with the EBP tubing that is well-known for becoming plugged. It's suppsed to really suck to try to get it out and clean it.

As for your APP question, I don't know exactly how that particular circuit works, but almost all control systems nowadays incorporate a "live zero" that explains why your signal won't ever read 0 volts or 5 volts. Say for instance a sensor did read all the way at the bottom of it's range and the reading was 0 volts. How would you know that the sensor was not just unplugged or it had failed?
By adjusting the input range of a circuit to incorporate a "live zero" you now have the ability to eliminate that possibility. For the sake of simplcity let's say that your range on the APP circuit is from .5 volts to 4.5 volts. That means you have a span of 4 volts from one extreme to the other. You now know that each volt will represent 25% of your range of the instrument, so if you had 1.5 volts you are at 25% throttle, 2.5=50%, 3.5=75%, and 4.5=100%.
Using the same math reasoning, if your throttle has a resistance that varies from 50 -5000 ohms (I have no idea what the actual range is), you have a span of 4050 ohms. divide that by 4 and you get 1012.5 ohms for every 25% of signal. Don't forget that you still have 50 ohms at idle so add the 50 to 1012.5 and you get 1062.5 ohms at 25%. Every increase of 1012.5 ohms from there represents another 25%.
Before you run out and check calibration on your entire truck though, keep in mind that the above only applies to sensors that use a linear signal. Some sensors use exponential outputs and you have to get into square roots to calibrate them properly.

I can't say this for sure but I suspect that you are not getting full throttle, only 67% of full throttle. you may be able to tweak something but before you do, measure the throttle position resistance at idle. If you manipulate anything, be sure that you don't change your idle so that you end up with 100% at WOT, but 43% at idle.

Post back and let me know how it works out.

Take a look here:
https://www.ford-trucks.com/forums/5...ge-on-tps.html

I read that most of the software based scanners have trouble with displaying the throttle %. Voltage readings are the best way to get the AP set up right like TJ said.

Great info-

Cuda you are the undisputed FTE Diesel diagram MASTER!

Bodabdan, Back at ya. I have to use the diagrams, I ain't smart enough to remember all that stuff LOL :)

the max voltage is around 4.6 or 4.7 before it will set a CEL. to change it you can rework the stop that limits the pedal travel.