Originally Posted by Pocket

I'll explain what I've learned from Cody at PHP about the accelerator pedal in reference to tuning (I've been playing around with the MFD table in relation to the throttle pedal to achieve a smoother pedal and to make it less touchy). The PCM interprets TPS voltage (on a 5v circuit) as AD counts. 0 volts equals 0 AD counts, and 5 volts equals 1023 AD counts. Now we know that the throttle pedal never reaches 0 volts, and never reaches 5 volts. Instead, it's closer to 100 AD counts at idle, and around 900 AD counts at WOT. The PCM equates 1 volt as 204 AD counts.

The tuning addresses this under the MFD table (mass fuel desired). This table takes throttle position (AD counts) and engine speed (RPM's) and plots the mass fuel desired (mg/stroke). Maximum fueling occurs at less than 1023 AD counts. This is because the engineers at Ford know the pedal will never reach a full 5 volts, so they adjusted the MFD table to compensate for that.

In addition, it appears they also put in faults for out of range high and low throttle inputs. The low range fault is 73 AD counts, and the high range fault is at 922 AD counts. So the proper TPS input is between those ranges.

So by modifying the throttle pedal, you won't gain much or any additional fueling. The end result is just a touchy pedal, as it ramps up the AD counts earlier in the pedal cycle (the physical cycle of pushing your foot on the pedal). For someone who plans to always keep their truck stock, it feels as if the pedal is more "responsive" on the bottom end. However, if a person chooses to add a chip or tuner, then a problem arises.

The problem is that with tunes, the MFD table is typically modified to increase the mass fuel desired by ramping it up. If the pedal is already ramped up, and the tuning also ramps up the mass fuel desired based on throttle position, you end up with an extremely touchy pedal. In some cases, it makes driving the truck difficult, and tough to maintain a steady speed on roads that aren't smooth.

As an example, I've taken my truck offroad many times. I have tried to offroad in higher HP tunes... and failed. With the additional mass fuel desired based on throttle position, the pedal was entirely too touchy and I was unable to control the throttle when hitting rough spots on Jeep trails. I was forced to offroad in either my lowest tow setting, or switch to stock tuning.

With my own personal tuning, I've modified the scalers on the MFD table, and smoothed out the table to give the throttle pedal a more linear feel. The stock MFD table is fairly linear up until just beyond half throttle, then rapidly jumps up to full throttle in a very short AD count range. By modifying the table, I have reduced this jump in fueling above the half throttle point, making the graph more linear. This way, 3/4 throttle feels more like 3/4 throttle, rather than full throttle.

Anyway, I hope this explains a bit more about how the pedal works, and how the PCM interprets pedal position. This is why modifying the pedal is something that I personally do not recommend, especially for someone who plans to add a chip or tuner in the near future.

Originally Posted by Action4478

If I were to modify anything on mine ,it would only be the lag in the IVS , & not touch the TPS..There is a lot of pedal travel before the IVS closes ...The Chip won't remove that ...

Originally Posted by superduty4x4

Yes the lag in the IVS bugs me. My SD didn't do it, or at least it wasn't near as noticeable.

Originally Posted by superduty4x4

That makes sense Jose... good idea actually.

Originally Posted by RÖENTGEEP

Thank you.
Here is the pic as promised: