The Hotfoot mod, pedal mod, whatever seems to have more of a following in the OBS trucks, don't hear about it much on the SD's.
To get better throttle response just squish the skinny pedal a little harder

 

so does anyone know if theres a difference between the original pedal and the new design? they look a lot different....and feel a lot different to.

maybe i've got a new mod

 

On the 94-97's you just bend the tab that hits the IVS.

 

Yep, that's the one. Of course the link in that thread is gone, but I think it also had pictures and step-by-step instructions. At any rate, you found it.

You'll get more response with an IDM mod on an OBS truck than you will on a Superduty.... especially a late 99 truck.

OBS trucks have 100 volt IDM's
early 99s have 110 volt
99.5-03's have 120 volt

The IDM mod bumps them up to 135-140 volt.

Basically it sends a bit higher voltage to the injectors. Higher voltage to the injector solenoid results in a faster current build up in the solenoid, and builds a stronger magnetic field which opens the injector slightly faster and holds it open stronger throughout the injection cycle.

It has no effect on actual "throttle response", but in a way it does slightly improve "injector response". Some people can notice a bit of a difference in how their truck runs, other folks can't tell a difference at all.

 

No, you have to drill out the holes in the TPS so that it can be rotated slightly to cause it to react quicker.

 

It also allows the PCM to see a return voltage closer to the reference voltage of 5 volts. This will allow for more WOT throttle fueling. This mod is for the early style pedal assembly that used separate TPS and IVS switches. IIRC, later models, beginning in the mid year 2000 production have a single integrated switch, such as on mine, that does not allow for any adjustment.

 

Actually, if you look at the tuning, you'll see that this is not the case at all.

 

I may have not worded that quite right. Since our trucks are "drive by wire", some TPS's do not signal the PCM with enough voltage to allow for a true full throttle application and, therefore, adjusting it to read it higher will give the "extra" throttle when fully pressed. Kind of like a linkage being "too long" and not pulling it far enough.

 

It is my understanding that every time it's started up the computer "zeros" the TPS voltage so it really doesn't matter. At least that's how it was in my Mustang and other Fords I've checked. As long as at closed throttle it's less than 1.2V +/-, then it uses whatever it's set at as its base. So if it's .99V then that's the starting point, if it's .50V then it uses that value.

 

You are correct, the reason for modifying/rotating the TPS is to get "full throttle" as close to 5v as possible without going over.

 

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.

 

Tried to rep ya Curtis but I'm in jail. Very informative... I should probably copy/paste this info to the OBS forum!

 

You're right. Curtis. Reps sent. This mod was intended for stock trucks looking for a "cheap" power mod. I didn't experiment with this because I have the later "non-adjustable" pedal assembly. Mine does, however, has a dead spot right off of idle that is noticable when accelerating slowly. I changed the pedal assembly 5 yrs ago and the old one didn't do it. I haven't played around with it to try and remove this dead spot. I have just become accustomed to it and work past it.
I also went back to the stock IDM, from the 140v, because of the extremely touchy throttle.