Throttle

Caution!
A stuck throttle is potentially a very serious and dangerous condition.
Please read this
Warning before proceeding!

The stock Mustang pedal in the FFR installation results in a throttle with extremely nonlinear travel. You get about 75% of the power in the first 25% of travel.

Because of this, it's extremely difficult to get the car rolling smoothly, especially in first gear. It tends to lurch as soon as you tip in the throttle, then your foot comes off the throttle a bit and the engine compression causes you to lurch forward, causing you to put in the throttle again, causing it to lurch back again, etc.

It's also difficult to modulate the throttle coming off of slow corners, something which is especially important in autocrossing and racing.

To address this problem, Nate designed and built an extremely clever modification to the pedal which causes the ratio to be much slower in the first part of the throttle travel, getting progressively faster as the throttle opens more. This gives much more linear power progression relative to throttle position and makes the car much easier and more fun to drive on the street and also makes it much easier to modulate the throttle coming off of slow corners.

Above right is a photo of the modified Mustang throtte pedal and pivot. The series of screws in the upper part of the pedal serve as a progressive series of fulcrums. The result is in effect a cam with very low "lift" in the initial part of the range and progressively higher lift as you go through the range.

Initially, the top screw acts as the fulcrum, making a very long lever, so there is very little throttle movement for the first part of the pedal range. As the predal is pressed further, the next screw down takes over as fulcrum, increasing the leverage and speeding the ratio. Finally the bottom screw takes over as fulcrum, so for the last bit of pedal travel the ratio is at a relatively high rate.
 

At left you can see the pedal from the front, with the series of screws marching down the length of the pedal arm.

Here's another photo of the pedal and lever from the side.

You can see the slotted pivot hole, which Nate slotted to allow the lever to slide, permitting the screws to act as fulcrums.

Here you can see the pedal and modified pivot. Note the large washers next to the pivot to help keep the pedal from rocking side to side as it slides.

The screw in the pedal is holding it together because one of the tabs broke off of the black rubber part when we were disassembling it to paint the arm.