Someone mailed this to me. I later found out it is from Gene Khan's site. He has pictures and may update it, so try there first.
I will leave it here as sort of a mirror site.
FD RX-7 Shortened Clutch Action
Last modified: 12-24-98
I modified the clutch pedal action so the pedal is at nearly the same height as the dead pedal. It also has a very short action as a byproduct.
Why do this?
The first reason to do this is to lower the clutch pedal to the height of the dead pedal. That's good because now you don't have to raise your foot to the clutch pedal every time you want to shift. Your shifts will be that much faster. I learned this from Ayrton Senna's book Principles of Race Car Driving.
The second reason is to shorten the necessary clutch pedal action. Only a very small portion of the pedal travel is actually used in disengaging the clutch. Usually that portion is somewhere in the middle of the clutch pedal's travel. That's not very precise. And since I only feel comfortable shifting when I feel the clutch pedal hit the floor, it's a big waste of energy mashing the pedal all the way down there when in reality the clutch is disengaged some way through the pedal's travel.
So the goal is to make the clutch disengage at the top of the pedal action. And to make me feel comfortable, the distance to the floor should be as small as possible, so the clutch pedal bottoms out as soon as the clutch is disengaged.
A final reason is for you with big feet or big wide sports shoes. I've noticed that the clearance between the clutch pedal and the wall is not much greater than the width of my Nike tennis shoes. When I try to put my foot on the dead pedal I often would touch the clutch pedal. Not only annoying, but a little scary. Putting the clutch pedal at the same height as the dead pedal cures this problem.
How to do this
It was very simple. Two changes need to be done in the driver's footwell. It takes about 20 minutes and it's not permanent at all.
The clutch master cylinder is actuated by an adjustable rod near the crook in the clutch lever. The lever's position on this rod is adjustable. Loosen the nut which locks the rod to the pedal. Turn the nut so it is all the way toward the firewall. Then turn the rod itself so the threads are all sucked into the nut. This should add a lot of play into the clutch action. Don't worry if you feel the rod wiggling around. That's just the play.
The second thing is to take up all that play and bring the clutch pedal down. You'll find a plastic pad thing on the clutch lever. That pad provides a slide for a sensor which detects whether the clutch is "let out" or not. The sensor also serves as the stop for the pedal when it is "let out". This sensor is attached to the bodywork by a metal plate through which the sensor sleeve threads.
If you look at the sensor sleeve there will be a nut which locks the sensor in place. Loosen that nut. It's an 18 mm nut, I think. Disconnect the sensor wire. It is a white clip. You remove this clip by depressing a tongue in its center and sliding the clip out of the sensor.
Once the wire is out and the retaining nut loosened, you can remove the sensor by turning it out. Remove the nut from the sensor sleeve. Replace the sensor. Twist it all the way down. Mine clicked when it made it all the way down. I don't really know why...it was dark and my flashlight was stolen (that's another story). Put the nut on the clutch side of the metal plate. That's the opposite side it came from. Tighten the nut to lock the sensor in place.
That's it. The clutch should be really low now...about at the height of the dead pedal. I think the remaining distance can be taken up by a cover for the dead pedal. I plan on buying the Racing Dynamics one to match my Racing Dynamics pedal covers.
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