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Old August 29th 2006, 01:22
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Humble Humble is offline
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Join Date: Jan 2003
Location: Boulder Creek, CA
Posts: 758
So far my hunt for the correct clutch master cylinder has been unsuccessful. I've had a lot of "that should work" but no hard calculations so I tried to figure it out on my own. I don't want to go through the whole return process (or eat the cost) of 3-4 MC's to find one that works.

*warning math ahead*

If you start with the presure plate and work backwards it makes a little more sense. Next in line is the throw-out arm, where the bearing side is 1.5" from the pivot and the cable eyelet is 3.5" from the pivot providing a ratio of 2.3:1.
The slave cylinder and master cylinder also have a ratio (at least with my preliminary setup on paper, I haven't commited yet incase this math is horribly flawed). I have a clutch master that's 1" diameter and a slave that's .88" in diameter giving a 1.136:1 ratio. and Last I have a tilton pedal assembly that's 5.5:1 pedal ratio.

So here's what I came up with:
Pr = force needed to release presure plate ie 3000# (guessing here)
T = thowout arm ratio on 091 tranny 2.3
M = master cylinder/slave cylinder ratio 1.136
Pa = Pedal assembly ratio 5.5

((Pr/T)/M)/Pa=Pedal force
or
((3000/2.3)/1.136)/5.5=208.76# at the pedal

Now playing with the values a little bit produces more realistic results but the biggest unknown is how much force it takes to release a KEP 3000# presure plate. Next guess 1500#
((1500/2.3)/1.136)/5.5=104.38# at the pedal, still a very heavy pedal

Trying the same 1500# release force with a different clutch master slave combo, a 1.125" master and same .88" slave give a ratio of 1.278:1 so...
((1500/2.3)/1.278)/5.5=92.78#

I wanted to bounce this off you guys to see if I'm totally crazy, or kinda close with my thinking here. Tomorrow I'll call KEP to see if I can get a better figure, but I'm more worried about my general formula here. Any Input would be a big help.
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