Quote:
Originally Posted by Mike
Guys
I don't know if any of you looked at the specification figures for the boosters, or are even interested in the numbers, but I have made some calculations based on the data given by MBM, which show a very interesting result: see if you agree with the following;
My brake details are:
Pedal centre to pivot centre 32cm - excuse mixed units - it does not matter
Pedal connection to servo to pivot - 8cm
Therefore my pedal ratio is only 4:1
My master cylinder bore = 22mm = 7/8" = 0.6 sq inch
Now assume 23” of vacuum and 100lbs of applied foot pressure for comparative purposes.
Based on my brake's details:
[edit: it will not hold spaces to make figure line up below]
Booster size “Manual Pressure” “Free Pressure” Total Brake Pressure
7” Metro 666 psi *1 587 psi *2 1253 psi
7” Dual 666 psi 815 psi *3 1481 psi *4
*1 = (100lbs x 4:1) / 0.6sq.inch = 666psi
*2 = Metro booster constant 352lbs / 0.6 = 587psi
*3 = Dual booster constant 490lbs / 0.6 = 815psi
*4 - The dual offers an increase of 18% of the total over the Metro. This does not sound too impressive.
I then considered if I reduce the distance of myservo connection to pivot by 1.6cm to 6.4cm
The new figures are:
New pedal ratio is 32/6.4 = 5:1
Same master cylinder bore = 22mm = 7/8" = 0.6 sq inch
Same 23” of vacuum and 100lbs of applied foot pressure.
Proposed brake's details:
Booster size “Manual Pressure” “Free Pressure” Total Brake Pressure
7” Metro 833 psi *1 587 psi *2 1420 psi
7” Dual 833 psi 815 psi *3 1648 psi *4
*1 = (100 x 5:1) / 0.6 = 833psi
*2 = Metro booster constant 352lbs / 0.6 = 587psi
*3 = Dual booster constant 490lbs / 0.6 = 815psi
*4 - The dual offers an increase of 16% of the total over the Metro, appears not so good
However, if we turn the calculation around to how much foot pressure is required to achieve the same total as with the original Metro, we see a significantly different result:
Original foot pressure to achieve 1253psi was = 100lbs
New foot pressure to achieve 1253psi = 52.4lbs *5
*5 = 52.4lbs x 5:1= 262lbs / 0.6sq.in = 438psi + 815psi = 1253psi
ie almost only HALF the effort
This has got to be worth a try!!
What master cylinder bores do you have?
What brake pedal ratio do you have?
Does anyone have a view on the calculations?
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Not looked inside my master cylinder to check bore but raised number 23 on casting maybe 23mm? From Google I found the following DLJ website link
http://www.dlj-autoparts.com/eng/pro...e=list&cid=485
which lists several master cylinders including one of 23mm bore which is for a Mondeo! Peter.
Master Cylinder Diameter
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