I've been doing more research on my brake upgrade and the following is what I
have found so far. If more knowledgeable souls are out there, I welcome your
input/criticism/outright yelling at me or what ever input you would like to
give.
I can't get to the pedal box very well since it is mounted to my car, but based
on my crude measurements I think the pedal ratio is close to 4:1 if my
measurements are correct. The formula for calculating Master Cylinder line
pressure is:
Pressure = (Leg force on the pedal) x (Pedal Ratio) divided by (Master Cylinder
Piston Area).
Just for comparison's sake I'm using 100 for the leg force on the pedal. Actual
pressure may be more or less.
0.7500" bore MC = 0.4418 sq. in of piston area
1.0000" Bore MC = 0.7854 sq. in of piston area
Therefore; OE MC with .75" bore P= (100 * 4.33)/0.4418 = 980 psi
New MC with 1.0" bore P= (100 * 4.33)/0.7854 = 551 psi
With the original 7" single diaphram booster you would gain about 494 psi of
free boost on the OE MC and about 381 psi with the 1" bore MC. But with the
dual
diaphram MC this would increase to around 490 psi free boost. This means the
total boost are as below:
OE 0.75" bore with 7" SD booster 980psi + 494 psi = 1474 psi total
New 1.0" bore with 7" DD booster 551psi + 490 psi = 1041 psi total
Although this is about a 40% difference, when you consider the OE application
was with a two piston caliper with about 3.3 sq/in of pad area compared to my
new 4 piston caliper with 6.63 sq/in of pad area and slotted discs then the end
result is actually improved braking over the OE even with the 1" bore MC. If I
use a smaller bore MC with all my new parts I would really have a lot more
force
at the brake disc which may actually not be that great of an idea.
I have thrown out my calculations for all to see (flawed or not) and now I wait
the gunfire.
Dan Eiland
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