Yugo L4-1300cc 1.3L (1991)
8 lbs divided by 0.1046 = 76.48 or 76 1/2 line pressure
Now, let's look at RATIO.
Ratio is the relationship in quantity, amount or size, between two or more things.
In our example ratio is: How many psi each pound of spring will add.
Pressure divided by Force = Ratio
EXAMPLE: 62 psi divided by 6.5 lbs = 9.5 ratio Each pound of spring will increase pressure 9.5 psi
Force x Ratio = Pressure
EXAMPLE: 6.5 lbs x 9.5 = 61.75 or 62 psi
(Let's add 1 lb of spring, and see if we get 9.5 more psi.)
Force x Ratio = Pressure
EXAMPLE: 7.5 lbs x 9.5 = 71.25
New pressure Old pressure = Pressure difference
71.25 minus 61.75 = 9.5 psi change (by adding 1 lb of spring)
Once you know the ratio, a lot can be determined. Pressure divided by Ratio = Force
62 psi (actually 61.75) divided by 9.5 = 6.5 lb spring
The ratio never changes. This means that if I know that line pressure is 55 psi at idle, in a 700 R4, the the PR spring must be 5.78 lbs.
Pressure divided by Ratio = Force
So, 55 psi divided by 9.5 = 5.78 lbs.
Now, let's look at a math formula for shift speeds.
Suppose we had shift speeds of 15 mph and 20 mph, for the 1-2 & 2-3 shifts on a transmission. 20 mph may be too early for the 2-3 shift. If we adjust
TV modulator, we will move both shifts. We don't want to do that because the 1-2 shift is fine, so let's work with just the 2-3 shift spring.
EXAMPLE: Original spring divided by Original MPH = Ratio
As, 4 lbs divided by 25mph = 0.2
Ratio x Desired MPH = New Spring
0.2 x 25 mph = 5 lb spring
A 5 lb spring will raise the shift on this transmission to 25 mph.
All you need to know is -- Where is it shifting now (at MINIMUM throttle) and what does the spring weigh.
This formula will get you very close, but may be a "tad" off, because we are not accounting for TV pressure helping the spring. This is why you want to
check it at minimum throttle, so TV has the least effect.
Speedometer Ratios
Finally, let's look at speedometer ratios.
Suppose we put an exchange transmission in a car, and now the speedometer is off, because the speedometer drive gear has a different tooth count. What
do we have to do to the driven gear to correct it?
Let's say the old drive gear had 7 teeth and the old driven gear had 21 teeth. The exchange unit had 8 teeth on the drive gear.
