So how do you know which weight to cut? Where do you source the correct spring? What about different factory shift timing from valve body, KD lever ratio, and high clutch spring changes as well as the different factory governors? And you can tailor the part throttle and the 1/2 to 2/3 shift rpms all with math? How close? Teach us.
Doug
The only way to do it is to change one thing at a time. So, many of the things you mentioned we can't control for, they need to stay the same as we make one change, the governor in this case. That was the nature of my initial question actually. Inside the governor we've got the outer weight, spring and inner weight. Lower speed shifts are driven by the weight of all three put together, higher speed shifts are driven by the inner weight and spring. As the governor spins the weights pull the governor valve open slowly, as it opens more, the pressure goes up. This pressure is on a larger area of the valves than the throttle pressure so eventually it always wins and gets the shift.
Let's say though, that when everything is adjusted nicely we get those early shifts at ~6 and 11 mph into 2nd and 3rd gears. That stinks so we want to move it up to say 12 and 22 without changing anything else. The governor is a spinning assembly and the centrifugal force of the spinning weight pulls against the hydraulic pressure of the governor. At some force the gov pressure is high enough to shift. So we want that same force at twice the speed. We can start with centripetal force of m*v²/r and the actual driveshaft speed and a whole bunch of other stuff but it all cancels out to be mass of the weight (all of it for this speed) * V². So a typical governor weight is 70g * 6² = 2520, and we want ?g*12²=2520 would mean that we'd need a 18g weight to move the shift that far. Well that's freaking impossible, you'll notice the factory never did it that way either. We need to alter other parts of the system like the 1-2 spring or 2-3 spring or throttle spring to get that kind of effect. So we do the most we can with the gov, which is to make the whole thing light. You'll see that with factory high perf govs, not much metal.
But now we go to the WOT area and we want to move 1-2 from 4800 to 5200rpm. The hydraulic pressures are much higher up here and the springs (on valves) have less of an effect and the gov has more. The big weight is out of the equation (bottomed out) but now the spring and inner weight are in it. Here, the actual speed matters because the spring isn't variable and we need a proper force number to work with. So in first, we've got 4800 rpm and a 2.45 gear so the output shaft is at 1959 rpm. **following numbers are representative, I don't have actuals in hand at the moment** If the centerline of the weight is 38mm from the center of the output shaft the weight is moving 3.9 m/s (.038*3.1416*1959/60). If it weighs (inner weight) 30g the force would be .03*3.9²/.038 = 12N. So that would be in some equilibrium with a spring and hydraulic pressure.
If we then jump to 5200 and churn through the same math we can find that we need only .0256g to get the same 12N, we can cut that off of the weight. Similarly we could pick a new spring that provides enough extra force to compensate for the extra speed at the installed length. I'd go to McMaster for that.
Same basic deal happens at 2nd gear but the forces are then up in the 34N range. There's another factor though. The governor pressure itself pushes against the spool valve and the pressure (both governor and line) is higher for the second shift. This is "return pressure" and equivalent to lightening the weight or making the spring heavier. This changes depending on where the shifts are. If you have a tranny that shifts 1-2 and 2-3 at 4800 rpm, a governor only adjustment will move the 2-3 farther than the 1-2 the farther you move it. So if you try to go for 6000 with 2-3 you'll bring the 1-2 up less. This will require a heavier spring in the 1-2 spool. Using a longer, lower rate spring for the same force in the governor helps minimize this but there's only so much room.
Anyway, that's the basics. Not too complicated and works pretty well for smaller adjustments. Go farther and there are more factors and more iterations to perfect it.
