Automatic transmission

[rookie1]

I think following is a way to calculate optimum shiftdown threshold,

When shifting gear from X+1 to X (ignoring clutch for the moment), the wheel speed should be continuous, so we have the following relationship just before and after the gear shift.

Code:

engine speed at gear X+1 / gear ratio at gear X+1 = engine speed at gear X / gear ratio at gear X

To have optimum shift, the engine speed at gear X just after shift should be at engine peak rpm (this is just my guess). So the threshold engine speed at gear X+1 should be

Code:

engine speed threshold at gear X+1 = engine peak rpm / gear ratio at gear X * gear ration at gear X+1.

Using 3S as an example,

Code:

peak-engine-rpm = 6500rpm
gear-ratio-1 = 3.31
gear-ratio-2 = 1.84
gear-ratio-3 = 1.31
gear-ratio-4 = 0.97
gear-ratio-5 = 0.76

Using the above formula, the threhold values are

Code:

From gear 5 to 4 -> 5145rpm
From gear 4 to 3 -> 4812rpm
From gear 3 to 2 -> 4627rpm
From gear 2 to 1 -> 3613rpm

Of course, this is from someone with completely nil experience in automobile engineering. Do the above values sound reasonable?