Update After Modifications

[fredmeister]

Originally Posted by TurboKraft

Ideally, a 1:1 drive ratio. For a 930 4-sp, 3rd is closer to 1:1 than 4th is.

Why is it so important for a 1 to 1 drive ratio?

I know running a higher gear gives you more time to get load and high boost on the engine, but do not understand the importance of 1 to 1 ratio in the tranny.

Fred

[WinRice]

Originally Posted by fredmeister

Why is it so important for a 1 to 1 drive ratio?

Because gear ratio can increase or decrease output torque by a factor of the gear ratio, not accounting for friction losses.

From Wikipedia:
A gear train can be analyzed using the principle of virtual work to show that its torque ratio, which is the ratio of its output torque to its input torque, is equal to the gear ratio, or speed ratio, of the gear train.

This means that the input torque T_A applied to the input gear G_A and the output torque T_B" on the output gear G_B are related by the ratio

where R is the gear ratio of the gear train.

[fredmeister]

Originally Posted by WinRice

Because gear ratio can increase or decrease output torque by a factor of the gear ratio, not accounting for friction losses.

From Wikipedia:
A gear train can be analyzed using the principle of virtual work to show that its torque ratio, which is the ratio of its output torque to its input torque, is equal to the gear ratio, or speed ratio, of the gear train.

This means that the input torque T_A applied to the input gear G_A and the output torque T_B" on the output gear G_B are related by the ratio

where R is the gear ratio of the gear train.

Got it now i feel stupid for overlooking this. I was thinking wheel horsepower and mistakenly thought gear ratio has no effect but you are right sir. So I guess the dyno does a conversion based upon the gear ratio you enter and then converts to RWHP. The of course you can back calculate HP at the crank using a good suitable tranny loss number which most people accept 12-15% for the 911.

Thanks
Fred