effects of engine rotating weight, flywheels, flexplates . . .

[mikedc]

Just got to wondering some things. I had posted this in the engine section but it's broader stuff than just the motor . . .


#1.

Flywheel lightening = faster throttle response, but not as smooth running motor as a whole.

engine rotating assy weight (crankshaft, rods, etc) reduction = same thing.

But if you can control the amount of rotating weight by just adding & subtracting weight at the flywheel in huge amounts, then why does anyone think about keeping weight off the crank/rods/etc for revving purposes?

(Yes, I know there are plenty of other good reasons to want a lighter mass assembly in the motor. But people often seem to talk about lightening the assembly specifically for the flywheel-type purposes. For example, you often hear people talk about how short-stroke motors love to scream and rev quickly compared to longer stroke motors.)

Is the engine's rotating weight just something that racers try to fight against (for flywheel-type purposes) only after they're already running the lightest flywheel that is practical?





#2.

What is the auto-tranny equivalent to lightening the flywheel/rotating weight?

A normal auto-tranny flexplate doesn't have any real excess weight on it in the first place. It's obviously not built with added weight for its own sake like a manual car's flywheel is. So if you wanna get that same trade-off effect (that a lightweight flywheel would have on a stick-shifted motor), then what do you do on an automatic?

Would you make that change with a different torque converter? I assume a much tighter one?


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