Flywheel weight?

[t walgamuth]

Originally Posted by xb-60

This is the bit I don't get.
OK, very slightly less gross vehicle mass with a lighter flywheel, but engine power and gearing are unchanged ..... so how does a lighter flywheel allow quicker acceleration?
Quicker to blip the engine - yes; quicker acceleration of the vehicle? ....no

I need a more convincing argument.

Cheers!
Glen

Science my friend. It takes longer to accelerate a heavier weight. And it takes longer to slow it down. Newton's third law I believe it is. Why would it accelerate an unloaded flywheel faster but not the car?

I've no way to test it and prove it to you but if you are a racer you always want to reduce weight even if it is not by much. I have won and lost autocrosses by one or two thousandths of a second. You might not be able to feel it but the clock will measure it.

On my race car my rule is never put a part back on the car until I seek a way to reduce it's weight.

[patrickt]

Glen, you must be having a mental block on this. A heavy flywheel acts just like the friction toys we had as kids. You know, you would "rev them up" by moving them along the ground rapidly, then place them on the ground and they would zoom away on their own. But, if you placed your friction toy race car at the top of the hill and let gravity take it down, it would lose to every other toy car that was not a friction car (and sometimes it wouldn't even go down the hill without being revved up first). That is the difference between a light flywheel and a heavy flyweel.

[1985 CCX]

Ok, I'll try

I do not dump the clutch as I am not a drag racer. With alloy flywheel it hesitates a touch once you begin to move unless on the gas hard. Inertia is not there however once you start to move it rips like a rocket. RPM's fast!
Its like a two stroke dirt bike, pulls like a freight train.

Example the ACMKIV car, steel flywheel, almost can catch momentum if you let the clutch out slow with no gas.
The MKII will stall unless you give it some fuel.

Once moving the MKII is like a rocket where the MKIV is like a regular car and also smoother.

Granted the MKII is set up different, best I can do to describe it.

[xb-60]

Originally Posted by 1985 CCX

Ok, I'll try

I do not dump the clutch as I am not a drag racer. With alloy flywheel it hesitates a touch once you begin to move unless on the gas hard. Inertia is not there however once you start to move it rips like a rocket. RPM's fast!
Its like a two stroke dirt bike, pulls like a freight train.

Example the ACMKIV car, steel flywheel, almost can catch momentum if you let the clutch out slow with no gas.
The MKII will stall unless you give it some fuel.

Once moving the MKII is like a rocket where the MKIV is like a regular car and also smoother.

Granted the MKII is set up different, best I can do to describe it.

Jeff, my engine is probably quite similar to the 302 HO(?) in your MkIV, so I need that intertia that you mentioned.
My engine is (I think) a local Australian version of that engine, local in that the engines came in from US fully built up, and were then stripped and blueprinted/rebuilt by Tickford in Melbourne.
I'm allowed no mods to the engine spec. if I want to jump easily and cheaply through our local road registration 'hoops'.
Standard engine? "yes, sir." A CO check and a noise check, both at idle, and all good to go as far as the engine goes.
I mention this as it's relevant for my choice of flywheel.

Cheers!
Glen

[xb-60]

Originally Posted by t walgamuth

Science my friend. It takes longer to accelerate a heavier weight. And it takes longer to slow it down. Newton's third law I believe it is. Why would it accelerate an unloaded flywheel faster but not the car?

I've no way to test it and prove it to you but if you are a racer you always want to reduce weight even if it is not by much. I have won and lost autocrosses by one or two thousandths of a second. You might not be able to feel it but the clock will measure it.

On my race car my rule is never put a part back on the car until I seek a way to reduce it's weight.

It's Newton's 2nd law .... the acceleration of an object depends on the mass of the object and the amount of force applied.
In my case (not a race car) the relevant mass is the total mass of my car, not the flywheel in isolation, and the accelerative energy applied to the car comes from the engine.

Cheers!
Glen