Is this how lightweight fly wheel should feel

[jakefed4]

2017 gt premium, long tubes,18 mani ,CAI, 47 injectors, lund 93

Got a mcloud clutch and the lightened steal fly wheel 3k miles ago. Ever since the switch from the oem clutch I feel like I have to give it more throttle in the low end and don’t feel the toque as much but picks up like a freight train after 4k. Is this what I should be feeling with the fly wheel?

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[Eyesac]

This is my understanding and my personal experience. A little easier to stall (you don't get to benefit from the mass of a heavier flywheel) and it seems to wind up faster.

 

[ShadesOfBloo]

...I feel like I have to give it more throttle in the low end and don’t feel the toque as much but picks up like a freight train after 4k. Is this what I should be feeling with the fly wheel?

One more vote for "That sounds about right".
The lighter rotating mass should help the engine go up and down the RPM range more easily, and free up a few more hp toward making the car go.
The fact that it can go down in RPM more easily ('cause the effect works both ways) sounds like it could make the car less forgiving for shifting.

 

[NGOT8R]

That’s also my personal experience with my lightened flywheel and twin disc clutch. It took a little getting used to, but now I don’t even think about it anymore.

 

[sms2022]

Yep. Torque is largely dependent on how heavy the reciprocating mass is on an N/A engine. That’s part of the reason why old big blocks would make 500tq but 150hp. They also had a flywheel that weighed 40lbs.

There’s an old wives tale about this that a guy swapped one of these flywheels onto his 396 Chevy and used to shut the engine down and let the clutch out and the car would still go 20mph down the street.

 

[NightmareMoon]

You should not notice the ligher flywheel when its engaged in gear, but blips and shifts will feel different.

if it did feel different it should just rev ever so slightly faster everywhere, more so at higher rpms (again, mostly with the clutch disengaed). Theres nowhere it should feel like it takes more gas, except during shifts “it depends”. The right about of blip is a different amount or duration of stab on the gas with a mass change at the flywheel.

the rotational energy of a couple lbs at the flywheel is just absolutely trivial compared to the work required to accelerate a 3800lb pig with wind resistance and all. When the clutch is disengaged and your’re just spinning the rotational engine components or the engine+transmission with the clutch engaged but manual transmission in neutral, thats another story.

 

[robvas]

Yep. Torque is largely dependent on how heavy the reciprocating mass is on an N/A engine. That’s part of the reason why old big blocks would make 500tq but 150hp.

wut

 

[sms2022]

wut

You got a 500 cubic inch engine spinning big solid trw forged pistons, massive forged steel rods and a massive forged steel crank. That rotating assembly is phenomally heavy and takes forever to slow down. Once it’s moving it keeps moving. combined with the cam profiles they put in those things this is what gives you their crazy torque rating.

 

[CrackedHorn]

You got a 500 cubic inch engine spinning big solid trw forged pistons, massive forged steel rods and a massive forged steel crank. That rotating assembly is phenomally heavy and takes forever to slow down. Once it’s moving it keeps moving. combined with the cam profiles they put in those things this is what gives you their crazy torque rating.

That just sounds like momentum/inertia.

The vertical movement of the pistons means that heavier pistons would counteract the effect of a rotating crank, as well.

Hopefully someone who remembers more from their physics class can chime in, here.

I would think that a heavy rotating assembly might FEEL snappier on a launch. But I can't see where it would increase power output.

 

[robvas]

You got a 500 cubic inch engine spinning big solid trw forged pistons, massive forged steel rods and a massive forged steel crank. That rotating assembly is phenomally heavy and takes forever to slow down. Once it’s moving it keeps moving. combined with the cam profiles they put in those things this is what gives you their crazy torque rating.

The cam profile is the only thing that determines torque vs hp

How long does a big block chevy keep spinning after you turn the ignition off?

 

[sms2022]

That just sounds like momentum/inertia.

The vertical movement of the pistons means that heavier pistons would counteract the effect of a rotating crank, as well.

Hopefully someone who remembers more from their physics class can chime in, here.

I would think that a heavy rotating assembly might FEEL snappier on a launch. But I can't see where it would increase power output.

It doesn’t increase power output. It increases torque while killing horsepower because at a certain point you’re right, the engine is fighting its own rotating mass. I also forgot one major detail which is stroke - a lot of these big blocks have a monster stroke to exert more leverage on the crank.

You’re exactly right - it feels snappier at the expense of horsepower. It has a ton of torque at 2700rpm or so but no wind past that.

 

[robvas]

I would think that a heavy rotating assembly might FEEL snappier on a launch. But I can't see where it would increase power output.

Lighter = more horsepower. Drivetrain, wheels, blah blah. Frees up power.

But a aluminum flywheel definitely has a different feel than a steel one.

 

[sms2022]

The cam profile is the only thing that determines torque vs hp

How long does a big block chevy keep spinning after you turn the ignition off?

Really? Rod ratio/stroke has nothing to do with it? Build a 428 with a 4.15 bore and shorter rod and then build a 428 with a 3.95 inch bore and longer stroke. Stick the same cam in it and see where the numbers end up.

 

[sms2022]

Lighter = more horsepower. Drivetrain, wheels, blah blah. Frees up power.

Not arguing with you there.

 

[robvas]

Really? Rod ratio/stroke has nothing to do with it? Build a 428 with a 4.15 bore and shorter rod and then build a 428 with a 3.95 inch bore and longer stroke. Stick the same cam in it and see where the numbers end up.

Nope. Cubic inches are cubic inches. As long as you're not shrouding the valves it won't matter.

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