How does increasing flywheel weight mean more power?
Could some one explain it to me.

 

An increase in wieght will make the power less peaky as the engine has more inertia, but it will also be slower to rev as you have more weight to get moving, this is a mod i doubt the rotax motor would benifit from. but it can be usfull on many two strokes and some of the new 450 stuff in dirt bikes.

So more wieght = more inertia which is harder to stop spinning, but harder to get going , I doubt if it would show any hp increase on a dyno.

 

Blue is correct.
The added weight would show a smoother yet slower RPM response and do nothing for added HP. The power band would be less peaky? or in other words, if you cranked on the throttle is would be slower to respond yet slower to respond when backing off the throttle as well. The only advantage I see is when climbing dunes and you have the RPM up it would be less likely to bog down giving you the impression of added HP.

 

Just to echo the current thought, a heavier fly wheel will slow the rpm increase and actually hurt the maximum attainable HP. Having to turn more weight will affect what it can achieve.
A popular desert mod on two stokes is to add weight to the flywheel giving the peaky two stroke more stability in the lower RPM's. I found that the added weight made my CR500 (back in the days of desert racing) a GREAT MOD. I didn't need anymore HP, but I did like the lugging ability it gave me on slippery surfaces.

.02

 

I can see a benefit of added flywheel weight in one situation only, in short drag races. If you could rev the motor and keep the rpms up then the added inertia could help you launch. Say you built the engine to produce extreme high end hp at a cost of low end hp. The inertia could help keep from the rpms dropping into range where it would be hard to recover. I believe the DS already leans this way due to the heavy stator that comes with the bike. This might be why the DS can launch almost as hard as quads that weigh considerably less.

 

This is an old thread, but fun reading, I was wondering is the stock flywheel better for dunning for big guys?? I have read on other post that the DS fly wheel is extreamly heavy and can handle up to a few lbs taken off, could being to Light effect the quad on hill side dunes will the DS BOG more?

 

the new 450's have very light everythings, to get the peak power they make of course. the heavier flywheel options available for some of them I think are mainly directed towards riders looking to keep from stalling so easy in low rpms, especially the kickstart boys.

the DS already has a heavy flywheel and doesn't stall easy at all, most people that lighten their flywheels for more peak power see very little impact on their woods trailability.

 

Heavy or lighter flywheels do not really effect torque or hp, but how work is related to acceleration. You all have heard that a lighter flywheel revs up faster, thus the time it takes to accelerate is affected. By adding weight to the flywheel does the opposite.
Size of motor, rpm range motor runs in and the application of the motor dictate what is the best weight of flywheel to use.

In the early days of drag racing it was popular to use a heavy flywheel, traction was poor because of tires, and thus to launch and not light the tires, you took off at a lower rpm and with a heavy flywheel accelerated at a rate that the tires would allow to get to the ground without breaking loose.

I would think that drag racing in sand could use this old theory. All I ever read is either they used too many or too few number of paddles. Too many paddles gives great launches but uses too much power on top. Opposite for too few paddles.
Sandbomber is building a Top Fuel motor that is going to run under 7k.
I bet his engine builder is going to use a slipper clutch and flywheel matched to the application.

OMR

 

but doesn't any decrease in rotating mass = more effective hp? lighter tires, lighter rims, lighter chains and sprockets, lighter cranks, core drilled cams and lobes, and lighter flywheels, all lend to more power don't they? or is the flywheel weight just too small of an amount to be of any significance in the hp dept., while still effecting rev?

 

Hightower, On a motocross track where you are constantly accelerating and decelerating, a lighter flywheel is a benefit, at least until the point you start stalling. In a drag race, you really have already started the race just by reving the motor. Imagine a grossly oversized flywheel on a quad, you could rev the bike, kill the ignition and still launch hard with the inertia of that flywheel alone.