Flywheel weight

[CarDemon04]

can anyone on here explain the benefits/downsides of putting a heavier or lighter flywheel on my car. I was talking to someone this weekend who told me that he put a heavier flywheel on his car, I was wondering what exactly this is supposed to accomplish

 

[WhalePirot]

I went lighter and am not sure it was the right thing. Heavier lends a smoothness, but hinders snappier revving; pure inertia. I have a problem smoothly leaving each stoplight with my all-new parts; the McLeod clutch and lighter flywheel.

 

[CarDemon04]

the person I talked to said that he put a heavier flywheel in his car because the stock flywheel was too light and that his tires would bite too soon, and his flywheel was incapable of handeling the power of the engine and the grip his tires got so it would just rev to 1600RPM(much like mine does) and do nothing(not spin the tires) when attempting a brakestand(very embarassing) . but from my (limited) knowledge of physics it would seem that a lighter flywheel would give you quicker responsiveness.

 

[grumpyvette]

CAST flywheels are VERY dangerous at high rpms and STRESS LEVELS, I STRONGLY advise useing CERTIFIED @ BALLANCED,BLOW PROOF STEEL FLYWHEELS, & CLUTCHES and a CERTIFIED SCATTER SHIELD.
you only need to see one car cut in 1/2 by a clutch explosion or one guy loose his feet before the cost of the better parts LOOKS CHEAP compared to the results a lifetime without FEET could cost!!
the heavier the flywheel is the more energy it can potentially store, and the smoother the engine will tend to run, simply because the rotating MASS will be less effected by the power pulse the piston and rod exert on the crank shaft throws on the engines power stroke, a heavier flywheel will also tend to make BALLANCING an engine easier.
on the negative side that same increased MASS of a heavier flywheel that tends too STORE energy at any given rpm that allows you to blast out of the starting line without bogging by resisting the tires trying to slow the rotational energy also tends to ABSORB some energy as your trying to accelerate, thus potentially holding your performance back on the high speed charge at the end of the track.
put another way, if your running slicks ans a suspension that can pull the front wheels before the tires spin, badly and if your engine produced its max power in the 4000rpm-6500rpm range and you cam launch at 5000rpm, the heavier flywheel will give you a distinct advantage, allowing you to stay in your most effective rpm range
but if you launch at 1500rpm to keep the tires from turning to smoke, and your engine needs to cycle from 1500 rpm up to lets say 7000rpm and back several times durring a run like in road racing a light flywheel will get you a much more responsive combo!
I generally run 30 lb steel flywheels on the lighter weight sbc drag cars , that operate over an extended pm range and 40-45lb flywheels on big blocks with thier lower total change in rpms or supercharged cars that weight more but have the suspension and SLICKS to allow that stored energy to be used

light weight aluminum flywheels are used most effectively on road race cars and circle track cars that must vary rpm ranges widely coming into and out of acceleration and braking the engine rpms, ALUMINUM flywheels also tend to get damaged much more easily due to excessive heat, if they slip badly on constant hard launchs

 

[CarDemon04]

ok, guys...thanks for all the help, I just have one more question. my car has the 2.59 rear gears, would I be better off going to a higher ratio gear than replacing the flywheel?

 

[taegdh]

The previous replies all hit the nail on the head.

Check JuLY 2004 edition of VETTE, page 54.

The article demonstrates the HP gains and time to RPM. They fail to mention that there are times and applications where a heavier flywheel is beneficial.

In a situation where breakneck accelleration isn't a factor, the heavier fly wheel although increasing the reciprocating mass, also causes less stress on the bearings, and if the engine is set up correctly will produce more torque. It does take much longer for the engine to reach the same RPM as with the lighter flywheel.

If you're just out to cruise and drive to work the heavier is ok.

If you're out to make 9000 rpm in the wink of an eye, so you can make the Prostock and Top Fuel Funny Cars with the blue oval insigina look like they are standing still, you need the lightest flywheel you can get, plus the scattershields, and other safety related equipment..

 

[grumpyvette]

"my car has the 2.59 rear gears, would I be better off going to a higher ratio gear than replacing the flywheel?"

once the clutch locks the drive train to the engine and the tires stop spinning, a light flywheel has some minor advantage compared to a heavier flywheel
nowhare near the pronounced effect youll feel by swapping to a 3.73 rear gear and the resulting increase in useable rear wheel torque multiplication that gives the car at launch and durring acceleration 2.59 rear gears, were installed for mileage and emmisions reasons NOT FOR PERFORMANCE !!
A LITTLE PORT CLEAN UP WORK,IN YOUR HEADS AND INTAKE, A NEW CAM AND 3.73 REAR GEARS WILL MAKE A VERY NOTICABLE IMPROVEMENT IN THE CARS ACCELLERATION
LETS ASSUME YOUR ENGINES CLOSE TO STOCK the differance in rear gear ratio will allow APROXIMATELY A 45% IMPROVEMENT in how fast you can apply that torque AT THE REAR WHEELS