Light weight Flywheel

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Many race engines use light weight Flywheels, How can a light flywheel make significantly more power? It seems any mass that is shaved form a flywheel to save inertia as the engine accelerates, would be quite small on anything other than a Formula car or Bike engine!
 
lightened flywheels simply mean that there's less rotating mass to accelerate, leaving more of the power to get the rest of things moving.

Of course the flywheel is only part of the rotating assembly, and it's usually matched with lighter clutches, driveshafts, and wheels.

(I often wonder about the forces on the flywheel bolts when people are doing "circlework" type burnouts).
 
Spitty, the lighter flywheel doesn't make any more power than a heavier one. It does allow the rotating assembly to accelerate or decellerate more quickly. To me, any weight that you can take off the ends of the crankshaft is good; to a certain point. Certain types of racing; motorcross for example, will add some weight to the flywheel and slow down the moment of inertia which makes the bike more rideable on certain race-tracks. Also, heavier vehicles need the extra energy of a heavier flywheel to get going from a dead stop.
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The comments above are correct, a lightweight flywheel in a racecar allows the rev's to be raised or drop more quickly to allow better control for rev-matching during gear changes. It allows for more accurate and often quicker shifts.

As elric said, on the other hand, lightweight flywheels often result in slower 1/4 mile times because you don't have the benefit of the energy stored in the heavier spinning flywheel when you launch from a stop.
 
Diesel engines by nature need heavier flywheels than gassers, and you can see why they have slow shifters but they make up with phenomenal low end flat torque curve.
 
Interesting thread as i just installed a lightweight flywheel and clutch in the car here. It is tracked often and agree that this setup, due to less mass, makes getting the car moving from dead stop a bit more challenging. Other gears are fine, as is first, provided the car is moving.

The car rev's more freely (faster) especially during the first three gears. The reasons for this upgrade was to lose weight while also adding durability as we are planning to Supercharge the engine. The stock clutch would not handle the extra power and while we were changing the clutch, changing the flywheel is easy.

Note: Have been told that this lowering of the clutch/flywheel mass could also have you adjusting the car's idle speed.

The below information is from a discussion that can be found on the FerrariChat discussion board, 308 section:

The Euro QV gear ratios found here: http://www.ferrarichat.com/forum/sho...64&postcount=7

1st: 13.072
2nd: 8.996
3rd: 6.473
4th: 4.756
5th: 3.514

So.. for example. If you lost 1 lb. at 6" from the center of the flywheel, it would be effectively like losing overall weight from the car:

1st: 83 lbs
2nd: 40 lbs
3rd: 21 lbs
4th: 12 lbs
5th: 7 lbs

[ratio]^2 * [mass] * [distance from crank axis]
--------------------------------------------- + [actual mass lost]
[radius of tire]
 
I have a lightweight flywheel for my 330ci designed to accomodate the beefier M5 clutch sitting in my garage. It will be installed if I go through with my master plan of supercharging my 330.

I'd have installed it sooner, but I have read that there is a noticeable rattle when the car is in neutral and the clutch is out.

I just have to figure out whether to supercharge the 330 or if a different car is in the cards.
 
The results are in. Went from a combined 30 lbs to about 15 lbs of flywheel/clutch. Results are via my in-car Traqmate data acquisition unit as compared two like track events. Acceleration is much improved with an average top speed of 5 to 10 mph before the braking zone where the exit speed from the apex was virtually identical. Of note is that rev matching during heel-toe is a also faster due to the engine needing to move less weight. This allows for faster shifting.

Other changes were made to the car including Front/Rear weight balance and also installed a newly refurbed Bosch K-Jetronic fuel distributor plus dyno tuned the car due to new fuel distribution system. Also added a new rear aero package. With that said, went from best lap times of 1:30ish to 1:26ish.
 
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