Lightened Flywheels

Purpose

The flywheel is designed to make a car drive smoothly, reduce stress on the differential in the transmission and to balance things.  From the factory, flywheels have a certain mass to them, designed to prevent the RPMs from dropping too quickly, to dampen the power pulses from the engine and make life easier for the differential, and to make driving the car smoother.

When the flywheel is lightened, the engine has less mass on the crankshaft, and therefore the RPMs can climb quicker and also drop quicker.  What this results in is quicker acceleration, as well as fast RPM drops during gear shifts.  If the flywheel is lightened too much, driving the car can become difficult, because there just isn't enough mass in the flywheel to allow for smooth operation.  On a street car, there is a limit to how much a flywheel should be lightened, but I do not know what this limit is.  Lastly, after the lightening is done, the flywheel has to be balanced.

I installed both a lightened flywheel and a 5-speed transmission at once, so it is somewhat difficult to say exactly what the lighter flywheel did to the car's characteristics.  The gearing and final drive of the 5-speed definitely helped with acceleration.

With the new flywheel, the RPMs definitely drop quicker between shifts, and I have to either shift quickly, or rev the engine up a little bit before engaging the next gear (this is when driving slowly and moderately).  When driving with enthusiasm, the RPMs drop nice and quickly during gear shifts.  Furthermore, when driving along and just mashing the gas pedal, acceleration seems quite instantaneous compared to what it was with the 4-speed and stock flywheel.

As I understand it, my flywheel was lightened "as much as possible" without compromising strength.  The weights were taken on our bathroom scale, and I zeroed it both times with the paper on it, so it's as accurate as possible using the equipment I had available.

 

	Stock		Lightened
	9.5 kg		7.0 kg
	20.5 lbs.		15.5 lbs.
					The raised "ring" was removed as much as possible.
					The contact surface was untouched.
					To be honest holding the two flywheels one right after the other, the weight difference wasn't really apparent.
					The pins were removed for lightening and balancing, but were reinstalled prior to putting it back in the car.

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