ZR-1 Flywheel and Clutch Upgrade

 

The dual mass flywheel that GM supplies puts a major damper on engine performance. The flywheel design uses additional mass to prevent the gears in the transmission from vibrating in response to the combustion energy pulses that are transmitted by the crankshaft.

If one is willing to accept some noise at idle in trade for increased dynamic power output, a lighter flywheel might be right for you. There will also be some low level growl from the transmission when accelerating lightly in the 1000 to 2000 rpm range.

An increase in dynamic power can be measured on a dynamometer that measures the rate of acceleration of an engine. Inertia dynamometers such as the Dynojet (tm) can quantify dynamic power. The driver of a ZR-1 with a significantly lighter flywheel will observe that the car accelerates faster in the lower gears. The greater the rate of engine acceleration the more noticeable the improved acceleration will be. This is especially noticeable in the first and second gears.

The stock flywheel weighs 37 pounds. The Fidanza aluminum flywheel weighs 13 pounds. Thus the dynamic weight reduction is 24 pounds. The Dynojet (tm) power output can be expected to increase by about 13. +13 wheel hp divided by a .85 correction factor (15% power train loss) equals +15 crankshaft hp.

The right selection of a clutch disk and lubricant for the transmission will minimize the transmission gear rattle. The stock clutch disk has a solid hub because the stock flywheel provides the spring isolation. With a solid flywheel the spring isolation must be provided by the clutch disk. The best clutch disk will provide two features. A sprung hub for torsional vibration control and OE or greater torque capacity. Our disk selection has urethane encapsulated springs for vibration control and Kevlar facing on one side for increased torque capacity. The three encapsulated springs can be seen in the picture. The other side of the clutch utilizes a stock like organic facing. The picture shows the Kevlar side of the disk. It also has a marcel spring like the OE disk. As a result; Gear rattle is minimized, The take up as the clutch is slipped is about the same as the OE clutch, And, torque capacity is increased by about 30%. The stock pressure plate is excellent and is retained if it passes inspection.

The OE transmission lubricant is 5W-30 viscosity mineral based oil. The ZF transmission company also approves the use of Castrol 10W-60 synthetic lubricant. The thicker viscosity lubricant is useful for dampening transmission noise. A synthetic lubricant is more stable in viscosity as temperature increases. As a result, the tendency for the gear rattle to increase with operating temperature is reduced. Overall this package will exhibit gear rattle that can be characterized more as a rumble than as a rattle. The results will vary depending on the idle smoothness of the engine. Engines with excellent idle quality will be quieter. Most installations are the quietest if an 800 rpm idle speed is utilized.