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ZR-1 Flywheel Upgrade

The original equipment dual mass flywheel 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. The transmission rattle noise will vary depending on the smoothness of the engine's idle and the clearances in the transmission. Engines with excellent idle quality will be quieter. Most installations are the quietest if a 750 rpm idle speed is utilized. There will also be some low level growl from the transmission when accelerating lightly in the 750 to 2500 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% drive line loss) equals +15 crankshaft hp.

The power to weight ratio of a 400 chp ZR-1 is approximately 9 lbs./chp (3600 lbs./400hp = 9lbs./chp). Based on this power to weight ratio, the car would need to be lightened 135 pounds to match the improvement in acceleration that is available with 24 pounds less flywheel weight (15 hp x 9 lbs./hp = 135 lbs.).

The original equipment disk and pressure plate are an excellent clutch. The OE disk and pressure plate are suitable for drag racing with street tires with up to 550 crankshaft hp. 

The OE transmission lubricant is 5W-30 viscosity mineral based oil. We have found that Red Line Shock Proof Heavy lubricant reduces the gear rattle the most. A synthetic lubricant is also more stable for viscosity as temperature increases. As a result, the tendency for the gear rattle to increase with operating temperature is reduced.

The cost of the Fidanza flywheel, balancing, correct length bolts, washers and Shock Proof lubricant is $720. Labor for installation is $552. The installed price is $1272. If the flywheel upgrade is installed along with any other service or upgrade that involves removal and replacement of the flywheel, the labor overlaps with the other service and therefore there is no $552 installation charge.

More information about drive line inertia reduction from another source.

Automotive engineer and popular automotive author David Vizard published an article in the February 2006 issue of Popular Hot Rodding magazine.

They tested two late '80's Mustangs, one with 240 whp and another with 425 whp. Flywheel weight was reduced by 12.7 pounds. On the Dynojet dynamometer, both cars produced about +15 whp. The cars were also drag race tested. The ET's were both approximately -.1 second. A back issue copy of the magazine can be purchased at  www.popularhotrodding.com.