Flywheel Replacement???

[Jake Raby]

Engine dynos test at steady state... even those that do a "sweep" of the RPM range are still sampling at steady state, just very quickly. Some chassis dynos can measure inertia accurately and may show some differences with lighter weight components.

This is why HP gains that are present from lightening components are very difficult, if not impossible to measure on an engine dyno, but they do show up very clearly on a stop watch in lap times.

The lighter components increase throttle response which gets a car out of the hole and off of a corner faster, increasing trap speeds..

Lighter parts will always increase acceleration and make any car feel faster, in a street car they cost drive-ability as the engine revs down just as fast as it revs up and that cost gas mileage as the driver is using the acclerator more and more up and down with the reduction in rotating mass.

In most any case a car with a lightened rotating mass will be faster than it was with stock weight parts, despite what the dyno says. This is why we run small 4" clutches with a reduces diameter, lightweight flywheels and even whittle 4 pounds off the crankshaft of our E and F production race engines.

Most lightened flywheels are also "single mass" meaning the factory harmonic dampening effect of the dual mass set up is eliminated. The factory flywheels were also balanced with the engine at the time of assembly as an indexed assembly, changing the flywheel removes this absolute balance- not good.

I have a 996/X-51 engine here at my shop now, it has a broken crankshaft and I feel VERY certain that this was caused by the lightweight flywheel that was used on the engine that could not be indexed to that engine as it was installed after the fact. Often times changing a flywheel creates imbalance and then removing the dual mass eliminates harmonic dampening. Double negatives that cost this 996 customer a 3,500 buck crankshaft- (we are replacing it with our billet unit to eliminate future occurrences)

(FYI- We also have IMS retaining bolts that feature a different design to that of the Porsche units and they also guard against oil leaks, especially when coupled to a sealant that we live by) We make all these as low profile as possible for interchange with as many different components as possible.