Flywheel Modification: To Maintain or To Reduce the Weight?

I believed all of us heard about lighten flywheel. It is an inexpensive and easy wake to wake up your Normally aspirated or Turbocharged eng...

I believed all of us heard about lighten flywheel. It is an inexpensive and easy wake to wake up your Normally aspirated or Turbocharged engine. Sorry for auto tranny owners as this is only applicable for manual tranny. The are no negative effects to lightening your stock flywheel unlike replacing it with an ultra-lightweight Aluminum flywheel. Most manufacturers make the stock flywheel very heavy because this makes the engine very smooth and enables it to retain energy at part throttle cruise and up long grades for better fuel economy.

However, an Aluminum flywheel goes completely the other direction with almost no weight. This lets the engine rev up very quickly and allows the engine to work easier due to the reduced weight spinning around on the back of the crank. This is fine as long as you are at full throttle and wide open throttle all the time like in a Road Race or Drag Race only car. As soon as you let off the gas the engine RPM drops instantly and the car slows down. In a road car this causes surging and bucking at cruise speeds and poor drive ability and clutch engagement. Thus a lot of people will tell you that lighten your flywheel will cause your car does not have enough momentum when driving uphill.

A lightened stock unit on the other hand gives you the best of both worlds. It is a compromise between the OVERLY HEAVY OEM unit and a TOO LIGHT Racing unit. You get the benefits of both with none of the bad qualities.

Turbo cars are exceptionally critical to flywheel weight. Too light a flywheel will make the car rev faster and possibly come on boost faster but that is only half the issue. When you let off the gas to shift the car will drop off of boost just as quickly causing a poor transition when you come back on the throttle.

Basically when lightened a stock unit, we will try to maintain it around 3.5-4.5kg lighter than the original yet still give the driveability needed for street use. By the way, lighten flywheel will only taken off the weight from the back side of the flywheel so the surface is still the same height and your clutch still fits and works the same.

Anyway, here is an example:
a) 10Kg of flywheel + Clutch Cover + Clutch Plate is rotating at 7000 rpm
b) 13Kg of flywheel + Clutch Cover + Clutch Plate is rotating at 7000 rpm

a will definitely has a better pickup compare to b but b will give better power at the higher rpm. At the end of the day, this is all depends on individual preference.

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