Wednesday, May 18, 2011

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 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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11 comments :

Syazrul.

great article about flywheel. I've always came across people saying they want to lighten their flywheel for better pickup, now I understand better. BTW what's the cost for lightening a flywheel? and which is better, lighten a stock flywheel or buy a lightweight flywheel? i'm drving an Iswara..

TQ Ben

Hi Syazrul,

Thanks a lot. The cost to skim the stock flywheel is around RM30-50. If your car is for daily usage, then better don't get the lightweight flywheel as what I stated above which you can't gain momentum to drive up the hill.

Hi Ben,

May I know which flywheel suitable for Proton Saga old model

Thanks

Hi Ben,

I heard that flywheel can only be skimmed once, second time need to change to new flywheel.. is that true?

Syazrul

Hi,

You may use Galant Supertouring.Supertouring flywheel is 8inch in diameter whereby 4G13/15 flywheel is 7.5inch in diameter. The extra size allow you to use the 1.6 clutch plate as of it has a larger friction area, better grip, improved acceleration. However, do remember to lighten the supertouring flywheel as it is heavier than 4G13/15. If not you will feel less pickup for your car.

Hi Syazrul,

Possible if the first time you skim your flywheel until too light. As of the post above explained, lighten flywheel you will lost the ability to maintain your momentum.

Hi

Do you have to balance your flywheel after lighten.
Regards
Feisal.

Hi Feisal,

The workshop who help you to skim your flywheel will help to balance it. So no worry about that.


Ben

where can i skim? and what type of flywheel can go into naza sutera?

Hi !tKeY87,

You can get it skim at any machining shop. Do take note that it might be balance. I'm sorry that I have limited knowledge about flywheel that can fit to naza sutera.


Ben

Hi ben

Just wanna ask you how far can my persona 1.6 at can do this modification? And what do you suggest for my persona 1.6 for higher perfomance?