onefastviking

Technically, it's not the weight of the flywheel that really is making any difference, it's the change in moment of inertia that is what counts. However, when you change to a lighter weight flywheel you are also changing the MOI for that particular engine/trans.

wildcat077

Strange that nobody with a 993 that actually installed a lighter flywheel and pressure plate responded to this thread as those are the cars which benefit the most from this upgrade.
All that is posted so far is mumbo jumbo theories ... i'm sure Patrick Motorsports and Kennedy Engineering have some valuable reasons why they sell so many lightweight assemblies to 993 owners and 3.2 911 owners alike !
Wish i could comment on the benefits for my car but i haven't installed mine yet,still sitting in the box for another month or so !

Cheers !
Phil

jhg41977

I installed the lwf and rs clutch package from FD Motorsports. Since my car had a bad clutch when I bought it and this car is the only Porsche I have owned or driven recently, I can't really offer a fair comparison. I love the wag it drives though! I also I stalled RS engine mounts and reinforced carrier.

boosted 89

As it was told to me, a light weight flywheel will allow the engine to rev faster and easier somewhat like having lighter connecting rods and a lightened crankshaft. Reducing the rotating mass will increase throttle responce and maybe the HP/torque curve of an engine. It also helps with engine braking which can be useful in a racing situation where less foot brake application is required to slow you down. I agree with byprodrivers explaination.IMO

trackdaycareracer

Try out these two experiments:

1) A circular plate has the same material, outside diameter and thickness as a circular ring. Obviously the ring weighs much less than the plate.

Put both on the top of a hill and let them start rolling down at the same time. Who would you think gets to the bottom of the hill first, provided they both roll in a straight line? The plate.

Reason being that the potential energy at the top of the hill splits into two energies once they start rolling: One that gives forward motion and one that gives rotation. In a circular plate, the mass is evenly distributed from the middle and out. The mass near the middle doesn't spend as much energy rotating as the mass near the outside. That extra energy is used to give the plate forward motion.
In a ring, the mass is obviously at the outside so more energy is spent on rotating than forward movement.

2) A circular plate has the same material and thickness as another circular plate with a smaller diameter. Obviously the plate with the smaller diameter weighs much less than the plate with the larger diameter.

Perform the same experiment as in # 1). Which plate gets to the bottom of the hill first? Both plates get to the bottom of the hill at the same time.

Even though the mass is different, the speed is the same because the potential energy, kinetic energy and rotational energy is proportional to the mass when two objects have the same shape.

How the heck it translates to flywheels? Well, the flywheels don't actually go anywhere do they. It is all rotation. For wheels though, it's food for thought. Getting the mass closer to the center is more important than the overall wheel weight. Anyway, back to flywheels: at a steady 3.000 RPM, the flywheel has stored potential energy and it has a rotational energy. Since most of us tend to stay at a steady RPM until the apex, when we start accelerating, that's the situation in a lot of corners, lap after lap. Wouldn't that potential energy turn into rotational energy once we start accelerating? If so, wouldn't the ideal flywheel when coming off the apex be heavier with a smaller diameter? Two seconds later, barreling down the straight, a lighter, smaller diameter flywheel would have less moment of inertia and provide quicker acceleration, right?

Thanks to those of you that have bothered to read everything

spare tire

The force of gravity is a constant. The force on an engine changes with throttle and other things. You are confusing yourself.

Here is a factual real world experience answer.
ROAD AMERICA, Wisconsin Turn 5 is a slow left (40-50 mph) followed by a short straight, 100 yards long, uphill, and you must brake before the overhead bridge at the top of the hill because if you do not, then you will go straight OFF into pea gravel. Turn 6 is slightly faster than 5 and also a left.
With a stock flywheel I used to Take corner 5 in second gear and red line shift into third gear about 75 to 80 yards of this 100 yard straightaway.

NOW with a LWFW I make the same redline shift into third at 40 to 50 yards up the the same straightaway. 25-30 yards sooner.
The car is a 996 a GT3. Red line in second is (82-83 mph from memory)

wildcat077

There we go ... hard facts,that's what i'm hoping for
with my little 3.2


Cheers !
Phil

dasams

How's this for a summary? dave

A lightweight flywheel has a lower moment of inertia (think angular momentum) than a standard flywheel. Since the MOI is a measure of the resistance to rotate, an engine with a LWFW will move more rapidly up and down the rpm range, all else being equal.

aglaes

When does the law of diminishing returns kick in? There must be some reason for the mass of a flywheel, otherwise why have it at all.

trackdaycareracer

I wonder why Porsche would install a heavier flywheel than necessary on a GT3 when the change in performance is as good as described in the post above. The only downside seems to be that it can be easier to stall the car. However, a GT3 is a driver's car that require skill to drive at ten tenths.

JustinL

I like this one.

You can calculate how much torque it takes to accelerate a disc fairly easily. To accelerate a uniform 6Kg .15m disc at a rate of 6000RPM/s takes 31 lbft of torque.

The biggest difference is you have to shift faster as the engine slows more quickly and you can miss the rev match on upshifts if you are lazily shifting. Throttle blips on downshift are faster and don't need as much throttle input. The added benefit of extra torque is only really an effect in the low gears.

modoz61

This link takes you through a good explanation of the advantages/reasons for LWFWs

Whether or not they are for your driving style comes down to practice and need

http://www.uucmotorwerks.com/flywhee...heel_works.htm

trackdaycareracer

Thanks mate, that clear things up quite a bit

Cheers,
Trackday/Daycare-racer

multi21

Because Porsche sells it as a street legal car. Stock FW in a GT3 on the street is good, not so good on the street with a LWFW

BOBBYFALI

If I am not mistaken, there more sportier GT3RS has the light weight flywheel. Actually that is what I have in my car , being it is part of the UMW clutch set up.


Thanks

Bobby Ali

ba