Lightened Flywheel

[Warpspeed]

It all depends on what else is done to the car, and what you use the car for.

Stored flywheel inertia and some clutch slip is the only way to get ANY manual transmission car moving from complete standstill without stalling. But so very much depends on available engine torque, vehicle weight, and overall gear reduction in first gear.

Once you are moving, the flywheel is nothing but extra weight and extra inertia you no longer need. A circuit race car is not normally doing constant starts, so a very light flywheel is usually an advantage.

A drag race car with excellent traction will launch harder with a heavy flywheel, but that same flywheel may slow down the rate of acceleration once it has launched.

Turbo engines are special, because they usually have minimal torque when off boost, particularly when starting off. If your engine is laggy and has a fairly high boost threshold, a light flywheel is going to make starting off even more difficult than it already is.

If you drive the car every day in heavy traffic, a very light flyweel is quite likely going to be a real pain in the arse, especially with a highly modified turbo engine.

In flat places like Melbourne, it will not be quite so bad as in hilly Sydney. Starting off facing up hills needs plenty of flywheel.

[Cubes]

Once you are moving, the flywheel is nothing but extra weight and extra inertia you no longer need. A circuit race car is not normally doing constant starts, so a very light flywheel is usually an advantage.

A drag race car with excellent traction will launch harder with a heavy flywheel, but that same flywheel may slow down the rate of acceleration once it has launched.

Turbo engines are special, because they usually have minimal torque when off boost, particularly when starting off. If your engine is laggy and has a fairly high boost threshold, a light flywheel is going to make starting off even more difficult than it already is.

Its 'almost' a little contradictory but not quite. The initial take off may require a few more rev's but once past this the car will (as I noticed) rev up quicker and feel as if it actually has a little more off boost acceleration. I didn't notice the more rev's requirement from a standing start under normal driving conditions, it was only when launching the car.

As I think I said earlier I found the gutless rb20 easier to launch with the lightened flywheel, it did require more rev's other wise it would bog but launching at the correct rpm it felt as if it was easier to control any wheel spin that occured and it simply got off the line cleaner.

An R32 GTS4.... I would most definitely stick with the stock flywheel, they require an almost redline launch not to prevent bog, in this circumstance a lightened flywheel would cause launching problems as a result possibly slower 0-100 and 1/4 times. As we all know the faster we can get up to speed earlier the quicker our 1/4 will be. The old Auto VLT's are a prime example of this running mid 10's with only ~300rwkw.

[Fixxxer]

I'm with Cubes on this one, and is the exact reason I'm going for a lightened flywheel when I change my clutch in the next few months hopefully. The RB20 is a dog for me driving into/out of the city every morning, stop start conditions, and off boost acceleration is very poor.

Also of note, what I picked up a few weeks back. The weight of a flywheel is not as important as the distance that weight is from the centre. I believe it is a radius ® squared relationship. Hence a 10kg flywheel with a large part of it's weight on the extremities will be a lot harder to turn than a 10kg flywheel with most of its weight near the centre. This is why you see standard flywheels being lightened with holes/removal of steel as near the extremities as you can get. This has big benefits even though it may only lighten the flywheel by a few kg's.

Fixxxer

[Greg]

I'm picking up my car this afternoon with a JUN 6.1kg lightweight flywheel fitted to the RB25DE - will post up my impressions.

[wilch]

I have a 4.5kg flywheel in my car.

Positives:

- engine revs easier

- revs drop really quickly

- less engine braking

Negatives:

- revs drop quickly between gear changes

- need revs to get the car off the line

- meh..

I like it.

[space_monkey]

Slightly cheaper price for what looks like the same item here;

http://www.tweakit.net/shop/index.php?cPath=326_367_374

Does anyone know the weight of the RB25DET standard flywheel?

Also Aluminium @ 5.0kg for around $520 or Chrome-Moly @ 5.5kg for $100 less???

[Cubes]

Go the molly.