[ispkarl]

does anyone know the weight in lbs. of a stock us rsx-s flywheel, i know the jdm r one is 10.36 lbs.

thanks

 

[adirondackR]

stock RSX-S weighs 16 lbs (taken from a clubrsx.com member who weighed it)

for reference - I just bought a toda flywheel (chromoly not aluminum) that weighs 8.2 lbs

I will be selling my dc5-R clutch & flywheel BTW :wink:

 

[ispkarl]

thanks

 

[TeamPacman]

Remember guys lighter is not allways better...

 

[k-dub]

pacman, can you let us know about not alway be lighter is better. I hear some say you can not have one or the other, like under drive lighter crank pulley or flywheel. our you end up with spun bearings, crap like that.

 

[Matador]

Well from what i hear for drag racing purposes only, a heavier(like stock wweight) flywheel is good as it helps you keep the revs steady. Some believe in this theory, others think its full of shit. Im still undecided. But ive launched my boys GSR with a 8lbs flywheel and i could still pull 2.2 60fts like my old stock flywheel'd prelude. But i also have never launched on slicks either. Im also interested in pacmans response, as i know he has a world of drag racing(and street racing) experience.

 

[k-dub]

yeah. we need the facts

 

[TeamPacman]

yeah. we need the facts

Ok. There has been a lot of talk lately regarding engine mods and bang for your buck. .....One of the modifications discussed was the old lightened flywheel. The mod has been used by motoring enthusiasts almost since the car was invented and even with today's modern cars, is still in use today. Now, lightening a flywheel is all well and good but, how many people really know what are the benefits, how are they produced and what must be sacrificed when bolting on a lightened flywheel.


Firstly, lightening a factory cast iron flywheel can have its dangers and is not recommended... So don't do this at all :shock: . The process of casting iron produces a metal component with a hard, fatigue resistant surface and a particularly soft core. If this hard surface is removed during the lightening process ( which it often is ) then this will seriously weaken the flywheel and could result in the wheel coming apart at high rpms, possibly taking the gearbox and your legs with it.


So how does a lighten flywheel work? Hmmmmm...... Amongst the majority, there are two schools of thought concerning light flywheels. The first is that they do not contribute to power output. The second is that they do. Which thought is correct? In fact both, in a way, are correct
but...


If I measured the power output of an engine first with light flywheel and then again with the standard part on an engine dyno, no change in power will be seen to occure. At first it appears that the light flywheel has done nothing and was a total waste of cash....
This is not the case. A dyno that shows max power at constant revs does not demonstrate what occurs to an engine's power output in real life situations - like acceleration. If an engine is accelerated on a dyno ( we are talking about a rate of around 2000rpm a second ) it would show a power output of around 20%-25% less than at the constant rev state.


The reason for this is that when accelerating a vehicle the engine not only has to push the total mass of the car but the internal components of the engine need to be accelerated also. This tends to absorb
more power as the extra power is used accelerating the internal mass of the engine components and is why a motor accelerating on a dyno will produce less power than at constant revs. Also it must be remembered that the rate of acceleration on the engine internals is much greater that the rest of the car. This would then suggest that by lightening the flywheel, less power would be required to accelerate it and therefore more power would be available to push the car along. .


Now, it may seen unbelievable that by removing a few kilos from the flywheel a noticeable difference to a 1000+ kg cars acceleration will be made. In fact the difference is quite noticeable and the secrete behind this is hidden within the gearbox. Everyone knows that cars accelerate at a greater rate in low gears, this is because a cars gear box basically a mechanical leaver and just like when using a leaver to lift a heavy object, the gearbox reduces the mass of the car that the engine sees. For example, in first gear an engine will see the cars mass as only around say 100kg but the engine internal mass would still remain around 20+kg .


It is now easier to see were the extra performance comes from when you lighten a flywheel. In some cases, and not necessarily extreme ones, you could effectively " lighten " a car by 20% in first gear just by removing mass from the flywheel. As the gear used increases this "lightening" effect is reduced. This is why carÉs acceleration reduces in higher gears, to almost no effect in top gear. Great for drags and tight race tracks but will not increase a cars top speed one bit.


Now if having Lightweight flywheels work so well, why are they so heavy from the factory? The answer to this is quite simple. When a lightweight flywheel is installed, smooth idling almost always suffers - more so if standard cam timing is used. If a longer period cam is used, the situation is not quite as bad. With such a cam the valves close much later in the cycle so it doesnÉt take as much flywheel energy to run the piston up on the compression stroke and the idle is by nature smoother.


Just one final point. If contemplating installing a lightened flywheel, it is much more important to remove mass which is close to the flywheels radius of gyration ( the flywheels rotating center on mass ) which is mostly found close to the flywheels outer edge rather than just all over. Due to this, it is possible to receive greater benefit from removing 1 kg from a flywheels outer edge than 4kg from the flywheels centre. If in doubt, seek an experts advice. ect...........

 

[Matador]

With all that said, how would you say if it benefits or hurts your performance in launching? Or if it doesnt even matter at all?

 

[supafly]

my 2cents...

I know some real race teams that have run same times with stock and lightened flywheel

 

[TeamPacman]

No it does matter, less rotational mass = less STORED energy for launching.

Think about it, you're sitting there at the line with the tach sitting on 6000 waiting for the tree to fall. If your flywheel is heavy it's going to be hard to slow down when the clutch is dropped. It's holding ALOT of energy with all that mass spinning so fast.

Now, same situation with a much lighter flywheel. It's holding alot less energy and will be easier to slow down when the clutch is dropped.....


There is a time and place for everything, and in high (read 1000 plus) hp drag cars with unlimited tranny gearing choices, aluminum flywheels are perfect..


Bottow line is to much lighten flywheel suck ass for launching....

 

[adirondackR]

Pacman - my car is not a drag car..but a daily driver which I plan to take to several autocrosses & MAYBE 1 or 2 track events each year. In your opinion would you stay with a stock flywheel.

Also if you know of the pros & cons of aluminum vs. chromoly - I would like to know

as stated above I did purchase the toda flywheel (which is chromoly & weighs 8.2 lbs or 3.7 kg i believe)

 

[Matador]

Straight. Im a probably stick with the stock k20 R clutch and flywheel when i begin my project for now.

 

[TeamPacman]

If you look at the number of stress cycles to failure when comparing aluminum to steel, you will see one nasty flaw. Steel will not change or wear out if the stress level never reaches a certain level. Aluminum on the other hand will fail eventually no matter how small the stress. It make take a million or so cycles, but it will fail.... Things that make it take less time are higher stresses and heat. Two things a flywheel sees a lot........



If you are road racing your car and want to keep the rpms high (above 5.8grand) then a light weight flywheel will help....


So the best way that I can say is that... Light flywheel will help but to a point....


So get one have fun and Enjoy that 10K rpm...

 

[11sec CR-X]

Got my ACT prolite!! 250!! ready to rev again!!