duboisr

a flywheel can not develop hp ,it can let the motor rev quickly which feels like more hp.

rynberg

That is not correct. The engine must spend energy to rotate the flywheel. A lighter flywheel or one with more of the mass towards the center will require less energy to rotate. The effect is more hp to the wheels. Max Cooper did some research and calculated that you will get around 50 more hp to the wheels in 1st gear, around 16 in 2nd gear, and neglible in the higher gears. It does not "feel" like more hp, it allows more horsepower to the wheels -- less drivelines loss.

http://www.maxcooper.com/rx7/parts_i...heel/index.htm

grampa

A light flywheel does not "take away power" it only delays the onset. It's not like the flywheel converts the "lost power" to heat or anything.
In effect a light flywheel reduces the rise time of power delivery, the draw back being that it also reduces driveline damping - the car will buck easier when starting out or misfiring.

TYSON

The flywheel does not make or take horsepower, as several people have suggested. Your test was done on a Dynojet, was it not? This test accelerates a given INERTIA. Your car is always accelerating on the Dynojet, hence the lighter flywheel allows more torque to be used to accelerate the rollers. You will feel this when ACCELERATING hence it feels like you have more horsepower when driving. It can't make horsepower, because it has nothing to do with getting more fuel and air into your engine.

adam c

iTrader: (2)

The only thing that matters is RW horsepower. A lighter flywheel will give you more RW horsepower.

kwikrx7

I don't know if I've ever seen a before/after dyno with a lightened flywheel but from what I've learned and experienced, you don't gain any peak hp. In other words you won't go from 350 rwhp to 360 rwhp with the addition of a flywheel. But the car gets it's power at an earlier rpm. My FD revved like a motorcycle and feltmore nimble when dropping gears. Like earlier stated, 1st and 2nd gears are very noticeable and the upper gears are negligible. It's definitely worth it for a street car since a lot of street races start from 10-40 mph roll-ons where a flywheel shines. Although it doesn't get you peak up up top, it gets you more hp throughout the powerband and earlier which is IMO the best mod for the FD besides a turbo upgrade

adam c

iTrader: (2)

Your engine puts out "x" amount of horsepower. In order to turn everything between the engine and the ground, some of this horsepower is being used. A lightened flywheel will reduce the loss of power between the engine and the wheels.

poss

iTrader: (5)

think about this. A light flywheel has similar, abet more drastic, effects as getting lighter wheels,at least when the clutch is out. so essentially some of you guys are saying that by getting lighter wheels, you could increase hp??
I disagree.
it has nothing to do with the amount of power created by the engine. where is this extra hp coming from?

I agree, you decrease rotational weight so the driveline can accelerate faster. This might appear as more hp on the dynojet because it uses the rate of change of velocity, or acceleration, to determine the amount of power. I think this is right, but i am not studied up on my dyno engineering.

just my $.02

anyway, I have a 9lb flywheel and my idle quality significantly decreased. however, other than that, I would recommend installing one. 1st doesn't last long now!

poss

iTrader: (5)

the flywheel doesn't really use and power, it simply stores it.

maxcooper

It takes a lot of power to accelerate the flywheel from one RPM to a higher RPM quickly. The amount of HP required goes up as the rotational inertia (related to the weight) and the speed at which you accelerate it. First gear goes by quickly, so it takes more power to accelerate the flywheel in first gear than it does in a higher gear.

-Max

adam c

iTrader: (2)

So the flywheel "stores" HP?? Maybe for use at a later time or date?

I don't think so.

There are 2 measures of HP. At the engine, and at the wheels. The measurement at the wheels is always less because some HP is being used to move the flywheel, transmission, driveshaft, rear end, rear axles, wheels and tires. I remember somewhere seeing this number quoted as around 13 percent loss on a FD. Don't quote me on that.

ptrhahn

iTrader: (9)

Its a nice mod,
i'd wait till you need a clutch, then do the whole deal, because there is a fair amount of labor involved.

93TTRX7

Crap, I can't believe I didn't get one...I cheapened out :/

r0t0r-rooter

This site talks about "storing" hp:
http://www.dim.com/~mackys/z/mods/flywheel.html
This site talks about the hp or no hp debate:
http://www.geocities.com/MotorCity/7177/flywheel.html

maxcooper

The flywheel does store energy, and it is probably more than you would expect. I calculated that it took 50 HP less to accelerate a light flywheel than a stock flywheel through first gear at full throttle. Of course, energy and HP are two different things, but 75 HP for two seconds is a good bit of energy, I would imagine. You use the stored energy when you shift -- it is converted to heat in the clutch and some forward motion for the car.

The amount of power required depends on how much rotational inertia the flywheel has (closely related to its weight) and how fast you need to accelerate it from one RPM to another RPM. The power lost to flywheel inertia is greatest in first gear and quickly drops off in higher gears because it takes a lot more time to rev in higher gears.

It probably takes less than 0.1 HP to keep a flywheel spinning at 8000 RPM; all you are fighting there is a little friction. It takes around a thousand times as much to accelerate it from 3000 to 8000 RPM in 2 seconds because you are up against the considerable inertia of the flywheel.

The drivetrain loss percentages are just a rough estimate. In reality, some of it is inertial, some frictional, etc. Because of the inertia part, the real losses will be quite different from gear to gear. But 13% or so seems like a reasonable estimate for a third or fourth gear dyno run, as evidenced by the dyno plots of cars with known flywheel HP quantities. But again, it is just an estimate, so be careful not to mistake the estimate for what is really going on.

There have been some eco-friendly car designs based on the principle of using a (big, heavy, fast-spinning) flywheel as an energy store. You "charge" the car by getting the flywheel spinning really fast, and then you use the energy stored in the spinning flywheel to drive the car around. As you convert the flywheel's energy to forward motion for the car, the flywheel slows down. At some point, the flywheel will need to be "recharged" by using an outside power source to accelerate it up to a higher speed.

-Max