Hi iv'e got a dumb question, but i just dont know and i'd like to learn. If you were to drop in a tranny with shorter ratios and heavily reduce the weight on the flywheel is that gonna put more power to the wheels or just give you better acceleration due to the shorter gearing? I know it's one of those seems obvious answers but i just dont know. Thanks

 

It will give you a little extra HP at the wheels. The shorter ratios change your final drive ratio, which affects wheel HP.

Both the closer ratios AND the lightened flywheel will give you better acceleration, the lighter flywheel allows the engine to spool faster.

 

gear ratio changes will not change your HP- but CHANGE the torque- the flywheel will gain you some HP and you will lose some torque. Yes it will spool faster.

 

Thank you, I stand corrected

 

thanks, it's just a wierd thought to be able to go faster without neccesarily gaining much HP, i guess you just stay in the powerband with a better tranny? why does the flywheel make you loose torque?

 

because the lighter flywheel will stop much faster then one that is heavier when you engage the clutch- basically just bottom end torque is lost.

 

"Flywheels cause you to lose torque and gain HP."

This is such a widely held misconception that no matter how many times I try to explain it, it never reaches anyone it seems. I'll try to dissolve this idea here.

Your engine produces torque. The rate at which the torque is produced is power. It's a simple formula: Power=Torque*engine speed, with some other numbers in there to make the units work... ANYWAY. When you put a lightened flywheel in, you make NO CHANGES to the torque produced by the engine. So, therefore, you make NO CHANGES to the power put to your wheels. However, it SEEMS like you lose some low-end torque, for this reason:

When the flywheel is spinning, it stores energy. The faster it's spinning, and the larger it's mass moment of inertia (related to the weight), the more energy it stores. Therefore, when you launch the vehicle, the energy stored in the spinning flywheel is transmitted through the clutch, transmission, and to the wheels, helping you accelerate. Let's say, for example, you launch your car at 1000 RPM. If you lighten the flywheel, there will be less energy stored by the flywheel at that engine speed. SO, it will FEEL like there's less torque available because of the reduced energy storage. And as a result, you have to put your foot into it harder. Theoretically, if you put a big enough flywheel in, you could simply let go of the clutch and the car would launch, because the flywheel had enough energy to perform that launch.

Once you've launched the car and are accelerating, there is no advantage to a heavier flywheel. The lighter flywheel will allow the torque produced by the engine to accelerate the vehicle instead of accelerating the flywheel inertia.

 

Good way to explain..

The Corvette racing team is doing this to the extreme. They are restricted to how much air they can allow into the engine.....therefore they are reducing the riciprotcating (sp?) weight in the engine.....lighter pistons, rods, crank, flywheel......everything that spins they are trying to lighten for the simple fact that the engine doesn't waste power trying to move the weight......

Rough analogy. At the flywheel the D16Y5 makes 115 horsepower. At the wheels it makes about 95. The horsepower isn't lost it just is being used to turn everything with a lighter flywheel you make more horsepower becuase the engine doesn't have to use it to turn the weight of the flywheel so you get 3 more horses with the lighter.......(Note: None of this is measured it is just examples)

The engine is still making more than 115 but it has to spin everything inside so it loses horsepower. With a lighter flywheel it could be making 118 at the flywheel instead.......Blah, I don't remember that article enough to truely explain sorry......


[Modified by Spade, 9:31 AM 1/17/2002]

 

Basically what I was trying to say without writing a book. Maybe I should restate it to say you loose some rotational inertia giving the driver the impression of lost torque on takeoff.

 

That makes sense, thanks for the info. so from my understanding the closer gears keep your rpm's up to stay in the powerrange, and the flywheel frees up power by needing less to move it???? correct me if i'm wrong. thanks

 

Will a lighter flywheel hurt you when you're shifting? I.E. because there is less weight, will there me be a feeling of less torque when you're changing gears... say... at the drag strip?

I read an article somewhere that was very detailed (I'll try to find it) but it explained the pros and cons of a lightweight flywheel. They basically said that it allows you to "get through: youre rpm range quicker. It explained how a light weight flywheel would be good for a hondas such as ours at the 1/4 track because if you look at a dyno graph, there's a huge spike when vtec hits.... so a lightweight flywheel would allow you to get into vtec quicker. It also stated that if your car has a smooth dyno curve, then it would help you out at the autocross track because youc an accelerate quicker out of turns. The main point was that it would hurt your everyday allmotor hondas for autocross events and help at the drack strip. Does this sound familiar to anyone here? I'm interested in finding out if a lightweight flywheel would help me out at the 1/4 track, and I'ld like to hear everyone's input

 

well- it is much more difficult to chirp tires when shifting- from the loss of rotational inertia. (phrase of the day) so you won't get that extra oomph during upshifts. Basically, my experience with mine is 1- very easy to stall (w/ non-stock clutch) 2- accellerates quicker (at least seems so) 3- no more chirping tires during upshifts. 4- very difficult to keep rpms steady between shifts (car likes to buck- girlfriend hates it) 5- casual (normal) driving is difficult to get used too. 1 month later I am almost used to it.

 

well the loss of wheel spin is good considering that most people have a huge problem putting the power to the ground. i hate 1st to 2cnd i have about 3 or 4 seconds of wheel hop before it grabs.

 

Any particular reason you're pulling the hammer out on me? This IS a technical forum, and I was attempting to give a technical explanation of the theory. Don't take it personally.

Sorry if you don't like "rotational inertia," but that's the physics of it.

Perhaps you do understand the issue, but many do not -- I've read "articles" and "reviews" by "knowledgable" people who insist that a lighter flywheel causes a loss of low-end torque. Simply untrue, and I want to dispell this thought-process.

 

Well said allenp

 

no flames from me- sorry you interpreted it that way- I was hammering myself.