I orderd a 11lb flywheel for my ka24de and I was thinking about adding a carbon fiber drive shaft, but was thinking it might make my rpm's drop too quickly when letting off the throttle or will the drive shaft not affect it as much as the flywheel will. if those 2 together will be fine will adding alight crank pulley over do it on top of those? thanks guys. Ive got full 3" exhaust, the cold air and headers which will be usles when I turbo but was cheap anyways. I also have the ac out of the car. I wanted to see how the car would perform with every bolt on you could do before turbo. I just started making money again so the drive shaft is really the last thing Im going to buy then turbo.

 

you will notice rpms fall faster than stock. but who can say if they fall TOO fast?

 

Hmmm...I cant see how it would make it drop quicker than your clutch pedal being prushed in. Why are you concerned about your rpms dropping "fast"? If you don't depress your clutch the drive line is going to keep it from dropping any faster than if it was a regular drive shaft. The advantage to the lighter fly wheel and drive shaft is less rotating mass...for quicker response

 

i'm assuming he is wondering if rpms will drop quicker after the clutch is pressed.

 

The weight difference on the driveshaft will make less of a difference then the weight of the flywheel... smaller diameter.
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Shouldn't be too much of an issue.

 

how well do CF drive shafts hold up when racing?

 

What kind of racing?

 

the rotational mass of the flywheel keeps inertia of rotation so the lighter the flywheel the less inertia will keep it spining. it will slow down faster. I wanted to know if the drive shaft had the same effect and would be overkill with the crank pulley.

 

I understand that...

What I am saying is with a smaller diameter it will make less difference.
Yes, you will have the same forces at work, but it will be in smaller amounts due to the smaller component.
So I would say, from a purely scientific standpoint. No... won't be because you will notice less of a change from lightening the driveshaft.

You will notice a quicker acceleration, but deceleration will be a little to non noticeable difference.

 

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The flywheel is the only thing mentioned that will really affect how fast the engine rpms fall with the clutch in. It will also allow the motor to rev faster with the clutch in (or in neutral). As people have mentioned, the flywheel's diameter and weight contribute to it's inertia. For those of you who haven't made it to the 10th grade yet, think of inertia as anti-acceleration; it tries to keep things from accelerating and decelerating. It's like momentum, but rotationally. So with less inertia holding the motor back, it will rev faster. Also with less inertia, it will lose rpm faster. This is all in neutral / clutch-in.

A driveshaft has no bearing whatsoever on how fast the engine loses rpms in neutral / clutch-in. In fact, it's not even connected to the engine in these conditions. A lightened driveshaft will decrease inertia in the drivetrain, making it more efficient. You may see an increase in whp even though you haven't increased the actual engine output. This is part of what we call drivetrain loss.

Someone mentioned a crank pulley. A lightened pulley may have some small effect on how fast the engine changes speed in neutral. Not really anything to write home about. Crank pulleys are more to reduce drivetrain loss from powering the accessories (underdrive pulleys only).

And someone questioned the durability of a carbon driveshaft... Every 350Z 6-speed on the road right now has a carbon driveshaft from the factory. They seem pretty durable to me.

Bottom line: an 11 lbs flywheel, a carbon/aluminum/whatever driveshaft, a crank pulley... all of that crap on one motor and it won't drop RPMs too fast.