alloy prop shaft - better then an exhaust upgrade?

[StanTheMan]

So....if you reduce the weight of the drive shaft it would have a effect on drivabiltity as well? Bit like a lightened flywheel?

is it a bit like the inertia which keeps the engine turning once it has speed? With a lighter driveshaft you would get to high RPM quicker but also loose it quicker onnce some resistance is added?

but at the end of the day. its less hp lost.

[Jeo]

How much are we talking for one of these?

[Tedsmx5]

"So....if you reduce the weight of the drive shaft it would have a effect on drivabiltity as well? Bit like a lightened flywheel?"
Stan,
One of the draw backs of a lightened flywheel is you have to pay more attention when taking of from a standing start as there is less potential energy stored in the flywheel to help move of without stalling.
As the tail shaft does not start turning until you move off, hence no energy loss issues to cause a problem.
Ted.

[StanTheMan]

"
As the tail shaft does not start turning until you move off, hence no energy loss issues to cause a problem.
Ted.

ahhhh yes......point taken.

[irwin83r]

"
As the tail shaft does not start turning until you move off, hence no energy loss issues to cause a problem.
Ted.

ahhhh yes......point taken.

might actually make it easier to drive

[Szemen]

Was browsing Miataroadster.net and they have CF drive shafts.

[irwin83r]

Was browsing Miataroadster.net and they have CF drive shafts.

gb!

[Rotary]

Doing the calculations, the Rotational losses due to the tailshaft, are around the 1Nm mark,

Here’s some light reading
http://en.wikipedia.org/wiki/Moment_of_inertia
http://theory.uwinnipeg.ca/physics/rot/node5.html

In the Overview in wiki, it describes, the important thing is how far the mass is distributed from its rotational axis,

so compared to a flywheel the propshafts mass is very close to its rotational axis,
add to this the fact that due to gearing its rate of change in rotational speed is less than a flywheels, until 4th – 5th where the rate of change in rotational speed is small anyway, then its easy to see that the benefits will be no where near that gained from lightening a flywheel

[wun911]

'The difference is requiring less of your engine's precious power to actually move it.'

If I install a CF drive shaft and I dyno the car, will I see power gains???

Thinking differently; if the exhaust is lighter than stock by 6 kg and it gave you more power, both sides of the equation have been improved are you more tempted with this option?

[Rotary]

If I install a CF drive shaft and I dyno the car, will I see power gains???

About 1/2 a Nm of extra torque in real life, Rotational Torque losses are dependant on how quickly there is a change in RPM, this will vary from dyno to dyno, and will vary from actual onroad results. with a dyno showing substantialy higher gains and losses, because the change in rpm is much quicker than would actualy occur onroad in 5th gear.

This could be why someone may see results on a dyno and report benefits without actually understanding the reason behind it. the faster the dyno ramps up, the more the losses will be as can be shown in the formulas

In real life though it depends on the cars acceleration, the faster a car accelerates the greater all rotational losses will be, so thats why there is actually more gain to be had from a lightened flywheel on a Turbo car than on a N/A car.

Appologies if i'm boring everyone with the tech talk, but I think this is why a manufacturer may honestly claim a benefit, after testing on a dyno, but these gains will not translate to real life, and they may not truly understand the physics behind it.

The formulas can also show how much gain or loss will appear on a dyno result just by plugging in the time taken to go from one RPM point to the other.
(Note: this applies to rotational inertia losses only)