aluminum drive shaft - anyone?

[rlpaul]

Originally Posted by Poodles

<snip>but CF is less durable for a street driven car.

Eh, there's a number of cars that come from the factory with CF driveshafts now. In the Mustang, Camaro, and GT3000 circles, there's people that have been running them on dailies for well over a decade.

The 'danger' is impact resistance. As long as you don't smack into a boulder, it should last just as long as any other type of material.

[Jaden]

Originally Posted by JDKane527

Definitely agree. The Kinetic Energy affects how much inertia the rotating assembly has. Decreasing overall inertia has benefits.
Angular kinetic energy is defined:
KE = (1/2)*(Iw^2)
I = moment of inertia
w = angular velocity

The faster a mass is rotating, the more effect it has on impacting Kinetic Energy. The crank pulley and flywheel are rotating at the same angular velocity. The flywheel would make a substantially larger impact than the crack pulley would make.

KE = (1/2)*(Iw^2)
I,flywheel >> I,crankpulley

The alternator pulley is rotating much faster than the crank pulley due to the pulley diameter. It could be argued that lightening the mass of the alternator would have more of a benefit than lightening the water pump pulley as the water pump pulley diameter is similar to the crank pulley diameter. It could also be argued that lightening the alternator may or may not cause harmonics/resonances in the engine as the rotating mass has been altered.

KE = (1/2)*(Iw^2)
w,alternator >> w,crankpulley

The case of the driveshaft, I is altered while velocity remains constant before and after.
KE = (1/2)*(Iw^2)
I,carbon << I,steel

I = mr^2
As m,carbon ~= (0.5) m,steel
Correct me if I'm wrong, but I hear the radius is slightly less for the carbon driveshaft.
r,carbon ~= (0.99) r,steel
I,carbon = (0.5)(0.99^2) I,steel
I,carbon = (0.4905) I,steel

KE,carbon = (0.4905) KE,steel

It would help for angular acceleration of the assembly slightly and for braking, but would not have as large of an impact as lightening a component with a higher angular velocity.

When talking about crank pulley affecting hp, you have to understand you're talking about two different things.

a lighter pulley won't have as much of an effect as an underdrive pulley.

An underdrive pulley will often be lighter as well, but it is reducing engine load from accessories by changing the rpm's of the accessories for a given engine rpm which reduces the engine load for accessories at any given rpm.
Anyone who tries to argue that under drive pulleys don't increase hp is smoking crack.

That would be like saying that super chargers don't increase load and take hp from the engine to operate.

Jaden

[JDKane527]

Originally Posted by Jaden

When talking about crank pulley affecting hp, you have to understand you're talking about two different things.

a lighter pulley won't have as much of an effect as an underdrive pulley.

An underdrive pulley will often be lighter as well, but it is reducing engine load from accessories by changing the rpm's of the accessories for a given engine rpm which reduces the engine load for accessories at any given rpm.
Anyone who tries to argue that under drive pulleys don't increase hp is smoking crack.

That would be like saying that super chargers don't increase load and take hp from the engine to operate.

Jaden

This could be another discussion on the benefits of reducing mechanical drag and load, such as deleting the engine driven water pump and the effects of changing the final drive.

[wootwoot]

Originally Posted by stugray

From page 5 -

If you reduce the 30 lbs driveshaft to 0 pounds (removing the energy stored in it entirely!) and do otherwise equal runs 0-100 MPH you WILL notice a 44 millisecond difference in a 16.2 second run!

It doesn't matter if you win by an inch or a mile. Winnings winning!

[Poodles]

Originally Posted by rlpaul

Eh, there's a number of cars that come from the factory with CF driveshafts now. In the Mustang, Camaro, and GT3000 circles, there's people that have been running them on dailies for well over a decade.

The 'danger' is impact resistance. As long as you don't smack into a boulder, it should last just as long as any other type of material.

The cars that came with them from the factory are more using what is more appropriately known as fiber reinforced plastics and it's quite a bit more durable. They also run guards under the driveshaft tunnel to prevent rocks from hitting them. It doesn't take a bolder to kill a CF driveshaft...

[Xinshadow]

Originally Posted by Poodles

The cars that came with them from the factory are more using what is more appropriately known as fiber reinforced plastics and it's quite a bit more durable. They also run guards under the driveshaft tunnel to prevent rocks from hitting them. It doesn't take a bolder to kill a CF driveshaft...

The JDM/Euro model underpannels provide basically the same function. I have a set on my car, keeps everything under there SOOOOO much cleaner.

[Poodles]

Originally Posted by Xinshadow

The JDM/Euro model underpannels provide basically the same function. I have a set on my car, keeps everything under there SOOOOO much cleaner.

Nope, they cover the sides.

[GT86_PRAGUE]

Originally Posted by stugray

From page 5 -

If you reduce the 30 lbs driveshaft to 0 pounds (removing the energy stored in it entirely!) and do otherwise equal runs 0-100 MPH you WILL notice a 44 millisecond difference in a 16.2 second run!

I was looking for REAL WORLD experience, not crunching some numbers.
You dont have this on your car and you will never have. You obviously are against this, so you are disqualified from commenting on this question.


I believe there is at least Rick from Rallyspo* who claims very positive things on their FRS. Anyone who bought this agree or not?

[cdrazic93]

Originally Posted by GT86_PRAGUE

I was looking for REAL WORLD experience, not crunching some numbers.
You dont have this on your car and you will never have. You obviously are against this, so you are disqualified from commenting on this question.


I believe there is at least Rick from Rallyspo* who claims very positive things on their FRS. Anyone who bought this agree or not?

disqualified lol. Yes, lets not believe the engineer because that's not what he went to school for or anything. Totally doesn't know physics, or math. Nothin like that. I'm so glad you made assumptions he doesnt have it, or wont ever own it.

[GT86_PRAGUE]

Originally Posted by cdrazic93

disqualified lol. Yes, lets not believe the engineer because that's not what he went to school for or anything. Totally doesn't know physics, or math. Nothin like that. I'm so glad you made assumptions he doesnt have it, or wont ever own it.

Dude, I was not asking for engineers point of view!

[JDKane527]

Originally Posted by GT86_PRAGUE

Dude, I was not asking for engineers point of view!

So real world experience point of view like butt dyno vs real dyno? Butt dyno registers over 9000 whp with rainbows being shat.

[cdrazic93]

Originally Posted by GT86_PRAGUE

Dude, I was not asking for engineers point of view!

Except engineers quantify real world data. Given a statement that can have a lot of subjective reasoning to it, you're left with a ton of opinions. Person A says "I like this mod because it appears to make me rev my car faster". Person B says "well I didn't seem to notice much of a difference". Do you see where the bias comes in? If it can be measured and proven with something that is non arguable (ehem...with math), it gives you a non biased real world answer without anyone sponsoring it (positive raving godlike review) or leaving their own bias because the product didn't work for them (negative review based on possible improper installation or defect...etc).

TL;DR In the real world this will have minimal acceleration gains at best, assuming you can shift properly at the peak of the power band every single time. That's what the science tells you.

[cdrazic93]

Originally Posted by JDKane527

So real world experience point of view like butt dyno vs real dyno? Butt dyno registers over 9000 whp with rainbows being shat.

Don't forget the unicorn manned corndog vending machines.

[GT86_PRAGUE]

Originally Posted by JDKane527

So real world experience point of view like butt dyno vs real dyno? Butt dyno registers over 9000 whp with rainbows being shat.

Originally Posted by cdrazic93

Except engineers quantify real world data. Given a statement that can have a lot of subjective reasoning to it, you're left with a ton of opinions. Person A says "I like this mod because it appears to make me rev my car faster". Person B says "well I didn't seem to notice much of a difference". Do you see where the bias comes in? If it can be measured and proven with something that is non arguable (ehem...with math), it gives you a non biased real world answer without anyone sponsoring it (positive raving godlike review) or leaving their own bias because the product didn't work for them (negative review based on possible improper installation or defect...etc).

TL;DR In the real world this will have minimal acceleration gains at best, assuming you can shift properly at the peak of the power band every single time. That's what the science tells you.

I didnt told I value more some guy who need to justified his purchase (or sell it like Rick) over an engineer. I just want to hear an opinion from someone WHO HAS IT and I would than make some assumptions myself.

I read the science above and I dont believe it either.
I can save 10kg on battery for 1/3 price of propshaft, so there must be more to this. Again, not asking for any engineering stuff, but possible oppinion of someone WHO PERSONALLY DID THIS.