Stock or aluminum?

[wil5bart]

There's some gain using aluminum drive shaft but to me not really worth the cost. I would spend my money on other performance upgrade.

[kingkenny]

Not worth the money in my opinion , mainly because trade off too much comfort .

Mine is CF shaft , it improve shifting feel and throttle is more responsive but also translate the movment from the diff. to front , also it make noise .

I had the diff. mount before the shaft , after the 1 piece shaft , i got engine mount done to stop the movment afterward. If i do it again i do the half shaft mount , and keep the 2 piece shaft .

[continuecrushing]

in for scientific explanation that no one will understand.

looking for something like this: 57*&14 oranges+110.2030303(4-7+2/4){444158.20} stock driveshaft-cf weave*8+32/cars weight^14=percent of improved performance

[totopo]

Originally Posted by Shutter

in for scientific explanation that no one will understand.

looking for something like this: 57*&14 oranges+110.2030303(4-7+2/4){444158.20} stock driveshaft-cf weave*8+32/cars weight^14=percent of improved performance

more like this?


seriously though:
http://www.w8ji.com/rotating_mass_acceleration.htm

Drive Shaft Example

Now let's think about a drive shaft. The driveshaft is a fairly thin hollow tube. Nearly all drive shaft weight is at the outside, since it is (of course) hollow. The shaft also turns at the same RPM no matter what the driveshaft diameter, because the RPM is set by the rear end ratio, tire diameter, and vehicle speed. If we make a driveshaft lighter and keep everything else the same, the vehicle acceleration change is often insignificant.

Why would it be insignificant in most cases?

In the first place, the drive shaft is small in diameter. With a small diameter, less energy is stored for a given weight. In the second place, a driveshaft is really not that heavy. A steel Mustang driveshaft weighs somewhere around 30 pounds, so we just can't take that much weight out.

Also, the driveshaft spins up gradually and smoothly over a long period of time. It accelerates fastest at slowest speeds, and that is when it needs the least energy to spin up. Because it has a long time to spin up, is a small diameter, and because it does not weigh much, the driveshaft does not remove very much horsepower at any instant of time. Despite what we are told, a change in driveshaft weight has, at best, a very small effect on acceleration. Likely any change is immeasurable in a street/strip car.

Now a lighter shaft certainly can help in a very light vehicle. It can also help in a road race car (as will a light crank and flywheel), because road racing requires instantly changing from acceleration to deceleration.

A light driveshaft won't change anything significant or measureable in a 3000-pound 11-second car, except how fast dollars leave your wallet!

Another worry is driveshaft diameter. If we go from a 30-pound 3-inch steel driveshaft to a 30-pound 3.5-inch aluminum shaft, we move the weight out 3.5/3 = 1.167 times. That increases stored energy 1.167^2 times, or 1.36 times. If we store 0.3 horsepower in the shaft, changing the diameter will increase that to 0.4 horsepower. We would have to reduce weight 14.3% to 25.7 pounds just to break even with the diameter increase.

The worst thing about a driveshaft is the diameter is so small, and the acceleration time is so long, there just isn't much horsepower being sapped from the system. A typical steel driveshaft in a typical 12 or 13 second car only stores an average of about 1/4 horsepower. If we got 100% of that back with a zero weight shaft, we would never notice it.

Good reasons to change a driveshaft are to get rid of vibration and harmonic resonances in the shaft, to make it stronger, or to simplify a two-piece driveshaft system. The silliest reason is to speed the car up. Even if we only pay $100 for a shaft, it would typically be much less than 1/4-horsepower average gain. That would be paying much more than 100/.25 = $400 per horsepower. Paying a lot more than $400 per horsepower is not a good investment.

[strat61caster]

Originally Posted by Shutter

in for scientific explanation that no one will understand.

looking for something like this: 57*&14 oranges+110.2030303(4-7+2/4){444158.20} stock driveshaft-cf weave*8+32/cars weight^14=percent of improved performance

$400 driveshaft < $600 tires

[justatroll]

Originally Posted by kingkenny

...throttle is more responsive ... .

How is the throttle more responsive?
The Driveshaft is connected to the Diff, not the engine.


With a LWCP, you can feel better throttle response with the engine disengaged from the trans, but not when it is engaged.

[ShadowSeraph]

I swapped mine to a CF one, if anything there was some weight dropped.

[justatroll]

Originally Posted by totopo

more like this?


seriously though:
http://www.w8ji.com/rotating_mass_acceleration.htm

Very nice writeup.


I personally like this one:

Originally Posted by stugray

Consider it another way:
If I stood back and clocked someone over the head with a 30 lb driveshaft that had 3800 joules stored in it, that person would likely get up and kick my ass.
If I hit that same person with a 2800 lb car that had 1272176 joules stored in it,it would separate all their appendages, then fly through the person and knock down the building behind them.

Just a simple visualization of the problem is all that is required to "see the forest through all the trees".

Entertaining read here:
http://www.ft86club.com/forums/showthread.php?t=82353

[jawn]

The only thing that these mathematical models usually fail to account for is the joint in the factory driveshaft, which does have a moment of inertia that ought to be accounted for.

That said, it's still not a good cost-to-benefit mod.

[Ashikabi]

Originally Posted by jawn

The only thing that these mathematical models usually fail to account for is the joint in the factory driveshaft, which does have a moment of inertia that ought to be accounted for.

That said, it's still not a good cost-to-benefit mod.

I noticed a benefit over feel of shifting/initial acceleration where you have the dead spot in the stock one. It would be one of my first upgrades if I had to do it again

[kingkenny]

Originally Posted by justatroll

How is the throttle more responsive?
The Driveshaft is connected to the Diff, not the engine.


With a LWCP, you can feel better throttle response with the engine disengaged from the trans, but not when it is engaged.

It is my gut feeling after I install my CF shaft , not like doing light weight crank pulley and light weight flywheel , the rpm don't rev and drop quicker when you disengaged the clutch . More responsive to get the power to the wheel , I guess that the different between 1 piece and 2 piece shaft .

[makesdrivingfunagain]

I think the aluminum is 11lb loss while cf is nearly 12. I think the aluminum is near $450.00. Weight reduction works and just a scale is needed to verify the loss. I know it is $450.00 but that 11 or 12 lbs and a 15lbs battery nearly saves 1 percent weight loss of entire vehicle (even though the battery is 14-15lb savings for my brialle 15lb battery). It is worth it for some people for sure. A good weight loss mod to be certain. In some cases for me to lose 11-10lbs say on wheels could cost just as much or more than just my cast lighter weight wheels. 2or 4lbs lighter wheels is huge. And the price to reduce from cast to Forge is huge also, which from my research for my 16" wheels would cost 2x as much with2-4lbs saved p/wheel. This driveshaft upgrade can be one way to supplement what some say is the best weight loss unsprung weight or drivetrain loss for certain application. Remove spare tire and jack stuff near 30lbs, certain tires in same category/size 2-3lbs ea. tire (8-12lbs total unsprung for tires). Little things add up, seats can be save10lbs sometimes (but with different benefits as well as weight like fitment and holding gforce) but much more costly than aluminum driveshaft (usually). Not trying to get off track just trying to show that weight savings cost money; and it works. Oh yeah lightened flywheels save weight too of course. Horsepower mods or increase is to produce a better power to weigh to move the car faster weight savings improves power to weight ratio as well. It is kind of different way to get there. Anyweighs not trying to get off track just trying to help enthusiast on the forum. : )

[humfrz]

Originally Posted by makesdrivingfunagain

I think the aluminum is 11lb loss while cf is nearly 12. .

OR, one could run with 2 gal less gasoline .......


humfrz

[makesdrivingfunagain]

Originally Posted by humfrz

OR, one could run with 2 gal less gasoline .......


humfrz

Yeah I know but after the 2 gallons is deleted I got to save somewhere. If two gallons is still in tank the weight loss from the driveshaft will still be there as well.