CF Driveshafts...

[Wolf_Zero]

I'll start off by saying this is a bit of a rant, now that that's out of the way I'll begin.

Why is it that when people install a CFDS they think their car is all of a sudden a shit ton faster? Do they honestly think they're freeing up that much power to the wheels? I mean seriously, the unsprung mass of a stock and CF driveshaft is not a huge difference. While yes since it is lighter weight it takes less energy to start rotating, but that does not magically translate into a whole lot more power going to the ground. If you want an example to prove my point, take a rod and lay it on a table and push it away with a finger. Than take a similar rod except maybe 2-3x heavier/lighter and again lay it on the table and push it with a finger. You won't notice much difference. I mean it's still attached to the rest of the drivetrain. Most of the gain by going to a CFDS is had in overall weight savings of the car as a whole. Another "big" gain from a CFDS is being able to remove two carrier bearings, but even than it's not like you're reducing the friction that much (unless said carrier bearings were really screwed up and/or need a good greasing). Hell I've driven a friends car (before and after) we installed a 2-piece aluminum shaft in it (which weighs about the same but retains 1 carrier bearing) and it didn't feel different at all. Seriously. I mean honestly, to me, most people are just getting a placebo affect by putting a CFDS on their car. If I'm missing something, please someone enlighten me.

Sorry, it's just annoyed me reading some of the stuff on 3SI about how glorious of a mod a CFDS is.

[TajMan]

Might not be AS glorious as some people make seem.

Just driven the differences with friends car and aluminum, not a car with the CFDS?

[BillyC]

They make a noticeable difference through the entire power band.

[GTO Assassin]

When you combine it with a good staged clutch, lightweight flywheel, it really does make a difference. Considering my 2 pce CFDS weighed in at 12 lbs, against my OEM 3 pce which was 21 lbs - almost HALF the weight of stock. That's gotta mean something. But you have to remember, alot of morons out there think they become invinsible once they put Carbon Fibre on their shitboxes. That's just a ricers life.

Scotty

[Hannibalzero]

I have a 1 piece ACPT drive shaft, and I love it. This was actually one of my favortie modifications. Its not that there is so much more horsepower, its that the acceleration is soooo much more responsive. The car feels better on launches, low RPM acceleration, and off-boost cruising. At WOT, the benefits are relatively unnoticeable. But for casual stop-and-go driving, there is a definite difference in feel.

[quote=""Wolf_Zero""] Hell I've driven a friends car (before and after) we installed a 2-piece aluminum shaft in it (which weighs about the same but retains 1 carrier bearing) and it didn't feel different at all. [/quote]

Try a 1 piece shaft made of carbon fiber. It weighs about 1/3rd of the stock drive shaft.

[Hannibalzero]

[quote=""GTO Assassin""]When you combine it with a good staged clutch, lightweight flywheel, it really does make a difference. Considering my 2 pce CFDS weighed in at 12 lbs, against my OEM 3 pce which was 21 lbs - almost HALF the weight of stock. That's gotta mean something. But you have to remember, alot of morons out there think they become invinsible once they put Carbon Fibre on their shitboxes. That's just a ricers life.

Scotty[/quote]

I believe the OEM was well more than 21 lbs.

[Hannibalzero]

[quote=""bluemax_1""]According to PST who make carbon driveshafts, the stocker is 44 lbs. the 1-piece is 17lbs and the 2-piece is 22lbs. (if I remember correctly for the carbon shafts).

[/quote]
Also, I believe the ACPT 1 piece came in a bit lighter. I want to say it was 16 lbs??? I remember looking at the two, then ultimately going with the one that was just slightly lighter.

[Jeremy C]

Though I won't argue that some people think a CFDS is the end-all be-all and are idiots, any rotational weight that can be removed is good. Your "push with a finger" example is actually rather poor, as most parts on cars would dream of living a life with that little energy being used and acted upon. A better example would be "throw a rod as hard as you can. Now get one that is 3X heavier and throw it as hard as you can. which one goes further?" When exerting the huge amounts of force that the average engine creates, saving weight anywhere from the assembly to the wheels will net great benefits. A rule of thumb that I was given a long time ago was that 2lb of rotational weight saved was equivalent to adding 1hp (or something close to that - I really don't remember the exacts).

[VR4Rob]

My CFDS is my second favorite mod, it totally changed the feel of the car.

[niterydr]

I made over 720awhp/600tq to the GROUND on a stock driveshaft last year.
I'd rather spend the $1000 on my 76mm turbo versus a driveshaft at this point, and my car has every mod pretty much .

[GTO Assassin]

You're parting your car out. You don't count ya quitter. Yeah, I said it. :blackbeltstance:

Scotty

[Hannibalzero]

Is he really? Bummer.

[niterydr]

Yeah I can't afford the car .

[VR4Rob]

Stock driveshafts only break at 310 awhp I twisted the rear section on mine.

[BillyC]

[quote=""GTO Assassin""]When you combine it with a good staged clutch, lightweight flywheel, it really does make a difference. Considering my 2 pce CFDS weighed in at 12 lbs, against my OEM 3 pce which was 21 lbs - almost HALF the weight of stock. That's gotta mean something. But you have to remember, alot of morons out there think they become invinsible once they put Carbon Fibre on their shitboxes. That's just a ricers life.

Scotty[/quote]


...wait...you've actually driven your car??

[moffman93']

Yea......the stocker weighs alot more than 21lbs scotty.

[Wolf_Zero]

[quote=""Jeremy C""] Your "push with a finger" example is actually rather poor, as most parts on cars would dream of living a life with that little energy being used and acted upon. A better example would be "throw a rod as hard as you can. Now get one that is 3X heavier and throw it as hard as you can. which one goes further?"[/quote]

Throwing a rod does not replicate the same type of motion/energy that goes through a driveshaft and as such is an even worse example. I admit, pushing a rod with a finger is a little bit of an oversimplification. If you want a real demonstration, take a rod and suspend it in something similar to carrier bearings. Than put a small gear driven tcase on it and connect a handle of some fashion to the transfercase. Turn that handle with a some meter to measure the amount of energy/force required to spin the rod. Replace the rod with a heavier/lighter one and repeat. Like I said, the amount of energy/force is going to be nearly the same. The unsprung mass of a driveshaft is not that great, this is due to the simple fact that most of the mass is close to the central point of rotation. Now if you were to do that same experiment but turn the rod so that it was connected to the transfer case in the same fashion as a propeller based aircraft you will notice that it requires more energy/force to get it to spin at the same speed. However, it will stay at that speed much easier because it will have more momentum. This is because most of the mass is further away from the central point of rotation and is traveling much faster.

Trust me when I say the biggest two gains from going to a CF driveshaft is the overall weight savings of the entire car and the removal of 2 carrier bearings. I gaurantee that the carrier barriers have more to do with the "incredible new feel" than the actual loss of weight, since you're removing two points for the motion to change direction. I'm doing quite a bit of physics work because of school. I have a pretty good idea about what I'm talking about

And no, I haven't driven a car with a 1-piece cfds yet. However if I can get my motor back together than I will be able to. But I don't think it'll be a fair comparison since I've removed quite a few other unnecessary things for racing.

[TajMan]

^seems to me like you're getting half the point and missing half of it at the same time. I'm too tired to argue anything right now.

[Wolf_Zero]

I'm sure I'm missing something which is kinda why I made this thread. Honestly a simple log of Stock vs. CFDS where it has RPM and Time would quickly solve this. But my car isn't running right now and I no longer have a stock driveshaft.

But let's be honest if you're freeing up power (or making more) to the ground than you're going to notice it in more than just initial acceleration. It could be that since the cf one is one piece that it doesn't flex (energy/motion doesn't like changing directions) which is making it feel faster under initial acceleration. But I don't know how the stock on behaves on a launch.

[TajMan]

As has been said, its not just "freeing up power".
This is rotational weight.
Less weight rotating = it takes less to change that current rotating state.
Engine revs quicker, FEELS more responsive in certain scenarios.
Goes hand in hand and more noticeable with a lightweight flywheel, lightweight pulley, etc. Nice light aftermarket pistons/rods will also make a similar difference in this rotational weight reduction.