i am also interested in an alum driveshaft!

 

Any word on this?

 

it is my understanding that you need to remove the trans to install a alum or carbon fiber drive shaft, i wonder how difficult they are to install, and if the gains are worth the headache

 

if it were the rear I see no reason for removal of the tranny

 

any new news i want this

 

Same said...

 

hey chuntington101,

DUDE, Have you ever heard of "unsprung weight?" And for that matter do you realize that not everyone wants a 40 thousand dollar car with the rear seats ripped out of it.????? Usually when your talking about any type of Evo mod, its expensive. So a thousand bucks to lose around 10lbs in unsprung weight is not a problem, I can swing it. Lighter car = quicker performance!
Thanks for your .02, just try to leave us with some valuable knowledge next time!

AND NOW FOR MY .02!
I have racing chassis setup book that I used religiously in my circle track days back in 1995 -96- 97. It has a section dedicated to Unsprung weight. The Manual states that every 1lbs of weight removed from the following items would be the equivalent of losing 10lbs of the sprung weight. So if the driveshaft is 10lbs lighter then it would like be losing 100lbs of your sprung weight. The manual is in storage at the moment. I am going to have to get it because it has a good tutorial about why it is this way. I remember this because my team and I spent many hours removing the weight off my race car. I know this much. I had the fastest car in my class on the track. I am on a mission to find some one that has a stock Evo VIII and purchased an Aluminum driveshaft or CF driveshaft. To be able to share with all of us the difference between the two. Cus truthfully that is what matters most. Some one that speaks from experience. It might be me. But if im going to spend a G on an Evo Mod. I’m going to concentrate on getting the power to the ground first. And that would mean my first mod will be the clutch. Which is far more the 1K. The driveshaft will more then likely be my second mod. If I can find someone that tells me how much it effects acceleration. Or maybe I will go light weight unsprung wheels!! For 2500 to 4000. hmmm what to do!

 

Unsprung weight from a driveshaft? Not hardly.

If you remove weight from your wheels and tires. Say 5 lbs per corner. You will see a noticable gain in acceleration and braking. Now if you remove 20 lbs from your drivshaft you will not notice any difference. The driveshaft spins 4 times slower than wheels and tires. And its mass is placed 1.375 inches from centerline. Wheels and tires are spinning masses 9-12 inches from centerline. Maybe we should open our books and study angular momentum.

In order to save 20 lbs from the driveshaft you would need to make the driveshaft one piece. While a one piece driveshaft may work okay on a race car where the motor is restricted in movement with solid mounts, it is not a good Idea for a streetcar. There is a reason these cars have three piece drivshaft.

The driveshaft in these cars is unique in that its the only car on the market where the engine is perpendicular to the drivshaft. All other rear drive cars(including subies) have a driveshaft that is parallel to the engine. With normal rear drive cars the driveshaft recieves a little extra twist during engine torquing. Not a problem. In the evo when the engine torques the front of the driveshaft moves up and down. Big problem. Now you know why there is a three piece shaft under your car.

 

saorry white MR, must have had a bad day

does anyone make hollow (ie gun barell turned) half shafts and drive shafts? these would (i think) be cheaper than a custom carbon item and should be a bit more robust!

thanks Chris.

 

a lighter driveshaft will decrease the overall weight of the vehicle but will also decrease rotating mass which will therefore reduce parasitic loss and put more hp to the wheels. it will also make the engine rev easier because it doesn't haven't that extra weight resisting its spinning motion. really interested to find out if someone has done this mod too!

 

bump

 

id consider it.

i hope a good manufacturer such as Mines or ATS or even ACPT gets on this..

 

You`re right i saw that on best motoring video "the 350 z shock"
But they made it more for crash issues then weight saving.

 

I'm not sure what the driveshaft has to do with unsprung weight besides that it's not part of it.

Anyway, you can actually calculate torque gain or loss from different rotating components with the equation T = Iw
T = trq
I = Mass moment of inertia (key element here)
w = change in rotational speed, RPM's
You'll have to calculate the torque loss between both driveshafts then find the difference between the two to find the gain. Some trickery may need to be done when the driveshaft is hollow. Probably easiest to manipulate the density of the hollow driveshaft by using displacement/mass of the entire driveshaft instead of the classic density of Carbon Fiber or steel.
So on top of just plain static weight reduction, moments are also being reduced as well yielding more available torque. Similar to a lightened flywheel.

White MR,
For now you can keep your $.02. What racing is it that you do? What class do you run in and for what organization? I hate to come down on a fellow evo enthusiast, but when you come in here spouting off bad information and telling us that you read a book on suspension like it has anything to do with a driveshaft some red flags begin to go off. The old assumption of "10lbs of unsprung weight equals 100lbs" is lame science with ZERO math backing it up. It is nothing but something you heard although it does steer you in the right direction, but who wants aproximate when you could have cold hard REAL data?
BTW, I've read some books too.
That said, I would personally find something better to spend $1k on. Only if I needed a winning edge in close competition AND regulations permitted it would I try the new driveshaft.

 

a drive shaft is one big long piece of metal.... changing that to a big long piece of cf is gonna be saving you weight in ways that you can't do anywehre else. plus it makes the car more responsive nad might get you less powertrain loss from inertial losses although you might get less gas mileage on the freeway. and people already stated that it helps driveability.

as far as the equations go... there is no trickery I is dependant on radius and mass and there are empiracle equations for different geometries... you would use a solid disc's moment of inertia for a solid drive shaft which is .5 MR^2 and for the hollow one you would use a thick ring which is just mr^2. you would have to do some integrating over the entire geometry but the basic process should be understood here.

and reducing the mass on the driveshaft would just be slightly different than flywheel. the flywheel mass has an extra purpose in that maintaining it's momentum is important, because it is a flywheel. a flywheel in non automotive terms is a disc that serves to store angular momentum and hence rotational energy so it can be transfered. a lightened flywheel stores less energy and therefore transfers less energy. that's why when you get a lightened flywheel it's only useful at speed... when you're starting outta first it's annoying as hell, what you lost in momentum from mass you have to make up for in rotational velocity.