Skyline6mt

iTrader: (1)

Nice! Post some pics of that vs oem. Also any chance you could weight them to get the exact difference from oem?

37hevn

iTrader: (1)

safety loops are $50 ish, buy 2 and the aluminum and pocket $500+. does anyone actually believe they can tell a difference between those. my point is unless you have a small d,i,c,k or you get a fuzzy feeling saying you have a cf driveshaft the aluminum one will do just fine. if you think youre that hardcare to need a cf over aluminum then you need a different car.

indyn

are you doing a before n after dyno? And would like to know the vibrations at higher speeds for the Aluminum.

37hevn

iTrader: (1)

^what he said. they said they dont advertise it as a hp gainer but it will increase dyno hp. if you have an automatic id like to know how much your 60 ft and 330ft drop

37hevn

iTrader: (1)

talked to z1, they said for a group buy on the aluminum they want 5 people...they also wouldnt give me a price until i had 5...dumb. the price is the incentive

ECain18

iTrader: (15)

Just installed mine.

Quality:
Great, VERY light over stock. I was pretty amazed. I'm very happy with it.

Installation:
Simply pull your exhaust off, unscrew 4 bolts, swap out the stock unit with the new one, and bolt back in. It takes longer to get the exhaust off. I was in and out in less than 45 mins.

Performance:
The car definitely pulls harder and probably "gained"(i.e. got back) a couple of felt horsepower. Nothing crazy but you will notice a difference. I'm all about light weight components as our car is heavy already. For the price, its worth it to me.

Noise:
As far as noise, I noticed it is every so slightly louder(hum) at low speeds and deceleration. I mean barely. Keep in mind I have had my shifter rubber/noise dampening out of my car because I just installed a short shifter and was waiting for some carbon fiber products from tony at CF elements. As such, I did not have any noise dampening between me and the driveshaft/road, only the rubber piece not screwed down. At high speeds, nothing is noticeable and I'm sure you will not hear the difference at all with your shifter area fully assembled. I have also recently had a noisy exhaust problem and can't hear anything over that. Im switching back to the stock manifold and cats so it will be better.

Vibration:
I have not felt any vibrations at any speeds whatsoever. I have not gone over 85 yet though, I'm a little cautious on highways now cops have been out in force around me!

indyn

Excellent feedback. Would be nice on this thing feels at higher speeds? This is a one piece, right?
are you doing dynos?


count me in.

JSolo

iTrader: (14)

@ECain18, while a different material driveshaft may change the characteristics of NVH, I find it very hard to believe there'd be much performance improvement, let alone anything you can feel.

The driveshaft itself is relatively small in diameter, so its moment of inertia is relatively small. The difference in weight would be negligible compared to the effort (torque) needed to rotate the differential/rear wheels.

Do several dyno runs to establish a baseline, then change out the DS. Lets see if there really is a gain.

Edit: Maybe it feels faster because you're feeling more vibrations now...

37hevn

iTrader: (1)

I have had people tell me that you wont get more hp from the driveshaft. But it doesnt make sense. They say all it does is make you rev faster. But get this, when drag cars get lighter driveshafts they are told by the company it will lower your 60' time. How could it lower your 60' time but not give you more power to the wheel?

if you go from 2.0 to 1.8 to 60' then you got there faster which means you had more power. im not saying it will be a lot but 16 lbs is quite a bit and i would guess close to 10 hp. stillen and the other brands that make the crank pulley advertise 5-10 hp with lightweight crank pully which is 3 lbs less than stock.

on the dyno you will rev faster. so if you compare a before and after and set the horizontal axis to "time" you will be able to see you get a higher hp in less time or "rev quicker"

G37Sam

Physics101: reducing the mass of a rotating body reduces the inertia required to turn it. In other words, less torque required by the engine to rotate it => more torque goes to wheels.

So reducing the weight of anything from pistons, connecting rods, crank shaft, cams, flywheel, clutch, gears, drive shafts, axles, brake rotors, wheels, tires etc.. will definitely improve accelaration, whether that is significant enough to be felt on a 1700kg car or not is a different story.

Just make sure safety is not comprimized.

jujubii

iTrader: (5)

im down if they safety of these things is accounted for. are they looking for someone to take measurements of the stock driveshaft?

JSolo

iTrader: (14)

@37hevn, I didn't say there wouldn't be any improvements, but it would be negligible.

Anyone here still in school familiar with physics. I think we need to compute the torque of a cylinder (a driveshaft is after all nothing more than a cylinder of certain radius, length and mass, rotating at a certain angular velocity). I studied this freshman yr in college many years ago but can't recall too much.

G37Sam

Get me its dimensions and I'll have a CAD drawing fpr you with its rotational inertia about all x, y and z axis

Torque required to spin it is a factor of the desired rotational acceleration too

JSolo

iTrader: (14)

Sam, consider a DS of 1M in length, 3" diameter (76mm), and for sake of simplicity, say 13KG and 6.5 KG mass.

You'll have to dig into your background for the angular acceleration.

G37Sam

What's the inner diameter of the OEM driveshaft?

I'll let the CAD software obtain the masses from there and compare steel with aluminum in terms of mass, inertia and strength

Something tells me though that the aftermarket aluminum driveshaft is probably slightly thicker