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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Thu, Jan-10-2019, 09:27:18 PM   #11
dothraki
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Default Re: J-Fiber E46 M3 CF Driveshaft Review

Please do update the initial review once you get more seat time in your car. I'd be interested to hear about the feel and speed of the gear changes, gear engagement, rev matching, acceleration, butt dyno feel, decrease sounds, and anything else you can share. I would imagine your boosted car probably makes the whole experience less than a NA car. Thx!
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Old Thu, Jan-10-2019, 10:41:37 PM   #12
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Default Re: J-Fiber E46 M3 CF Driveshaft Review

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Originally Posted by WALKD_U View Post
Stock driveshafts are made from heavy steel and are designed for maximum noise, vibration, and harshness dampening. Your stock driveshaft is also designed to last the life of your daily driven car and is not designed with performance in mind. The heavier any rotating part on your car, the more engine power is used to move these items. As you lower the weight, you free up more horsepower to the wheels. This will also allow the engine to rev up much quicker to help get you into your power band sooner. This is not to be confused with gaining horsepower from simply adding a lighter driveshaft. You will make the same amount of power, but you are lowering the amount of power being lost from spinning the drivetrain; thus, allowing more power to reach the rear wheels.
  • Carbon fiber driveshafts are stronger than aluminum and produce less noise
  • Carbon fiber is also safer to run because when aluminum fails it shatters whereas carbon fiber shears
Carbon fiber is a miracle material. Itís even lighter than aluminum and has more torsional strength than steel. A carbon fiber driveshaft will typically weigh about 1-2 pounds less than an aluminum driveshaft. The slight weight difference gives it a slight advantage over aluminum, but the biggest benefit to a carbon fiber driveshaft is its ability to absorb vibrations and other rotational harmonics commonly transmitted by steel and aluminum driveshafts. Since carbon fiber is many layers, the plies of the driveshaft will absorb and dissipate the vibrations. Carbon fiber is also safer if it were to fail. When an aluminum driveshaft breaks it can throw shrapnel all over the place and cause serious damage the underside of your BMW. When a carbon fiber driveshaft fails, it will shred back into fibers.

Carbon fiber driveshafts are rated to withstand up to 2000HP. Carbon fiber driveshaftís also come with upgraded U-joints and CV joints to deliver strong connections between the engine and the rear axle. By switching to a carbon fiber driveshaft, you will have the least amount of vibration over any other available option. Most people find a carbon fiber driveshaft is the best choice in keeping cabin noise down as well.

Carbon fiber offers many benefits over aluminum, but that comes with a cost. On average, carbon fiber driveshafts cost about 30-50% more than their aluminum counterparts. If you are looking for a driveshaft to lower ETs, make the car rev more quickly, and donít mind a little extra noise, the aluminum driveshaft is the way to go. If you are looking for improved performance, a refined driveline, and do not mind spending the extra money for that refinement, a carbon fiber driveshaft is right for you.
Thx!
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Old Fri, Jan-11-2019, 12:49:02 AM   #13
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Default Re: J-Fiber E46 M3 CF Driveshaft Review

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Originally Posted by WALKD_U View Post
Stock driveshafts are made from heavy steel
I think stock shafts are lightweight aluminum. The CF cuts the weight from maybe 22 lbs to maybe 12 lbs. Any rotational loss helps but the diameter here is small so not as much energy is used to rotate it as with a wheel where the weight is around a bigger diameter. The CF shaft is not a top priority mod. Itís more for the person who is chasing power and has done everything else.
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Old Fri, Jan-11-2019, 01:46:55 AM   #14
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Default Re: J-Fiber E46 M3 CF Driveshaft Review

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Originally Posted by pbonsalb View Post
I think stock shafts are lightweight aluminum. The CF cuts the weight from maybe 22 lbs to maybe 12 lbs. Any rotational loss helps but the diameter here is small so not as much energy is used to rotate it as with a wheel where the weight is around a bigger diameter. The CF shaft is not a top priority mod. It’s more for the person who is chasing power and has done everything else.
According to my very legit bathroom scale, the factory 2 pc d/s is just under 20lbs.
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Old Fri, Jan-11-2019, 03:44:54 AM   #15
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Default Re: J-Fiber E46 M3 CF Driveshaft Review

My buddy with a 350z kept bragging how his Z came with cf driveshaft from factory. Now I can see how impressive that is.

Thanks for the review
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Old Fri, Jan-11-2019, 06:04:55 AM   #16
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Default Re: J-Fiber E46 M3 CF Driveshaft Review

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Originally Posted by Paulo M View Post
My buddy with a 350z kept bragging how his Z came with cf driveshaft from factory.
which is actually heavy as fuk to dampen the vibrations. It was actually not designed to be light, it is a steel shaft with carbon fiber reinforcement, as far as I know.
The thing with aftermarket CF shafts is that they are also generally wider, putting the rotating mass at a larger moment arm.
The M3 stock shafts are hollow, at 18 pounds, so 11.5 to 12 pounds is saving you 6 pounds, but doing so with a larger diameter (again correct me here), but even so, as mentioned above the diameter change would be small, and the overall effect would be minimal? Just speculating here, would love to see Dyno numbers. I know Stan picked up a few ponies due to the drive shaft so it's an automatic win there.
My only concern with a CF DS would be if it comes in contact with the heat-shielding at some point, would it unravel back to strands or damage it enough to go out of balance? Other than that, it would be nice to see what difference it makes on the dyno
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Old Fri, Jan-11-2019, 04:19:21 PM   #17
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Default Re: J-Fiber E46 M3 CF Driveshaft Review

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Originally Posted by WALKD_U View Post
The heavier any rotating part on your car, the more engine power is used to move these items. As you lower the weight, you free up more horsepower to the wheels. This will also allow the engine to rev up much quicker to help get you into your power band sooner. This is not to be confused with gaining horsepower from simply adding a lighter driveshaft. You will make the same amount of power, but you are lowering the amount of power being lost from spinning the drivetrain; thus, allowing more power to reach the rear wheels
These CF driveshafts sound interesting, but I wonder about the claim to free up horespower. How can this reduction in rotating weight increase horsepower any more than a lightweight flywheel (which doesn't). It allows the motor to spin easier, but doesn't increase HP. Only reducing drag in the drivetrain can increase HP (polished gears as an example). In a drag race scenario I can see the benefit, but not so much for a track car that is accelerating 75 - 125 mph.
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Old Fri, Jan-11-2019, 04:32:14 PM   #18
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Default Re: J-Fiber E46 M3 CF Driveshaft Review

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Originally Posted by Michael9218 View Post
These CF driveshafts sound interesting, but I wonder about the claim to free up horespower. How can this reduction in rotating weight increase horsepower any more than a lightweight flywheel (which doesn't). It allows the motor to spin easier, but doesn't increase HP. Only reducing drag in the drivetrain can increase HP (polished gears as an example). In a drag race scenario I can see the benefit, but not so much for a track car that is accelerating 75 - 125 mph.
A lightweight flywheel doesn't increase horsepower, but it should increase wheel horsepower. It decreases rotational inertia, allowing more of the power to make it to the wheels.
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Old Fri, Jan-11-2019, 04:58:59 PM   #19
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Default Re: J-Fiber E46 M3 CF Driveshaft Review

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A lightweight flywheel doesn't increase horsepower, but it should increase wheel horsepower. It decreases rotational inertia, allowing more of the power to make it to the wheels.
That is correct! I am anticipating 13% drive-train loss then 15%. So if you do the math on bhp x .85 = 940whp. My bhp is 1,105.88235. So my new 13% drive-train lose whp should be around 962.117647. If my calculation is correct I should get about a 22whp gain from reducing the rotational inertia...
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Old Fri, Jan-11-2019, 05:04:45 PM   #20
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Default Re: J-Fiber E46 M3 CF Driveshaft Review

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Originally Posted by WALKD_U View Post
That is correct! I am anticipating 13% drive-train loss then 15%. So if you do the math on bhp x .85 = 940whp. My bhp is 1,105.88235. So my new 13% drive-train lose whp should be around 962.117647. If my calculation is correct I should get about a 22whp gain from reducing the rotational inertia...
I'm not sure that logic follows.

As in, my intuition says it takes a certain (absolute) amount to spin up a given weight a given speed. So while a light weight flywheel might give 2% less drive train loss at 333hp, what it's really doing is using 6.66 hp to spin it up. I can't intuit a reason it would take more hp to spin it up on an engine with more hp on offer.

But, this is based on nothing other than pondering.

Edit: unless it's because a faster engine spins up faster, and therefore needs more hp to spin it up at that faster rate
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Discussing J-Fiber E46 M3 CF Driveshaft Review in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)