Demystification of carbon driveshafts.
"These build journal entries are part of a special series on the development of the E46 M3 V2 Carbon Driveshaft by YFCM Composites.
This specific journal entry aims to correct misunderstandings, myths and inform E46 M3 owners that time do change, and progress can be made :) This serves as my unboxing impressions.
These entries are written in collaboration with M Lee: lead engineer and patent holder to YFCM's innovations."
"The tubes are weaker than steel!"
They are up to 3x stronger than steel.
Many believe BMW M dropped the carbon driveshaft in the F8X M3/M4 due to carbon tube weakness.
That is wrong.
The reality is carbon tubes achieve much higher torsional rigidity specifications.
I highly recommend to watch the following video by Richard Hammond comparing material properties of carbon vs steel driveshafts at the Lotus factory.
If you break this tube, I will refund you in full.
"They unglue at the flange!"
This isn't totally wrong: it is technical challenge many brands failed at.
BMW M suffered from ungluing transmission flanges. They issued an official recall on the F8X M3 & M4.
MFactory notoriously failed when attempting to retro-engineer the authentic, patented product you're about to read on today.
Due to their poor transmission flange design, they had to use a larger diameter carbon tubes to match the outside diameter of the transmission flange.
Below is the counterfeit MFactory V3 using a transmission flange riveted to the tube. You can read more about this saga here.
M. Lee patented a self-locking flange: it will never unglue.
The flange is a self-locking, sealed design. It eliminates all probabilities for the tube to spin free of the flange, no matter the torque.
It locks over the carbon tube.
Machined from 7075 forged aluminum. The flange is weight optimized and anodized for corrosion resistance. A new, shorter flange was designed for the 6spd owners. We don't need the clearance that SMG guys require for their actuators.
Vibrations are the results of poor engineering [...]
The ungluing transmission flange problem led many brands making carbon driveshafts to use a double CV joints or U joints.
These designs eliminate the flexdisc (guibo) that is specifically designed to reduce drivetrain vibrations and clunk noises.
[...] and quality control.
The results are much heavier driveshafts, added vibrations and a product with a very narrow range of use.
The added weight, larger diameter tubes and riveted flanges make balancing the carbon tube of these inferior products extremely difficult.
They "fixed" it by using balancing weights across the tube. That doesn't work.
Below is the MFactory counterfeit V3 driveshaft on the right that I personally tested on my E92 DCT M3.
It had 3x weights across the tube and vibrated in specific speed ranges. You can read more about the comparaison here.
YFCM retains use of the OEM guibo.
The picture below shows the YFCM E46 M3 driveshaft that retains use of the OEM guibo.
Below is the telescopic CV flange on the YFCM driveshaft to bolt up to the differential.
"Even BMW M dropped it!"
BMW M dropped the carbon driveshaft as they needed space in the transmission tunnel to fit emissions related equipment. The carbon tubes have larger diameters.
"BMW will begin adding a particulate filter to the exhaust system at some point in the future to stay compliant with stiffening emissions regulations.
Carbon fiber driveshafts have a larger diameter and therefore take up too much space under the car. The "M-specific high-performance" steel driveshaft being used in its place is narrower enough to work."
- Source: Autoblog.
Up Next: I document the preliminary checks, procedures and validations steps to installing the V2 carbon driveshaft to my E46 M3.