Here is the negative horsepower graph of the two driveshafts. You can plainly see some of the resonance in the 1LE aluminum shaft (blue graph), and how it was aleviated by the ACPT carbon fiber shaft. The Carbon Fiber shaft weighed in at 9.3 lbs, while the 1LE Aluminum shaft weighed in at 12.2 lbs. Click here for pictures of the two driveshafts both in and out of the car.
In this case, the dyno doesn't tell the entire story. The smoothness and reliability
of the carbon fiber driveshaft is amazing. The carbon shaft has a critical speed of over 300mph with stock 3.42
gearing, where the 1LE aluminum has a critical speed of 175mph. While 175mph is not achieved on a regular basis,
being closer to the critical speed means more vibration at lower speeds.
The difference in vibrations even at a mere 60mph were quite noticeable. My wife even noticed the lack of vibration. This shaft also has a .5" larger diameter than the 1LE, and the carbon fiber's elasticity gives it more shock dampening ability than the aluminum.
During our recent Nevada Open Road Challenge race, where we averaged 125mph over 90 miles of highway, the car was buzz-free and smooth even at our tech speed of 140mph. To put it through even more testing, we will be competing again in the Silver State Classic Challenge in September of 1998 in the 135mph class or so, with a tech speed of 165mph. See the Events page for more details.