[Neanderthal Racing]

Originally Posted by ValvetrainEngineer

Honestly, the improvement from the CF wasn't huge in my opinion as well as on the dyno. I posted my before / after pulls in the big thread, gains were fairly small.

that doesn't surprise me, engineer. i always thought the reality would never quite meet the expectations some people had.

Originally Posted by ValvetrainEngineer

This makes sense when you think about the physics, also makes sense that the flywheel feels awesome in low gears! Flywheel is better bang for the buck,

as you know, there's a downside to lighter flywheels, too.

Originally Posted by ValvetrainEngineer

but CF also has some other benefits like lower torsional spring rate and more weight reduction.

if you don't mind hacking your undercarrriage, aluminum offers more torsional flex to help buffer the tranny on launches and even lower weight by a lb. i'm not sure what you mean by "lower torsional spring rate" but anything the twists less is going to transfer more shock.

[grim09]

Originally Posted by BruceChapman

if you don't mind hacking your undercarrriage, aluminum offers more torsional flex to help buffer the tranny on launches and even lower weight by a lb. i'm not sure what you mean by "lower torsional spring rate" but anything the twists less is going to transfer more shock.

Bruce this is not true. That is actually gained by the carbon fiber driveshaft because it acts as its own vibration dampener; because the carbon fiber will twist more than an aluminum shaft will, it is able to relay the power down to the wheels smoother than aluminum or steel; also because of this, it will save wear and tear on your transmission and rear diff due to the fact that it will absorb the torque shock better than steel and aluminum. All that you gain going from steel to aluminum is a lighter metal driveshaft. steel and aluminum still share the same properties because they are metal. The critical speed is not much different from steel to aluminum and same with the flex of the shaft. also over time the metal driveshafts will begin to fatuige the more they are launched, eventually the end yokes will become out of faze and never return to thier natural position; then you will have to replace it because it will vibrate and can never be balanced correctly again. Also Aluminum is heavier than carbon fiber, the only reason these shafts might be lighter is because the ACPT driveshaft uses steel ends that are bonded to the driveshaft, if they were able to use thier aluminum ends the shaft would be about 3 to 4 lbs lighter than the aluminum driveshaft.

[ValvetrainEngineer]

Grim, you can't say that steel and aluminum are the same because they are both metals. They have significantly different moduli of elasticity.

At this point I'm not taking sides between which metal DS has the lower torsional rigidity (i.e. twists more under a given torque). You can't base the conclusion solely on material properties either - you need to consider tube diameter and material thickness.

[grim09]

Originally Posted by ValvetrainEngineer

Grim, you can't say that steel and aluminum are the same because they are both metals. They have significantly different moduli of elasticity.

At this point I'm not taking sides between which metal DS has the lower torsional rigidity (i.e. twists more under a given torque). You can't base the conclusion solely on material properties either - you need to consider tube diameter and material thickness.

i am not saying they are the same, i am stating they share similar properties, and you are right tube diameter and thickness matter which is why the aluminum driveshaft has to at least 3.0" or larger to work for the STI and the carbon can be a 1/2 inch smaller and still achieve a higher critical speed and hold more torque than the aluminum driveshaft.