[slicknick112]

My USDM DS weighed 29.7 lbs last night when I took it off, the CF drive shaft weighed 14.5 lbs. I just received it last week, did the install last night (took me 1.5 hours from drive in to the garage to drive home). I need to check it this afternoon because I've got a slight vibration under WOT between 2000-5000 rpms. The clearance is almost zero in two different spots and I'm worried that I might be rubbing.

The benefits were immediately noticeable. It gets up to speed so effortless. Much more responsive to throttle input, excel and decel. The quality of ride is better, less vibration overall, smoother ride. I was also able to fix an exhaust rattle and vibration while I was down there.

Thanks Jim, I'll have my customers project STi in the shop next week for the complete over haul of TBE, Driveshaft, Accessport V2, hardened mounts and other miscellaneous upgrades.

[BlueWRXSTi2005]

Still waiting for mine to come in. Two months now and counting. Grrr. I'm hoping sometime this week. Everyone keeps saying about how beneficial this DF is; just looking to verify the claims myself.

[JJ18Sniper]

Originally Posted by BlueWRXSTi2005

Still waiting for mine to come in. Two months now and counting. Grrr. I'm hoping sometime this week. Everyone keeps saying about how beneficial this DF is; just looking to verify the claims myself.

Be sure to post your comparisons... each and everyone will help the product become more popular. I am still on the fence, not in its ability to provide function, but its value for the dollar. Hopefully I can get past that by summer

[SilverSurfer]

Yeah. I'm waiting too. A cool G is a lot to spend to drop 15 lb of weight, even if it is drivetrain/rotational inertia weight...

[jlp7t]

Seriously, a back-to-back dyno plot has the potential to sell so many of these driveshafts. The only conclusion I can come to is that it must not show $1k worth of an improvement, or else ACPT or a vendor would have posted the comparison months ago.

Hopefully I'm wrong, I'd love to find another way to make more power without swapping turbo/injectors/etc.

[nhsilversti]

Originally Posted by jlp7t

Seriously, a back-to-back dyno plot has the potential to sell so many of these driveshafts. The only conclusion I can come to is that it must not show $1k worth of an improvement, or else ACPT or a vendor would have posted the comparison months ago.

Hopefully I'm wrong, I'd love to find another way to make more power without swapping turbo/injectors/etc.

installing the driveshaft will not "get you more power"

it will allow more of the power to get to the wheels.

[La Mer]

Originally Posted by jlp7t

Seriously, a back-to-back dyno plot has the potential to sell so many of these driveshafts. The only conclusion I can come to is that it must not show $1k worth of an improvement, or else ACPT or a vendor would have posted the comparison months ago.

i've pretty much come to this conclusion as well. it only makes sense to dyno the thing right away.

FWIW, i own the DS.

[HSPN.com]

Originally Posted by jlp7t

Seriously, a back-to-back dyno plot has the potential to sell so many of these driveshafts. The only conclusion I can come to is that it must not show $1k worth of an improvement, or else ACPT or a vendor would have posted the comparison months ago.

Hopefully I'm wrong, I'd love to find another way to make more power without swapping turbo/injectors/etc.

We have every interest in providing independent dyno testing, drag strip runs, track runs, and 0-60, 0-100, and other tests on video to stream across our sites like www.hspn.tv and www.subie.tv. Unfortunately, we do not charge people to watch our videos and we do not sell subscriptions like magazines. Sponsors are few and far between and paying for bandwidth consumes almost all of the money sponsors do provide, so this project has been delayed as we try and save up for it.

ACPT does not market their products, provide individual dyno tests for each and every application, or try to get you to buy their shafts because the driveshaft business is so small compared to their main business which is supporting the aerospace industry. The driveshaft business only came about because one of the owners wanted a driveshaft for his car. When those results were seen by others, they built a few shafts for some other applications over the years.

[STInk]

Does Rays Engineering need to dyno a set of forged wheels to sell them? Does Toyo need to dyno their light tires to sell to Joe Ahole? Why does Nissan spend the extra dough to make the 350z steering wheel magnesium? The shaft makes the car feel a LOT lighter and more nimble. Nobody's gonna hold your hand when you type your credit card info; sorry.

[300hp@6000rpm]

Personally, the user feedback alone has pursuaded me to make this piece my next purchase (if only one of the vendors would get them in-stock). Any dyno information will do little to sway me from NOT purchasing one as the amount of positive feedback from people who own the D/S is overwhelming.

Besides it seems the most significant gains will be seen on the track.

[resonant_evil]

Originally Posted by RainMaker

Man oh man. I went to www.importimage.com . NOT what I was looking for. 8-/

Compare the moment of inertia to the brake rotors. You can replace our rotors and lose 20lbs (all 4 wheels) at a larger distance from the axis. AND thats weight loss that seriously benefits the suspension. OR get lighter wheels and tires...theres 4-5 lbs a corner there easily.

For the cost of this mod, there seems to be many better choices for your money, according to physical theory.

i agree with what you are saying about the moment of inertia of rotors and wheels. the further the weight is from axis the higher moi. money better spent, maybe for brakeman rotors at around 10lbs saved a corner. same price even, this is my dilemma (better braking and weight savings). i went to import image and i was looking also.
i think for the cost people really arent looking into this mod before they have some basic mods done. this is not really a beginner mod (even though it could be a good one) due to price.

Originally Posted by RainMaker

Im sorta with Dave (Rootus) on this one. The change in mass of the driveshaft is so close to the axis about which it spins... is so trivial that physics just doesnt seem to back up the claims.

i think the change in mass is what you are neglecting. if you use slicknick112's numbers then the mass is cut in half. (i am trying to order a drive shaft now but xmas is in the way) since i dont have a cf ds on hand i will assume the diameters are close, which would cut the moi in half also. if you use newtons second law (of rotation) (net external torque = moment of inertia x angular acceleration) you will see with a constant torque, a large change of moi will affect the angular accel. (in this case increase it)
change your angular accel, you change your avg angular velocity, which changes your angular displacement.
all i am saying is physics backs up everyones claims, in this case it is not the distance from the axis it is the total mass loss which effects this feel. there is also the dampening and strength of cf to consider.

[SoJDM.com]

For those of you waiting for STi driveshaft, we at SoJDM are banging our heads trying to get these things. We paid for a production run a while ago, but so far have only received a ready supply of the WRX shafts. The STi shafts have not come through in any quantity. A few here and there which cannot satisfy the demand. Our understanding is that there was a problem with a batch which caused a run to be trashed. Even so, there should have been some by now.

[telum01]

hopefully the supply issue gets sorted out... i'll be ordering mine soon, tax season at the latest (can't wait for some serious returns!). it's taking everything in me to not whip out the credit card right now.

[resonant_evil]

i just paid mine off!

so i could get the shaft!

[resonant_evil]

any updates on the shaft?