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Old 02-27-2014, 11:55 AM   #1
roadtrip1098
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Default PST Carbon Fiber Drive Shaft (06 STi)

The UPS truck just left and my birthday present to myself just arrived. It is a PST Carbon Fiber Driveshaft. I purchased it from RallySportDirect.com for $1071. There are other vendors that may sell it for less, but I know RSD is reliable.

Initial thoughts: This thing is beautiful. The shaft has a nice even pattern on it, the ends look to be of high quality. It feels very solid. It feels so solid that I actually had trouble believing the weight - to the point where I put it on a scale. 14.6 LBS on the dot, exactly what was advertised.

I'll be adding an install video and acceleration comparison doing a couple 2nd and 3rd gear pulls and post it up later with a performance review. Until then, here's some carporn pics.





Why did I pick this upgrade? I have a 2006 STi with about 50k on the clock. Presently, it has EL headers, DP, 3 in exhaust, drop in air filter, bigger top mount, water meth, light crank pulley, and a tune that I wrote for it. The car is great, pulls awesome, and I'm happy with it in general. I have built big turbo cars before, and I do love the top end, but having the VF39 reminded me what it's like to have torque almost instantly on tap. I think I'm pretty much maxed out on the power I'm going to squeeze out of it without turbo, injectors, fuel pump, ect. So for now I'm focusing on drive line weight. Old school racers will tell you that every pound of rotating mass is like dropping 8 static LBS. Since I don't need a clutch yet, my rotors are barely broken in, and the stock BBS are pretty light already. I went with an easy bolt on that drops just as much weight as light rotors or a light flywheel (about 14 LBS). Don't get me wrong, I will get the lightweight flywheel and rotors as they are needed. I just consider those maintenance items - it's an easier sell on the wife. In addition, with the last car I had, going to a lighter flywheel killed driveability - having a lightweight DS should help offset that.

Is it worth it? Really, I don't know. I would guess that it's all suggestive. You can get an aluminum one or a single piece steel one a lot cheaper, but each have their downsides. For me the CF was the best choice, the only drawback was price. To me, I'd say it's worth it as I move forward with building my car.
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Old 02-27-2014, 08:20 PM   #2
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Subscribed been looking at one of these for a while
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Old 02-27-2014, 09:13 PM   #3
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The aluminum ones and steel like to come inside the car when they break... the carbon fiber shafts "broom" when they break which is much more safe.

Nice upgrade. Im curious about how the installation process goes. Please let us know if you experience any vibration around 60-80 mph.
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Old 02-27-2014, 09:13 PM   #4
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Installation should be even easier than the stock DS.

I look forward to your after install driving impressions. I've been wanting one for a while but am concerned about a couple things.
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Old 02-28-2014, 06:09 AM   #5
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I just finished getting video of acceleration (roll ons) in each gear with the stock shaft. Hopefully installing tonight and getting the post install videos. It will take a couple days to get the videos synced up, but install pics should be here tonight.
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Old 02-28-2014, 12:09 PM   #6
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Great news everyone! RallySportDirect has a huge promo going on right now you can get one shipped for $887.15 - Almost $200 in savings!

As for their customer service, they are giving me a gift card for the difference - Now that right there is quality customer appreciation.
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Old 02-28-2014, 05:16 PM   #7
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Thats great customer service.

Glad you are enjoying your CD drive shaft. Though I run the DDS one I feel this upgrade makes a huge difference on our cars.
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Old 02-28-2014, 09:33 PM   #8
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Just finished the install, took about an hour, and I'm fat and slow. After reading other reviews I was expecting the increase in acceleration and smoother shifts, which the shaft does deliver on, but what really surprised me was how quiet the car is now... I never even really noticed how loud my STi was before, but I sure as heck notice that it's a lot quieter. Absolutely no vibrations right up through 100, lets say kph just in case there's any law dogs out there. Rowing through the gears is much faster without trying to be fast, 1st gear is not jerky at all anymore, and engine breaking is silky smooth. It may just be me, but it feels like the car stops quicker and is more tail happy. There's not one specific ultra improvement, but instead several very noticeable improvements. All in all, yes, it was worth it. Yes I would buy it again. Had I known all the little annoyances that we end up getting used to could nearly all be solved for a $1000 part I would have made this a priority a long time ago.
One drawback is that with it building boost a little quicker, some boost spikes have presented themselves in my map (5th and 6th gear pulls). Nothing I can't tune out with some less aggressive WGDC's.
I'll get some video tomorrow to show the before and after pulls. I haven't reviewed anything yet, but I'm expecting that it will be gains you can see.
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Old 02-28-2014, 11:39 PM   #9
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It would be interesting to see 0-60 time difference, if you have some data on that. Or maybe RPM change vs time at WOT in similar driving conditions (old shaft vs new obviously).
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Old 03-01-2014, 05:47 AM   #10
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Quote:
Originally Posted by kab View Post
It would be interesting to see 0-60 time difference, if you have some data on that. Or maybe RPM change vs time at WOT in similar driving conditions (old shaft vs new obviously).
That's exactly what I'm going to do, not the 0-60 because there's no way I could guarantee that the shifts would be exact. But I have WOT runs for 3rd, 4th, 5th, and 6th. I didn't do 1st or 2nd because to be honest those gears are pretty much useless on my car now. I haven't moved the gopro mount, so they should be at the same angle and record speed. The only uncontrolled items will be the outside air temp and fuel level.

Here's my car stats as it sits right now:
2006 STi

EL Headers
Perrin DP
3 in eBay exhaust
3 Port BCS
Larger TMIC
Modified scoop air splitter
Second IC spray nozzle
Drop in filter and snorkus delete
Grimmspeed LW crank Pulley
Water Meth
Self tuned using Tactrix
(21 PSi tapered to 18 with lots of timing adjustments)
Tires are 235/45/17 on stock BBS

Pretty sure that's all there is that would have any impact on the acceleration.
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Old 03-01-2014, 05:56 PM   #11
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If you have data logs that are appropriate from before the swap, I would use those and compare them to similar data logs after. That way you have numbers to work with that you could play with in excel. Just a thought. Either way, it will be cool to see if/how much of difference there is. So far it sounds like the subjective things are much better, which is neat too.
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Old 03-01-2014, 08:39 PM   #12
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Well the bad news first, the GoPro couldn't really keep up with the gague sweep with the new driveshaft on the second gear pulls.
Good news is that after syncing up the videos, 2500 RPM to 6000 RPM in 2nd gear happens at the very least 0.21 seconds faster with the Carbon Driveshaft. I'm working the 3rd and 4th gear vids right now. My laptop has a jacked up battery at the moment, so datalogs aren't really a possibility until the new battery comes in - or until I steal the wife's laptop.
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Old 03-02-2014, 09:53 AM   #13
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Okay, I've had it in for a few days. I'm still impressed across the board with this. The performance gains are very similar to what you would see with a lightweight flywheel, but you don't lose any drivability. In fact the car is noticeably easier to drive. If you are thinking about getting one, stop thinking and just do it. The Rally Sport Direct sale should be enough to get you off the fence.
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Old 03-02-2014, 11:02 AM   #14
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Great stuff and glad you like it. Can't wait to see some videos and #s.

Do you have any pictures of the fitment into the tail end of the transmission?
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Old 03-03-2014, 12:00 AM   #15
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Now that you mention it, I remember someone commenting in a thread a long time ago that the shaft quiets drivetrain whirring. Thanks for reminding me... looks like I have a new part to buy!

You mentioned your turbo tapers off to 18psi. Is that just your boost targets or does the turbo actually hold 18psi to redline?
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Old 03-03-2014, 02:03 PM   #16
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18psi is the target, and it holds pretty well, just barely starts to drop off maybe to 17.5 on the gauge at redline. To be honest I barely ever run the car up that high, most of my power occurs prior to 5500. I credit a lot of that to modifying the hood scoop and running the bigger OEM top mount from a 2011 STi as well as the EL headers and exhaust wrap. Pressure drop is pretty negligible. I want to see how hard I can push the car with a stock motor turbo and fuel system with just tuning and bolt on improvements.
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Old 03-06-2014, 12:41 AM   #17
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Thats all a fun STi needs... these cars arent really designed to breathe above 6500 anyways...
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Old 03-06-2014, 07:10 AM   #18
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The only time I ever bring it up higher is maybe the last 100' at a drag strip where shifting would cost me more time. Not that it's all that impressive but my 1/8th trap speed for last year was 81.8 mph for the only run I've ever done with it (didn't launch it, rode the clutch out) I did beat the other guy though who was a V8 fanboy. I may do one this Summer to see if there's an improvement.
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Old 03-07-2014, 07:52 PM   #19
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I have a DSS CF DS and it certainly made commuting a lot better. No more buckling, shacking, lashing nonsense. Still some internal gear slack & sprung clutch bounciness, but you'll never get away from that. I got to the point though where I couldn't stand driving the car with the stock two-piece DS, so this mod was essential for me. Hopefully I can get a large chunk of the price back when I sell it.
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Old 10-24-2014, 03:24 AM   #20
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Are there any cons to using a carbon fiber driveshaft vs the stock steel one? I've only read good things with the exception of possible transmission oil leak from another thread on here and boost spikes as noted above. I'm looking at getting the PST one from RallySportDirect when they run their next promo, these suckers aren't cheap!
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Old 10-24-2014, 07:05 AM   #21
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It is expensive and it looks great, but it is underneath the car so no one will ever know it's there.
During installation, if you're not careful and rush, you can damage the seal on the back of your transmission. It's a pretty inexpensive fix though (about $20).
Aside from that some users mention a slight vibration at certain speeds and report that rotating the shaft 180 degrees on the rear diff fixes the issue. No idea why a 180 degree rotation would fix it, unless the u-joints weren't set correctly the first time.
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Old 10-30-2014, 08:32 AM   #22
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Default cons of CFRP

There are a few, albeit potential cons. In the course of fabrication there can be disbonding at the metal-to-carbon interface, porosity (though it'd take a lot of porosity), foreign material. Use and abuse cons are that it can get delaminated and water can seep in and freeze and it will continue to propagate. Impact damage...... One good thing (maybe) is that if it is a lemon it can break quickly.

If I had one I'd check it out before and after every winter.
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Old 10-30-2014, 11:03 AM   #23
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The new bonding process on newer shafts is rated to some astronomical high torque value between the CF and the U joint. Someone would have to be having a pretty horrible day on the assembly line for that to be an issue.
I haven't seen any complaints about Winter usage or wear, and have seen several people that claim to have been using them for years in austere environments. With as low as our cars sit, not many foreign objects make it to the DS, especially with the exhaust blocking it off. In the end, we drive Subarus, so the rear quarters will be gone long before the shaft ever deteriorates.
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Old 10-30-2014, 02:24 PM   #24
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Quote:
Originally Posted by roadtrip1098 View Post
The new bonding process on newer shafts is rated to some astronomical high torque value between the CF and the U joint. Someone would have to be having a pretty horrible day on the assembly line for that to be an issue.
I haven't seen any complaints about Winter usage or wear, and have seen several people that claim to have been using them for years in austere environments. With as low as our cars sit, not many foreign objects make it to the DS, especially with the exhaust blocking it off. In the end, we drive Subarus, so the rear quarters will be gone long before the shaft ever deteriorates.

Right, I forget that the bonds with carbon fiber can be stronger than the surrounding fiber.

Though I would love to see a high mileage WRX with a CF shaft break from usage. That'd say something
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