[Clypher]

Originally Posted by jmanrex

why are some people waiting for dyno results on this to decide whether or not to get this driveshaft--this piece does not make horsepower--it allows your car to put more power to the wheels because of the weight savings over the stock unit--less rotational mass to spin means your car can put more of its power to your wheels instead of the driveshaft--it is like putting on:
lighter wheels
lighter rotors
gutting your interior
lighter battery
and so on

do you guys ask for dyno sheets for a lighter battery or wheels--i sure hope not--if you do then you have no business modding your car

A lighter battery and a gutted interior will make your car faster, but will NOT show up on a dyno, and will NOT affect whp, the former of which you established. However, less rotational mass (The variety the other things you listed is) theoretically should show up. The same reason AWD sucks more hp from the engine to the wheels is the same reason lightening the rotational pieces reverses it, the engine has less work to do. This in the end translates to more whp, and you guessed it, higher dyno whp numbers.

Originally Posted by jmanrex

i have had the shaft for almost a year now and love it -- when i first put it on the car drove like an automatic with the seamless shifts because the shaft was still spinning at the same rpms when i had the next gear in

This confuses me. Again using simple physics, this should be the other way around. You're saying your new lighter driveshaft does not slow down as much between shifts. Lighter means less momentum and that means it should slow down more between shifts.

[BoostJunkie]

Maybe he means it was easier to rev match on downshifts? That would make sense.

[jmanrex]

Originally Posted by BoostJunkie

Maybe he means it was easier to rev match on downshifts? That would make sense.

yes and no--the engine will blurp when you push in the clutch and because the new drive shaft weighs less it will continue to rotate at a same speed for a longer period of time because of the extra blurp even though yes it will slow down faster than a piece that weighs almost double --thus allowing the revs match up better between shifts

does that make sense or am i not smarter than a fifth grader??

[jmanrex]

Originally Posted by Clypher

A lighter battery and a gutted interior will make your car faster, but will NOT show up on a dyno, and will NOT affect whp, the former of which you established. However, less rotational mass (The variety the other things you listed is) theoretically should show up. The same reason AWD sucks more hp from the engine to the wheels is the same reason lightening the rotational pieces reverses it, the engine has less work to do. This in the end translates to more whp, and you guessed it, higher dyno whp numbers.

This confuses me. Again using simple physics, this should be the other way around. You're saying your new lighter driveshaft does not slow down as much between shifts. Lighter means less momentum and that means it should slow down more between shifts.

while what you are saying in the first paragraph is true--my statement is that they will only see a max of 5% if that on the dyno and now a days people for some reason are fix'd on being dyno queens--but there are way more benefits to this shaft than just a dyno number that will not put out huge numbers--your set horsepower is already there you are just unlocking more to wheels

now in the second paragraph you state "using simple physics" that a lighter driveshaft means less momentum and slows down more--a lighter drive shaft means less energy spent to turn it but the fact remains that a 13 pound drive shaft and a 30 pound drive shaft still spin at the same revolutions when you drive--30 mph is 30 mph--you can just get there easier with the lighter shaft

now i did edit this once i got to work after enjoying my driveshaft again--and was thinking that you can't really use simple physics to compair the two because you have other variables involved between the stock shaft and the carbon fiber one--for one the stock has 3 pieces--2 shafts and a carrier bearing and the carbon fiber is only a one piece

maybe i am not explaining my self correctly/right but this piece is worth may more to your car and driving experience than just dyno numbers--it is just like boostjunkies gb for the qrack--it really doesn't do anything for performance but will make your driving experience easier and more enjoyable

[xrocket21]

Originally Posted by jmanrex

yes and no--the engine will blurp when you push in the clutch and because the new drive shaft weighs less it will continue to rotate at a same speed for a longer period of time because of the extra blurp even though yes it will slow down faster than a piece that weighs almost double --thus allowing the revs match up better between shifts

does that make sense or am i not smarter than a fifth grader??

That doesnt make sense... The driveshaft is fixed to rotate at the same speed as the wheels, it shouldn't help make shifts easier like a lighter flywheel does. Your statement sounds more like something related to the flywheel.

[Clypher]

Originally Posted by xrocket21

That doesnt make sense... The driveshaft is fixed to rotate at the same speed as the wheels, it shouldn't help make shifts easier like a lighter flywheel does. Your statement sounds more like something related to the flywheel.

^Right. I forgot about that pretty important piece of information.

[jmanrex]

Originally Posted by xrocket21

That doesnt make sense... The driveshaft is fixed to rotate at the same speed as the wheels, it shouldn't help make shifts easier like a lighter flywheel does. Your statement sounds more like something related to the flywheel.

your car does slow down between shifts--so why doesn't that make sense

like i said previously maybe i am not explaining myself right but i welcome anyone to drive their car with a stock shaft and then my car or a car with the carbon shaft and you will feel a difference -- why are there other people on here that experience the same feeling--i don't have a lightened flywheel

i guess i am not smarter than a fifth grader then

[HarlanPepper]

Another update on the ACPT DS for those on "the list" or who have already paid. Talked to Jim at SoJDM yesterday and he said ACPT have once again delayed the delivery of the STI version. There are still only a handful of them (5-10?) coming, but apparently ACPT wanted to re-test the STI shafts to make sure they are balanced correctly, so it will be a few more days. They will be sent out directly from ACPT and should go out sometime early (?) next week. I'll be calling on Tuesday to check...

Of course, there are plenty of WRX shafts in stock!

[OrangeDot3083]

Keep us up dated. I was told I am in spot two or three on that list. I am just waiting for that PM from SoJDM so I can throw my money down.

[HarlanPepper]

Update #247...

Called Jim at SoJDM this morning and the word is that only 2 STI driveshafts are complete and have been sent to the people who paid in full, directly from ACPT. I'm not totally clear on where that puts the people on the waiting list or how many more are coming. They're definitely trickling out of ACPTs warehouse - it didn't sound like they were ever going to be "in stock" so if you want one, the best bet is to put the money down and just wait for your turn.

I paid on Feb 8th, so if I'm lucky I'll get mine within 1 month of ordering Apparently, mine was one of the two that went out, which is good news. But Jim has been having trouble getting tracking info. from ACPT, so I'll just be on the lookout for a long tube here at work

[OrangeDot3083]

Hell had I know that I would have paid a long time ago. Thanks for the update!!!!

[HarlanPepper]

1 month to the day! Here are some pics. Getting it installed ASAP...




I wouldn't mind installing it myself if I knew what I was doing. Most likely just go to a shop nearby and have them do it

[pharo]

That is awesome Harlan. I can't wait to read your impressions!

[HarlanPepper]

Update - got it installed this morning at the local mechanic's shop. The guy who did it owns a WRX, so he was familiar with the routine. Unfortunately, some fluid dripped on the cat in the process of installing it, so my car is currently a bit smelly as it burns it off. I took it out for a little loop around town and on the freeway, getting up to about 95mph in the process. My impresssions:

No vibrations detected up to 95 - I was most worried about that. I'll be able to push it a bit faster next month at Laguna Seca, so I can see how it does >100mph. But that was a big relief. Even if there is a vibration at 120mph, I could care less. I spend very little time at those speeds

The biggest change is in the shift feel, as others have commented. Hard to describe, but it's like the car holds RPMs between upshifts now. The 1-2 shift has lost much of the jerkiness that was there before. Heel/toe downshifts felt a bit better, too. Driving around town is a joy now... I could never shift this smooth before.

Didn't notice much difference in "seat of the pants" power, but I'm stock engine-wise. I expect you'd feel a bigger difference if you were stage 2 before installing the DS. Lower gears feel faster just because of the ease of shifting - higher gears (5th & 6th) actually do feel a little more responsive on the freeway. But it's subtle.

Overall, I'd have to give it a big thumbs up! I only tested it for 20-30 minutes, so I'll come back with more impressions if anything changes. Props to ACPT for a product that bolts on and WORKS with no hassle.

[grim09]

glad you enjoy it b/c i know i enjoy mine! let us know how it performs at Laguna Seca.