Aluminum Driveshaft DOES in fact improve performance

Discussion in 'SRT Hellcat Performance' started by Driver72, Jul 11, 2015.

  1. Driver72

    Driver72 Gold Member

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    So I did a bit of a before and after test.

    On a flat road by me, on the way to the shop yesterday morning, I hooked up my Vbox and I did a rolling acceleration test.
    Here was the test:

    30-100 mph
    in 4th gear the whole time.
    Everything in Street mode except tranny in Track.
    A/C off
    A8 in Manual mode.
    The tranmission allows you to shift into 4th at 26-27 mph. So that's what I did.
    Rolled out into open road, got up to 27 mph.
    Then just mashed the throttle.
    Stays in 4th for the whole run.

    First run totally stock was 8.8 seconds
    Slowed back down pulled over for a minute or so, let some oncoming traffic clear.
    Once totally clear pulled back out, did same thing.
    Second run totally stock was again 8.8 seconds.

    Aluminum DS was installed yesterday, went out again this morning within 15 minutes of the same time I did it yesterday. I checked DA calculators, and DA's were within 100 feet of each other. 1,345 first day, 1,266 today, not enough to make any real measurable difference I'm sure.

    But did the exact same test, on the exact same road and got a
    30-100 mph time of 8.6 seconds.....three times (I did it an extra time this time as I wanted to make sure).

    So the more Solid, lighter Aluminum Driveshaft, shaved .2 seconds off a 30-100 mph 4th gear pull.
    Even if one wanted to argue that the 100 feet of DA would account for a tiny bit, ok, that's fine, but what .05 of a second at most? That would still mean .15 seconds faster with the aluminum shaft over stock.

    So on a 1/4 mile drag strip, since you are able to launch it harder, and you still have the advantage of the more solid, lighter (less rotational mass) shaft during the entire run, which is around 11 seconds (give or take) I think it's safe to say, that it would help the same .15 -.2 seconds. Seems to be about right too.
    Since it seems those who have run on just DR's have gotten 10.8's and those who've done it with DR's and the driveshaft have done a tenth or so quicker.
    This would also clearly add a bit to trap speed as well (probably 1-2 mph over the approximately 10.8-11.2 second run.
    But I did not test a time to speed since there are launch variables there, but clearly if you go the same 30-100 mph in a quicker time, you've accelerated faster, therefore you're "trap" speed would be faster.

    I know some have discounted my previous statements that the aluminum or CF driveshaft would improve times and trap speeds, but I argued how could it not? You are improving a drivetrain part that is more solid, allowing a bit stronger launches, and you are reducing rotational mass, not just any rotational mass, but drivetrain rotational mass, so a bit more power is making it to the rear tires. Always seemed logical to me, but I always like to check. And my test showed it in fact does help acceleration by a bit.

    The next question is, how much distance does .15-.2 seconds mean in this 30-100 mph test I did.
    If I had to guess, I'd say 1/2 to 3/4 car length. I wish I would of tested distance covered in those tests.
    I probably could extrapolate it from the data card if I wanted too. But either way, I got the affirmative results I had stated all along, the aluminum or CF Driveshaft will improve your times and traps by a bit.
    Cheers
     
    Last edited: Jul 11, 2015
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  2. Next Phase

    Next Phase Silver Member

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    That's good info and thanks for sharing....

    .10 in the quarter mile with approx 11 second car will be 1 car length.

    I'll be adding a DS, one of the next items on my list.

    Which DS did you go with?
     
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  3. Driver72

    Driver72 Gold Member

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    No problem.


    It's an estimation on the distance in the 30-100 mph roll I was guessing with the 1/2-3/4 CL, and I'm probably pretty close.
    .1 second = 1 car length in the 1/4 mile, is probably close too, and a sort of "educated guess" that we all have also commonly said over the years, just like we say
    10 hp gain = .1 second decrease in time or
    100 lbs lost in weight is = to 10 hp gain.
    But those educated guesses are often flawed because it varies based on many, many aspects.
    But yes, it's a rough baseline estimation.

    I've been testing stuff like this for many years, but I need to start looking at distance travelled during those times too, so I can extrapolate that info and share as well. Because it's often just as useful and maybe more so.

    I went with the aluminum one (from Driveshaft shop via DrB) based on what people had told me was the best choice for what I wanted.
    I was going to go CF, but literally a couple people including the shop I went too, which is a premier Mopar shop in this state, recommended the aluminum one to me.
    I think the CF may be best if you plan to go 1100+ hp but to be honest, I'm not really sure why there would be a need to spend the extra $600 for it. Sure it's 2.5-3 lbs lighter, so that may help a smidge more, but seems there may be a bit more flex in them (??) and not sure if they are as heat safe as the aluminum (??)

    But I'm not a mechanic or engineer, just going off what I was told, unless you plan on going say 1100 hp, there seems no real reason to go with the CF over the aluminum.
     
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  4. Dragon

    Dragon Gold Member

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    cool thanks for this info. I still have not made my mind up for what DS I want.
     
  5. Aaron Vogel

    Aaron Vogel Silver Member

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    One thing i'll add, is that most people didn't disagree on it making the car faster or not. I think everyone agreed on that aspect. But it isn't a HP gain. Its mostly do to it being 1 piece not 2. Its just transferring all the power more directly, not one piece to a guido joint, then to the 2nd shaft to the rear.
     
  6. Driver72

    Driver72 Gold Member

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    Well there were several people who when I commented that the Driveshaft would help their times and traps said, "doubt it, or nah, it's just stronger but their isn't a performance gain from it" or something similar.
    Someone even linked something in one of my posts that said the aluminum driveshaft would not gain any performance, blah blah. And I even think that DSS own website states somewhere something like, it won't give you more power....which technically is true, its not "giving" you more power, or "making" anymore power, it's just freeing up some power and allowing more to get to the rear wheels. But I don't think their website even says that much.

    But when I questioned a few people's drag times when they got 10.8's and even 10.7's I remember stating in one of them, that their aluminum driveshaft surely helped, and they replied, "not for trap speeds" or "not even measurable difference"

    So I do know there were lots of skeptics, many buying it just for the safety net of not having a snapped driveshaft (which is why I bought it, even though I'll never put DR's on mine). And the driveshaft's help probably can't even be measured on a dyno.
    But this is why I like doing real world road tests, not paper tests, to see what benefits mods really give.
    And .15-.2 seconds decrease and probably 1-1.5 mph increase in the 1/4 mile from an aluminum driveshaft is a nice bonus for the security of knowing if you get a good hard launch (or go to the drag strip often) you aren't going to have a snapped driveshaft like you have to think about with the stock one.
    And they are right, the car definitely goes forward quicker off idle when you apply throttle than it did with the two piece.
    You don't realize their is that tiny bit of lag in the 2 piece until you put in the 1 piece and drive off for the first time. :D
     
  7. Fionn MacCumhaill

    Fionn MacCumhaill Irish A'Hole - Wanna Fight About It!? Hellcat Car Club HCC Charter Member

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    Thanks for the testing information and data! I was already going to get a aluminium DS anyways, this justifies the purchase even more.
     
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  8. 70Cuda

    70Cuda Yep, its got a HEMI

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    other than the cost any down sides to the ALU shaft???
     
  9. Lord Hellcat

    Lord Hellcat Gold Member Hellcat Car Club Gold Supporting Member HCC UK President HCC Charter Member

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    Great information. Good job. Not sure if I will ever fit one but if I do I thought carbon fibre was perhaps the way to go as it helps relieve some of the shock loading through the drive train
     
  10. Driver72

    Driver72 Gold Member

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    The aluminum does the same I'm sure.
    I think the CF is for those who are going to go even higher than the 1,100 hp point where even the aluminum one would probably not be safe. But if you are going that high anyway, you need to upgrade many parts other than just the driveshaft.
    The CF is probably for those who want a bit more undercarriage bling too. :)
     
  11. Driver72

    Driver72 Gold Member

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    Not that I have heard of or learned about.
    I was keeping a close eye and ear to reports of the aluminum DS after I learned of a couple people snapping their OEM one simply by adding DR's on their car.
    i'm not putting DR's on my car, but am putting 315/35/20 tires that are clearly wider and rated higher on Tirerack.
    Plus maybe minor power mods like CAI or catback exhaust.
    So the fact some had snapped a OEM driveshaft with stock power and simply adding DR's was enough for me to wait a bit and see if there were any negative reports of the aluminum DS.
    Since I didn't hear of any since I got my Hellcat in mid March, I figured the piece of mind of having one, was worth the $887 plus $350 install price. I may only take the Hellcat to the drag strip a couple times, but it would be more expensive and a MUCH bigger pain in the rear if the OEM did snap even on slightly wider max performance tires and mild power increase.
    So I went ahead and ordered it.

    Driving the car only 20 miles since install, other than the more immediate take off from the time you touch the gas pedal, it feels totally stock. No additional noise, no vibrations, no weird feelings, nothing.
    Unless you told someone or they got under your car while on a jack or lift, they'd never know you have it on. It's very smooth.
     
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  12. Aaron Vogel

    Aaron Vogel Silver Member

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    I fully agree with how much more "connected" the car feels with a 1 piece, i had the 1 piece CF and loved it. I know on the DSS site it says it can help 1/4 etc by .2 of a second. Its not even really "freeing" up any HP, it still 707hp, its just used/managed more efficiently. I'm not a fan of the term "freeing" up HP, it leads people to thinking that your making extra HP or something. I guess its just the semantics of the wording at that point haha. The other thing DSS did say with the CF over AL is that the CF will absorb shock loading betting in being able to twist a little and that it will reduce NVH issues a more then just the AL one. But when looking at the price you have to decide if the extra $500+ is worth it.
     
  13. Driver72

    Driver72 Gold Member

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    Yes, it's not a power added, so it's still 707 hp. But it does essentially "free up" more power to the tires. So more of the power is getting to the rear wheels, which allows a bit more acceleration.
    Similar to getting lighter wheels/tires. You'll improve performance due to less rotational mass, but you aren't getting any more power coming from the engine. I agree, guess it's just how you word it, or interpret the wording.

    I think it's $600 difference between CF and Aluminum
    $899 to $1,599 MSRP

    To me the itty bitty difference in any performance between the CF and aluminum was so minor it wasn't worth it. And that's what I was advised by several people. Now again if I was going to build the motor up to make say 1100+ hp I'd of gone CF. But again, I'd need to do way more to the chassis and other drivetrain parts than just that to safely handle 1,100 hp.
    I look at it this way. For less money than just the CF driveshaft costs, I can get the Aluminum one and the AFE CAI.
    If there was a well known sizable advantage to the CF one, I would of for sure gotten it. But since there really isn't, I went with the tried and true Aluminum one that everyone advised.
    Cheers
     
    Last edited: Jul 11, 2015
  14. VanishingPoint

    VanishingPoint Silver Member

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    You mean like here?

    [​IMG]
     
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  15. Aaron Vogel

    Aaron Vogel Silver Member

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    And that kind of the distinction that people say when they talk about the DS, whether its CF or AL. When it comes to a DS, the rotational mass POV is irrelevant. Going from a stock shaft to the CF or AL ones nets you maybe, maybe 1/4 of a HP. That said, getting lighter rims, or flywheel does more for you then a DS. It comes down to here the mass is. Rims, flywheels are big in mass, small in how it is distributed, so reducing weight has a bigger impact. A driveshaft, given how long it is, and how small it is, the extra HP you free up equal about 1/4 of a HP. Thats why i try to differentiate between freeing up HP and using HP more effciently.
     
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