aluminum drive shaft - anyone?

[Xinshadow]

Originally Posted by Caspeed

The ony time a lighter driveshaft will have any effect on shifting is if your car has a driveshaft between the clutch and the tranny. Think Porsche 928.

Double clutching matches the speed of the input shaft with the next gear on the output shaft, which is turning at diff speed. That is all.

Reducing rotational mass is generally a good thing. But remember that it's effect is determined by it's moment of inertia. The further from the center of rotation the greater the effect. 5Lbs from a wheel/tire assembly will be greater in it's effect (not even counting unsprung weight) than 5Lbs on a driveshaft.

That makes sense, its probably a placebo effect from lighter overall weight then. I have a buddy who has a brz he insists on maintaining as stock, so once a year I'll drive his car against mine to see how I'm coming along performance wise. My car is definitely easier to heel-toe, which I attributed to the driveshaft but given this info its more likely that this is just a side effect of the cumulative change in powerband and lower weight on my car due to all my mods as a package.

That said, if you're trying to strip weight off the car, I see no season why you wouldn't jump on this for less than $400. It would be silly to do a lightweight flywheel, upgraded clutch, and not do the driveshaft since you're down there anyway.

[Koa]

Originally Posted by Xinshadow

That makes sense, its probably a placebo effect from lighter overall weight then. I have a buddy who has a brz he insists on maintaining as stock, so once a year I'll drive his car against mine to see how I'm coming along performance wise. My car is definitely easier to heel-toe, which I attributed to the driveshaft but given this info its more likely that this is just a side effect of the cumulative change in powerband and lower weight on my car due to all my mods as a package.

That said, if you're trying to strip weight off the car, I see no season why you wouldn't jump on this for less than $400. It would be silly to do a lightweight flywheel, upgraded clutch, and not do the driveshaft since you're down there anyway.

orr people who know what the benefit is don't see the benefit of sinking $400 into something that literally gives little to no realizable performance gain (read: the driveshaft upgrade can be seen as a structural integrity upgrade moreso than a performance one), and put that money into something that will yield far more benefit, such as brake upgrades or tune.

Some people love to throw money at things, others like to optimize their cost/benefit. It's no right or wrong answer, just one that 'works' given the goals and environment the system is in.

"Down there anyway" the driveshaft is actually pretty far away from the clutch, FW (other side of tranny ) and literally takes 10 minutes to take out..

[Xinshadow]

Originally Posted by Koa

orr people who know what the benefit is don't put the $400 into it, and put that money into something that will yield far more benefit, such as half a BBK or tune. Some people love to throw money at things, others like to optimize their cost/benefit. It's no right or wrong answer, just one that 'works'.

"Down there anyway" the driveshaft is actually pretty far away from the clutch, FW (other side of tranny ) and literally takes 10 minutes to take out..

Haha fair enough. But I thought to myself, "Well, since I did all this work to get the car up enough on jack stands to comfortably pull the clutch in my garage, I'm not going down there again for a while. Might as well put in a lighter driveshaft and get those underpannels on!"

I agree that the money is better spent on other items, but once you have those done, why not pick up the last bits of easy hanging fruit? It's a cheap and pretty easy mod, and every little bit helps!

Edit: is there a bbk that runs in the 800 range? Ones I've seen seem to all be 1200+, and at that price the money does better going into my superchager nest egg. If there is a quality bbk that cheap, might have to look into it!

[Koa]

Originally Posted by Xinshadow

Haha fair enough. But I thought to myself, "Well, since I did all this work to get the car up enough on jack stands to comfortably pull the clutch in my garage, I'm not going down there again for a while. Might as well put in a lighter driveshaft and get those underpannels on!"

I agree that the money is better spent on other items, but once you have those done, why not pick up the last bits of easy hanging fruit? It's a cheap and pretty easy mod, and every little bit helps!

Edit: is there a bbk that runs in the 800 range? Ones I've seen seem to all be 1200+, and at that price the money does better going into my superchager nest egg. If there is a quality bbk that cheap, might have to look into it!

I edited to say brake upgrades.. you could piece together a used setup (sti?) for around 600-800... buuuut that probably does not ensure quality and YMMV on that one haha

The aluminum driveshafts are super cool, don't get me wrong.. would love to have one, even if it tricks my butt dyno and gives me that much more peace of mind that my severely underpowered engine won't ever twist it (jokes, stu, jokes, don't call that out!)

but they are awesome. Especially if you want to go big, big power, it makes a lot of sense

[Dimman]

Originally Posted by stugray

Good link!
Here are a few quotes (anything sound familiar?):

"I am thoroughly happy there is another math man on here.

I do appreciate the effort. However as you know cars are a system of systems. Overall the mmi of the driveshaft is very small when compared with the rest of the drive train. Consider a 40lb crank with weights out at the ends. A 20-30lb flywheel/ torque converter with a huge radius. 30lbs of small radius components in the trans. A big heavy ring gear. Big heavy brake rotors and very big heavy wheels and tires. That is a lot of rotating weight. IMO the effect of the driveshaftis negligible. Both designs, steel and aluminum, are quite efficient compared to the rest of the system.

IMO the biggest advantage of the aluminum shaft is its corrosion resistance. "

AND

"Rotational energy = 1/2 m*rs^2*w^2
Translational energy = 1/2 m*v^2
m=mass; w=angular velocity; v=velocity of car; rs = radius of driveshaft ;

Let's say that the rear diff is 3.73 then the angular velocity of the ds is w=3.73*v/(8.67*rs)
The 8.67 is the ratio of the wheel radius over the driveshaft radius.
It turns out that the overall energy needed to rotate a driveshaft is about 1/10th that needed to move it forward. Then compare it with a 3000 lb car and it's a tiny fraction of the energy."

AMEN!

Look, I launch BIG rockets for a living. Does Physics say that IF I replace the 50 Steel bolts on the 1st stage adapter ring with titanium (for a difference of 1 pound), that physics says there will be a difference in the acceleration when the rocket leaves the pad? - YES!.
But HOW much difference when talking about a launch vehicle that weighs 1.1 MILLION pounds at liftoff? IN THE NOISE

Stu, you need to chill.

You've already said that you acknowledge there is a small benefit of reducing drive shaft mass.

What you're doing now is coming off as a total fucking tool with your smarter than us attitude. With the only purpose of supporting your personal OPINION that it's not a terribly efficient mod from dollars to results. You don't get to make that decision for others.

Basically, you're a d!ck.

[stugray]

Originally Posted by Dimman

Stu, you need to chill.

You've already said that you acknowledge there is a small benefit of reducing drive shaft mass.

What you're doing now is coming off as a total fucking tool with your smarter than us attitude. With the only purpose of supporting your personal OPINION that it's not a terribly efficient mod from dollars to results. You don't get to make that decision for others.

Basically, you're a d!ck.

So now quoting OTHER peoples posts makes me a ****?
You DO know how stupid that makes YOU sound right?

Or is it when I point out complete bullshit pseudo-science that others try to make sound like fact?

You know what I GET sick of? Anytime someone mentions that they are an engineer, the pricks come out of the woodwork to piss all over them.
So YES If you MUST know, I AM smarter than your average bear.
AND I slept at a Holiday Inn express last night.

And I am sorry if my grasp of physics is a threat to you.
Piss off

[Dimman]

Originally Posted by stugray

So now quoting OTHER peoples posts makes me a ****?
You DO know how stupid that makes YOU sound right?

Or is it when I point out complete bullshit pseudo-science that others try to make sound like fact?

You know what I GET sick of? Anytime someone mentions that they are an engineer, the pricks come out of the woodwork to piss all over them.
So YES If you MUST know, I AM smarter than your average bear.
AND I slept at a Holiday Inn express last night.

And I am sorry if my grasp of physics is a threat to you.
Piss off

Go throw some ideal gas law or something in an NA thread to show them how they should all go turbo. Seems you get off on that shit.

Tool.

[Xinshadow]

Originally Posted by Dimman

Stu, you need to chill.

You've already said that you acknowledge there is a small benefit of reducing drive shaft mass.

What you're doing now is coming off as a total fucking tool with your smarter than us attitude. With the only purpose of supporting your personal OPINION that it's not a terribly efficient mod from dollars to results. You don't get to make that decision for others.

Basically, you're a d!ck.

Ah, Stus ok. I work in cell phones, I get the same kind of rage when someone says "I need to have this serviced, I got an email forward from my gammy that says it emits radiation that will make my prostate fall out"

I get the annoyance at going on butt dyno vs hard science and numbers.

You remember that Top Gear where the Stig sets a laptime in a twingo and Clarkson says "Stig is here, I thought France made the stig violent"

Every time I see a post about lightweight driveline components and I see the term rotational inertia I think "Rotational inertia...I thought that made Stu violent"

Don't take anything on here too seriously, overall I think we can all appreciate solid reliable info backed up by numbers at the end of the day.

[Koa]

Originally Posted by Dimman

Stu, you need to chill.

You've already said that you acknowledge there is a small benefit of reducing drive shaft mass.

What you're doing now is coming off as a total fucking tool with your smarter than us attitude. With the only purpose of supporting your personal OPINION that it's not a terribly efficient mod from dollars to results. You don't get to make that decision for others.

Basically, you're a d!ck.

basically you can't take how real he is. He's pushing the convo forward while you continue to rock on your heels and say "well you admitted this... and... i didn't waste my money.. and.. and.."

It's not an opinion if he's stating facts from a hard science.

[Dimman]

Originally Posted by Koa

basically you can't take how real he is. He's pushing the convo forward while you continue to rock on your heels and say "well you admitted this... and... i didn't waste my money.. and.. and.."

It's not an opinion if he's stating facts from a hard science.

Real asshole, maybe.

What facts? That Jimmy won't see as much a benefit from it as he thinks? Same as the NA vs Turbo argument. Not his business to bitch about how someone wants to spend mod money.

[CBR600RR]

Originally Posted by stugray

Try this.

If a cyclist were to do the following two experiments, what would the results be:

Test A - Remove 10 grams from the perimeter of the tire and compare that to removing 10 grams from the seat.

Test B - Remove 10 grams from the wheel HUB and compare that to removing 10 grams from the seat.

What do you think?

The analogy applies this way for our cars:
Remove weight from the perimeter of the flywheel vs same weight removed from the spare tire: Noticeable difference! (removing from flywheel made a significant difference to rotational inertia)

Remove weight from the driveshaft (or the engine pulley) vs same weight removed from the spare tire: NO Noticeable difference!

What???!!!???

removing 15lbs from drive shaft

vs

removing 15lbs from spare tire

Obviously removing 15lbs of rotational mass in the drive train will net a better performance increase, because either way, you are reducing 15lbs, but one option reduces rotational mass and helps put more power to the ground.

I'll go for the drive shaft option every single day. I think you need to go back to school and learn some general laws of physics.

[Sypher]

Originally Posted by Koa

basically you can't take how real he is. He's pushing the convo forward while you continue to rock on your heels and say "well you admitted this... and... i didn't waste my money.. and.. and.."

It's not an opinion if he's stating facts from a hard science.

I have agreed with some of his points (drive shaft is not the best upgrade when looking to loose rotational mass).

He is however pushing he opinion. "IMO the effect of the drive shaft is negligible." He also is implying that in his opinion lighter drive shafts are a waste of money for a "street car". This is his opinion based on what he believes to be negligible gains vs money spent. Again his opinion.

on another note everyone i know that has gone with an aluminum drive shaft has already installed lighter wheels (and wider), crank pulley and flywheel. the drive shaft is just part of their effort to reduce the cars overall rotational mass.

my opinion is to buy a light weight drive shaft if you are intending to lighten up more of the car. if its just a daily that you have fun with don't bother with a drive shaft and go straight for a flywheel and wheels.

[Koa]

Originally Posted by CBR600RR

What???!!!???

removing 15lbs from drive shaft

vs

removing 15lbs from spare tire

Obviously removing 15lbs of rotational mass in the drive train will net a better performance increase, because either way, you are reducing 15lbs, but one option reduces rotational mass and helps put more power to the ground.

I'll go for the drive shaft option every single day. I think you need to go back to school and learn some general laws of physics.

He said noticeable difference bro. That, combined with the findings that the ratio for rotational to nonrotational mass is 1.1:1 (I.E no realizable difference when we're looking at 10 pounds, which would mean that 10 pounds taken from the driveshaft equals 11 pounds taken anywhere else)

Sorry bud but you can't argue with physics. Love that you ignore everything in the forum and focus on what you can wrap your mind around

[Koa]

Originally Posted by Dimman

Real asshole, maybe.

What facts? That Jimmy won't see as much a benefit from it as he thinks? Same as the NA vs Turbo argument. Not his business to bitch about how someone wants to spend mod money.

He's just trying to enlighten us as to what the physics (HARD SCIENCE) says about this, and to help people not waste their money on non-performance gains when that $400 could do MILES better in other arenas. But hey, it's their money at the end of the day, you're right about that