Like the subject says does anybody have any figures of waht kind of HP an aluminum driveshaft adds to our cars? for some reason I don't have one like they came w/ and am looking ot get one. thanks

Josh

 

it may free up a horsepower or two but nothing youll be able to feel

There are always some for sale either on ebay or in the classified, just do some searching, im sure you can find one pretty easily.

 

none, like was already said. what they do, besides maybe freeing up some HP, is reduce the rotating mass of the part, therefore an aluminum drive shaft is easier or faster to accelerate.

 

well I should have phrased that differently. I know it doesn't add power to the crank, but I've heardit does at the RWHP and thats what I was talking bout.

 

It doesn't "add HP"; rather, by reducing the rotating mass that has to be accelerated from 0 RPM to 5000 RPM or whatever, it has the same kind of effect that lightening the car does. Just like if you take out your spare tire, that doesn't "add HP" to the engine, but the car goes faster just the same. The engine simply has less work to do in order to speed up the car.

 

ok thanks everybody, I thought it addes RWHP. but I understand about the whole rotating mass thing because I've built several engines. thansk again

 

good mod to do..

 

Because of the way most chassis dynos work, it will result in higher readings, because they read HP as the motor accelerates. If you used a steady-state type of dyno, where the drivetrain just stayed at one constant speed and allowed you to vary the load on it (electrical generator type dyno) then it would make no difference at all.

So the "higher RWHP" numbers are simply a measurement artifact, not real power, even though the car will in fact accelerate faster.

 

Ok so it will accelerate faster, but the driver won't be able to feel it since it's the same as getting rid of a few pounds from other parts of the car,,,right? Just wanna make sure I understand this.

 

just assume that you lose 20% of the power your engine makes through the drivetrain (tranny, driveshaft, rear end, etc.), with an aluminum driveshaft (less rotating mass for the tranny to turn), you might now only be losing 19.8% through the drivetrain. i guess that would be an easy way to explain it.

 

it will also be more stable at high speeds. so u will have less vibration at around 80-90 MPH i think..

 

Better yet, does anybody have any e/t numbers to show the difference?

I can see the connection between taking out the spare and what not, but I don't agree with it. Taking out the spare is just removing dead weight. However, taking a few pounds off what the engine has to turn does change how fast the engine will spool up. I'ld just like to see some numbers showing the change in time.

-The Gunny

 

It's exactly the same thing as getting rid of dead weight; except that instead of dead weight that just has to be moved 1320', it's dead weight that has to go from 0 RPM to 5000 RPM or whatever. Same principle, different part of the total system.

I'd be real surprised to see a .1 ET change from the Al DS alone. But, like so many other things, it can add up, if you consider it as part of the package. Just like removing your spare: you might not see a whole lot of change; but remove the spare, remove the back seat, remove the carpet, remove the radio, remove the window regulators, remove the A/C, remove the cruise control.... each thing by itself doesn't amount to alot, but after you're done, there's 350 lbs of stuff sitting on the ground by your car, and you've gone from 3500 lbs to 3150 lbs, and that's close to ½ second, without spending a penny.

Lighter wheels, non-steel-belted tires, drilled rotors, aluminum hubs, etc. are similar mods to the Al driveshaft... less spinning mass that has to be accelerated from 0 RPM to traps RPM.