I would assume the driveshaft weight is similar to flywheel weight in that a heavy flywheel takes more energy to accelerate, but then tends to stay at speed more easily; whereas a lightweight flywheel accelerates much quicker, but is not so good at maintaining the speed. Now a driveshaft's rotating mass is very close to the centerline of rotation, so I would expect any effects to be negligible.
Any advantage to aluminum driveshaft--'94 Mustang 5.0
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How does the weight/material/density of a driveshaft that's properly made free up horsepower? I don't understand how a part that's rotating on it's (balanced) axis is able to transfer less energy along its length than something else. I can believe instantaneous losses due to twisting of different materials but by the time the power's been on for more than a split second, that material has probably deformed as much as it's going to and it won't continue to twist.
I also thought that underdrive pulleys worked by increasing the leverage of the crank pulley working on the belt which also happened to slow the belt down (underdrive) which also can cause things like improper charging and "glitchy" A/C systems. More leverage for the pulley means less work for the engine to make things turn.
I thought the primary advantage to lightweight rotating and drivetrain parts was for engine acceleration; the engine doesn't have to work as hard to get all that stuff spinning so it revs up quicker. But again, if everything is balanced properly, it should be able to rev just as high as anything else, shouldn't it? In fact I've heard in heavier drag cars and trucks used for towing that having a heavier flywheel is better because there's more energy stored in it's momentum than in a lightweight one and when you're trying to get rolling, that can "feel like" more torque.
I'll shut up now; please set me straight on this stuff.....trying to learn and don't have the bucks to go find out for myself
Thanks!
Greg
I also thought that underdrive pulleys worked by increasing the leverage of the crank pulley working on the belt which also happened to slow the belt down (underdrive) which also can cause things like improper charging and "glitchy" A/C systems. More leverage for the pulley means less work for the engine to make things turn.
I thought the primary advantage to lightweight rotating and drivetrain parts was for engine acceleration; the engine doesn't have to work as hard to get all that stuff spinning so it revs up quicker. But again, if everything is balanced properly, it should be able to rev just as high as anything else, shouldn't it? In fact I've heard in heavier drag cars and trucks used for towing that having a heavier flywheel is better because there's more energy stored in it's momentum than in a lightweight one and when you're trying to get rolling, that can "feel like" more torque.
I'll shut up now; please set me straight on this stuff.....trying to learn and don't have the bucks to go find out for myself
Thanks!
Greg
427Z06,
Ok lets see if I can get this right.
Its a 91 Dodge Stealth. Pulled the motor and replaced it with a 3rd gen 3000GT with 4 bolt main. Yanked the transmission and transfer case out, send them away and had the gearing and splines buffed up, as well as having an LSD installed (front and rear LSD's now). Splines were increased in both number and thickness, eliminating one of the 3000GT's chief weaknesses.
Stock ECU was replaced with an AEM EMS. Tuning was performed at altered atmosphere. Stock turbo's were replaced with Super 15G's
Injectors replaced with 550cc's (Going to put 720 or 760's in next (forget which is the right number)).
Intercoolers were replaced with considerabily larger ones, new ignition system, boost controller, intercooler/turbo piping, speed density airflow system instead of MAF/IAT based. Added an alcohol injection system (not included in the mapping) for safety reasons, which begins spraying at 16-17 psi. Turbo's run 16-18 psi on the street (depending on gear) and 20-22 on the track.
Last mod was the CF drive shaft which showed a 20-30 whp gain in 3rd gear pulls, depending on the dyno. (Over 50 runs there is always variance)
Oil is 15w-50 mobil1. Upcoming mods are stage 3 heads (ported and polished) with a portmatched intake plenum, and oversized valves.
Exhaust is HKS (no cats) with an HKS downpipe.
Final goal is 450-500 whp. As of right now, people with similar setups run high 11's. My father used to be an old school drag racer...i don't think his need for acceleration will ever be satisifed.
Driving the car right now is almost terrifying. If you aren't sitting back in the seat when the accelerator is depressed, it'll throw you down like a WWF wrestler. Shift and all 4 tires chirp
.
Here's a photo of the stealth's stock driveshaft (3 piece) and a replacement unit (alumnium in this instance). Gives you an idea of why an aftermarket one might result in a 1 lb = 1hp gain. Most owners see a 0.2 1/4 reduction from the CF driveshafts. (Dyno and Track proven)
[ February 20, 2005, 02:15 PM: Message edited by: crossbow ]
Ok lets see if I can get this right.
Its a 91 Dodge Stealth. Pulled the motor and replaced it with a 3rd gen 3000GT with 4 bolt main. Yanked the transmission and transfer case out, send them away and had the gearing and splines buffed up, as well as having an LSD installed (front and rear LSD's now). Splines were increased in both number and thickness, eliminating one of the 3000GT's chief weaknesses.
Stock ECU was replaced with an AEM EMS. Tuning was performed at altered atmosphere. Stock turbo's were replaced with Super 15G's
Injectors replaced with 550cc's (Going to put 720 or 760's in next (forget which is the right number)).
Intercoolers were replaced with considerabily larger ones, new ignition system, boost controller, intercooler/turbo piping, speed density airflow system instead of MAF/IAT based. Added an alcohol injection system (not included in the mapping) for safety reasons, which begins spraying at 16-17 psi. Turbo's run 16-18 psi on the street (depending on gear) and 20-22 on the track.
Last mod was the CF drive shaft which showed a 20-30 whp gain in 3rd gear pulls, depending on the dyno. (Over 50 runs there is always variance)
Oil is 15w-50 mobil1. Upcoming mods are stage 3 heads (ported and polished) with a portmatched intake plenum, and oversized valves.
Exhaust is HKS (no cats) with an HKS downpipe.
Final goal is 450-500 whp. As of right now, people with similar setups run high 11's. My father used to be an old school drag racer...i don't think his need for acceleration will ever be satisifed.
Driving the car right now is almost terrifying. If you aren't sitting back in the seat when the accelerator is depressed, it'll throw you down like a WWF wrestler. Shift and all 4 tires chirp
Here's a photo of the stealth's stock driveshaft (3 piece) and a replacement unit (alumnium in this instance). Gives you an idea of why an aftermarket one might result in a 1 lb = 1hp gain. Most owners see a 0.2 1/4 reduction from the CF driveshafts. (Dyno and Track proven)
[ February 20, 2005, 02:15 PM: Message edited by: crossbow ]
Superphat!!
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I've never heard of an Audi CF prop shaft disintegrating.
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With 172 hp? You gotta be kidding.
Medium blue. Hey, all the posts convinced him go look into a higher rear end gear. Here are his tranny ratios:
3.55
1.99
1.33
1.0
0.68
He's looking at changing out the 2.73 to either a 3.27 or a 3.55, but someone told me he needs to go minimum 3.73 for performance. He is shifting around 5500 and wants to be no higher than 4000 when he hits 2nd and 3rd. I think the main thing is that he won't be having to shift late in a race and that first gear doesn't get too short.
"Effective gear ratio" is what matters here. He needs to think about how he'll be using the car and the tires he'll be running. The reason the drag racers run such short gears ( 3.55, 3.73 ) even with pretty much stock motors is because they're usually running a taller and stickier tire than stock.
Put the same car on short low profile tires for street use and you'll get sick of the engine screaming all the time, not to mention 1st gear will become worthless.
My almost stock 5.0L with 3.08 gears and 225/60 x 15 street tires has traction problems in 1st unless the pavement is good. It's almost as bad with 225/50 X 15 sticky autocross tires...
Thanks jsharp. I am starting to think that the ideal rear end geaing is largly determined by what will make the launch most effective and not getting first too short. Anything beyond that is a waste. He's not going to do a lot of mods to this car as it is mostly for fun (he also has a red '84 5.0 4 speed Mustang). Says his tires are 25.7 inches tall. I will have to run some numbers, but would think a longer first gear is advantageous. For example, my '84 F50 was highway geared and I could run 1st out to aroun 40 mph (4000 rpm max), but had to have a rolling start for a good go; whereas my '95 has better gearing, but it took me a while to get used to having to shift to second around 20-25 mph. Sure moves out better from a dead stop though (not that I am racing, just having fun). So Bro's Stang I figure needs a first that gets him around 5500 rpm at say 25 to 30 mph. I have to run the calculations when I get a chance.
We could go so steep on the rear to make 2nd the effective first gear, but what is the point? Then you just throw out highway economy. Might as well keep all five gears.
Yep jsharp, you hit the nail on the head. Thanks
We could go so steep on the rear to make 2nd the effective first gear, but what is the point? Then you just throw out highway economy. Might as well keep all five gears.
Yep jsharp, you hit the nail on the head. Thanks
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