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Old 09-21-2012, 09:56 AM   #16
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Some of them do, yes. BMW's , Honda's to name a few. And what difference does it make if you are changing the rotational vector? It's still torque and ratio's

Can you back this assertion up with some math ?

Dave
im not talking about those bikes .. im taking about the GSXR (as to what it says in that graph) to a BMW 328 diff. Before I get into math I think you need to understand what a diff does and the different types.
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Old 09-21-2012, 09:58 AM   #17
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How about you enlighten me. I'm all ears.
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Old 09-21-2012, 10:27 AM   #18
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How about you enlighten me. I'm all ears.
The graph there is comparing a ratio change in the sprockets (there is no differential on that bike) a differential is called a differential because of a difference in motion.

Here is what a bike sprockets would look like and conversion change ..



now here is a differential in a car ..



when people talk about drivetrain hp loss they are comparing to fwd cars and rwd cars etc .. there is no diff in a GSXR so there is no drivetrain loss. That graph is apples to oranges and the physics is different. I thought this was common sense to you but maybe you didn't know that about motorcycles.
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Old 09-21-2012, 10:34 AM   #19
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The graph there is comparing a ratio change in the sprockets (there is no differential on that bike) a differential is called a differential because of a difference in motion.

when people talk about drivetrain hp loss they are comparing to fwd cars and rwd cars etc .. there is no diff in a GSXR so there is no drivetrain loss. That graph is apples to oranges and the physics is different. I thought this was common sense to you but maybe you didn't know that about motorcycles.
So you are claiming there is no loss of power in the chain ?

I thought a differential was this ...

A vehicle's wheels rotate at different speeds, mainly when turning corners. The differential is designed to drive a pair of wheels while allowing them to rotate at different speeds. In vehicles without a differential, such as karts, both driving wheels are forced to rotate at the same speed, usually on a common axle driven by a simple chain-drive mechanism. When cornering, the inner wheel needs to travel a shorter distance than the outer wheel, so with no differential, the result is the inner wheel spinning and/or the outer wheel dragging, and this results in difficult and unpredictable handling, damage to tires and roads, and strain on (or possible failure of) the entire drivetrain

Agreed there are more losses in a differential due to bearing friction and gear friction but there are losses in a chain too.
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Old 09-21-2012, 10:45 AM   #20
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So you are claiming there is no loss of power in the chain ?

I thought a differential was this ...

A vehicle's wheels rotate at different speeds, mainly when turning corners. The differential is designed to drive a pair of wheels while allowing them to rotate at different speeds. In vehicles without a differential, such as karts, both driving wheels are forced to rotate at the same speed, usually on a common axle driven by a simple chain-drive mechanism. When cornering, the inner wheel needs to travel a shorter distance than the outer wheel, so with no differential, the result is the inner wheel spinning and/or the outer wheel dragging, and this results in difficult and unpredictable handling, damage to tires and roads, and strain on (or possible failure of) the entire drivetrain

Agreed there are more losses in a differential due to bearing friction and gear friction but there are losses in a chain too.
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Old 09-21-2012, 03:33 PM   #21
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I like how this is going.
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Old 09-26-2012, 08:07 PM   #22
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OK wow, a differential doesn't change horsepower or torque, its alters the rpm vs gear and speed. for instance my e30 with it's 4.10 diffis at 3000 rpm at 80 in 5th gear, with a 2.93 diff my car will sit at lower rpm's. the way the power is felt is changed obviously and acceleration can be improved but horsepower/ torque is not changed.
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Old 09-26-2012, 10:27 PM   #23
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OK wow, a differential doesn't change horsepower or torque, its alters the rpm vs gear and speed. for instance my e30 with it's 4.10 diffis at 3000 rpm at 80 in 5th gear, with a 2.93 diff my car will sit at lower rpm's. the way the power is felt is changed obviously and acceleration can be improved but horsepower/ torque is not changed.
Really, and what magic force improves acceleration ?
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Old 09-26-2012, 10:30 PM   #24
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Really, and what magic force improves acceleration ?
The gearing...

Same reason 1st gear accelerates faster than 2nd gear in a car. When you switch gears, the horsepower and torque doesn't change.


The ONLY way to change horsepower is to modify the engine or reduce drivetrain loss.

If the diff ratio changed horsepower, that would mean an automatic M3 with a 3.38 ratio would have more horsepower than a manual with a 3.23. Which isn't the case.
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Old 09-27-2012, 05:50 AM   #25
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It doesn't change horsepower, torque at the wheels is changed. Think of it like using a longer wrench. The ring gear is bigger or the pinion is smaller, which results in the lever being longer. That is what changes.
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Old 09-27-2012, 06:32 AM   #26
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Put the new one in last night, gravity helps getting the old one out, it's not such a great help putting the new one in.
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Old 09-27-2012, 09:48 AM   #27
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from the engine it doesnt change but torque goes up at the wheels. there is no argument against that.
the shorter the final drive the higher the multiplication at the wheels, of torque.

Dynos account for final drive ratios,rpm blah blah to give you a 1:1 output number.


1.66(3rd gear)*2.93*210 = 1021
1.66*3.23*210= 1125


A lot more goes into acceleration but in short, a bolt on car will accelerate faster with a higher final drive ratio.

provided you have traction the shorter drive will typically out accelerate the longer one.
even turbo cars benefit from it...though there you get into issues with traction ,keeping the turbo spooled properly etc. Theres more of a balancing act there and testing needed on a case by case basis.
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Old 09-27-2012, 07:56 PM   #28
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Really, and what magic force improves acceleration ?
Stupid.. you just cant fix it.

Here's an idea go play Forza build a car with all the mods and then put a race transmission on the vehicle. then change the final drive. what you will notice is that as your acceleration goes up your top speed goes down and vice versa. that improvement in acceleration is because your car now sits in the power band earlier at speed and your car would fall closer into the power band between gear shifts.

(

THE FOLLOWING IS STRICTLY AN EXAMPLE RESULTS WILL VARY

Imagine your power band is between 4000 and 6000rpm that is where the most torque and horsepower exists

if your in 3rd and change gears at 6000rpm in a car with a 3.23 your car may drop to 3600rpm

and then do the same with a 2.93 your car may drop to 3300rpm therefore taking you further away from your power band.
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Old 09-27-2012, 08:34 PM   #29
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This thread cracks me up.

For a couple of hundred bucks, it is a good mod for people with 328's. Ever see someone do a burn out or drift with a stock diff? FAIL !!!

GLWS dude

(BTW, what did u upgrade your diff to???)
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Old 10-03-2012, 09:05 PM   #30
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This thread cracks me up.

For a couple of hundred bucks, it is a good mod for people with 328's. Ever see someone do a burn out or drift with a stock diff? FAIL !!!

GLWS dude

(BTW, what did u upgrade your diff to???)
I upgraded to 3.38, and yes the thread is rather funny.
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