4.56 Final Drive Question about Acceleration

[jaorocks1]

Is the only reason you accelerate faster with a shorter final drive because you are in a higher RPM than the stock final drive?

With a 4.56 I heard you are having to shift into 4th on the highway instead of 3rd to pull hard, doesn't this practically even out the effect of the final drive?

[go_a_way1]

Originally Posted by jaorocks1

Is the only reason you accelerate faster with a shorter final drive because you are in a higher RPM that the stock final drive?

No you move through the RPM ranger faster as well as the gearing is shorter. In effect you are putting more power to the ground as well. If you did a dyno in first gear the FRS would make like 400+ WHP or w/e it works out to due to the gearing. We measure WHP in 4th for autos and 5th for manual's as thats when the gearing is 1:1 (means the engine turns once so does the wheels cuz in first engine turns once wheel turns .5 or w/e the real ratio is my numbers are just made up examples)

[jaorocks1]

Originally Posted by go_a_way1

No you move through the RPM ranger faster as well as the gearing is shorter. In effect you are putting more power to the ground as well. If you did a dyno in first gear the FRS would make like 400+ WHP or w/e it works out to due to the gearing. We measure WHP in 4th for autos and 5th for manual's as thats when the gearing is 1:1 (means the engine turns once so does the wheels cuz in first engine turns once wheel turns .5 or w/e the real ratio is my numbers are just made up examples)

Awesome thanks for the detailed answer.

Last question, since on freeways I'll be having to go into 4th with a 4.56 for a nice pull instead of 3rd with a 4.1 would I see about the same acceleration? In other words does it would an FRS pulling in 3rd with a 4.1 FD pass an FRS pulling in 4th with a 4.56 if both were going 70?

This is the only thing holding back since that is most of the time I usually downshift to pass cars for fun.

Thanks for your help bro,

[go_a_way1]

Originally Posted by jaorocks1

Awesome thanks for the detailed answer.

Last question, since on freeways I'll be having to go into 4th with a 4.56 for a nice pull instead of 3rd with a 4.1 would I see about the same acceleration? In other words does it would an FRS pulling in 3rd with a 4.1 FD pass an FRS pulling in 4th with a 4.56 if both were going 70?

This is the only thing holding back since that is most of the time I usually downshift to pass cars for fun.

Thanks for your help bro,

I don't really want to do the math but I don't think it will be that big of a difference. Dropping to 3rd (if you still can with those ratios) will net you a faster acceleration then dropping to 4th no matter when the FD is. It will pull harder in 4th then it did before though not as hard as 3rd used to. you will reach the power band a little faster which is always nice. Don't forget you will be giving up MPG doing this. When I get around to it I am planning on going with a 4.88 lol balls to the wall for me.

Short answer is likely NO If you are both in 4th yes you will pull away but he (the other FRS drive hypothetically) has a better gearing mechanical advantage in 3rd with a 4.1 then you do in 4th with a 4.56 (Again I didn't do the math but this is most likely true)

Your welcome for the answer. anything else let me know

[Icecreamtruk]

If the 4.1 final drive car is in third gear and you are in 4th, he will outaccelerate you until he needs to shift to 4th, where you will gain back on him again. In the same gear, the difference is very big tho. Check out this video, it is the exact situation you are trying to see. The white car starts in 3rd, the car with the camera (the one with the 4.67 final drive) starts already in 4th. See how the car in 3rd pulls momentarly, then falls back hard when he needs to shift.

[ame="https://www.youtube.com/watch?v=qgWwfprYvI4"]https://www.youtube.com/watch?v=qgWwfprYvI4[/ame]

[ame="https://www.youtube.com/watch?v=TI7uuFHrwi8"]https://www.youtube.com/watch?v=TI7uuFHrwi8[/ame]

[go_a_way1]

^ Perfect, thanks for taking the time to post that for him!!!

[jaorocks1]

Originally Posted by Icecreamtruk

If the 4.1 final drive car is in third gear and you are in 4th, he will outaccelerate you until he needs to shift to 4th, where you will gain back on him again. In the same gear, the difference is very big tho. Check out this video, it is the exact situation you are trying to see. The white car starts in 3rd, the car with the camera (the one with the 4.67 final drive) starts already in 4th. See how the car in 3rd pulls momentarly, then falls back hard when he needs to shift.

perfect example! Thanks for the help! Looks like I'll be doing this mod soon!

[ajc209]

Think of it as keeping the engine closer to peak power. Area under the curve. In an ideal world its sit at max power revs and transfer it all to the wheels...

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[go_a_way1]

Originally Posted by ajc209

Think of it as keeping the engine closer to peak power. Area under the curve. In an ideal world its sit at max power revs and transfer it all to the wheels...

Sent from my GT-I9300 using Tapatalk

LOL no think of it like a big gear turning a smaller gear the big one doesn't take much turning force to reach set speed from the little gear now make the little gear smaller and it takes even less effort to turn said little gear at same speed. however at the same force said smaller little gear will spin faster (thus you have to shift sooner for a give MPH)

Hope that makes sense haha

[jaorocks1]

Originally Posted by go_a_way1

LOL no think of it like a big gear turning a smaller gear the big one doesn't take much turning force to reach set speed from the little gear now make the little gear smaller and it takes even less effort to turn said little gear at same speed. however at the same force said smaller little gear will spin faster (thus you have to shift sooner for a give MPH)

Hope that makes sense haha

Give it a day or two and i'll get it... hopefully lol!

[ajc209]

Originally Posted by go_a_way1

LOL no think of it like a big gear turning a smaller gear the big one doesn't take much turning force to reach set speed from the little gear now make the little gear smaller and it takes even less effort to turn said little gear at same speed. however at the same force said smaller little gear will spin faster (thus you have to shift sooner for a give MPH)

Hope that makes sense haha

...... the only reason closer gearing makes the car accelerate faster through the gears is because the average power the engine is putting out is closer to max power. If you had really wide gearing lets say you red line in 1st gear then shift up to second and it drops to 4k rpm. Ypur engine is now ptting approx 100hp or half of full power and revs need to build in order to build power. Now consider closer gearing where 2nd gear is at 5.5k rpm. The engine is outputting 175hp at those revs. So in the example above with the long gearing the engine is running from 150-200hp as it revs throught the gears, with the closer gearing the engine is running from 175-200hp as it revs through the gears. It easy to see that with closer gearing the engine is putting out more power on average, or area under the curve if you were to plot it on a graph.


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[ajc209]

Originally Posted by go_a_way1

In effect you are putting more power to the ground as well. If you did a dyno in first gear the FRS would make like 400+ WHP or w/e it works out to due to the gearing.

Nope. Sure you'll have tons of torque in first gear but the wheels wont be spinning very fast and thus they wont be donig any more work than in 4th gear. The only thing that will change the WHP is drivetrain losses in 1st gear vs 4th gear and rolling road losses because you are putting down mor torque - this is usually corrected to some extent.

Originally Posted by go_a_way1

We measure WHP in 4th for autos and 5th for manual's as thats when the gearing is 1:1 (means the engine turns once so does the wheels cuz in first engine turns once wheel turns .5 or w/e the real ratio is my numbers are just made up examples)

Wrong again. That's when the gear box is 1:1 but the diff is 4.1:1 so the engine is turning 4.1 times per wheel rotation in 5th gear.

At 60MPH or 1Mile per minute you'd need to travel 1620 meters. Wheel circumference is 1.96M.

=> 1620/1.96 = 826 rotations per mile.

The engine isnt revving at 826 rpm at 60mph in 5th is it? try multiplying by 4.1 = 3389rpm.

[go_a_way1]

Originally Posted by ajc209

...... the only reason closer gearing makes the car accelerate faster through the gears is because the average power the engine is putting out is closer to max power. If you had really wide gearing lets say you red line in 1st gear then shift up to second and it drops to 4k rpm. Ypur engine is now ptting approx 100hp or half of full power and revs need to build in order to build power. Now consider closer gearing where 2nd gear is at 5.5k rpm. The engine is outputting 175hp at those revs. So in the example above with the long gearing the engine is running from 150-200hp as it revs throught the gears, with the closer gearing the engine is running from 175-200hp as it revs through the gears. It easy to see that with closer gearing the engine is putting out more power on average, or area under the curve if you were to plot it on a graph.


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Your right thats part of it to.

Originally Posted by ajc209

Nope. Sure you'll have tons of torque in first gear but the wheels wont be spinning very fast and thus they wont be donig any more work than in 4th gear. The only thing that will change the WHP is drivetrain losses in 1st gear vs 4th gear and rolling road losses because you are putting down mor torque - this is usually corrected to some extent.



Wrong again. That's when the gear box is 1:1 but the diff is 4.1:1 so the engine is turning 4.1 times per wheel rotation in 5th gear.

At 60MPH or 1Mile per minute you'd need to travel 1620 meters. Wheel circumference is 1.96M.

=> 1620/1.96 = 826 rotations per mile.

The engine isnt revving at 826 rpm at 60mph in 5th is it? try multiplying by 4.1 = 3389rpm.

Lol yeah totally forgot the diff ratio hahahaha my bad there