Final gear ratio (Final drive) explain in (simple way)

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jblackrevo9
After doing a lot of research and playing around with the transmission, I figured out exactly why cars recieve their final drive like why some cars have a 4:1 ratio or 3:1 ratio.

Pay attention to the motor size and the amount of power and torque each car has.

Example:

Horsepower:276

Torque:328lbs

(Loses about 60 percent of torque at redline.)

Honda NSX has a 4:1 final drive ratio (about 4.785). The crankshaft that transfers engine power to the differential spins 4 times for each rotation of the tire. A pivot or pinion gear is attached at the end of the crankshaft which is responsible for turning the bigger gear that controls tires. I'm not going to go into details, just want to keep this simple.

Now back to what I was saying....

The NSX has the 4:1 ratio because it does not have a very powerful engine or enough torque for 3:1 ratio, basically this would under perform unless you increase it.

The engine size , torque,horsepower, and weight plays a part in determining final drive.

The appropriate drive helps out in racing around circuit since each tires travels differently around turns.

Another example would be Nissan GT-R which has a 3:1 final drive or 3.700.

4WD are heavier and all power are going to all 4 tires which is why it's is necessary to have the crankshaft spinning fast and not slow.

4 cyclinders seem to have higher final drives since they don't have powerful engine or not a lot of torque most if the time.

To add to this. The Final drive is also determined based off of gas mileage too.Some cars (stock) are purposely underpowered to have better gas mileage.

If you were to add more power and torque to a tuned car then it is possible for the vehicle to perform well at a different ratio.

Example:

Going from a 4:1 to 3:1 final drive

If you notice with gt500 cars or below. They have 3:1 ratio and this is because it provides a balance of power and gas mileage since this vehicles are used for endurance races.

But keep in mind it is not so simple. Having a 4:1 ratio does not mean you will always have better acceleration, you will have to set appropriate gears with powerband and having the proper final drive.


RATIOS


In Granturismo 6 gears size is determined by the final gear ratio in this game.

A 2:1 means the gear connected to the crankshaft (pivot gear) becomes bigger while a 4:1 ratio means it has become smaller.

Not all car can handle a 2:1 ratio since engine and power varies.

FF or front drives are trick since they don't have a crankshaft and don't have a 2:1 ratio in the game.a few can go as low as 2.500.

2:1 ratio would be good for drag racing but used for circuit and you're going to face a problem with the car doing to much work to maintain cruising speed. Remember torque comes after acceleration.

Example

1st 5.890
2nd 4.900
3rd 2.878
4th 1.900
5th.1.700
6th 1.200

final: 2.000

Yes It works in the game but in real life it wouldn't work so great.

In the last gear (6th) you have a 1.2:1 which means that the engine is putting in more work than the transmission (1) which it shouldn't since the car is already in motion and weight is irrelevant at this point. The engine has to work more harder to move this big gear as compared to a .700:1 ratio where torque takes over and continues the work.

Remember not all cars are the same and this could work on a car with a less powerful engine.

4:1 ratio provides better acceleration and performance but not always as a 3:1 can also do the same. It comes down to ENGINE,TORQUE, and Horsepower.


Acceleration gets car from 0-100

Torque keeps it moving and stay moving against friction which acts against vehicle.


Makes since?

Typical

4WD drives should have a 4:1 but if you are doing a endurance race, you will have to compromise and go for a 3:1 ratio with lower gear (big number) to balance.

4 cylinder engines also do great with a 4:1 ratio

V6 engine is pretty versatile and can range from 2:1 and all the way up to 5:1

V8 engine are versatile but mainly a mid to high ration since most of the time they have a lot of torque.

V10 engine is versatile.

V12 is versatile.

a V12 and a V10 engine can do well at 2:1 or higher since these engines are more powerful.

REMEMBER

You will still need to set your transmission gears with appropriate powerband. If you do not do this then you car will still under-perform even with the proper final drive or final gear ratio.


Any questions....hit me up
 
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I think there has been some confusion. The final drive ratio is just like any other gear ratio, in that it's essentially a torque multiplier. The bigger the ratio, the greater the torque.

The same goes with the wheels by the way. The smaller the wheels, the greater the force. So if in real life you fit bigger wheels to your car and you notice a lack of performance it's likely because you have less wheel torque than you used to have.

What the engine can or can't handle is down to the combination of gear ratios, final drive and tyre size, so you can't really say that a final drive of X is unsuitable for engine Y, because if you adjust the gear ratios to compensate for a different final drive ratio you end up with the same product, and it's the product that's interesting: Gear ratio * Final drive.

Example

1st 5.890
2nd 4.900
3rd 2.878
4th 1.900
5th.1.700
6th 1.200

final: 2.000

Yes It works in the game but in real life it wouldn't work so great.

In the last gear (6th) you have a 1.2:1 which means that the engine is putting in more work than the transmission (1) which it shouldn't since the car is already in motion and weight is irrelevant at this point. The engine has to work more harder to move this big gear as compared to a .700:1 ratio where torque takes over and continues the work.

The work that the transmission do is the same amount of work that the crankshaft do, provided that there is no clutch slip. Work is force acting through a distance, and although the 6th gear in your example will complete less rotations in any given period of time than the crankshaft, the torque that it carries is greater than the crankshaft's and by such proportions that it cancels out the rotational difference.

If the work done by the crankshaft is 50 Nm by one revolution, and we have one gear ratio that is 1.2:1 and another that is 0.7:1, then we get the following:

50 Nm * 1 revolution = (50*1.2) Nm * (1/1.2) revolutions = (50*0.7) Nm * (1/0.7) revolutions

No matter the gear ratio, the work stays the same, and it's always the same amount of work that the crankshaft does.

Also, the gear ratios aren't indicators of gear size, it's the ratio between the teeth. For instance, a ratio of 1.2:1 could be 24:20 while 0.7:1 could be 21:30. The latter couple would have a bigger combined radius than the former couple and thus more inertia (all else equal). However, the inertia of the gears is small enough to be neglectable, especially when compared to the inertia of the wheels and the flywheel. I would be surprised if gear inertia is even included in the physics model.

4:1 ratio provides better acceleration and performance but not always as a 3:1 can also do the same. It comes down to ENGINE,TORQUE, and Horsepower.


Acceleration gets car from 0-100

Torque keeps it moving and stay moving against friction which acts against vehicle.

A 4:1 Final drive combined with a 3:1 gear gives the same acceleration and performance as a 3:1 Final drive combined with a 4:1 gear. The product in both cases is 12:1, the crankshaft does 12 revolutions while the wheels do 1.

Power is what accelerates a car, since acceleration is a change in velocity per unit of time, and power is the measure of work done per unit of time. Torque produces work, and when you talk about how fast the work is being done you are talking about power. Kinetic energy is what keeps the car moving, and if you want to overcome the forces of wind resistance, rolling resistance and gravity you need to add more power.

Given fixed gear ratios, a 4:1 final drive gives more wheel torque than a 3:1 final drive, but the rate by which it produces work is slower, so the power stays the same.
 
Sorry for the confusion, I only put the transmission gear ratio example as the typical ratio and final drive that some players use when tuning their cars.

The description was intended to only talk about the final drive ratio and not the transmission.

I completely understand what you're saying but again I apologize it you received a different view from it.
 
The final drive can't be spoken of without including at least one transmission gear, as they combine to become the overall ratio, and the overall ratio is what matters most. A car with a 0.86 high gear and a 3.23 final is going to have a higher theoretical top speed than a car with a 2.89 final--and a direct drive high gear. Of course the latter is going to be the better torque multiplier.
I apologize if you received a different view from it.
That's some apology, too. Kinda like saying "I'm sorry you're not smart enough to comprehend what I was saying."
 
Sorry for the confusion, I only put the transmission gear ratio example as the typical ratio and final drive that some players use when tuning their cars.

The description was intended to only talk about the final drive ratio and not the transmission.

I completely understand what you're saying but again I apologize it you received a different view from it.

But the final drive is part of the transmission. What's important is the overall ratio: gear multiplied by final drive (and divided by wheel+tyre radius, when the torque is converted to force).

Let's take an example:

1. An engine produces 100 Nm of torque at 4000 rpm.

The currently selected gear has a ratio of 4:1.
The input shaft delivers 100 Nm and revolves by 4000 rpm.
The output shaft delivers 100*4 = 400 Nm and revolves by 4000/4 = 1000 rpm.

The final drive has a ratio of 3:1.
The input shaft delivers 400 Nm and revolves by 1000 rpm.
The output shaft delivers 400*3 = 1200 Nm and revolves by 1000/3 = 333 1/3 rpm.

The wheel + tyre has a total combined radius of 0.3 meters.
The wheel delivers 1200 Nm and revolves by 333 1/3 rpm.
The force delivered from the contact patch is 1200/0.3 = 4000 N and the contact patch travels a distance of 333 1/3 * 0.3 * 2pi = 100 * 2pi = 628.3 meters per minute = 10.5 m/s = 37.8 km/h.

If the car has a weight of 1000 kg, the force is capable of accelerating the car by 4000 N / 1000 kg = 4 m/s^2

The power is obtained by multiplying force with velocity: 4000 N * 10.5 m/s = 42 kW = 56 bhp.

2. The same engine produces 100 Nm of torque at 4000 rpm.

The currently selected gear has a ratio of 6:1.
The input shaft delivers 100 Nm and revolved by 4000 rpm.
The output shaft delivers 100*6 = 600 Nm and revolves by 4000/6 = 666 2/3 rpm.

The final drive has a ratio of 2:1.
The input shaft delivers 600 Nm and revolves by 666 2/3 rpm.
The output shaft delivers 600*2 = 1200 Nm and revolves by (666 2/3) / 2 = 333 1/3 rpm.

With the same wheel + tyre radius as in the first example, the force delivered from the contact patch is 1200/0.3 = 4000 N and the contact patch travels a distance of 333 1/3 * 0.3 * 2pi = 628.3 meters / minute = 10.5 m/s = 37.8 km/h.

The acceleration is naturally the same: 4 m/s^2 and so is the power: 56 bhp.
 
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I'm sorry to get into this but @jblackrevo9 : You try to expain the final drive ratio, and you mention horsepower, acceleration, engine capacity, drivetrain, etc. etc. and not even once do you mention rpm, you dont see the problem with that mate?
The simple advice I can give you is to listen to @eran0004 , as he has great understanding of these things.
 
The final drive can't be spoken of without including at least one transmission gear, as they combine to become the overall ratio, and the overall ratio is what matters most.

Why not?
There is always some torque delivered to final gear, if we assume at there is no changes done on transmission gears then we just can discuss final gear itself.
i.e. If car has 4.100 final and it struggles bit on acceleration with it, and there is plenty of traction on tires you can just put shorter final to gain more acceleration, shorter means 4.100+ values. Shortening final until you are facing tire traction loss you have seen limits of your current setups final ranges, on short side, in GT6 most good final gear changes to original final gear are found in +/-0.400 from original value, don't think at this is only range what could be valid, but most cases when using fully custom transmission with just speed slider changes.

Shortening bit final gear can help a lot on acceleration, and if gearbox is running on long gears it can even help you get higher speed on low powered cars, mathematically shortening final shortens reachable overall speed, but you have to have power to get car there, lacking power and you need better torque ratio what you can easily achieve by shortening final.
 
Why not?
There is always some torque delivered to final gear, if we assume at there is no changes done on transmission gears then we just can discuss final gear itself.
i.e. If car has 4.100 final and it struggles bit on acceleration with it, and there is plenty of traction on tires you can just put shorter final to gain more acceleration, shorter means 4.100+ values. Shortening final until you are facing tire traction loss you have seen limits of your current setups final ranges, on short side, in GT6 most good final gear changes to original final gear are found in +/-0.400 from original value, don't think at this is only range what could be valid, but most cases when using fully custom transmission with just speed slider changes.

Shortening bit final gear can help a lot on acceleration, and if gearbox is running on long gears it can even help you get higher speed on low powered cars, mathematically shortening final shortens reachable overall speed, but you have to have power to get car there, lacking power and you need better torque ratio what you can easily achieve by shortening final.

It depends on what you want to do. If you want to discuss how final drive ratios can be used to tune the gearbox without having to touch the other gears, then yes, we can isolate the final drive and talk only about it.

If you, however, want to discuss how some final gear ratios are better suited for some purposes than other final gear ratios, then it's just nonsense, because it's the product of final drive * gear ratio that's interesting - not the final drive per se. Intuitively one might think that the final drive is unique in some sense and that certain ratios provide certain benefits, but in reality it is just like any other gear: a torque multiplier.
 
@eran0004 true.
Mostly you start your gearbox tuning by choosing approx(desired/designated) value on final gear and doing then gears to match your engines torque/power bands.
If you start doing so with long final on low powered engine you probably will enter hard cornering car with crazy transmission gearing.

About cornering, final gear tuning is easiest way to settle tires on corner when almost everything is tuned and fine but you still encourage some not wanted behaviour during cornering, like small understeer you just put but shorter final and you're done, or small oversteer then doing opposite, longer final there.
Still speaking low/medium torque engine, things can vary when playing with high torque engine, but good tuner feels what and why rear slips or pushes.

I'm assuming at gears are set fine and whole setup is good.
 
I don't want to start unnecessary conflict and once again this thread was intended to talk about final gear and not the transmission.

It was created to explain it in a simple way.Most here have explained in a technical way that some may not be able to grasp right away.For those here that understood what I was talking about then thank you for not jumping to conclusions.
 
I'm not knocking your intent, it was admirable, I'm simply stating that simple is oversimplified when necessary values are excluded. You yourself included a hypothetical gear stack to convey a point that couldn't have been made without it.
 
I'm not knocking your intent, it was admirable, I'm simply stating that simple is oversimplified when necessary values are excluded. You yourself included a hypothetical gear stack to convey a point that couldn't have been made without it.
I understand maybe be next time I will go into more details on that part ( my bad lol) but again I think you for your respectful response.Others who I ran into on here would have taken this in a different approach.
 
How would you fund the final drive ratio?

You'll find it in the gearbox settings, it's called Final Gear.

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A value like 3.000 means that it divides the speed by 3 and multiplies torque by the same amount. So lower number (called "tall gear") = higher speed and less torque; higher number (called "short gear") = lower speed and more torque.
 
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