Gear Ratios

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GT_Nige
I've just created this tune for a Countach LP400 https://www.gtplanet.net/forum/showthread.php?t=197476 which I'm pretty happy with.

The only trouble I'm having is gear ratios. I can't get close enough to my lap times with the standard gearbox. What I make of it is that you have to try to get each gear to fall into the peak torque band and maximise at the peak BHP. Is this the right way of thinking? As it stands the LP400 at full tune has a peak torque around the mid rev range, which calls for the gears to be quite long and tall. I've tried to apply this theory but it doesn't seem to be right in practice.

Somebody please enlighten me! 💡
 
Well, I also mess around with gears very much, and I havent understod it either. Read the gt4 tuning guide, very good information. The question is if you can apply real life tuning in gt5, and wich impact it will have? Many people claiming real life tuning works in gt5, other people just doing trial and error. One thing is certain, always rev to redline if you want maximum power. If your gears are to long, your wont have maximum power.

According to the gt4 guide, you multiply peak torque with the gear ratio to get the transmission torque or something like that. For example, I have 3.300 gear ratio in first gear, and my torque is 629 @ 4900rpm. 629x3.300 = 2076. Before my gear ratio was like 3.274. 629x3.274 = 2060, and I was a little bit slower than now. I also had really long gears before, but it didnt work since my transmission torque was to low. Try shorten your gears a little bit.
 
TT3AZ
Well, I also mess around with gears very much, and I havent understod it either. Read the gt4 tuning guide, very good information. The question is if you can apply real life tuning in gt5, and wich impact it will have? Many people claiming real life tuning works in gt5, other people just doing trial and error. One thing is certain, always rev to redline if you want maximum power. If your gears are to long, your wont have maximum power.

According to the gt4 guide, you multiply peak torque with the gear ratio to get the transmission torque or something like that. For example, I have 3.300 gear ratio in first gear, and my torque is 629 @ 4900rpm. 629x3.300 = 2076. Before my gear ratio was like 3.274. 629x3.274 = 2060, and I was a little bit slower than now. I also had really long gears before, but it didnt work since my transmission torque was to low. Try shorten your gears a little bit.
Click to expand...

Will look into this, cheers:tup:
 
TT3AZ
One thing is certain, always rev to redline if you want maximum power. If your gears are to long, your wont have maximum power.
Click to expand...

This is absolutely untrue. In many cars, this holds true. But take a car that has a substantial drop off in power between its horsepower peak and its redline and this will not be the case.

Car that makes 270 peak hp @ 7000 rpms and 245 hp @ 9000 rpms in 3rd gear. 1.77 ratio and drops 2000 rpms between redline and the next gear will create these numbers.

9000 rpms 3rd gear tq to wheels = 253.06 (ignoring final drive ratio)
7000 rpms in 4th gear (1.35) = 273.48 tq to wheels.

In this case you would be better off shifting before redline, not after. To find out exactly how much, create a tq to wheels table using RPM and horsepower measurements multiplied by individual transmission gear ratios. If you need any more information, see my thread about transmission tuning.

About your second statement, that is also untrue. The gearing should be based around the power curve of the engine. Some engines work better at larger RPM ranges then others. Looking at the power curve will help you find this out. Again, create TQ tables will also allow you to see this information. Gearing a car while ignoring the power curve of an engine is like playing darts with a blindfold. Sure, you could hit the bulleye. But, you are more likely to miss the board completely.
 
grenadeshark
Car that makes 270 peak hp @ 7000 rpms and 245 hp @ 9000 rpms in 3rd gear.
1.77 ratio and drops 2000 rpms between redline and the next gear will create these numbers.

9000 rpms 3rd gear tq to wheels = 253.06 (ignoring final drive ratio)
7000 rpms in 4th gear (1.35) = 273.48 tq to wheels.

In this case you would be better off shifting before redline, not after.
Click to expand...

In an attempt to better understand, humor me with a dumb question.
Why would you ever shift after 7000rpm in the first place? (for the example you've provided anyways)
 
grenadeshark
This is absolutely untrue. In many cars, this holds true. But take a car that has a substantial drop off in power between its horsepower peak and its redline and this will not be the case.

Car that makes 270 peak hp @ 7000 rpms and 245 hp @ 9000 rpms in 3rd gear. 1.77 ratio and drops 2000 rpms between redline and the next gear will create these numbers.

9000 rpms 3rd gear tq to wheels = 253.06 (ignoring final drive ratio)
7000 rpms in 4th gear (1.35) = 273.48 tq to wheels.

In this case you would be better off shifting before redline, not after. To find out exactly how much, create a tq to wheels table using RPM and horsepower measurements multiplied by individual transmission gear ratios. If you need any more information, see my thread about transmission tuning.

About your second statement, that is also untrue. The gearing should be based around the power curve of the engine. Some engines work better at larger RPM ranges then others. Looking at the power curve will help you find this out. Again, create TQ tables will also allow you to see this information. Gearing a car while ignoring the power curve of an engine is like playing darts with a blindfold. Sure, you could hit the bulleye. But, you are more likely to miss the board completely.
Click to expand...

Well I base my claims on drag racing. I still claim, as Scaff writes, allways shift at redline, because if you shift to early, the rpm will drop under the peak torque rpm. "in any gear, at 7000 rpm, the transmission torque output is always higher than at any rpm in the next gear up".

Short gears will allways generate more output torque to the wheels, regardles of your power curve. That means that shorter gears will make your car reach top speed in less amount of time.

If you redline at 7000 rpm, and your torque is 389 ftlb at 1st gear, changing into 2nd gear will make your rpm drop to 5000 rpm, which will give you 277 ftlb of torque. But if you rev to 5500 rpm in 1st gear, which will give you 471 ftlb (peak torque), and change gear, the rpm will drop to like 3500 rpm in 2nd gear, and that will give you output torque of 243 ftlb. As you can see from this example, shifting before redline, gives you less amount of output torque in the next gear.
 
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grenadeshark is right. you guys need to draw out the table. for many cars, shifting at redline just works out. for others it does not. below is a table that propably will not align correctly for a muscle car that makes a lot of torque down low

off the top of my head, the car made 305hp@4800 & 390@3000 lb/ft (go SBC). peak numbers aren't really important. the torque curve is. if you can visualize the torque numbers below, you will "see" the motor has a very flat curve that peaks early. not uncommon for v8s.

gear ratios are:

Gear...Ratio....Shift Point......New RPM
1st.....2.5325..5250.............0
2nd....1.915....5000.............3969
3rd.....1.53.....5000.............3994
4th.....1.23.....5000.............4019
5th.....0.99........................4024.

RPM....Engine Tq...1st...........2nd..........3rd.........4th..........5th
2000...373...........944.6225...714.295.....570.69....458.79.....369.27
2250...375.5........950.95375..719.0825...574.515...461.865...371.745
2500...378...........957.285.....723.87......578.34.....464.94....374.22
2750...384...........972.48......735.36.......587.52.....472.32....380.16
3000...390...........987.675.....746.85......596.7.......479.7.....386.1
3250...388...........982.61......743.02.......593.64.....477.24....384.12
3500...386...........977.545.....739.19......590.58.....474.78....382.14
3750...379...........959.8175...725.785.....579.87.....466.17....375.21
4000...372...........942.09......712.38.......569.16.....457.56....368.28
4250...359...........909.1675...687.485.....549.27.....441.57....355.41
4500...346...........876.245.....662.59......529.38.....425.58....342.54
4750...326...........825.595.....624.29......498.78.....400.98....322.74
5000...306...........774.945.....585.99......468.18......376.38...302.94
5250...284...........719.23......543.86.......434.52......349.32...281.16
5500...262...........663.515....501.73.......400.86......322.26 ...259.38
5750...237...........600.2025...453.855.....362.61......291.51...234.63
6000...212...........536.89......405.98.......324.36......260.76...209.88

The numbers in the gear column are engine torque * gear ratio (ie. torque at tranny). you guys will say torque at wheels is what we're concerned with and that would equal engine tq * gear ratio * final drive - drivetrain losses. while true, i subscribe to KISS (keep it simple stupid) - final drive is a constant so we can omit it and drive train losses we're going to have to live without.

The formula to get where you will be in the next gear rpm wise after changing is rpm*(gear2ratio/gear1ratio)

I believe this cars redline is at 5750rpm. using the chart we can see the best acceleration is achieved by shifting at 5250 in 1st and about 5000k afterwards. if i had more rpm vs torque points plotted you could get real precise. the idea is to shift gears when the torque @ tranny in the next gear is equal to torque at tranny in current gear. if you shift too late, say 5750 in 1st and end up at 4500 in 2nd, you are not utilizing the engine & tranny to its optimum
 
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articzap
Ask the drag racers, never, ever shift past your peak horsepower rpm.
Click to expand...

Don't have to. Not enough corners on a 1/4 mile to care. They are geared to accelerate only and in a straight line, and up to a specific distance.. I doubt very much they will take into account the speed and gear used in any corner.

Tuning the gears is not about maximizing straight line performance but more about maximizing cornering performance while factoring in top speed and acceleration. Adding to one side takes from the other, when it comes to TS & acceleration. Something else drag cars need not factor in is past the 1/4 mile, they shut off, we have to keep going.
 
some info for those comparing with drag racers

drag race engines are made for peak power (perfectly exemplified by huge turbos and immense lag), so those engines while make more and more torque as you raise rpms, adn the "redline" is set, no by manufacturer, but by the tuner or owner, at the limit the engine can support.

heavily tuned cars (let's say NA tune 3 and big turbo) will have similar torque values, but more normal cars, adn including any diesel or muscle car like setup will have an important drop in torque well before redline

as the date just up there shows (previsous post by esoxhntr), there is a point where it's better to shift

also never forget the difference between redline and rev limiter, which are quite different. And if you happen to bounce off the rev-limiter, it's much much too late already
 
esoxhntr
Gear...Ratio....Shift Point......New RPM
1st.....2.5325..5250.............0
2nd....1.915....5000.............3969
3rd.....1.53.....5000.............3994
4th.....1.23.....5000.............4019
5th.....0.99........................4024.

RPM....Engine Tq...1st...........2nd..........3rd.........4th..........5th
2000...373...........944.6225...714.295.....570.69....458.79.....369.27
2250...375.5........950.95375..719.0825...574.515...461.865...371.745
2500...378...........957.285.....723.87......578.34.....464.94....374.22
2750...384...........972.48......735.36.......587.52.....472.32....380.16
3000...390...........987.675.....746.85......596.7.......479.7.....386.1
3250...388...........982.61......743.02.......593.64.....477.24....384.12
3500...386...........977.545.....739.19......590.58.....474.78....382.14
3750...379...........959.8175...725.785.....579.87.....466.17....375.21
4000...372...........942.09......712.38.......569.16.....457.56....368.28
4250...359...........909.1675...687.485.....549.27.....441.57....355.41
4500...346...........876.245.....662.59......529.38.....425.58....342.54
4750...326...........825.595.....624.29......498.78.....400.98....322.74
5000...306...........774.945.....585.99......468.18......376.38...302.94
5250...284...........719.23......543.86.......434.52......349.32...281.16
5500...262...........663.515....501.73.......400.86......322.26 ...259.38
5750...237...........600.2025...453.855.....362.61......291.51...234.63
6000...212...........536.89......405.98.......324.36......260.76...209.88

The formula to get where you will be in the next gear rpm wise after changing is rpm*(gear2ratio/gear1ratio)

I believe this cars redline is at 5750rpm. using the chart we can see the best acceleration is achieved by shifting at 5250 in 1st and about 5000k afterwards. if i had more rpm vs torque points plotted you could get real precise. the idea is to shift gears when the torque @ tranny in the next gear is equal to torque at tranny in current gear. if you shift too late, say 5750 in 1st and end up at 4500 in 2nd, you are not utilizing the engine & tranny to its optimum
Click to expand...

To the bolded part: Why?
Why would shifting from 719.23 @ 5250 to 712.38 @ 4000
provide more acceleration than...
987.675 at 3000 to 719.0825 @ 2250?

Not only does this example have more torque at both the high and low end of the RPM range, but my example GAINS power through the RPMs whereas yours loses power the entire duration of the gear.
I assume there's a reason yours works better, I'd just like to know what it is?
 
TT3AZ
Well I base my claims on drag racing. I still claim, as Scaff writes, allways shift at redline, because if you shift to early, the rpm will drop under the peak torque rpm. "in any gear, at 7000 rpm, the transmission torque output is always higher than at any rpm in the next gear up".
Click to expand...

Completely untrue. Depends 100% on the power curve. Example

Tranny gearing 1.65 and 1.25 3rd and 4th gear.

Lets say the car makes 300 hp from 5000-1000 rpms flat curve.

In 3rd gear at 10,000 RPM, car makes (300 * 5252/10000) * 1.65 = 259.97 TQ.

In 4th gear at 7500 RPM, car makes (300 * 5252/7500) * 1.25 = 262.60 TQ

Any questions?

The correct statement should be

In any gear, at 7000 rpm, the transmission torque output is always higher than at 7000 rpm in the next gear up.

Short gears will allways generate more output torque to the wheels, regardles of your power curve.
Click to expand...

True (mostly).

That means that shorter gears will make your car reach top speed in less amount of time.
Click to expand...

Not always true. Again it depends on power curve of engine.
 
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Adrenaline
To the bolded part: Why?
Why would shifting from 719.23 @ 5250 to 712.38 @ 4000
provide more acceleration than...
987.675 at 3000 to 719.0825 @ 2250?

Not only does this example have more torque at both the high and low end of the RPM range, but my example GAINS power through the RPMs whereas yours loses power the entire duration of the gear.
I assume there's a reason yours works better, I'd just like to know what it is?
Click to expand...

Because he didn't use real numbers when making his graph. Used guestimate numbers which create phenomenons like this. His theory and bolded part is basically what you should look at.

Use real life numbers from a real life dyno graph and tables make sense.

To answer your second part, its simple. Shift really early and look at the numbers on the next gear over. They will lower at a higher rate then the previous gear. There are RPMs in every gear where individual TQ ratings are higher then the gear before. The simple solution is looking at power to the wheels over a given time period. You will see that staying in first gear up to a higher RPM vs shifting at really low points provides higher acceleration.

Now, the TQ rating at any given RPM will always be higher in the previous gear.

To expand on this theory, let me explain a few things. Here are a couple of constants.

1. The higher the gear ratio in any gear, the less amount of load is put on the engine.

2. The less amount of load an engine has on it, the faster it will rev (up until a maximum point)

3. The TQ output to the wheels will be higher in a lower gear at the same RPM as a higher gear.
IE. The car outputs more torque in 3rd gear at 7000 rpms then 4th gear at 7000 rpms.

Adrenaline, the reason you continue to stay in 1st gear is because of the reasons above AND because the TQ output is higher at every given RPM then in the next gear over. If you look at the values in 1st gear, you will see that the out goes from 900 down to 700 at the highest rpms.

The power to the wheels in 2nd gear starts at 700 and moves down to around 600.
 
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Because he didn't use real numbers when making his graph. Used guestimate numbers which create phenomenons like this. His theory and bolded part is basically what you should look at.

Use real life numbers from a real life dyno graph and tables make sense.
Click to expand...

actually I did. :D stock small block chevy dyno graphs are somewhat easily found on google. there are also several 'desktop dyno' apps that contain various popular motors. the values line up fairly well with what i see in the game. the car is a '69 vette convertible with the chev 350. tho i may have fudged the lower rpm ie. ~2k figures a lil maybe..

the nice (for tuning) and crappy (for realism) thing about Gt5 and Horsepower modifications is that, with the exception of the three turbo options they do NOT alter the shape of the power curve, it just goes up. which means you can take a stock engine, figure out your gearing and run with it. in real life, adding cams hell, even a free flowing exhaust will alter its shape to some degree.
 
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Adrenaline
To the bolded part: Why?
Why would shifting from 719.23 @ 5250 to 712.38 @ 4000
provide more acceleration than...
987.675 at 3000 to 719.0825 @ 2250?

Not only does this example have more torque at both the high and low end of the RPM range, but my example GAINS power through the RPMs whereas yours loses power the entire duration of the gear.
I assume there's a reason yours works better, I'd just like to know what it is?
Click to expand...

grenadeshark explained it. if you shifted that early, you'd be missing out on a helluva good time in 1st (ie. why shift from ~980 tq @ tranny [3krpm] to ~720 tq @ tranny [2.25k rpm] when you can keep going in first gear to 5250rpm and have more tq @ tranny [torque @ wheels is higher in 1st than anywhere in 2nd until you hit 5250rpm]). Also, you'd have to shorten 2nd gear to end up at 2250. this would give you a narrower rpm 'range' to work with in the gear - again not using the wide power band to your advantage.

have a read: http://www.allpar.com/eek/hp-vs-torque.html

the example they use is a neon, and, for that car, shifting at redline is best.

and let me re-iterate, for a good number of cars in GT5, shifting at redline with the shortest possible gears is the way to go. PD loves japanese rice burners. ;)
 
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