Gearing, longer = faster?, not always

  • Thread starter sucahyo
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sucahyo

sucahyo

2,171
I am the writer of the gear tuning part in Gran_Turismo_4_:_Tuning. What I write in there is what I already test in GT4, mainly from my 300mph experience. Unfortunately if anyone of you want me to prove it, I can't do it right away, since I can only play GT4 occasionally. But it is not hard to try it yourself isn't it?

There is one aspect that I still not able to test yet, the final drive ratio effect on acceleration. It should have the same effect as lighter flywheel (in a less degree). So smaller final drive should have quicker acceleration and more tire spin.

It is a common knowledge for all of us that lower final drive ratio give higher top speed but also slower acceleration. But this is GT1 tuning practices. Starting from GT2 you can even make lower final drive slower than higher final drive.

In GT4, if you do auto 1 at whatever final drive, on most car, it willl give around 150mph top speed. Just like when you change the auto to 25 at whatever final drive resulting just bellow 320mph top speed.

Remember, auto 25 at 5.000 means that you change the final drive to 5.000, and then change the auto from anything TO 24 and then to 25. Auto 16 at 3.300 means that you change final drive to 3.300 and then change the auto from anything to 15 or 17 and then to 16.

For the acceleration bit, I only test it in one car, R92CP. It's been month so I forget the detail, this is what I remember: using auto 25 at.5000 the car spin the tire up to 2nd gear, using auto 25 at 2.000 the car spin the tire up to 3rd gear. From my GT2 experience, lower final drive behave like lighter flywheel. As I can't play GT4 often, I intend to create this thread later waiting my chance to create 300mph running comparison video, but as I already spill it already I have to do it now :).


RXGem
Try playing with just the final drive and even just a difference of around +/-0.1 will make a quite noticable change to the power down.
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Yes, I know that. But, that is not what I meant.

RXGem
Personally, I don't like to use the 'Tranny Trick'.
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I have suspect that my higher than average position in 300mph leaderboard is the result of using tranny trick, I am still not sure if there is anyone else using tranny trick in 300mph like me.

RXGem
I like to have my gears reach a certain speed depending on the amount of power the car produces and then fine tune the final drive according to the amount of traction I'm getting whilst on the throttle.
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That can be done on any final drive value, except when you tune for 300mph.

RXGem
Generally, low torque cars will require 'shorter' (higher value) final drive ratio's so that there is more of a direct throttle response. Especially when drifting, there feels as though there is more torque when traction is broken and there is no sudden loss of power once coming off and on the throttle. High torque cars will require a 'taller' (lower vaule) final drive ratio to help 'spread' the torque band a little. Once traction is broken there is no sudden increase of power, which will result in a spin or too much wheel spin and not enough grip on exit. The throttle may feel a little less sensitive, but on the other hand, more controllable when traction is broken.
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I don't know anything about this, so, Ok.
What I know is race engine usually have very instanious response, sometimes, fitting lighter flywheel on this car induce acceleration problem. For this car I will use higher final drive. Other than that I will use value as low as possible for final drive.

RXGem
A taller final drive ratio is definately something I would use for a Speed 12. If you're losing too much traction on your Speed 12 try lowering the value of the final drive.
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If you mean is tire spin, we can reduce tire spin by reducing final drive value AND gear ratio value. If both value is already minimum, the tranny trick can be helpfull. Notice that my Audi R8 can reach 109 mph at the 1st gear, it is usually around 80mph if you use auto 25 at 5.000 and then lowering final drive.

RXGem
That's why I don't use the tranny trick. Transmission tuning can make quite a difference to the balance of a vehicle when done right. Some people don't see much of a difference I guess, or some just think that close and evenly spread gears is the best way (Tranny Trick)..
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Tranny trick making the distance between 1st gear 6th gear closer. So we can have longer 1st gear with the same 6th gear ratio as the normal way does. It is best applied on car with steep power curve. For car with wide power curve normal way (auto ? at ? only) is enough. I never see car that need ultimate long gearing though.

RXGem
I don't understand why some people would spend hours trying to tune their cars for balance and then take a shortcut with the transmission when it can be such an effective tuning tool!
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True, I only spent 3 minutes on each my 300mph car for gear tuning, but I don't think it's bad. With my java midlet calculator (using formula in my signature), I can estimate the gear ratio needed to reach certain speed at any final drive.
For example, I use 360mph goal for my 356mph Audi R8. The first thing I do is testing the auto 1 at 5.000 speed. After I get the speed (which is ofcourse 150 mph), I enter this speed, final drive (5.000), 6th gear ratio (I forget :P) in my calculator, and also entering the new final drive (2.000) and new speed (360). The calculator will then show me the gear ratio needed to reach 360mph.

In addition, I can also calculate the other gear ratio needed for certain speed without testing it :). The accuracy is good enough for me, I don't complaint if the actual speed is 351mph when I enter 350 on the calculator :D.
Edit: Correction, I do whining when I want sub 350mph for my Bentley and R92CP and getting 350.6mph :P.
 
This is very interesting, and I can contribute a bit if you like.
In my findings when tuning gears for 300 mph, I have discovered that different cars require different approaches to geartuning. I have found three types of cars; those who benefit from a "normal" trannytrick, those who need a "reverse" trannytrick, and those you better not do any tricks on, or at least try not to unsettle the gearratio vs. torque range too much. Examples of cars for these behaviour are; Most LMP cars (not the Bentley) seem to benefit from the "normal" trannytrick (final ends fairly high, over 3.000). The Group C cars seem to like the "reverse" trick (final end fairly low, below 2.700). The third category is hard to tell when you start tuning, and mostly they show from "trail and error". One example is the Bentley, whos torquecurve is fairly unique.
As a rule of thumb though - with the obviuos exceptions of course - I can say that the cars with high rpm torque likes low gearnumbers with a high final number, and cars with low rpm torque likes high gearnumbers and low final number. the exceptions usually like a combination of high final number and a high as possible autoset.
 
Errrr ... I always do it like this, and I've never seen it fail. I look at the torque curve of the car, and according to that, I set the auto gears. With a wide range of available torque (usually big engines or turbos), I set auto to 25, cause I want the gears to be long to cover as much of that tourque as possible. With a small range of tourque (smaller, sometimes high-revving engines), I set the Auto to let's say 15 or something, to keep the revs up when shifting up.

After I've done that, I set the final ratio according to the top speed and acceleration I want. With a small car, I ususally don't want to be able to go faster than 150mpg, so it gets a fairly high final ratio. For top speed runs or fast races, the torquey engines get a rather low final ratio. Then I make test runs to determine which one gives the best top speeds. You need to find the right proportion between wind resistance and engine power, so sometimes, it can be right to set this a bit too high or low, cause it will make the car go faster.

Anyway, I never set the auto gears after I've altered the rest, cause they change everything over again. I use the auto gears to match the engine, and the final ratio to match top speed and acceleration. Like I said, this has always worked for me, and I don't see anything wrong with it. And to be honest, I don't quite get what you guys are doing there exactly. :dunce:

Regards
the Interceptor
 
This is a subject that I have discussed with sucahyo via PM and have carried out a few test on myself.

Heres the PMs from my end (with a few quotes by sucahyo), theres nothing in here that I believe sucahyo would have a problem with me putting on the public forum.

The are in cronological order, so oldest first and I have to admit I did not have a firm grip on what sucahyo was saying at first (my bad).


Original request & Reply - for background)
Scaff
sucahyo
Just in case you not notice this before:
- changing auto to 16 when final drive is 2.500 have the same top speed (and gear speed) as changing auto to 16 when final drive is 5.000.
- auto 16 can give fairly the same top speed on most car. This is based from what GT4_Rule told that his 88C-V reach 320mph and R92CP reach 316mph, qsiguy pescarolo reach 319mph. All car should be able to reach higher than this. GT4_Rule use auto 25 for his car, maybe qsiguy too.

Can you test do smaller final drive have the same effect as lighter flywheel? All I know is R92CP 2.000 final drive has more tire spin compare to 5.000 final drive. It give slower 1000mph time.
This is the same behaviour as GT2, where race car with very responsive engine is slower with lighter flywheel or smaller final drive. In GT2 using smaller final drive in slow car will give faster time, I am unbeatable in GT2 1000m.
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Sucahyo

A lot of the above I am covering in the second of my tuning guides (which will be covering gear ratios, differentials, downforce and few more bits), a friend is reading over it at the moment to check it and it should be avaliabelin a few days time.

I would be more than happy to look at the the flywheel vs final drive subject and put together a few tests on that one.

Regards

Scaff
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I get the wrong end of the stick - Doh
Scaff
sucahyo
? All I know is R92CP 2.000 final drive has more tire spin compare to 5.000 final drive.
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Just given this a try as it did not sound right and I have to say its not right, but I can understand were its come from.

Let me try and explain.

First the R92CP develops 689 ft/lbs of torque at 5,600rpm and if you look at the power curves for the car, you will see this is a sharp curve. It rises to this point and then drops quickly.

You may also notice when you test the car that 5,600rpm is the point at which the tyre spin is worse (and when it first starts) this is due to the torque at the driven wheels.

Driven wheel torque is calculated by taking the engine torque (at the rpm you are looking at) and multiplying it by first the gear ratio and then the final drive ratio. This gives torque at the driven wheels.

So @ 5,600rpm the figures would be as follows (all for auto slider set to the default 17 and first gear).

Final Drive 2.00
689 * 3.568 * 2.00 = 4,916.7 ft/lbs (or 2,458.35 ft/lbs per wheel)

Final Drive 5.00
689 * 3.568 * 5.00 = 12,291.8 ft/lbs (or 6,145.88 ft/lbs per wheel)

Now if you start both cars from rest and pull off the wheel spin in the FD 5.00 car is far worse in first gear than in the FD 2.00 car. However once you get moving and start to change gear something interesting happens.

The FD 5.00 car when you change up, the revs never drop below approx. 6,500 rpm, so the car is never able to use the peak engine power avaliable in the higher gears (as the peak torque drops quickly after 5,600 rpm). This is the reason the car seems to be generating less wheel-spin (but will spin the wheel in both firstand second far worse than the FD 2.00 cars - you just haveto drop the revs) and why it slower 0 - 1000, the gear ratios are so close that the car can never use its peak power.

Regards

Scaff
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Get there in the end - and thsi might help explain what is going on)
Scaff
sucahyo
This is not what I meant. If 3.568 is first gear ratio then you are NOT doing it right, you must change the auto from 17 to 16 to 17 EVERYTIME you change FD. The gear will not change if you only select auto and not move it to the left or right. There is no way auto 17 will give the same 1st gear number for different FD.
Please do this when you test FD:
- FD 2.000, move auto from 17 to 16 to 17. run
- FD 5.000, move auto from 17 to 16 to 17. run

You will notice that even when the 1st gear ratio is DIFFERENT the speed is the SAME. On your test the gear ratio is the same and ofcourse the speed is different.

Please try again if you have time.
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Ok I get what you are saying now (by the way its perfectly possiable to get the same individual gear ratios when you change the FD - just set the auto first and then don't change it again - I do this all the time).

Just given it a go, and no big surprise with the results to be honest, all the (rather crude) Auto tool is doing is adapting the individual gear ratios to the FD you set to make as close a match to the auto value as it can.

If you work out the driven wheel torque or use a gear speed calculator on the gear ratios and FD value it becomes obvious

FD 2.00 + 1st Gear
689 lb-ft * 6.244 * 2.00 = 8,604 lb-ft

FD 5.00 + 1st Gear
689 lb-ft * 2.497 * 5.00 = 8,602 lb-ft

Its the same for every gear.

All thats happening is that the auto tool appears to have a set gear value (in this case it appears to be approx. 12.48 (6.244 * 2 = 12.488 & 2.497 * 5 = 12.485) for auto 17). Once you set the FD and then change the auto from 17 to 16 and back to 17 the system matches the individual gear ratios to the FD to get the 'set' gear value.

Its why I always change the Auto first, to get the range of vales I want and then change the Final Drive and then the Individual Gear Ratios.

Regards

Scaff
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Final Drive Vs Racing Flywheel
Scaff
Sucahyo

I've been testing this one out with an SLR running on R3 tyres, an FC box and a racing flywheel.

Looked at 0-1000m times with the FC G.box set to auto 13 and then at FD 2.00, FD 2.647 (FC default value), FD 5.00, and then FD 2.647 with the flywheel.

Results are (all averages of 6 runs)

FD 2.00 (No R.Flywheel) - 20.06

FD 2.647 (No R.Flywheel) - 20.11

FD 5.00 (No R.Flywheel) - 20.33

FD 2.647 (With R.Flywheel) - 19.90

So the 0-1000m runs with the lowest FD setting do see to have a similar effect to using a lighter flywheel (but not as great).

However is this down to the lower FD values or the higher individual gear ratios? Tnats the question I want to answer.

Have to do some more testing on this one as it will have an impact if you change the individual gear ratios.

The main thing is the benifit of using the lower FD/Higher gear ratios is not as great as the advantage of using a racing flywheel (but of course you can always do both).

Regards

Scaff
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Well that little lot should help open things up a bit.

Regards

Scaff
 
the Interceptor
Errrr ... I always do it like this, and I've never seen it fail. I look at the torque curve of the car, and according to that, I set the auto gears. With a wide range of available torque (usually big engines or turbos), I set auto to 25, cause I want the gears to be long to cover as much of that tourque as possible. With a small range of tourque (smaller, sometimes high-revving engines), I set the Auto to let's say 15 or something, to keep the revs up when shifting up.

After I've done that, I set the final ratio according to the top speed and acceleration I want. With a small car, I ususally don't want to be able to go faster than 150mpg, so it gets a fairly high final ratio. For top speed runs or fast races, the torquey engines get a rather low final ratio. Then I make test runs to determine which one gives the best top speeds. You need to find the right proportion between wind resistance and engine power, so sometimes, it can be right to set this a bit too high or low, cause it will make the car go faster.

Anyway, I never set the auto gears after I've altered the rest, cause they change everything over again. I use the auto gears to match the engine, and the final ratio to match top speed and acceleration. Like I said, this has always worked for me, and I don't see anything wrong with it. And to be honest, I don't quite get what you guys are doing there exactly. :dunce:

Regards
the Interceptor
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You are right in what you are doing, so I think you know what we´re up to :)
The thing with top speed (and acceleration in many cases) is though, that sometimes the final ratio should be lower than it can be (2.000 - 2.500 depending on car), wich means you need a different approach, IE a reverse trannytrick, to be able to get the most out of that cars torquerange! And there are differences between cars, on what is the optimum use of ratios, like this; Most cars will do with the final ratio, ending fairly high on the scale - the higher the number, the better efficiency you get from the torque. Other cars though, will benefit from high ratios in the gears themselves, and a low final ratio, for best efficiency, and others still will need a combination of the two - high gearatios and a high final ratio! I´ve yet to encounter a car that needs low gearratios and a low final ratio, but I´m sure I´ll meet one someday!
 
What confuses me most is the constant referral to a lightened flywheel... which doesnt make one iota of a difference to the gear ratios. It reduces the rotational inertia of the engine, which means it can respond (accelerate) much quicker; however the lower inertia causes problems with smooth running and also apparently losing speed going uphill - not quite sure how that works but I have noticed it in GT4. Anyway, this is independent of what gears you set the car with. You set a car to accelerate quicker, and it will - add a lightened flywheel and the engine will be more responsive, potentially giving quicker acceleration for that same gearing.

I could have completely missed the point... (a discussion regarding autosets and final drives).
 
You're right, the lightened flywheel doesn't affect the gear ratios at all. Still, the gear ratios can have a similar effect on engine behaviour than the lightened flywheel. Depending on the engines characteristics, you can make it very easy or very hard for it to rev up. So, with a false ratio setup, you can make your engine all greasy and lifeless, but with the right one, you can even make a tiny little burp of an engine rev the soul out of itself.

Regards
the Interceptor
 
I haven't been trying the 300mph thing, but I have been trying to set good ratios for the Nurburgring, which I drive all the time in 2P mode.

What I've been doing is using the highest possible Final Gear, which is 5.5 in most cars(6.0 in some cars like Evos). This gives me the best possible acceleration(just a personal preference). Then I come up with a decently short Auto Set and tune the individual ratios as necessary.

In most of my moderately tuned cars(under 500hp), I end up doing a 'Tranny Trick' of my own. I'd look to see what the gears from an Auto Set of 8 or 9 would be, then select 11 or 12. I would set ratios 1-5(on a 6-speed) as close as possible to the lower Auto Set of 8 or 9. Then I would use the 6th gear ratio from the higher Auto Set. This usually got me pretty close to the highest possible top speed(not bouncing off rev limiter in 6th too early, but not falling short of redline either) on the final straight on my first test run.
 
Thanks Scaff :).

I said something that is uncorrect:
sucahyo
In GT4, if you do auto 1 at whatever final drive, on most car, it will give around 150mph top speed.
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I forget my experience in TVR speed 12 and other car, when I use auto 1 at 5.500 the top speed is 145mph for both car. Both Pescarolo auto 1 at 5.500 top speed is 109mph. Supra RZ auto 1 at 5.500 top speed is 120mph.
So, the correct assumption should be:
In GT4, if you do auto 1 at whatever final drive, you will have the same top speed. Different car with same characteristic may have the same top speed.

So car that have different max final drive or unusual engine can have different top speed on the same auto setting.

Team666
I can say that the cars with high rpm torque likes low gearnumbers with a high final number, and cars with low rpm torque likes high gearnumbers and low final number
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Do "like" in here mean you can get faster actual top speed even if you use the same theoritical top speed?
In my 300mph run, as I never notice rpm needle instability, I always use lowest final drive. Maybe I should compare with highest final drive next.

the Interceptor
I look at the torque curve of the car, and according to that, I set the auto gears. With a wide range of available torque (usually big engines or turbos), I set auto to 25, cause I want the gears to be long to cover as much of that tourque as possible. With a small range of tourque (smaller, sometimes high-revving engines), I set the Auto to let's say 15 or something, to keep the revs up when shifting up.
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When tuning my gear, I usually test what is the lowest final drive that I can use (give no problem). Then I determine what is the top speed I want for the car. After that I calculate what the individiual gear ratio that I need. If the car have wide power curve I can use longer gear. As many car have steep pAs ower curve, I tend to use short gear ratio.
As guide, I usually make my gear so that:
if I shift, the rpm do not drop too much bellow the optimum power curve
at low gear, the car do not spin as much
at high speed, the car work at the optimum power curve

Tranny trick trick work for me because it give longer 1st gear and shorter gearing at once.
For car with steep power curve, I consider having 110mph 1st gear and 360mph 6th gear better than having 80mph 1st gear and 360mph 6th gear.

the Interceptor
I use the auto gears to match the engine, and the final ratio to match top speed and acceleration. Like I said, this has always worked for me, and I don't see anything wrong with it. And to be honest, I don't quite get what you guys are doing there exactly.
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I offer another alternative to that. You use final drive to match the engine, and playing around with gear to match the top speed. Same top speed can be achieve on any final drive, although I admit that this way of tuning is complicated. And if we do it without calculator we need much longer time than normal.

RenesisEvo
however the lower inertia causes problems with smooth running and also apparently losing speed going uphill - not quite sure how that works but I have noticed it in GT4
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In a car that have that problem I will use higher final drive, and for race car that have fixed flywheel, I think playing with final drive ratio is the only option we have to reduce that problem.

VQuick
This usually got me pretty close to the highest possible top speed(not bouncing off rev limiter in 6th too early, but not falling short of redline either) on the final straight ofirst test run.
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If I don't carry my calculator, I usually doing auto something at lowest final drive that can give me the needed top speed in the track. Then I will do auto 1 at something final drive that can give me the exact same 6th gear ratio. After that I change the final drive to lowest again.
This will result in shorter gearing with the same top speed.
 
sucahyo
Do "like" in here mean you can get faster actual top speed even if you use the same theoritical top speed?
In my 300mph run, as I never notice rpm needle instability, I always use lowest final drive. Maybe I should compare with highest final drive next.
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That is what I have found. The "theoretical" top speed can be altered with a few tweaks in the gearbox. I always try out all the different gearboxtricks to see wich one suits that particular car.

And you can´t actually have a high final drive, only fairly high, like ranging from 3.200 to 4.200 depending on car. That however will give you very low gearnumbers, with a 6th gear in the 0.500 to 0.800 range. Some cars like it that way though.
 
Team666
That is what I have found. The "theoretical" top speed can be altered with a few tweaks in the gearbox. I always try out all the different gearboxtricks to see wich one suits that particular car.
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I see, interesting :) 👍.
 
I can basically tell that you can have good acceleration with a short gear but with a lower top speed. On the other hand a long gear has a high top speed but slows acceleration. The key is being good at finding the best balance between acceleration speed and top speed in the ratio.

Shorter ratios will work better with tracks with a large amount of corners but shortish straights.

Longer ratios will work better on tracks with long straights such as Twin ring Motegi.

For mildly balanced tracks of these aspects such as Nürburgring Nordscleife require these hard-to-find ratio settings.

The key to having a good lap time and an easy win is setting up gear ratios according to track type, opponent type and tyre type.

Also keep in mind that suspension setup, weight and aerodynamics have an effect in the way the gear ratios work.

The other parts in the transmission category such as the flywheel, carbon driveshaft, LSD and clutch affect the way the ratios work quite surprisingly.

If you find this text useful, please let me know via the Red Tick.

Cheers

T4 GTR
 
T4 GTR
I can basically tell that you can have good acceleration with a short gear but with a lower top speed. On the other hand a long gear has a high top speed but slows acceleration. The key is being good at finding the best balance between acceleration speed and top speed in the ratio.
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Yes. But you should know that we can have both, short gear and high top speed, using tranny trick.

example on GT2 (forgive me I can't play GT4 right away :guilty:, but this should work in GT4 too, otherwise I won't be bothering you all :) ).


Lotus Motorsport Elise, 24" tire (calculated), rev limiter at 8100rpm
Code: 
ratio  speed(mph)
==================
a. auto 14 at 4.200
2.714    51
1.750    79
1.235   111
0.924   149
0.732   188
4.200

b. auto 7 at 5.500
2.416    57
1.623    85
1.173   117
0.895   154
0.722   190
4.200

c. auto 14 at 2.500
4.561    51
2.941    79
2.076   111
1.553   149
1.230   188
2.500

d. auto 1 at 4.308
3.764    61
2.619    88
1.932   119
1.502   154
1.230   188
2.500

e. auto 25 at 4.200
2.345    59
1.420    97
0.697   142
0.700   196
0.540   255
4.200
You see that a,c and d configuration have the same top speed, but the 1st gear speed is faster in d config even though it has the exact same top speed, this means d have shorter gear than a.
 
sucahyo
Yes. But you should know that we can have both, short gear and high top speed, using tranny trick.

example on GT2 (forgive me I can't play GT4 right away :guilty:, but this should work in GT4 too, otherwise I won't be bothering you all :) ).


Lotus Motorsport Elise, 24" tire (calculated), rev limiter at 8100rpm
Code: 
ratio  speed(mph)
==================
a. auto 14 at 4.200
2.714    51
1.750    79
1.235   111
0.924   149
0.732   188
4.200

b. auto 7 at 5.500
2.416    57
1.623    85
1.173   117
0.895   154
0.722   190
4.200

c. auto 14 at 2.500
4.561    51
2.941    79
2.076   111
1.553   149
1.230   188
2.500

d. auto 1 at 4.308
3.764    61
2.619    88
1.932   119
1.502   154
1.230   188
2.500

e. auto 25 at 4.200
2.345    59
1.420    97
0.697   142
0.700   196
0.540   255
4.200
You see that a,c and d configuration have the same top speed, but the 1st gear speed is faster in d config even though it has the exact same top speed, this means d have shorter gear than a.
Click to expand...

Yes indeed you said it all. That is the only thing I can never define - Tranny Trick.

Cheers

T4 GTR
 

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