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RPM and Gear Ratios

Discussion in 'RACE 07 - Official WTCC Game' started by Jarrod Crossley, Feb 18, 2009.

  1. Some how I've confused myself so a little point in the right direction is needed.

    When setting up gears you always try and find the final gear so that its just hitting optimal point just before the breaking point of the corner, and then move other gears so there are evenly balanced but on a simlar scale for the corners they are needed for.

    But that said if we were to take a Seat Leon and the info provided then this is where I get all confused.

    Seat Leon info

    Engine: 2000 CC
    Horsepower 287 BHP @ 7750 RPM
    Max Torque 272 Nm @ 6750 RPM

    So going of the above the optimal gear point is 7750 RPM, per gear.
  2. Yep, my dad told me something years ago about torque and power graphs but he said after that point the car just loses power and its not a efficient way to shift.
  3. So wait, you are meant to change up at that point on the revs? Or just after or before? I'm confused too :p
  4. You are surposed to change when the engine is at its highest point on the BHP graph so that would be 7750 RPMon the seat Leon. I think anyway.
  5. Hmm just to make matter even more confusing the max revs for the Leon in setup 8500. So your allready going above the optimal piont, My head hurts now.

    @ Jamie

    Find the longest stright (usally the start finish stright) at the point you would start to brake for the corner, in-game - on the hud the gear 6 should just have changed to red. this is the optimal point for the final gear.

    So extending this:

    Youv've just slowed down and selected the correct gear for the corner. You need to alter the length of the gear so that your hitting its optimal point just as you exit the corner.
  6. Im going to do some research into this lol. and also wait or me Dad to come home from work ill ask him.
  7. A quote from an old post that might interest the OP.

    Regarding real world (RL) shifting...

    It depends on the torque/power curves and how the engine is mapped.

    So many things can be typed about this... will try to be short.

    For instances, in a big engine a (with lots of torque), like the Viper's one (in GTR2 if you have it you can see this), ideally you should shift in the torque peak because the power peak is very near (right after it I think).

    On a "rever" engine ("low" torque "high" power) like a “small” V12, where for instances , as it more it revs, more power it has and the torque is much less, you should change gear very late (without blowing the engine).

    On endurance mode (let’s call it), you should change gear in the torque platform (hard to explain without a graph) and the power band should be mapped (even if less power will be produce by the engine) near that same torque platform.

    Damn, this sound too confusing (sorry), but it isn't...
    With graphics, for different engine mappings, it is actually very easy to spot the "ideal" shifting point.

    Be warned though, that in Race07, as the things stand, most of the cars, more you rev it, more it goes (I'm not saying they won’t explode). I'm not sure what’s the idea of SimBin behind this decision...

    Will give a few examples.

    • The BMW M3 GT2, more you rev it, more it screams, more it goes.
    • The C6R GTP, has an optimum shifting zone, if you shift later, you are losing time.
    • The Vertigo GTClub, what is stated in the on screen specifications (power/torque rpm) is plain wrong... just drive the car and you will see why ;)
  8. Yeah lot of cars do that, but there are a few that not! F.e. the Camaro:)
  9. Damn, that cup is scheduled in a way it isn't compatible with my RL compromises.

    Yes, the Camaros are a good example of a good torque inertial machine... the idea of using only 3 (or even only 2) gears in most tracks is annoying to me (the gear ratio can't be changed in the class). In ovals they should be a blast though…

    Sorry for the "small" topic hijack...
  10. it is easier when viewed in graph form i think

    Attached Files:

    • leon.jpg
      File size:
      143.2 KB
  11. No flat spots there hey.
  12. The theoretical optimal rpm for a shift depends on the power graph and on the gear ratio. To keep things simple let s assume we accelerate and wanna shift from 3rd to 4th gear (having a 5th gear too) and the rpm of the engine will go down about 2500rpm after the shift. To get the most power during that acceleration the integrated rpm-area between the two rpm points (before and after the shift) must be a maximum.

    To see what i mean just examine the rpm graph Neil has given us. I marked the powerarea for the "max_powerpoint_shift" and the "max_powerarea_shift" and as one can clearly see, just to shift at the rpm of the highest power isnt the best cause you have less integrated power for your further acceleration.

    I know that the rev for the seat is at 8500rpm and that my ideal shift for maximum powerarea shows 9000rpm because of that drop of 2500rpm, but in that way it is easier to see what i wanted to explain and i hope it s a little bit more clear now.

    Or to become more concret: As long as your gear ratios result in a drop of more than 1000rpm for that car, you can rev out (8500rpm) your engine. An exception of this is setting the last gear for reaching topspeed (i.e. nordschleife) which then should end at 7750rpm, maybe 8000rpm as well regarding the graphics. All this is only valid in respect to the maximum of integrated power and does not take endurance into account.

    Because of symmetry in the nearness of the maximum power one must not always calculate integrated powergraphs cause there one can use the rule: For a maximum of acceleration you should shift at that rpm, when the engine will have a higher power after the shift than it has before the shift. If this would be beyond the rev you must rev out your engine. For those who want to claim that torque is the key for acceleration i just say no without any explanation, it s power and only power.

    Attached Files:

  13. Dave Stephenson

    Dave Stephenson
    Technical Administrator Staff

    That's pretty much how I understood it. That you accelerate most effeciently when at shift time your revs drop to the max torque area of the graph. If that drop ios achieved by shifting at the max power then you have yourself a perfect world engine/gearbox combo if not then you must pass it a little as above.
  14. Torque is the key! :laugh2:

    No, in truce, "shift to maximize transmission output torque" wish equals (and it is easier to view) to "Shift to maximize engine Power".

    Just one thing, you typed about this but maybe not many people gave it a real look....

    There is no time variable here, engine live will not be the longest this way... in other words, even in this game, you can stress the engine in endurance racing.

    Of-course, in sprints what I think most people here do (or even less real, time-attacks), there is no problem as the boss will buy a new engine after the over-stress. :D

    An example, the BMW M3 GT as stated has typical rev-out mapping where it compensates to rev it max, but I’ve seen a few people (with low engine temperatures) stay by the road with a silent engine in endurance racing ;)

    It seems this tool is for rFactor... rFactor isn't Lizard (Pacejka).. is there a similar tool for Race07/Evo/STCC?
  15. Ok, now it’s the time - sorry for hijacking the thread but in some way this was part of the question, i guess:

    Power versus Torque
    When a car does accelerate best?

    The acceleration (a) of a car is proportional to the force (Fw) which is coming from the driven wheels and therefore proportional to the torque at the wheel (Tw), which depends on the torque of the engine (Te) and on the transmission ratio (ne/nw), which is the rpm of the engine (ne) divided by the rpm of the driven wheels (nw) and thus a summary of everything in between engine and driven wheels like the radius of the wheels (rw), the diff-settings and the gear ratio. Introducing Power (P) as P=T*2*PI*n - thus meaning Power is proportional to the product of Torque and rpm; PI is that 3,14… - we can examine the acceleration using the general relations F=m*a and T=F*r as

    a = Fw / m = TW / (rW*m) whereas m is the mass of the car of course.

    Now we use the transmission ratio to switch to the torque of the engine with Tw=Te*(ne/nw) and get

    a = Te * (ne/nw) * 1/(rw*m) and name that equation with (I).

    Needless to say in a racing forum that Te varies with ne. Now it’s time for the Power of the engine and we can use Pe=Te*2*PI*ne to replace the torque of the engine

    a = Pe/(2*PI*ne) * (ne/nw) * 1/(rw*m)

    and sorting things in a different way leads us to

    a = Pe/(2*PI*rw*nw)* 1/m

    which now gives us the idea to detect the actual velocity v=2*PI*rw*nw of the driven wheel rolling on the track which is under assumption of full grip the velocity of the car. So we finally have

    a = Pe/v * 1/m and name that equation with (II).

    Needless to say that Pe varies with ne, too, of course.

    Now we have everything together.

    Examining equation (I) we’ll see that for a fixed transmission ratio the acceleration would be at maximum for a maximum torque, but a fixed transmission ratio means we must stay in a fixed gear and we are not allowed to gear up or down! The assumption of having only one allowed gear is not very practical. Much more practical is the question: Having the same actual velocity at present, maybe we could reach a better acceleration with another gear?

    Examining equation (II) which is independent of any transmission ratio we’ll see that for a given velocity the best acceleration is just where the Power is highest and so we choose our gear and rush away! This can’t always be the absolute maximum of power, because we are examining a given velocity and a somehow given gearbox and that must not fit.

    Well, within our simulation we can adjust this somehow given gearbox and now that’s the point. Let’s go back to our Seat with a maximum torque of 272 NM at 6750 rpm – i have 277 in my excelsheet derived from the gamedata by someone from rsc, but anyway – and a maximum power of 287 BHP at 7750 rpm. I have attached a new graph for an “ideal shift according to the seat” and we just think back our up-shift. The new gear will have its best acceleration at 6750rpm as we know from equation (I). We derive this from the torque graph and mark this in the power graph. Now we go horizontal to the right and see where we will cross the powergraph again cause there should be the shiftpoint for our old gear – yes, quite above the maximum of power cause for that present velocity the new gear must reach an equal or better power according to equation (II)!

    By the way: If we would set the old gear in that way, that he hits the absolute maximum of power at 7750rpm, we always would gain a better acceleration with our old gear in the power maximum then with our new gear in the maximum of torque! So in general the acceleration is at its best for the absolute maximum of power! Just to confuse you but true: The absolute maximum of acceleration is always reached using the 1st gear (or often even the reverse gear) at torque maximum - cause here we can't choose an "old" gear which could hit the absolute maximum of power; think about it...

    So going down to the scale we read something like 8830 rpm, maybe it is 8839 or 8843 but let’s say 8830 rpm. Therefore we spread out our gears with distances of 2080 rpm – thus the difference of 8830 and 6750 – to have an absolute optimum of acceleration.

    Now we should drive our old gear a lot over the power maximum (7750rpm) up to 8830rpm, so that when shifting up our new gear will have equal or better power at the present velocity according to equation (II) and in addition to that the absolute maximum of acceleration for our new gear according to equation (I) is reached as well. That’s the optimum for a drag car!

    But we wanna drive racecars and they must be adjusted to the track, so:

    (_) Setting up a racecar to a track therefore means just take the last gear to reach the highest speed in the maximum of power, take the first gear to the slowest corner and spread out the gears in between equal or maybe in respect to some corners – and don’t care about torque.
    (_) Shifting with that gearbox always will mean that you have to shift up if the new gear will have a better power than your present one and that must be after the maximum of power with your old gear, of course, and anyway if it’s a drag-setup or a track-setup! – Shifting at the absolute maximum of power always means a lack of acceleration.

    But don't forget endurance in longer races:

    I think i will have a bear now, cheers. :beer:

    Attached Files:

  16. Nico Major

    Nico Major
    Premium Member

    Very detailed explanation ZuLuM4tRiX. If these equations are too much for you (like they are for me :) ) just believe him!!! Power is all that counts! Don't think aboute the engine torque. It's meaningless to the driver. The power tells you how much work is done in a certain slice of time and your goal is to get the most power you can get every single moment.

    @Neil: Do you have more of these figures? I was looking for something like that for all the different types of cars we can drive but did not find a single one.
  17. I find it weird that a game like NFS Underground 2 has dyno charts, but GTR Evo does not.
  18. partly correct in that this tool was made as a physics editor for rfactor engine files but rfactor uses a version of Image Space's ISI game engine as does race07/evolution/stcc and it does not use the Lizard game engine as you have stated.
    The fact the app was made for rfactor matters not as we are still using the same type of engine files.
  19. I did start to do one some time back for the GT Evo cars which also included true weight and drag factors but had to stop part way through after they went and changed some cars cars with an update and just never got back to it, but if you want specific data on any one car just pm me.
  20. Well I started off slightly confussed, Now I'm just going to stick my head the sand and hope for the best. I just knew using this MOTEC would just make life a lot harder.