The Torque Thread. And other little things you might find useful...

Discussion in 'GT6 Tuning' started by yannagas, Mar 7, 2014.

  1. Otaliema

    Otaliema

    Messages:
    5,489
    Location:
    United States
    @whitepanther65 to kill wheel spin using a transmission you might try a reversed first gear.
    Make second as long as it will go, now start making first shorter do t worry about spacing here. You after a result not a set up.
    Then set 5th and 6th gears as short as they will go, use third to bring fourth to nice middle point to fifth adjust it as well if needed. This will not give you a nice spaced transmission but it will give you a effective transmission that has low/no wheel spin in second, good acceleration in 3,4 gears and the pull to get high speed in 5,6 gears. First gear is just there it will never get used
     
    MrGrado likes this.
  2. whitepanther65

    whitepanther65

    Messages:
    14
    Thanks Lionheart, but the problem is that I don't understand the "slider" logic. So for the moment I will not use it....
     
  3. whitepanther65

    whitepanther65

    Messages:
    14
    I am not following anymore you Otaliema here. You say the solution is to "kill" the first gear by never using it and obtain a 5 gears instead of 6 gears box? If I understood correctly this is a very, very bad solution imo. It simply kills the motor: having more gears is obviously better.

    I still don't have an answer to my question, but I keep on trying. Up to now, I have concluded that in order to know the relationship between accelerating force after and before gear change you should look at the power vs RPM curve, not the torque curve. That's already something.
     
    Otaliema likes this.
  4. OdeFinn

    OdeFinn

    Messages:
    2,643
    Location:
    Finland
    If your transmission allows you to run high rpm always (on peak hp) and you'll get all parts of track/turns covered by that way, then it's fine. Often you're facing places where your transmission will drop rpm under effective range during cornering and making you change gear while in corner, what is not good idea, you might want to setup your gears longer. And then comes that place where you need bigger rpm range to been used for gear, often lowest well operating rpm value is close to point where torque and hp are closest each other.

    You should go and read this http://www.ls1gto.com/forums/showthread.php?t=334833
    After that check again Otaliema transmission thread.

    Joke, close to truth and reality:
    Torque kicks mass on move, horse powers them pull more when mass is already moving.
    Torque= body builder
    Horse power= long distance runner
     
    Last edited: Apr 15, 2016
    Otaliema likes this.
  5. eran0004

    eran0004

    Messages:
    8,603
    Well, torque kicks mass on move, but power tells you how fast it's done. Little torque and high power kicks mass on move faster than lots of torque and little power.

    Say that we have two body builders, A and B. They're equally strong (same torque). Now we give them an assignment: "Inside that house there are 200 chairs. Take 100 each and carry them out here on the lawn."

    They get to work, and as they're both equally strong each of them can carry just as much as the other. They can take 20 chairs each per run, so they will both have to complete 5 runs to carry all of the chairs out on the lawn.

    So far so good, but although they both carry the same weight, body builder A is able to run slightly faster than body builder B, so he got all his 100 chairs out on the lawn faster than body builder B. They both performed the same amount of work: carrying 100 chairs from the house to the lawn, but since body builder A did it faster than body builder B, body builder A produced more power than body builder B.

    Body builder B is upset about this and wants a new match. This time he'll surely win, because now he's facing a new opponent, body builder C, who is only half as strong as him.

    They get the same task and get to work. Body builder B can still take 20 chairs per run, while body builder C can only take half of that, 10 chairs. Body builder B is convinced that it's going to be a walk in the park, but lo and behold! Body builder C, although he's only half as strong as body builder B, can run more than twice as fast between the lawn and the house! By the time body builder B reaches the lawn with his first batch of chairs, body builder C has already started on his third run! In the end, body builder C wins this race and body builder B is humiliated!

    "Racing is boring", says body builder B, "can't we just admire my muscles instead?"
     
    OdeFinn, Ridox2JZGTE and Otaliema like this.
  6. OdeFinn

    OdeFinn

    Messages:
    2,643
    Location:
    Finland
    @eran0004 or quicker exemple:
    Body builder can push heavy wagon on move but doesn't have stamina to run and push it on high running speed, but when mass of wagon is already moving it's easy for skinny fast runner to keep it rolling and increase slowly speed of moving mass. Faster it goes easier it is to push, till certain point..
     
  7. Otaliema

    Otaliema

    Messages:
    5,489
    Location:
    United States
    If your dealing with a car that keeps spinning its wheels in first gear don't use it and make second gear the new first gear, the ratio and torque/power makes up for the long gear. The fastest time between two points is not always the highest speed. If over 200m first gear spins the tires for 100m than grips and hits 120 km/h and second gear spins the tires for 50m and hits 110 km/h, it will get there just a head of first because of grip difference.
    Horse power=sales gimmick. It's an arbitrary number that was guessed at a hundred years ago and has never been changed.
    The ONLY measurable numbers on a engine is torque and RPM.
    Where the engine makes its peak torque, total RPM and when the torque falls flat.
    Example the engine makes 252 ftlbs at 2800 rpm it makes 134.3 hp
    Let's say it keep that torque until 5000 rpm it makes 239.9 hp. Let's say the engine red lines at 8000 rpm but looses 60% of its torque by that point so at 8000 rpm it's making 100.8 ftlbs of torque and 153.4 hp so that engine it making more power at 40% of its max torque than at the start of its power band.
     
  8. eran0004

    eran0004

    Messages:
    8,603
    If the body builder is torque and the skinny runner is power we've got a problem, because the body builder is a part of the skinny runner, as torque is a part of power. It's better think of both of them as an engine, and say that both have torque and power. The body builder is strong (high torque), but not running very fast, which gives him kind of medium power (high torque * low speed). The skinny runner is weak (low torque) but fast, which also gives him medium power (low torque * high speed). All the skinny runner needs, to be able to accelerate as fast as the body builder, is shorter gears, so that his high speed becomes the same as the the body builder's low speed. Same power delivered at the same speed = same torque. And all the body builder needs, to be able to reach the same speed as the skinny runner, is taller gears, which in turn would reduce his torque.

    The unit horse power may be a sales gimmick (which might be why the SI unit is Watts rather than horsepower), but what it's measuring isn't. In fact, power is the only meaningful measurement of the performance of an engine, because it measures the rate at which it produces work. Torque alone doesn't really mean anything, saying "my car produces 200 Nm of torque" is about as meaningful as saying that "my supercar can do 300 kilometers" without specifying how long it would take for the car to drive those 300 kilometers. Does it take an hour? Two hours? Half an hour? The time is a vital piece of information here, just as the engine speed is when we're talking about performance.

    The confusion surrounding power and torque probably stems from the fact that high torque cars often are better at drag racing, so a lot of times the conclusion is that torque is good for acceleration and power is good for... something else. Speed perhaps?

    When in fact, the reason why high torque cars so often are better at drag racing is because the high torque (which often is delivered at a relatively low rpm) gives them a more favourable power curve. Early on in the drag race they'll produce more power, and because of that they're able to perform work at a faster rate. That is what gives them the edge.
     
    Lilium, Sharpie, Scaff and 2 others like this.
  9. OdeFinn

    OdeFinn

    Messages:
    2,643
    Location:
    Finland
    @eran0004 yep, you're right on your examples, but you forget mention one thing, what is actual torque on wheels.
    I.e. If 5000rpm gives 100hp/100Nm and 7500rpm gives 150hp/66.7Nm actual torque on wheels is identical at same gear on both cases.
    Erf.. Actually.. Getting back soon.. Working and writing same time is hard.. But yes didn't make mistake on above, checked what typed.. Lol
     
    Last edited: Apr 15, 2016
    Otaliema likes this.
  10. Otaliema

    Otaliema

    Messages:
    5,489
    Location:
    United States
    Very true but over long straights the 150/66.7 will do better as it will consistently get to higher speeds as each rpm is doing less work so the engine can pull more.
    Power configuration should be based on the track in ideal situations anyways. The 100/100 will accelerate hard but die off at speed while the 150/66.7 will accelerate steady all the way past the 100/100 set up to another 15-30 km/h prolly. After a certain distance anyways.
     
  11. eran0004

    eran0004

    Messages:
    8,603
    It's easier to get the maths right if we work with SI units, because then there's no need to convert the values:

    So let's change from rpm to radians per second, so that 5000 rpm is approximately 500 rad/s, and 7500 rpm approximately 750 rad/s.

    Then we get:

    100Nm * 500 rad/s = 50 kW

    And in the second case:

    66.7Nm * 750 rad/s = 50 kW

    So the power is the same in both cases, there would not be a 50% increase in power. It would be if the torque remained the same, like this:

    100Nm * 750 rad/s = 75 kW
     
    Otaliema and OdeFinn like this.
  12. OdeFinn

    OdeFinn

    Messages:
    2,643
    Location:
    Finland
    @eran0004 my multitasking capacities are limited, equal power on wheels. :)
     
    Otaliema and eran0004 like this.
  13. whitepanther65

    whitepanther65

    Messages:
    14
    When you shift, the ratio between the accelerating force before and after the shift is given by the ratio of the powers corresponding to RPMs before and after the shift. After shift, the accelerating force follows the torque curve. Don't know what much else there is to say, frankly. And, Otaliema, thanks but renouncing to a gear still looks like a bad idea to me.
     
    Otaliema likes this.
  14. Otaliema

    Otaliema

    Messages:
    5,489
    Location:
    United States
    Skipping a gear is best when you can't control wheel spin only. Cars with that much power don't notice :lol:
     
  15. MrGrado

    MrGrado

    Messages:
    1,198
    This is exactly how to tune a gearbox. There is not enough adjustment available to use all 6 gears effectively on a 6 speed gearbox. If you adjust the transmission so the car works well in first gear for low speed turns, you will not be able to get the tune in to high enough RPM in sixth gear, generally speaking.
     
    Otaliema likes this.
  16. fordracer

    fordracer

    Messages:
    491
    A couple of things I would like to interject here.....
    1). Horsepower is a theoretical figure based ON torque and RPM. There is no way to measure horsepower. You measure the torque and plug it into a formula.

    2) There IS a torque multiplication factor in gears. Both rear end gears and transmission gears. Using rear end gears as an example, you will get more torque to the ground with a 4:11 than you will with a 3:42. 15% more if I remember correctly. Same with a transmission. I HAVE seen this on a semi truck chassis dyno. So, @Otaliema's idea is not so far fetched. I prefer to move 1st higher and stretch the top out. I also do not believe more gears is better, you can spend all your time shifting. Depends on the car.
     
    Otaliema and OdeFinn like this.
  17. OdeFinn

    OdeFinn

    Messages:
    2,643
    Location:
    Finland
    @fordracer understand your point, then comes car/driver/track needs, should you focus on maximum pull on some gear, i.e. 4th, 5th or 6th, like doing transmission, or just picking right final drive for Nordschleife to get maximal pull on 5th gear in uphill part, sometimes just correct final will do job and gear spread can be untouched.
    Often you will find people discussing maximum ratio of gearbox, i.e. 0.78 and stuff like that, several claims around it, and what final suits with it..
    Few things why "short" final (bigger number) is good of its purpose, when you loose traction, resistance from tires disappear and engine revs quickly to maximum revs, wheels spins relatively high speed, but much slower what would happen if same situation comes on "long" (smaller number) final drive. Difference of tire spinning speed on i.e. Rev area 5500-7500 on both finals i.e. 2.000 vs 4.000 is double speed free spin on tire, gaining traction again from slower spin if definitely easier.
    But best final drive allows you to use moderate throttle even on cornering and on case of traction loss it's measured in way what gives you good change to recover it.
    Again back to long final, when high speed spinning wheel finally or suddenly grabs traction there is few "problems", either it grabs suddenly(high compounds) and giving snap back because your engine isn't giving proper/enough torque there and tires stall on tarmac. Or on lower compounds it leaves you sliding around because your throttle control have to be way more precise than on shorter final, same amount of throttle on long final spins tires faster than on short final, matching tire speed on cars body speed is way harder on long final.

    Then determining what is long and what is short and where is perfect final is from several things, car mass, amount of power/torque on engine, used compound and LSD locking rate and most important, drivers driving style. (That torque multiplication is thing what should be counted twice, between engine and gearbox, and gearbox and final gear, it makes difference where that total multiplication comes)

    Mathematically you can use any final or gear ratio making total ratio same, that's true until traction starts to break.
     
    Otaliema likes this.