Modelling Torque and Torque Converters.

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[Would you like to see this in-game?]
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As far as I’m aware, the current modelling of the drivetrain in game uses 1 power value, this is presumably supplied at all RPM’s?

Ideally, a full torque graph should be used, in the same way jet engines in game have thrust map with speed.

Nearly every engine in game has a known maximum power and maximum torque, therefore every engine has 2 known datapoints, inbetween, estimated data can be used where it is not publicly available, this is the same for jets, and can be corrected if needed for the required performance. The added benefit of this, is that different engine types produce differing torque curves; this adds an extra level of realism to the game, gas turbines will perform differently and show their benefits over diesel engines in certain conditions and vice versa.
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As for torque converters, a similar technique can be used, a torque converter acts as a fluid coupling between the engine and drive. However the lesser known benefit of a torque converter is torque multiplication. This occurs at the “stall point”, when the drive/vehicle is stationary. At this maximum point, torque can instantaneously increase by upwards of 2 times, this gives tanks extra grunt when the engine speed is high relative to the speed of the connecting transmission.
Leopard 2 - 2.5x
Leclerc - 2.3x
Abrams - 2.2x
Challenger 2 - 3.5x

In game, torque converters are replaced by adding extra gears to vehicles, keeping the engines at a roughly constant rpm when accelerating. However these gears are evenly distributed, the effect of a torque converter is only at low speed/early gears, above these low gears the converter is locked. Meaning these additional high speed gears are meaningless anyway.

As with the torque curves, the maximum multiplication effect can be given a default value for all tanks, and changed when public data is able to prove otherwise, or it is needed to achieve verified performance. The multiplication effect decreases to 1X as the engine rpm comes closer to the transmission input rpm. A generic curve can be used to account for this.
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This will give vehicles a more dynamic drive performance, and improve performance in some areas significantly.

3 Likes
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Not to be rude at all, but do you have any proof that it is modeled the way you described?

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Vehicles only have 1 value for power in their files, I don’t see how they can model it any other way.

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My only question is whether power is the same at all rpm’s in game.

5

I’ve tested my M4A3 (76) by starting from 0 km/h at 5th gear using manual transmission mode, and it doesn’t seem to be the case.

At very low speeds, the the time to reach 5 km/h from 0 was higher than, for example, reaching 10 km/h from 5 km/h. This would indicate that, at the very least, some multiplier gets applied to your horsepower depending on engine RPM.

At higher speeds, the opposite effect became true, likely because the increase in horsepower was lower than the increase in terrain resistance, even though I ran the test in a good road in the Cargo Port map.

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That actually makes sense, torque for the same power is lower as rpm increases. I’m actually mildly surprised that’s the case in game too.

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However this equally doesn’t make much sense, since you’re in 5th gear; when starting your engine rpm should be starting from 0 and staying below 1000, producing minimal torque even with a diesel.

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Unless of course, Gaijin models a clutch which allows you to keep your engine at peak, but that should in theory make your acceleration greater as your speed increases.

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I don’t think you quite understood (the way I phrased it was probably confusing).

I specifically said that the acceleration from 5 to 10 km/h was greater than that from 0 to 5 km/h (hence, the time to reach 10 km/h from 5 was shorter than reaching 5 from 0).

So acceleration does seem to increase, at least at low speeds were terrain resistance is minimal. However at higher speeds, it seems that terrain resistance becomes more meaningful the faster the tank goes, so even if there is an increase in horsepower the acceleration still becomes slower.

In short, engine horsepower does seem to fluctuate depending on RPM.

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Ahhh time to reach oops.

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What about at higher speeds, if they modelled a clutch I would imagine in a high gear, acceleration would initially increase as the clutch locked up, and then decrease.

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In my testing the acceleration started go become slower at higher speeds.

I would post the results themselves but I have since deleted them because at the time they were just a quick, interesting test.

However, I will run the tests again and post the results

1 Like
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Interesting, would also be interesting to see what the engine rpm is doing during the acceleration too. I’ll probably do my own testing as well.

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After running a quick test using the M4A3 (76) without add-on armor on the Cargo Port map, these are the times I obtained to reach different speeds in intervals of 5 km/h, with the tank starting from 0 km/h on 5th gear:

Km/h Seconds
5 1.40
10 3.67
15 6.67
20 9.57
25 12.17
30 14.60
35 17.03
40 19.57

Subtracting the times between each “milestone” speed gives us the time it took to go from one speed to another, giving us this table.

Km/h Seconds
0-5 1.40
5-10 2.27
10-15 3.00
15-20 2.90
20-25 2.60
25-30 2.43
30-35 2.43
35-40 2.53

I have to say, the results are not what I expected, nor what I said at the start. I can blame my memory on that one because I was purely remembering what I thought the results were as I didn’t have access to them.

It’s possible that engines follow a very basic “torque curve”, where a multiplier is applied to the horsepower. My guess is that peak acceleration in every gear is achieved at around 65% to 75% of the engine’s RPM.

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I’ll work on a theory when I get back based on this data.

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So i did some testing with the CR2 in 8th gear. So it sets off at idle/neutral rpm(600), and slowly increases.

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So it seems like a clutch system is used until the engine hits its idle rev count, where it then direct drives all the way to max rpm.

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I’ll see if i can do some timings for that

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0-5: 1.63s
5-10: 2.77s
10-15: 3.87s
15-20: 3.8s
20-25: 3.97s
25-30: 3.44s
30-35: 3.3s
35-40: 2.97s
40-45: 3.07s
45-50: 3.07s
50-55: 3.33s
55-59: 2.73s
55-60: 3.41s interpolated

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