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Way to manually input horsepower instead of just torque?

Discussion in 'Content Creation' started by LionsTheBoss, May 25, 2020.

  1. LionsTheBoss

    LionsTheBoss
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    I'm wondering if you can manually input horsepower as well as the torque in the jbeam files. Low displacement engines with super aggressive cams don't put out these high torque numbers needed to get the realistic hp numbers.

    Any help is greatly appreciated!
     
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  2. Diamondback

    Diamondback
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    BeamNG Team

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    Hey,

    what you ask for is not possible, power is a function of torque, if a certain engine makes power X at rpm Y it WILL make torque Z at that rpm.
    This is because Power = Torque x RPM (using the correct SI units).
     
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  3. Vehicular Bonanza!?

    Vehicular Bonanza!?
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    To demonstrate with a real world example taken from the car I'm concerned myself with right now, the following torque/power curve is taken from the owner's manual


    Curve 1 is power, curve 2 is torque (ignore 3, that's supposed to be fuel consumption but I don't understand the unit). Power is measured in k (stands for "konská síla" which means horsepower), therefore we need to multiply all values in the right column by about factor of 0.7. Torque is measured in kpm = 9.81 Nm (I googled this - it's the analogue to the american foot pounds, where the force is treated like a weight it corresponds to on the surface of the earth rather than a proper force). The x-axis is measured in ot/min (stands for "otáčky za minutu" and it means revolutions per minute), to convert to radians per second (SI unit of angular velocity) we multiply by pi/30.

    So when I take e.g. power @3000 rpm (314.16 rad/s), that's 38 hp = 28.34 kW. According to the torque curve, we get 9 kpm = 88.3 Nm, which gives us power of 27737 W, or 27.7 kW, pretty close to 28.34 kW.

    So apart from the batshit crazy units car engineers came up with and we have to be careful about them, power = torque * omega. You can set one or the other, but not both independently.
     
  4. rottenfitzy

    rottenfitzy
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    Close. Power is -imperially- (torque x rpm)/5252.

    Metrically, it is KW= NM /~9.2.


    As you can see, there is no need for any separate horsepower input because it is already a function of torque. Torque is work, and horsepower is work divided by time, which can be done with the RPMs of the engine.
     
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  5. Vehicular Bonanza!?

    Vehicular Bonanza!?
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    I don't see how this is the case. A car that has a torque of 80 Nm at 1000 rpm has a power of 8.4 kW. A torque of 72 Nm at 5000 rpm gives 37.7 kW. In no way kW is a constant multiple of Nm (where does the conversion factor of 9.2 come from?).
     
  6. Diamondback

    Diamondback
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    Sorry, but no. Power is the product of torque and angular velocity, if you use the correct SI units for both (power ist W or J/s, angular velocity is rad/s) then you end up with Power = Torque x AV, or in unit terms [W] = [Nm] x [rad/s]
     
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  7. Davazz

    Davazz
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    Power = torque x rotational speed, irrespective of units.

    In freedom units you generally use something like [lbf*ft/s] = [lbf*ft] x [1/s], and in metric units you use [W] = [Nm] x [rad/s]

    Horsepower = torque x rpm / 5252 when using the imperial system in pound-foot units.
     
  8. burilkovdeni

    burilkovdeni
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    OK, how make an engine with 300 torque and 100 hp then?

    AKA most USA V8's form 1970'-1990's.
     
  9. Vehicular Bonanza!?

    Vehicular Bonanza!?
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    If your torque value is in Nm, then we get 300Nm*omega(rad/s) = 100hp*0.747(kW/hp)*1000, from which omega = 248.567 rad/s, i.e. 2373.64 rev/minute. Totally plausible, if you'd ask me...

    If the torque is in ft-lbs, that is 406.754 Nm we get omega = 1750.71 rev/minute instead. Still plausible...
     
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