What determines how powerful an engine is?

DeWolf · 2017-08-21T21:45:53.000Z

Electric motors have a power stat and an epower stat, which I presume mean how powerful said motor is and how much electricity it uses respectively. However as far as I have seen in the jsons combustion engines only have an epower stat so I am wondering what determines how powerful an engine is? Also for the engine items I have seen a stat called displacement can someone tell me what that is if you can?

Vollinger · 2017-09-01T10:09:18.000Z

github.com

CleverRaven/Cataclysm-DDA/blob/44310f6bba6e3b60eb3ecbd58859a72e1219ec52/src/vehicle.cpp#L1357


// engines provide, whilst alternators consume.
int vehicle::part_power(int const index, bool const at_full_hp) const
{
if( !part_flag(index, VPFLAG_ENGINE) &&
    !part_flag(index, VPFLAG_ALTERNATOR) ) {
   return 0; // not an engine.
}


const vehicle_part& vp = parts[ index ];


int pwr = vp.base.engine_displacement();
if( pwr == 0 ) {
    pwr = vp.info().power;
}


if (part_info(index).fuel_type == fuel_type_muscle) {
    int pwr_factor = (part_flag(index, "MUSCLE_LEGS") ? 5 : 0) +
                     (part_flag(index, "MUSCLE_ARMS") ? 2 : 0);
    ///\EFFECT_STR increases power produced for MUSCLE_* vehicles
    pwr += int(((g->u).str_cur - 8) * pwr_factor);
}

seems like ‘displacement’ is pretty much ‘power’ stat for combustion engines, with some penalties for damage or engine faults

DeWolf · 2017-09-01T16:41:12.000Z

[quote=“Vollinger, post:2, topic:14158”]https://github.com/CleverRaven/Cataclysm-DDA/blob/44310f6bba6e3b60eb3ecbd58859a72e1219ec52/src/vehicle.cpp#L1357

seems like ‘displacement’ is pretty much ‘power’ stat for combustion engines, with some penalties for damage or engine faults[/quote]
Welp I should have been doing this by now but I guess it’s time for a bit of experimenting.

Coolthulhu · 2017-09-02T07:02:26.000Z

It’s just the displacement.
It determines power, fuel usage, minimum fuel usage (huge engines waste more fuel when idle) and noise.
Power of an engine is equal to its displacement. Fuel usage scales linearly with load on the engine (ie. two engines doing same work will use same amount of fuel energy).

DeWolf · 2017-09-02T07:28:24.000Z

[quote=“Coolthulhu, post:4, topic:14158”]It’s just the displacement.
It determines power, fuel usage, minimum fuel usage (huge engines waste more fuel when idle) and noise.
Power of an engine is equal to its displacement. Fuel usage scales linearly with load on the engine (ie. two engines doing same work will use same amount of fuel energy).[/quote]
Thank you for the more indef explanaition.