Engines

Vehicle engines work. The vehicle model is fairly sophisticated, and complicated, but is reasonably understandable.

Engines

Engines produce power, drain electrical energy, and consume fuel based on their overall size, with larger engines consuming more fuel and producing more power.

Table of engines

name	epower (W)	cruising power (kW)	power (kW)	consumption (kW)	fuel type
foot crank	0	1.6 + 0.14 * (ST - 8)	64 + 5 * (ST - 8)	N/A	muscle
set of hand rims	0	0.8 + 0.05 * (ST - 8)	32 + 2 * (ST - 8)	N/A	muscle
small 1-cylinder engine	0	2.2	3.7	9.3	gasoline
1-cylinder engine	0	4.4	7.4	18.4	gasoline
V-twin engine	-50	22.4	37.3	124.5	gasoline
Inline-4 engine	-150	55.9	93.2	311	gasoline
V6 engine	-200	89.5	149.2	497.5	gasoline
V8 engine	-250	145.3	242.2	808.2	gasoline
V12 engine	-350	268.6	447.6	1492	gasoline
tiny electric motor	-1,750	1.3	1.5	battery
small electric motor	-8,500	6.7	7.4	battery
electric motor	-41,500	33.57	37.3	battery
large electric motor	-160,000	134.3	149.2	battery
enhanced electric motor	-207,250	167.9	186.5	battery
V6 diesel engine	-250	97	149.2	373	diesel
I6 diesel engine	-350	145.5	223.8	559.5	diesel
V8 diesel engine	-350	157.4	242.2	606.3	diesel
V12 diesel engine	-400	290.9	447.6	1119	diesel
makeshift steam engine	0	36.4	55.9	112	coal
small steam engine	0	60.6	93.3	186.5	coal
medium steam engine	0	97	149.2	298.5	coal
bicycle alternator	36	-0.1	0.1	0.1	-
motorbike alternator	360	-0.7	-0.7	-0.7	-
car alternator	780	-1.5	-1.5	-1.5	-
truck alternator	1,320	-2.2	-2.2	-2.2	-
7.5kW generator	7,500	-10.4	-10.4	-10.4	-
minireactor	149,200	0	0	variable	plutonium cell
solar panel	50	0	0	0	sunlight
upgraded solar panel	100	0	0	0	sunlight
quantum solar panel	300	0	0	0	sunlight

• epower is electrical power in watts, with negative values meaning the engine drains power.
• cruising power and power are effective power in kW. Cruising power already takes into account the effective cruising power multiplier by engine type mentioned above.

A vehicle's safe cruising speed is proportional to the sum of the cruising power of its engines. Cruising power is displacement multiplied by a fixed value by engine type:

Engine Type	Cruising Power Factor
Muscle	45
Gasoline	60
Diesel	65
Steam	65
Electric	90

A vehicle's maximum speed is proportional to the sum of the power of its engines.

In both cases, a vehicle with multiple engines reduces effective engine power by 4 / (3 + engine count), like so:

Engine Count	Effective Power	Gain for additional identical engines
1	100%	+0%
2	80%	+60%
3	66%	+100%
4	57%	+129%
5	50%	+150%
6	44%	+166%
7	40%	+180%
8	36%	+190%

It is possible to reduce total effective available power by engaging a smaller engine: any additional that produces 25% power of the largest engine or less is an absolute loss in terms of effective power.

Total effective safe engine and maximum power are displayed next to the "Engines" line in the middle column of the display when examining a vehicle.

Safe and Maximum Velocity

For both safe and maximum velocity, the effective engine power is compared to the vehicle's aerodynamic drag force and rolling resistance force. Lighter vehicles vehicles go faster than heavier vehicles for the same engine power. More aerodynamic vehicles go faster than less aerodynamic vehicles for the same engine power. Vehicles with fewer wheels go faster for the same engine power than vehicles with many wheels. Vehicles with treads go much slower than vehicles with wheels for the same engine power. Vehicles always go faster with more engine power, but more engine power increases fuel consumption.

A vehicle's effective motive force is safe or maximum engine power (in Watts) divided by current velocity (in meters/second). Motive force is reduced by aerodynamic drag force and rolling resistance force. When the sum of aerodynamic drag force and rolling resistance force is equal to the motive force, the vehicle cannot accelerate any further and it reaches its safe velocity or maximum velocity. Prior to that velocity, the remaining force is divided by vehicle mass in kilograms to get acceleration in meters/second per second.

Aerodynamic Drag

Aerodynamic drag force has a large effect on reducing vehicle speed, and that effect increases exponentially as the vehicle goes faster. The following factors increase a vehicle's aerodynamic drag and reduce maximum speed:

• Wider vehicles have more aerodynamic drag.
• Taller vehicles have more aerodynamic drag. Aisles and full boards increase vehicle height a lot, while roofs, turrets, floodlights, and solar panels increase vehicle height a little. Stowboards count as fullboards and floor trunks count as aisles.
• Exposed drivers and passengers increase aerodynamic drag. Passengers are considered exposed if there isn't a roof over their head and doors, full-boards, or windshields surrounding them.
• Not having an aerodynamic profile increases drag. The ideal profile starts with quarterpanels, followed by a windshield, followed by a passenger compartment with a roof, and is more than twice as long as it is wide.
• Turrets increase aerodynamic drag.

In all cases, length refers to the the size of the vehicle in the direction of forward motion, and width refers to the size at 90 degrees to the length. Because CDDA has a "top down" view, height is inferred and not displayed.

Rolling Resistance

Rolling resistance has less of an effect on reducing vehicle speed than aerodynamic drag, and that effect increases linearly as velocity increases. The following factors increase a vehicle's rolling resistance:

• Small wheels increase rolling resistance.
• More wheels increase rolling resistance.
• Treads dramatically increase rolling resistance.
• Vehicle weight largely determines rolling resistance, so heavy vehicles have much more rolling resistance than light vehicles.

Best Acceleration

A vehicle's best acceleration is the highest of the vehicle's acceleration at its highest speed or its acceleration at 1/4th its maximum velocity.

Fuel Consumption

Every time a vehicle accelerates, engine Strain is calculated as actual acceleration divided by maximum acceleration. Engine strain times engine fuel consumption for 1 second produces the amount of energy required to produce that acceleration. The vehicle then burns enough fuel (by volume) to produce that much energy.

Approximations of vehicle fuel consumption rates are displayed in the vehicle interaction menu for each fuel type. These approximations are very rough and are only accurate if the vehicle is travelling on pavement at safe velocity. Especially in low fuel situations, its important to monitor the actual fuel consumption rate.

Alternators

Alternators are treated as though they were engines that consume power and produce electrical energy.

Solar panels

Solar panels produce electricity when the weather is sunny, clear, or cloudy. Solar panel energy production was severely reduced from previous version, and vehicles powered solely by solar panel need to be very lightweight and slow or only used infrequently. The solar car, made entirely of extra light frames with 13 upgraded solar panels and two electric motors only produces 10% of the necessary epower.

Previous Versions

Guide created using an unknown version of Cataclysm DDA.
The information present here does not apply to the current version of CDDA.

“ [09:52] <cib0> Man the vehicle code is a complete mess. ”

Ultimately engines work, but teasing out the specifics of how they work isn't easy. Here are some basic understandings of how engines work in vehicles. There aren't details on things like how power works with weight, fuel efficiency, top speed, and acceleration because those things simply aren't apparent. (At least, to me!)

Engine details

• epower is the drain on a vehicle's energy stored in batteries
  • This represents the minor power needs in combustion engines for spark plugs as well as direct fuel in electric engines
• power is how much true power an engine generates to turn wheels or alternators; this shows for electric engines in the vehicle window, but not for gas or diesel
• Electric engines have a "fuel usage" but that is ignored for their epower use
• Gasoline and diesel engines spawn in a range of liter sizes, this liter size is multiplied by 100 to get their power
  • 0.53L 1 cylinder engine has 53 power
  • 12.43L V12 has 1243 power
• Power for variable size engines is listed with the min and max as well as an average to compare against the fixed power engines
• Fuel use is tied directly to power, it is power divided by 100, with 1 minimum and rounded down otherwise
  • 0.53L 1 cylinder engine is fuel use 1 because 53/100=0.53
  • 12.43L V12 is fuel use 12 because 1243/100=12.43
• Muscle power engines have their output adjusted by a factor of 5 for pedals and 3 for hand rims, based on strength
• The minireactor is the only engine that generates battery power without alternators
• Durability and damage mod determine how the components take damage in the vehicle

Table of engines

name	damage modifier	durability	epower	power	min power	max power	fuel type	fuel usage
small electric motor	80	120	-6000	15	15	15	battery	1
electric motor	80	200	-29000	70	70	70	battery	1
enhanced electric motor	80	200	-160000	400	400	400	battery	4
large electric motor	80	400	-137000	350	350	350	battery	3
V6 diesel engine	80	400	-200	500	400	600	diesel	5
I6 diesel engine	80	400	-400	600	500	700	diesel	6
V8 diesel engine	80	400	-300	700	600	800	diesel	7
V12 diesel engine	80	600	-400	???	???	???	diesel	12?
small 1-cylinder engine	80	120	0	33.5	22	45	gasoline	1
1-cylinder engine	80	150	0	55	35	75	gasoline	1
V-twin engine	80	200	-50	112.5	75	150	gasoline	1
Inline-4 engine	80	300	-100	225	150	300	gasoline	2
V6 engine	80	400	-150	400	300	500	gasoline	4
V8 engine	80	400	-200	650	500	800	gasoline	6
V12 engine	80	600	-350	1200	800	1600	gasoline	12
foot crank	50	50	0	45	45	45	muscle	-
set of hand rims	50	50	0	32	32	32	muscle	-
minireactor	80	580	149200	100	100	100	plutonium cell	-

Engines in 0.D (Danny)

The vehicle code has been significantly cleaned up in 0.D (Danny). Engines no longer spawn with variable size: a V8 diesel is the same size as every other V8 diesel. Engines produce power, drain electrical energy, and consume fuel based on their overall size, with larger engines consuming more fuel and producing more power.

A vehicle's safe cruising speed is proportional to the sum of the cruising power of its engines. Cruising power is displacement multiplied by a fixed value by engine type:

Engine Type	Cruising Power Factor
Muscle	45
Gasoline	60
Diesel	65
Electric	90

A vehicle's maximum speed is proportional to the sum of the power of its engines.

In both cases, a vehicle with multiple engines reduces effective engine power by 4 / (3 + engine count), like so:

Engine Count	Effective Power	Gain for additional identical engines
1	100%	+0%
2	80%	+60%
3	66%	+100%
4	57%	+129%
5	50%	+150%
6	44%	+166%
7	40%	+180%
8	36%	+190%

It is possible to reduce total effective available power by engaging a smaller engine: any additional that produces 25% power of the largest engine or less is an absolute loss in terms of effective power.

Total effective safe engine and maximum power are displayed next to the "Engines" line in the middle column of the display when examining a vehicle.

For both safe and maximum velocity, the effective engine power is compared to the vehicle's aerodynamic drag and rolling resistance. Lighter vehicles vehicles go faster than heavier vehicles for the same engine power. More aerodynamic vehicles go faster than less aerodynamic vehicles for the same engine power. Vehicles with fewer wheels go faster for the same engine power than vehicles with many wheels. Vehicles with treads go much slower than vehicles with wheels for the same engine power. Vehicles always go faster with more engine power, but more engine power increases fuel consumption.

Aerodynamic Drag

Aerodynamic drag has a large effect on reducing vehicle speed. The following factors increase a vehicle's aerodynamic drag and reduce maximum speed:

• Wider vehicles have more aerodynamic drag.
• Taller vehicles have more aerodynamic drag. Aisles and full boards increase vehicle height a lot, while roofs, turrets, floodlights, and solar panels increase vehicle height a little. Stowboards count as fullboards and floor trunks count as aisles.
• Exposed drivers and passengers increase aerodynamic drag. Passengers are considered exposed if there isn't a roof over their head and doors, full-boards, or windshields surrounding them.
• Not having an aerodynamic profile increases drag. The ideal profile starts with quarterpanels, followed by a windshield, followed by a passenger compartment with a roof, and is more than twice as long as it is wide.
• Turrets increase aerodynamic drag.

Rolling Resistance

Rolling resistance has less of an effect on reducing vehicle speed than aerodynamic drive. The following factors increase a vehicle's rolling resistance:

• Small wheels increase rolling resistance.
• More wheels increase rolling resistance.
• Treads dramatically increase rolling resistance.
• Vehicle weight largely determines rolling resistance, so heavy vehicles have much more rolling resistance than light vehicles.

Alternators in 0.D (Danny)

Alternators are treated as though they were engines that consume power and produce electrical energy.

Solar panels in 0.D (Danny)

Solar panels produce electricity when the weather is sunny, clear, or cloudy. Solar panel energy production was severely reduced from previous version, and vehicles powered solely by solar panel need to be very lightweight and slow or only used infrequently. The solar car, made entirely of extra light frames with 13 upgraded solar panels and two electric motors only produces 10% of the necessary epower.

Table of engines

name	epower (W)	cruising power (kW)	power (kW)	fuel type
foot crank	0	1.6 + 0.14 * (ST - 8)	64 + 5 * (ST - 8)	muscle
set of hand rims	0	0.8 + 0.05 * (ST - 8)	32 + 2 * (ST - 8)	muscle
small 1-cylinder engine	0	2.2	3.7	gasoline
1-cylinder engine	0	4.4	7.4	gasoline
V-twin engine	-50	22.4	37.3	gasoline
Inline-4 engine	-150	55.9	93.2	gasoline
V6 engine	-200	89.5	149.2	gasoline
V8 engine	-250	145.3	242.2	gasoline
V12 engine	-350	268.6	447.6	gasoline
tiny electric motor	-1,750	1.3	1.5	battery
small electric motor	-8,500	6.7	7.4	battery
electric motor	-41,500	33.57	37.3	battery
large electric motor	-160,000	134.3	149.2	battery
enhanced electric motor	-207,250	167.9	186.5	battery
V6 diesel engine	-250	97	149.2	diesel
I6 diesel engine	-350	145.5	223.8	diesel
V8 diesel engine	-350	157.4	242.2	diesel
V12 diesel engine	-400	290.9	447.6	diesel
bicycle alternator	36	-0.1	0.1	-
motorbike alternator	360	-0.7	-0.7	-
car alternator	780	-1.5	-1.5	-
truck alternator	1,320	-2.2	-2.2	-
7.5kW generator	7,500	-10.4	-10.4	-
minireactor	149,200	100	100	plutonium cell
solar panel	50	0	0	sunlight
upgraded solar panel	100	0	0	sunlight
quantum solar panel	300	0	0	sunlight

• epower is electrical power in watts, with negative values meaning the engine drains power.
• cruising power and power are effective power in kW. Cruising power already takes into account the effective cruising power multiplier by engine type mentioned above.