Cogito, ergo sum


From Unreal Wiki, The Unreal Engine Documentation Site
Jump to: navigation, search

Each piece of a real vehicle and how their function can be simulated in Unreal.

  • Applies to ALL vehicle types!
  • For clarity, the Real and Unreal have separate subSections. (No pun intended!)
  • The more facts that are listed for a single device, the more valuable that information becomes.
  • Don't worry too much about documenting items in the correct section.

Related Classes[edit]

Vehicle Anatomy[edit]

Basically, this section exists to help people understand and code realism into their vehicle.

tup: If any 'factoids' can be better summarized with an equation, please edit them freely. Just make sure others will know what the equation is for.


Supplies the power needed for the vehicle to function.

An internal combustion engine used in many vehicles today.
Compresses at a ratio of 8
  • 1 to 12:1.
An internal combustion engine.
  • Better power efficiency then a car engine due to a higher compression ratio of 14:1 to as high as 25:1.
  • 2 Stroke Diesel: Can be found in many diesel locomotives, large ships, and generating facilities.
    • Horsepower typically rates at 4,300!
  • Slower and fewer moving parts makes a more reliable engine.
  • Produces little if any vibrations.
  • Produces 3x the power of standard cylinder engines. (This may not be accurate: my source ( says smoother power not more power?!?)
  • Low air/fuel compression ratio
    • Uses more fuel.
    • Typically not environmentally friendly.
Gas Turbine
Also known as the "Jet Engine" because you see them on nearly all jets.
  • You can find them on many jets, some helicopters, small power plants, and even the M-1 Tank!
  • Typically creates ~1,500 horsepower.
  • The amount of power generated is very good, compared to their weight.
  • Smaller than their reciprocating (Cylinder, Rotary, etc) counterparts of the same power.
  • They tend to use more fuel when they are idling.
  • Variations:
    • Used for large Jetliners, the engine is housed inside another cylinder shape casing with a larger fan in front. This is done to improve thrust by dramatically increasing the amount of air moving through the engine.
    • Turboprop: Similar to a turbofan, a slower-moving propeller is used instead of a fan.
Pistons are arranged in a radial fashion, perpendicular to the 'main rod' that powers the pistons.
  • ~1,200 horsepower.
  • With their inherit low RPM, they can directly power airplane propellers.
  • Today, you can still see a 2 cylinder version in many motorcycles.
Generally... Water is broiled to produce steam. This steam is diverted to alternating side of a piston to produce a usable force.
An extremely efficient engine that uses the natural changes in pressure (due to rapid temp changes) to alternate motion between two pistons.
  • Has no standard design.
  • Needs external Heating and Cooling sources.
  • No combustion takes place inside.
    • No Explosions.
    • No intake or exhaust.
Fire once/2 revolutions.
  • Orientation - May have problems with oil flow unless upright. Solving this problem can add complexity and weight to the engine.
Fire once/revolution, twice more than their 4-Stroke equilivants.
Can be found in
  • Dirt bikes, Mopeds, Jet skis, Small outboard motors, and Radio-controlled model planes.
  • Works correctly in any orientation.
  • No valves (ie: lighter and simpler engines).
  • 2x better power/weight ratio than 4-Stroke equivalent.
  • Not as reliable, lacking any dedicated lubrication system.
  • Not fuel efficient!
  • Produces a lot of pollution.
A reaction system is used for propulsion.
  • The action is to throw some mass in one direction, the reaction is to move in the opposite direction.
  • Typical rocket exhaust velocities for chemical rockets range between 5,000 and 10,000 mph!
  • Must carry everything it expels for thrust (ie: fuel).
  • Solid-Propellant Rockets:
    • Thrust cannot be controlled.
    • Once ignited, the engine cannot be stopped or restarted.
Liquid-Propellant Rockets
  • Fuel and an oxidizer are pumped into a combustion chamber, burned, and the resulting high-pressure gases are expelled at high-velocities. These gases flow through a nozzle that accelerates them even faster.
    • Typical exit-velocities run from 5,000 to 10,000 mph!


  • HEMI Engines
  • NASCAR Engines
  • Champ Car Engines


Allows the gear ratio between the engine and the drive wheels to change as the car speeds up and slows down.

Manual Transmission
Gears are shifted manually by the driver.
Temporary connects the engine to the transmission, as long as the 'gas' peddle is being pressed. This enables the wheels to slow down and completely stop while the engine is still running.
Automatic Transmissions
Gears are shifted automatically.
Torque Converters
Has the same function as a clutch, for Automatic Transmission vehicles.

Drive Train[edit]

Uses leverage, hydraulics, and friction to apply friction to the wheels.
Break Types
  • Drum, Disc, Power, and Anti-Lock.
      • Vehicles in UT'04 (and previous) do not have the anti-lock ability.
Enables the car to pull itself on land.
  • If water can't escape from under the tire quickly enough, the tire will lift off the ground and be supported by only the water. Because the wheels will have nearly zero traction. The vehicle is likely to veer out of control.
  • Coefficient of Rolling Friction: A measurement of how much drag (or rolling resistance) is caused from the rolling wheels.
Force needed to move on Wheels
    • Force Applied (F App) == Weight * (Coefficient of Rolling Friction)
Various Coefficients of Rolling Friction
Low rolling resistance car tire 0.006 - 0.01
Ordinary car tire 0.015
Truck tire 0.006 - 0.01
Train Wheel 0.001
Source Information


'Cheesy' as it may (or may not) seem, these things could be simulated for that extra 'coolness' factor :cool:.

Cruise Control Systems
Allows a vehicle to maintain its speed without user interaction.
  • Disengages when the break peddle is used.
  • Adaptive Cruise Control - This new feature will adjust vehicle speed to adapt to traffic ahead. When the road is again clear, the cruise control will gradually return to its original set speed.
Fuel, oil, temp, etc...
Keeps track of the distance driven (in miles or kilometers).
Door Locks
Keeps others from entering, :rolleyes: duh.
Remote Entry
  • Lock/Unlock your vehicle from a distance.
Player in Vehicle + Gun + Window + Enemy... You do the math.
Compresses the air-intake before it enters the engine. This enables the engine squeeze more air into a cylinder, meaning that more fuel can be added. Therefore, you significantly improve the power-to-weight ratio for the engine.
  • Overuse may result in "Knock". In such a situation, the temperature is hot enough to ignite the fuel before the spark plug fires! This is caused by an accumulation of heat do to the continuous over-compression of air.
  • Turbo Lag: It takes a second for the turbine to get up to speed before any boost is produced. A common way to combat this is to reduce the inertia of the rotating parts by making them lighter.
  • The size of the charger inversely affects speed and level of capable boost.
    • Large -> Slower with more Boost.
    • Small -> Faster with less Boost.
  • A Watergate may be used to hookup a small 'extra' turbocharger, reducing Turbo Lag.
Turn Signals
Take a wild guess O_O.
  • Today, it's typical for a car to automatically disengage an active signal when the steering wheel reaches a specified angle of rotation.
  • Vehicles that have extra signal lights behind the side mirrors are already starting to appear.
Windshield Wipers
Keep the windshield clear of precipitation.
Wiper Arrangements
    • The Tandem System - Typical setup in cars, this arrangement has the blades always running in parallel to each other. One blade is positioned specifically for the driver, while another is positioned for the larger coverage of the center and opposite side of the windshield.
    • Opposed system - The 2 blades are each mounted below opposite sides of the windshield. While this covers each side of the windshield, the top of the middle windshield area is obviously unreachable.
    • Single Arm - A single blade mounted below the center of the windshield. This configuration is often seen on the back of minivans.
    • Single Arm (Controlled) - Like the "Single Arm" setup, except it moves with its rotation for maximum coverage of the windshield.
The speed and precipitation level is directly proportional to the wipers ability to keep the windshield clear. In other words
  • "the faster the car is traveling" and "the more precipitation that occurs"... the more rain that will impact the windshield, making it harder for the wipers to keep the windshield clear.
  • The faster the blades move, the more precipitation they can handle.

Note: A few items are almost pointless to simulate in Unreal and are listed only for clarity (ex: "Torque Converters", if basically simulated, would only need a couple lines of code). Some are listed for that rare circumstance that someone might wish to simulate it (like "Windshield Wipers").


Code that provides to-the-point explanations of how individual parts of a vehicle can be simulated in Unreal.

In-Game Snippets[edit]

User Snippets[edit]

Related Topics[edit]

To Do:[edit]

  • Convert all occurrences of horsepower to something more useful.
  • Compression ratios should be rewritten as a set of equations describing general fuel efficiency.


odo324: This was a very difficult page to do! What could and couldn't be "relevant" on an UnrealWiki page is very unpredictable! Also, as we document Unreal equivalents to real vehicle anatomy, this page-layout will almost certainly need to be modified.

SuperApe: This seems to exist somewhere between Mod Ideas, Movement Metrics (UT2003) and a reference that should belong outside UnrealWiki. I see the connection being made, but it's a strain to see how useful this is to UnrealScript. At best, I can see a useful comparison between the transfer of energy in an engine, versus the chain of events in the control of an Unreal vehicle.

StarWeaver: It's a . . . very bizarre page, for sure. I didn't even get the point till I'd read most of it. The author's claim of keeping the real and unreal seperated at the top seems moot, as it's almost all random information about real physics and vehicles. The detail-level of information is very . . . random, between topics, too. I would want to change this to be essentially "Here's how engine types A and B work briefly, here's what to consider in simulating them in code and how the real life differences correpsond to code differences, here's links to all the different kinds of engines work on wikipedia. Here's a list of all the other components that you might forget to consider when making a vehicle, and any real-life<->game considerations that come to mind abuot them, here's links to real-world info." . . . . I don't have nearly enough knowledge to put something like this together currently, though.

sweavo: IMO this should be under the personal pages of the person who wrote it. There's probably some interesting info here, but none of it about UT.