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The '''accessory_engine_data''' unit class is used to define the engine characteristics for the [[Documentation/Engine/Game_data/Player_trucks_definitions|player's vehicle]], as well as some upshift and downshift characteristics for automatic transmission gameplay. Units of this type are usually defined in '''/def/vehicle/truck/<makebrand.model>/engine/*.sii'''
== Attributes ==
|-
|info
|array<string array>
|
|Three This member is attribute of accessory data, however three '''info''' members are usually defined for '''accessory_engine_data'''.
<syntaxhighlight lang="cpp">
info[]: "197 @@hp@@ (147@@kw@@)" // The first is the rated power
|torque
|float
|0.0
|This defines the maximum torque output of the engine in N·m.
|-
|secondary_torque
|float
|0.0
|If positive and greater than zero, this defines the secondary maximum torque output of the engine in N·m for multi-torque engines. ''(Added in 1.30)''
|-
|secondary_torque_gear_ratio
|float
|1.0
|This defines the transmission gear ratio below which '''secondary_torque''' is used on multi-torque engines. ''(Added in 1.30)''
|-
|torque_curve
|array<float2 array>|''See description''
|This defines the torque output of the engine at various engine speeds, relative to the maximum torque defined in '''torque'''. If unset, the default curve is used:
<syntaxhighlight lang="cpp">
</syntaxhighlight>
The torque output is linearly interpolated between data points. For engine speeds outside the domain of the data points, the output is clamped to the values at the highest/lowest rpm points. The valid range for torque output is 0-1.
|-
|secondary_torque_curve
|array<float2>
|''See description''
|This defines the secondary torque output of a multi-torque engine at various engine speeds, relative to the maximum torque defined in '''secondary_torque'''. If unset, '''torque_curve''' is used instead. The syntax is the same as '''torque_curve'''. ''(Added in 1.30)''
|-
|resistance_torque
|float
|-1
|This is the resistive torque in N·m at 2000rpm, used for passive engine braking and consumption. ''(New as of ETS 1.27/ATS 1.6)''
{{Note|When unset, or when set to any negative value, resistance_torque is calculated as (''volume'' × 20.0).}}
|-
|rpm_idle
|float
|550
|This is the engine speed the virtual engine controller will attempt to maintain with no throttle input. Valid range is 500-850 rpm.
|-
|rpm_limit
|float2
|(1000, 1500)
|Defines the downshift and upshift engine speeds in high-range gears- typically peek torque range. (Automatic transmission)
|-
|rpm_range_engine_brake
|float2
|(1500, 2500)
|Defines the downshift and upshift engine speeds while the engine brake is operating.(Automatic transmission)
|-
|rpm_range_power_boost
|float2
|(550, 450)
|Defines the rough rpm range ''change'' to '''rpm_range_low_gear''' and '''rpm_range_high_gear''' at full throttle when if more power is requested - used either in hills or for adaptive automatic shifting, especially power mode. (Automatic transmission is enabled).
{{Tip|Be careful that the resulting values when '''rpm_range_power_boost''' is added to '''rpm_range_*_gear''' don't exceed '''rpm_limit'''. Otherwise, the transmission may fail to shift correctly in adaptive automatic mode.}}
|-
|engine_brake
|float
|1.0
|Engine braking torque relative to a typical exhaust brake on an engine of the same '''volume'''.
|-
|engine_brake_downshift
|bool
|true|When true, automatic transmissions will downshift upon beginning engine brake behavior, to keep rpm within '''rpm_range_engine_brake'''. When false, the regular rpm are kept.
|-
|engine_brake_positions
|volume
|float
|0.0
|The (four-stroke) volumetric displacement of the engine in liters. It is used in fuel consumption calculations. {{Note|For two-stroke diesel engines, this should be roughly twice the swept volume.}}
|-
|no_adblue_power_limit
|float
|1.0
|When the AdBlue tank is empty, the engine's power is scaled by this factor.
|}
=== Torque from Power and Speed (English Units) ===
T [lb<sub>f</sub>·ft] = ( P [hp] × 5252 ) ÷ N [RPM]