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RC Glossary


New to the RC Hobbies? What does buggy, bulkhead, nitro mean in radio control car hobbies? Check out the glossary for remote control cars below.


  • Idle Bar (Glow Plug) --
  • Refers to a glow plug that has a metal bar across the tip, similar to an automotive spark plug. This bar helps prevent raw fuel from splashing onto the coil and cooling it, which helps the engine maintain a low speed idle.

  • Idle Screw --
  • An adjustment screw found on the side of the carb, as part of the carb barrel, that defines the position of the barrel at idle. Adjusting the idle screw determines how the engine idles without driver input. In general, the idle screw should be adjusted so that about about 1mm can be observed between the end of the barrel and carb body. This may need to be increased if the engine tends to die between 10 to 15 seconds of constant idle, or decreased if the clutch tries to engage (i.e. if the model tries to 'lurch' forward during idle). The idle screw should only be adjusted after the high speed needle is set.

  • Idle Up --
  • A feature found on most high end radios that is operated by a button or switch. This allows the user to select a preset amount for the throttle servo to open the carb when idle up is selected (usually expressed in %). This is useful during initial starting of an engine or when starting a hot engine. If you use idle up, don't forget to turn it off once the engine is running.

  • Idler Gear --
  • A spring loaded arm with a pulley or bearing that applies pressure to the belt on a belt drive model. This helps to prevent the belt from skipping as it stretches from wear or as the chassis flexes.

  • IGR --
  • Abbreviation for Internal Gear Ratio

  • Inboard Shocks --
  • Refers to a shock set up that has the shocks mounted horizontally on the chassis instead of being mounted upright between the suspension arms and shock towers. This lowers the CG, moves weight to the center of the chassis, and helps to protect the shocks from damage. With inboard shocks, pushrods transfer motion from the arms to cantilevers (rockers), which transfer the motion to the shocks.

  • Induction Port --
  • An opening machined into the crank journal. This opening lines up with the air induction hole once per revolution, transferring the air / fuel mixture from the carb into the crankcase.

  • Inline Steering KnucklesíVInline Pivot Blocks --
  • Refers to steering knuckles or pivot blocks designed so the kingpin is centered with the bearings. This increases steering throw, but decreases the stabilizing effect of trailing knuckles.

  • Inner Foams --
  • Another term for insert.

  • InRunner --
  • Refers to the typical RC car brushless motor - The inside (rotor) spins, while the outside (can) remains stationary.

  • Inserts --
  • Foam strips or donut-shaped cutouts that support a tire on a wheel. The car can be tuned with inserts, much like full-size race cars are tuned with tire air pressures.

  • Intercooler --
  • An alloy extension placed between the carb and engine block of a nitro engine. In theory, an intercooler helps cool the air / fuel mixture before it reaches the crankcase, resulting in a denser mixture with better combustion properties.

  • Internal Decal --
  • As the name implies, this is a 'sticker' designed to be placed inside a clear lexan body before painting. Internal decals have the image printed on the 'sticky' side, and are backed with white to prevent the paint color from 'shining through' once the body is painted. If you stick these on the outside of the body, they will look like crap.

  • Internal Gear Ratio - IGR íV Internal Drive Ratio íV Reduction Ratio íV Transmission Ratio --
  • This is a fixed ratio between the drive gears of a model, and is basically determined by dividing the number of teeth on the larger diff or tranny gear (or pulley) by the number of teeth on the smaller diff or tranny gear (or pulley) - LARGER GEAR / SMALLER GEAR. This ratio is expressed like: 3.6:1 (as an example), and can be multiplied by the primary gear ratio (PGR) to determine the final drive ratio (FDR). Determining the IGR (Internal Gear Ratio) is different depending on the model:
    - 3 Gear Tranny (2WD Trucks & Buggies) --BOTTOM (DIFF) GEAR / TOP (INPUT) GEAR. Divide the number of teeth on the larger bottom gear (diff or output) in the tranny by the number of teeth on the smaller top gear (input). Don't bother with the center (idle)
    - Belt Drive --DIFF PULLEY / LAYSHAFT PULLEY. Divide the number of teeth on the larger diff pulley by the number of teeth on the smaller layshaft pulley. EXAMPLE: A belt drive model has diff pulley with 50 teeth and a layshaft pulley with 21 teeth - 50 /
    - Shaft Drive --DIFF (RING) GEAR / OUTPUT (SHAFT) GEAR. Divide the number of teeth on the larger diff (ring) gear by the number of teeth on the smaller output (shaft) gear. Don't bother with the spider or planetary gears). EXAMPLE: The diff on a shaft dr

  • Internal Resistance - IR --
  • A measurement of electrical resistance and efficiency - a lower IR is better. Refers to the amount of 'drag' a cell (battery), connection, or length of wire has. Lower IR = more initial voltage ('punch').

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