Automotive Technical Terms

Send This Page To A Friend
Throughout this site we use many technical terms, and given the breadth of readership our site enjoys, sometimes we are remiss and incorrectly assume everyone knows what we are referring to. For those that do not, here are some explanations of the technical terms use.

Energy Absorbing:

Refers to a construction technique for body panels, chassis or steering columns that allows them to collapse progressively upon impact.

Final Drive Ratio:

Gear reduction in a differential or other last transmission unit in a drive train. A reduction of 3:1 refers to the input shaft turning three times faster than the output shaft.

Flat Four/Six:

Horizontally opposed four cylinder or six cylinder engines, most commonly found in the Volkswagen Beetle, Porsche and Subaru iterations.

Flat Spot:

Refers to an engine’s performance being poor in one particular part of the rev range.

Front Wheel Drive:

Abbreviated to FWD, refers to a car in which the front wheels rather than the rear are driving the wheels.

Frontal Area:

The front surface of a vehicle that presents an obstruction to the airflow past the vehicle at speed. Used in conjunction with the coefficient of drag to determine the aerodynamic efficiency of a vehicle.

Fuel Pump:

Electrical or mechanical device that delivers fuel from the fuel tank to the carburetor.

Fuel Injection:

A system where petrol is metered in accurately measured quantities directly into the cylinders, rather than being mixed with air and drawn into the cylinders by the manifold vacuum as it is with a conventional carburetor set-up.

Gear Ratio:

Used to define the number of times that an input shaft turns in relation to the output shaft.


The upper portion of the automobile comprising the windscreen, side windows, rear window and roof. More applicable to modern cars with large glass areas.

Ground Clearance:

Minimum distance between the lower side of the automobile and the ground.

Gudgeon Pin:

Also called the “piston pin” or “wrist pin”, it connects the piston to the top of the con-rod by the little end bearing.
Unique Cars and Parts USA - The Ultimate Classic Car Resource