Shift light
Encyclopedia
A shift light is a warning lamp fitted to vehicles in order to indicate to the driver that maximum RPM
has almost been reached. Ideally a shift lamp will illuminate at the engine speed beyond that which delivers the maximum BHP such that the BHP before and after shifting is the same. Accelerating the engine beyond this point is not conducive to rapid acceleration. In use a shift light allows the driver to judge the exact point that a gear change should be carried out without having to glance down at the tachometer
. This also increases safety for the driver by keeping his focus on the track at all times.
Beginning in the early 1980s, many US-market vehicles equipped with a manual transmission
began to have shift lights as standard equipment; these would usually signal for an upshift at an engine speed that provided maximum fuel efficiency
, lower than the ideal engine speed for maximum BHP. The reason for this was, for a time EPA
fuel economy
testing rules stipulated that shift lights would be followed on vehicles so equipped- thus, they were calibrated for optimum fuel mileage on the EPA test cycle. Some in the 1980s even had buzzers to alert the driver it was at a certain rpm.
Revolutions per minute
Revolutions per minute is a measure of the frequency of a rotation. It annotates the number of full rotations completed in one minute around a fixed axis...
has almost been reached. Ideally a shift lamp will illuminate at the engine speed beyond that which delivers the maximum BHP such that the BHP before and after shifting is the same. Accelerating the engine beyond this point is not conducive to rapid acceleration. In use a shift light allows the driver to judge the exact point that a gear change should be carried out without having to glance down at the tachometer
Tachometer
A tachometer is an instrument measuring the rotation speed of a shaft or disk, as in a motor or other machine. The device usually displays the revolutions per minute on a calibrated analogue dial, but digital displays are increasingly common...
. This also increases safety for the driver by keeping his focus on the track at all times.
Beginning in the early 1980s, many US-market vehicles equipped with a manual transmission
Manual transmission
A manual transmission, also known as a manual gearbox or standard transmission is a type of transmission used in motor vehicle applications...
began to have shift lights as standard equipment; these would usually signal for an upshift at an engine speed that provided maximum fuel efficiency
Fuel efficiency
Fuel efficiency is a form of thermal efficiency, meaning the efficiency of a process that converts chemical potential energy contained in a carrier fuel into kinetic energy or work. Overall fuel efficiency may vary per device, which in turn may vary per application, and this spectrum of variance is...
, lower than the ideal engine speed for maximum BHP. The reason for this was, for a time EPA
United States Environmental Protection Agency
The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...
fuel economy
Fuel economy in automobiles
Fuel usage in automobiles refers to the fuel efficiency relationship between distance traveled by an automobile and the amount of fuel consumed....
testing rules stipulated that shift lights would be followed on vehicles so equipped- thus, they were calibrated for optimum fuel mileage on the EPA test cycle. Some in the 1980s even had buzzers to alert the driver it was at a certain rpm.