Transportation Technology

Engine Terms

C. Stemmler

4 Engine Terms

Engine Terms

The following terms are commonly found in automotive literature, e.g., repair manuals, advertising

all of these terms relate to the internal combustion engine.

Engine Terms--continued

TDC Top Dead Centre

Cylinder

Piston

is the farthest point of upward travel, of the piston, in the cylinder.

Engine Terms--continued

BDC Bottom Dead Centre

is the lowest point of downward travel, of the piston, in the cylinder.

Engine Terms--continued

Bore Inside diameter of

the cylinder

measured in inches or millimetres.

Engine Terms--continued

Stroke The distance

traveled by the piston as it moves from TDC to BDC (or top to bottom)

Engine Terms--continued

Piston Displacement (PD)

The volume that the piston displaces as it travels from TDC to BDC

Engine Terms--continued

Total Displacement

X(times)

PD # of Cylinders

=

Engine Terms--continued

Total Displacement displacement of all the pistons

added together each cylinder will have exactly

the same displacement Units: CID or cubic inches, 351 cc 5000cc L 5.0 liter

Engine Terms--continued

Total Displacement

To calculate:

TD = (1/2 of bore2) X stroke

Engine Terms--continued

Torque

Turning or twisting force--imparted on the driveline by the engine.

Engine Terms--continued

Horsepower

Gross No accessories (fan, alternator, etc.) connected to the engine during testing.

Net Accessories connected to the engine during testing.

Brake Actual horsepower develop by the engine when measured at the crankshaft.

Engine Terms--continued

Volumetric Efficiency Ratio between the amount of fuel/air that

enters the cylinder (on intake stroke) and the amount required to fill the cylinder.

Turbo-chargers, after-coolers, headers, ram-air, and super-chargers increase efficiency.