Transportation Technology

Engine Operation:4 Stoke Cycle

C. Stemmler

4 Four Stroke Engine

4 Stroke Cycle

“cycle” is considered to be a repetitive series of operations

4 Stroke - requires the piston to move four times--up then down--four times to complete one cycle (two revolutions of the crankshaft)

most automotive & diesel truck engines are 4 stroke engines--due to emission laws

4 Stroke Cycle -- Intake Stroke

Piston Direction downTDC to BDC

Intake Valve open

Exhaust valve closed

Movement of gases enters cylinder

Pressure 14 hg. of vacuum

Intake valve

Compression Stroke

Piston Direction UpBDC to TDC

Intake Valve closed

Exhaust valve closed

Movement of gases squeezed Pressure 120 to 150

psi

Exhaust valve

Power Stroke

Piston Direction DownTDC to BDC

Intake Valve closed

Exhaust valve closed

Movement of gases rapid expansion

Pressure 800 to 1000 psi

Exhaust Stroke

Piston Direction UpBDC to TDC

Intake Valve closed

Exhaust valve open

Movement of gases expelled or pushed out

Pressure 20 to 30 psi

The camshaft turns in one complete cycle - which is degrees of crankshaft rotation.

The crankshaft turns degrees during one stroke.

There are crankshaft revolutions in one cycle - which is degrees of crankshaft rotation rotation.

4 Stroke Cycle - Complete

two720

180

once720