ASVAB CampEngine Fundamentals and Four-Stroke Cycle flashcards
8 cards with the formulas, rules and traps from this lesson. Answer in your head, then flip to check.
Fact · 1/8
What is the order of the four strokes, and which way does the piston move in each?
Intake (down), compression (up), power (down), exhaust (up). Memory aid: suck, squeeze, bang, blow. Only the power stroke pushes on the crankshaft.
Rule · 2/8
Valve positions during each of the four strokes?
Intake: only the intake valve open. Compression: both closed. Power: both closed. Exhaust: only the exhaust valve open.
Formula · 3/8
How fast does the camshaft turn compared with the crankshaft?
. One four-stroke cycle takes two crank revolutions (720 degrees), and each valve opens once per cycle. A 3600 rpm crank turns the cam at 1800 rpm.
Formula · 4/8
How do you count power strokes per minute in a four-stroke engine?
, with n cylinders. Each cylinder fires once every two revolutions; a 4-cylinder at 3000 rpm gives 6000.
Formula · 5/8
Swept displacement of one cylinder from bore and stroke?
: B is bore (diameter), S is stroke, same units; cm give cc. Multiply by cylinder count for total; 1000 cc = 1 L. Doubling bore quadruples volume.
Formula · 6/8
Compression ratio formula?
: swept volume plus clearance volume, over clearance volume. 450 cc swept and 50 cc clearance give 10:1. It is unitless.
Fact · 7/8
How do gasoline and diesel engines ignite their fuel?
Gasoline: spark ignition; a compressed air-fuel mix (about 9:1 to 12:1) is lit by a spark plug. Diesel: compression ignition; air alone is squeezed (about 15:1 to over 20:1) until hot enough to light injected fuel.
Term · 8/8
Jobs of the connecting rod, crankshaft and flywheel?
The connecting rod links piston to crankshaft; the crankshaft turns reciprocating motion into rotation; the flywheel stores rotational energy to smooth speed between power pulses (it creates no energy).