Piston Engines Part 1

Question 1

Compression ratio:

Compression ratio can be expressed as:

Total volume / Clearance volume.

Total volume is: the volume, or space, between the __ of the piston when it is at ___ and the __ of the inside of the ______.

Clearance volume: This is the volume, or space, between the __ of the piston when it is at ___ and the __ of the inside of the ______. Effectively this area is the combustion chamber.

Answer 1

Total volume is: the volume, or space, between the top of the piston when it is at BDC and the top of the inside of the cylinder.

Clearance volume: This is the volume, or space, between the top of the piston when it is at TDC and the top of the inside of the cylinder. Effectively this area is the combustion chamber.

Question 2

Timing:

The inlet valve is timed to remain open until -

Answer 2

50 and 75 degrees past bottom dead centre

Question 3

Timing:

The spark plug ignites -

Answer 3

between 20 and 35 degrees before top dead centre

Question 4

Timing:

Exhaust valve opens -

Answer 4

between 50 and 80 degrees before bottom dead centre

Question 5

Timing:

The inlet valve opens -

Answer 5

10 to 55 degrees before top dead centre

Question 6

What is the location of the needle valve?

And what is the purpose?

Answer 6

The needle valve is located before the float chamber

It control the inlet flow to the float chamber

Question 7

The component that controls the needle valve?

Answer 7

The float

Question 8

Where is the main metering jet located?

And what is the purpose?

Answer 8

Between the float chamber(after the mixture control valve) and the diffuser/fuel discharge nozzle

To limit the fuel flow once the throttle butterfly valve is fully open

Question 9

Before fuel is discharged, the component that pre-mixes air drawn, from an area not affected by the venturi, with fuel is?

And where is it located?

Answer 9

The diffuser/discharge nozzle

In the throat of the venturi

Question 10

The mixture needle valve is located?

Answer 10

between the float chamber and the main jet

Question 11

The type of mixture control that use differential pressures?

Answer 11

The back suction mixture control

Question 12

When the throttle is opened from idle to full throttle fairly rapidly, a large volume of air is drawn in through the air intake of the carburettor. Because of the slow response of the fuel metering system to supply adequate fuel to maintain the correct mixture, the fuel/air mixture is temporarily leaner, causing a hesitation called a weak cut, or more commonly a flat spot. This is overcome by installing -

Answer 12

an accelerator pump

Question 13

To assist in dissipating the heat at full throttle settings, and to prevent detonation, the fuel mixture is automatically richened by a device attached to the throttle control called an -

Answer 13

economiser

Question 14

When the butterfly valve is in the fully closed position, the velocity of air through the venturi may be so low that it is unable to draw enough fuel from the discharge nozzle to keep the engine idling. To solve this -

Answer 14

An adjustable idling jet is placed on the inlet side of the butterfly valve

Question 15

The crank assembly consists of

Answer 15

crankshaft, connecting rods and pistons.

Question 16

An impulse coupling is installed on a magneto of a piston engine to:

Answer 16

Provide a stronger spark on top dead centre for engine starting

Question 17

On a normally aspirated engine, the manifold pressure gauge always indicates:

Answer 17

A lower value than atmospheric pressure when the engine is running