Turbochargers

Question 1

How does a turbocharger work

Answer 1

Use excess speeds and pressure of the exhaust gases to spin a turbine which directly spins a compressor which compresses the fresh intake air ready for entry to cylinder.

Use excess energy leftover in exhaust gasses we would not otherwise use

Question 2

Altitude Boosting (Turbocharger)

Answer 2

Compress air into cylinder to delay the drop in power due to the increase in density altitude

Question 3

Ground Boosted Supercharger

Answer 3

Increase the overall power at sea level rather than maintain it

Engine will need to be strengthen to withstand + cooling system

Question 4

Manifold Absolute Pressure Gauge Displays what?

Answer 4

Displays absolute pressure in the manifold measure in Inches of mercury

Should always be positive

Question 5

MAP indication is lower at takeoff than on the ground why?

Answer 5

At take off power engine will not get back to the static pressure value

Question 6

Turbocharger is comprised of

Answer 6

Turbine linked to impeller by shaft - lubricated by engine oil
Driven by exhaust gases
Turbine rotates at very high speed

Connected by shaft to compressor which compresses the incoming air into the manifold
Centrifugal compressor with a diffuser raises the pressure

Question 7

Critical Altitude

Answer 7

Waste gate is completely closed yet MAP is decreasing - power no longer sufficient for density altitude

Question 8

Density Controller

Answer 8

Prevents exceeding upper limit of manifold air pressure below critical altitude at full throttle

Question 9

Waste Gate System

Answer 9

At the exhaust end
Controls speed of turbocharger by directing the amount of outlet gas to the turbine

Question 10

Waste Gate system in the climb

Answer 10

Will close as air density decreases to increase turbine rpm

Exhaust back pressure increases
Reducing volumetric efficiency
Engine power for a given value of MAP will decrease

Question 11

Waste Gate position on engine start + idle power + TO

Answer 11

Engine Start - fully open due to spring pressure

Idle power - little exhaust gas so moves to fully closed position

Take off - almost fully open for leeway in QNH increases

Question 12

Rated Power

Answer 12

Max power which engine can be operated continuously

Question 13

Rated Boost

Answer 13

The manifold pressure allowed at rated power

Question 14

Rated altitude

Answer 14

Max altitude continuous power can be maintained on turbocharged engine

Question 15

Supercharger

Answer 15

Forced induction device utilising the engine to produce more power
Mechanical direct connection to the engine
Less efficient by more responsive than turbocharger

Question 16

How do you increase the critical altitude

Answer 16

By climbing at a higher MAP

Set a lower MAP therefore on climb wastegate can close a bit more

Question 17

Where is the inter cooler on a turbocharged engine

Answer 17

After the compressor and is installed to restore density

Question 18

Air in piston engine turbocharger enter the centrifugal compressor

Answer 18

At the eye of the impeller and leave it almost at a tangent to the periphery

Question 19

Best conditions for highest engine power

Answer 19

Cold and dry air at high pressure

Increased density and provide best efficiency and power

Question 20

Exhaust back pressure

Answer 20

Turbochargers lose slight amount of power due to restriction of exhaust gases from engine when wastegate closed.

Question 21

Exhaust back pressure reduces with

Answer 21

Altitude in normal aspirated or supercharged engine

Question 22

Two types of compressors are

Answer 22

Axial flow
Centrifugal compressor

Question 23

Centrifugal compressor composed of

Answer 23

An impeller
A diffuser
A casing

Question 24

How centrifugal compressor works

Answer 24

Impeller rotates as air enter the eye of impeller

Picked up by rotating vanes and propelled outwards by centrifugal forces

Diffuser vanes on the outside trade airs kinetic energy for pressure energy

Question 25

Maintain a constant MAP in climb the power output will…

Answer 25

Increase

Reduce in exhaust back pressure more fuel and air mix into the cylinder

Question 26

Full throttle heigh

Answer 26

Critical altitude in a supercharged engine

Question 27

Role of the intercooler in turbocharger

Answer 27

Fitted at induction manifold of turbocharger. Cold ram air ducted from atmosphere after compressor

Question 28

How do you reach rated altitude

Answer 28

Climbing at rated boost and rated rpm

Question 29

Rated Boost

Answer 29

Manifold pressure allowed at rated power

Question 30

Rated Altitude is

Answer 30

Max altitude at which max continuous power can be maintained on supercharged engine

Question 31

Operation of a turbocharged variable pitch propeller A/C

Answer 31

Rev up Throttle back - increasing power

Reduce throttle first then RPM for reducing power

Question 32

Purpose of intercooler in turbocharger

Answer 32

Minimise risk of detonation - placed between the supercharger and the inlet valve

Question 33

Exhaust back pressure is

Answer 33

Back pressure from restrictive flow when wastegate is closed meaning exhaust gases are not removed effectively meaning a small amount of power loss in turbochargers

Exhaust back pressure on a normal/supercharged engine reduces with altitude