Diesel Engines

Question 1

What is different from a diesel engine compared to a gas engine?

Answer 1

• engine only draws in air on intake phase
• no spark plugs; the compressed air reaches temperatures to 500 degrees, and it ignites the afm.
• higher torque and volumetric efficiency.

Question 2

What happens on the intake stroke of a diesel engine?

Answer 2

• intake valve opens
• piston moves down and sucks in clean air; no afm.

Question 3

What happens on the compression stroke of a diesel engine?

Answer 3

• piston moves up and compresses air to about 400 - 600 psi
• air reaches temperatures of about 500 degrees or higher.

Question 4

What happens in the power stroke of a diesel engine?

Answer 4

• piston moves down
• fuel is injected at high pressures.
• high compression ignites the fuel mixture.
• torque is created pushing the piston down.
• fuel is injected till the crank is at a 30 degree rotation.

Question 5

What happens in a exhaust stroke for a diesel engine?

Answer 5

• Exhaust valve opens.
• piston moves up
• burnt gases escape through exhaust valve

Question 6

Why does there need to be a high compression for a diesel engine?

Answer 6

• compression helps atomize fuel
• high compression ignites the fuel

Question 7

How much compression is there in a diesel engine?

Answer 7

400 - 600 psi

Question 8

Why is injection timing critical?

Answer 8

injection initiates combustion; if the injection were off the engine wouldn’t run at a max capacity.

Question 9

What can the air/fuel ration range from a diesel engine?

Answer 9

20:1 for heavy loads
70:1 for light loads

Question 10

What two type of combustion chambers are there for diesel engines?

Answer 10

• direct injection
• indirect injection

Question 11

Explain direct injection for diesel engines.

Answer 11

• fuel is sprayed directly into the engine
• mexican hat design helps circulate/atomize fuel.

Question 12

Explain indirect injection for diesel engines.

Answer 12

• fuel injection happens in its pre-combustion chamber.
• pre-combustion chamber creates turbulence for the afm.

Question 13

What is the reasoning for glow plugs?

Answer 13

• Helps heat the combustion chamber to prevent cold starts.

Question 14

What are some advantages of a diesel engine?

Answer 14

• high torque: suitable for pulling heavy loads
• lots of Volumetric efficiency
• fuel efficient
• longer life span
• no electrical system needed
  -safer than gasoline

Question 15

What are some cons for the diesel engine?

Answer 15

• slower acceleration
• much more expensive to fix/build
• cant tolerate fuel contamination
• more torque needed to move engine
• requires more energy to start