190201d

Question 1

The main 4 components of a piston and connecting rod assembly are:

Answer 1

• Piston
• Piston Rings
• Piston Pin
• Connecting Rod

Question 2

What TEMPERATURE and PRESSURE does a piston encounter in a running diesel engine?

Answer 2

Pressure - 2000psi (13789.5kPa…though current pressures are near 3k-4k)

Temperature - 3500F

Question 3

Why is aluminum used for the construction of diesel engine pistons?

Answer 3

Aluminum is:

• lighter
• produces less engine vibrations
• 3x the heat conductivity of cast iron
• provides a bearing surface for piston pins

Question 4

What is the main characteristic of a TRUNK TYPE piston?

Answer 4

The crown and skirt are manufactured as one piece

Question 5

What are 5 main parts of a piston?

Answer 5

• Valve reliefs
• Crown
• Skirt
• Piston pin bore
• Piston ring grooves
• Dome
• Ring lands
• Oil holes

Question 6

The purpose of CAM GRINDING the skirt of a one-piece aluminum piston is to:

Answer 6

Allow the uneven expansion in the piston pin bore area

Question 7

In a piston, what purpose do the holes in the oil ring groove serve?

Answer 7

To allow oil to freely move when lubricating the cylinder wall.

Question 8

Ring groove inserts are used in aluminum piston construction to:

Answer 8

Reduce wear in and reinforce compression ring grooves

Question 9

What is the purpose of the slipper skirt piston design?

Answer 9

To provide clearance between the slipper skirt and crankshaft, when the piston is at BDC

Question 10

What is the advantage of using a two-piece piston design?

Answer 10

• The piston head/crown is made of strong material to withstand high heat and pressure
• Combustion forces are transferred directly from the crown a bushing a piston pin assembly
• Piston crown motion is reduced
• Direct loading and a greater pin bushing area reduce bending stress on the piston

Question 11

What is a semi-floating piston pin?

Answer 11

A pin that freely rotates in the piston, but is fixed to the connecting rod

Question 12

What is the most common type of piston cooling used in a medium/high-speed diesel engine?

Answer 12

Oil sprayed through a piston cooling nozzle

Question 13

What are the two types of piston rings used in an engine?

Answer 13

• Compression rings

- Oil control rings

Question 14

The purpose of piston ring end gap is:

Answer 14

to allow clearance for ring expansion (from heat)

Question 15

What 3 factors help a compression ring create an effective seal along the cylinder wall?

Answer 15

• Oil film
• Ring tension
• Cylinder pressure

Question 16

The purpose of an oil ring expander is to:

Answer 16

Provide the needed ring tension for oil control

Question 17

The two main advantages of a KEYSTONE ring over a RECTANGULAR ring are:

Answer 17

• Stronger ring lands due to the tapered groove

- Self cleaning (greater resistance to buildup)

Question 18

Chromium plating is used on compression rings because:

Answer 18

It increases heat transfer and reduces friction

Question 19

What is the purpose of a connecting rod?

Answer 19

It forms a link to transfer combustion force from the piston to the crankshaft

Question 20

Identify 5 parts of a connecting rod:

Answer 20

• Nut
• Balance pad
• Thrust face
• Rod bearing bore
• Parting line
• Beam shank
• Piston pin bushing
• Piston pin bore
• Bolt

Question 21

What are four methods of maintaining connecting rod and cap alignment?

Answer 21

• Fracturing
• Dowel pins
• External markings
• Shouldered bolt
• Tongue and groove joint
• Serrated joint

Question 22

Identify two connecting rod designs:

Answer 22

• Straight cut
• Bias cut
• Fork and blade
• Articulated