201D - Piston, Piston Rings and Connecting Rod Fundamentals Flashcards
Running diesel engines operate with cylinder temperatures and pressures of:
3500F
2000psi
201D pg. 4
What are advantages and disadvantages of aluminum pistons?
Advantages:
- Lighter
- Less engine vibrations
- 3x heat conductivity of cast iron
Disadvantage:
- 2x expansion rate of cast iron
201D pg. 5
Hypereutectic aluminum alloys are sometimes used to manufacture pistons. What are the benefits of this?
Higher silicone content
- Increased strength & durability
- Light weight
- Reduced thermal expansion
201D pg. 5
What material is most commonly used to manufacture pistons?
Steel
- Lower thermal expansion than aluminum
- Good longevity
- Good weight & strength
201D pg. 5
What are three methods of manufacturing pistons?
- Permanent mold casting
- Die-casting
- Forging
201D pg. 6
What are the two common piston designs?
- Trunk (one-piece)
- Two-Piece
201D pg. 7
What is the crown on a piston?
The top portion of the piston above the ring land.
201D pg. 7
What are heat dams on engine pistons?
A groove or slot cut into the circumference of the piston, or part of the crown, to reduce the heat transfer from the crown to the ring lands and skirt.
201D pg. 8
A steel trunk piston is also known as a:
Monotherm piston
A one-piece, forged, steel piston
201D pg. 8
Why are piston skirts tapered?
Tapered from top to bottom as the top expands more due to heat. Once the piston warms up, it properly seals.
201D pg. 10
What is a cam ground piston?
When the piston skirt is manufactured in an oval shape.
When cold, the piston is narrower across the pin bore.
When warm, the area across the pin bore expands and the becomes round.
201D pg. 10
What are three piston skirt designs?
- Full
- Semi-slipper
- Slipper
Slipper and semi-slipper are used to clear the crankshaft at BDC.
Most heavy-duty diesels use a full or semi-slipper style.
201D pg. 11
What are advantages of two-piece pistons?
- Combustion forces are transferred directly to the piston pin assembly
- The skirt does not absorb the force of combustion
201D pg. 12
What is the difference between a crosshead and articulating piston?
Crosshead:
- Semi-floating pin (typically on gas engines)
Articulating:
- Full-floating pin (continually changing wear surface)
201D pg. 13
What are four methods of engine oil piston cooling?
- Splash
- Spray
- Circulation
- Shaker
201D pg. 14
What are three common piston oil control ring types?
- One piece
- Two piece (most common)
- Three piece
201D pg. 22
What are three types of piston ring joints?
- Butt joint
- Angle joint
- Step joint
201D pg. 23
What are the differences between a straight cut and bias cut connecting rod design?
Straight Cut:
- Parting line is 90 degrees to the rod beam
Bias Cut:
- “only” used in inline engines
- Reduced width so it can be removed through the bore
201D pg. 26
What connecting rod designs are used in large displacement, Vee type engines which allow two connecting rods to be mounted on one journal without having to be side by side?
- Fork & Blade
- Articulated
201D pg. 27
