copper pistons

[Dozernut]

"uummm... Caterpillar Diesel engines have only two compression rings."

Just a guess, I think the two rings on the Cat diesel engines are because the pistons are bigger, they also have a slower rpm. A bigger piston means larger compression rings with more contact with the cylinder wall providing adequate cooling. The pistons in a diesel automobile or marine engine have a higher rpm and would be a lot smaller and would need the third ring for cooling.

Merry Christmas to all!

 

[PoorMansCat]

Duramax 6.6 engine only has two piston rings. Powerstroke 7.3 has two piston rings, Cummins 5.9 uses 2 piston rings.

 

[Kyle_in_Tex]

Lot of engines use oil sprayed underneath the piston to cool the pistons. Surely recommend synthetic for this type of engine.

 

[muddstopper]

Duramax 6.6 engine only has two piston rings. Powerstroke 7.3 has two piston rings, Cummins 5.9 uses 2 piston rings.

Well, a continental 4cyl gas uses 3 compression rings and a oil ring.

 

[PoorMansCat]

Well, a continental 4cyl gas uses 3 compression rings and a oil ring.

yep... the point i was trying to make is that MANY diesel engines use just two compression rings, whether they are larger or small displacement.
Many natural gas engines use 2 ring pistons, although I know of one application on a Cat 3412 NG Genset package that uses 3 ring pistons. That series was initially built as a 2 ring piston, but after a couple years of field testing it was determined that if the engine was ran continually at low engine loads, it would actually cause excessive carbon formations in the cylinders. Cat made the change to a 3 ring piston.

 

[sd455dan]

yep... the point i was trying to make is that MANY diesel engines use just two compression rings, whether they are larger or small displacement.
Many natural gas engines use 2 ring pistons, although I know of one application on a Cat 3412 NG Genset package that uses 3 ring pistons. That series was initially built as a 2 ring piston, but after a couple years of field testing it was determined that if the engine was ran continually at low engine loads, it would actually cause excessive carbon formations in the cylinders. Cat made the change to a 3 ring piston.

I wonder if it has to do with the diesels that employ cooling jets?- I should have known that the article was suspect- (Never say Never) i just watched a video tonight of a Hyundai container ship diesel engine rated@ 108,000 horsepower it had 3 comp rings- they had doors to walk in to the rod crankshaft area for each cylinder... HUGE

I just checked out some of the Cat pistons and rings and - sure enough 2 compression rings-it does employ cooling jets and the top Plasma coated ring does appear to have a thicker edge- which would explain at least part of the article I Quoted- being in error..

 

[Midniteoyl]

I think its more about better metallurgy and machining.

 

[jimcolt]

A couple of things for comment:

- A link to a 1929 American patent for alloying copper into aluminum pistons for internal combustion engines. Sounds like it improves strength and allows for increased combustion temps. Undoubtedly used for aircraft engines in WWll! link" Patent US1920233 - Aluminum-copper piston alloy - Google Patents


- Heat transfer from pistons is primarilly through the oil film on piston skirts to the liquid cooled cyclinder walls. Some is transferred through the rings, but not much.

- Pistons with less thermal expansion can transfer heat more efficiently, hence the reason for getting the correct level of silicone alloying. Commonly known "Hypereutectic" pistons are used in the vast majority of automotive engines today.

Jim Colt Hypertherm