what classifies a "medium duty" engine?

[SLangegger]

What are the guidelines of a medium duty engine? I know the Cummins is, but what about the D-max & PSD?

 

[nickleinonen]

emissions rating and engine speed are also different between a light duty and medium duty. our lil b's turn slower when in a true medium duty application, and with tier 2/3 emissions, pollute less. for the psd's, the 7. 3 is a navistar t444e and the 6. 0 is a navistar vt365. both turn lower speeds in the medium duty application with tighter emissions ratings. the dmax 6. 6 is not used in any medium applications other than the medium/light duty c4500/c5500 trucks. there is also the 7. 8 dmax which is an inline 6 around the same size/weight/specs as a 3126e cat engine used in the c6500 - c8500

 

[Buffalo]

A number of years ago, I read that some of what determines what a Med. Duty vs. Light Duty is, how strong engine parts like the crankshaft, connecting rods, pistons, etc. , are. I believe that the bearing surface area is looked at, also. The Cummins have 7 main bearings vs. 5 for the V-8's.



I'm sure there is more, also.



Joe F. (Buffalo)