Two stroke diesel oil consumption 2

[turbomotor]

I am trying to get a reasonably sound and fact-based estimate of oil consumption for a six liter six cylinder two stroke uniflow scavenged and turbocharged diesel engine. So my question is: Can you provide an estimate of the expected oil consumption of a newly rebuilt (to original standards) DDC 6V71 rated at about 250 hp @ 2100 rpm and operating constant speed variable load (slow and infrequent changes to load setting) with an average load of about 80% full load? Or the same for a 6L71, as I don't think they will differ. I am trying to determine a range, but any data based on experience will help. One quart every five hours of operation? One quart every ten hours of operation? Something outside that range? If it makes the question any simpler, ignore the turbocharger oil consumption, as I have a different model for that. Thanks for your advice!

https://www.powerlinecomponents.com/literature/detroit_diesel/brochures/6v71na-t_ind.pdf

 

[TugboatEng]

On 71 series Detroit diesel engines, the oil consumption is set with the oil control expander ring. I believe the lowest consumption is the gray colored ring. In good condition, with high tension expander, a Detroit 71 series will likely burn less than 2 gallons of oil in 500 hours.

 

[enginesrus]

Most of them leak more oil than they burn. Other than rings there are blower seals that can leak as well as turbo seals. What part of the world are these engines allowed to operate nowadays?
With all the emissions talk how are these still in operation?

 

[turbomotor]

TugboatEng - thanks very much for the info. My short but happy experience with a test engine (series 92 bore and stroke) is that we scuffed the cylinder wall when we used the oil control ring with the highest tension expander. We were testing with 10 bar airbox pressure, so that may have created a lot more air velocity through the ports than experienced in a more typical engine. Have you experienced any problems with scuffed cylinder walls when trying to control how much oil is used to lube the cylinder wall just above the intake ports?

enginerrus - you make a realistic and good point. I am looking at an aviation engine, which doesn't come under quite the same emissions scrutiny as the remainder of the piston internal combustion engine world. We still get away with using 100LL aviation gasoline per ASTM D910, which has a (not very low) lead content of (maximum per spec) 0.56 grams/liter Pb introduced into the fuel as tetraethyl lead at a concentration of 0.53 ml/liter.

Check out this uniflow scavenged 6 cylinder engine intended for aviation applications:

http://cmdavio.com/gf56-aircraft-engine/

 

[TugboatEng]

10 bar? Did you have to reinforce the air box covers?

I know of the expander ring differences because the gray rings were specified by a company called Clean Cams Technology Systems. They developed a kit that retrofitted DD 2-strokes to be US EPA Tier 2 compliant. Their kit used hardened liners. Perhaps this would solve your scuffing problems.

The high tension expanders were often referred to as city bus rings. The lowest tension were used in military rated engines.

Scuffing may not be the fault of the oil control ring. Electro-Motive had scuffing issues at high power. They found the piston rings were being overheated. The solution was to include an air gap between the crown and ring pack to reduce heat transfer to the rings.

ERUs, Detroits have air box drains which is why they got the reputation of being leakers. However, the engine itself is just as tight as any other engine from the period.

 

[turbomotor]

The 10 bar airbox testing was a government sponsored program done with a single cylinder test engine. Only the bore size and rings were DDC production hardware. A very intelligent man named Dr. Jim Bennethum was overseeing the program just before he passed away in 1992.

http://profiles.sae.org/james_e._bennethum/?utm_source=google&utm_campaign=GPM_TN_E_Mobilus-Core_PH