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Old 02-04-2019, 04:14 PM   #99
DavidM
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City: Litchfield, Ct
Join Date: Aug 2012
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"Diesels love to be run at their rated continuous operating speed with the correct load."

"Never once ran any of them @ 35%. Heck, on many diesel engines, 35% just barely gets the oil and water circulating correctly"

Two quotes on the same subject and both may be true, but only for some engines.

Take Yanmar's liberal definition of continuous operation at 200 rpm off of top. If you do that for long with some of their 70-80 hp per liter engines, they will be lucky to last 2,000 hours. But do that with a John Deere or a Cummins continuous duty definition (most Cummins continuous duty engines are rate at 1,800 rpm for genset use) and you will be ok for 5,000+ hours.

Same thing with the second quote. I ran my Yanmar 370 hp engine at 1,600 rpm or about 55 hp or 15% load and it is quite happy there. But most sailboat engines as well as Krogens and Nordhavns run at 50% all day long.

That is why the concept of running at a recommended pct load is pure BS.

A much much better way of looking at it is Tony Athens rule of thumb (supported by various engine builders data sheets) that 35 hp per liter is a good maximum continuous cruising load. And that rule is only good for high performance turbo charged engines. Many NA engines won't make that at full load.

David
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