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Old 18-02-2008, 10:10   #31

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The differences go deeper, or further back, than just that. My friend's father lived in the engine room of a WW2 destroyer, and explained that naval engines at that time were normally de-rated by 2/3 of their power. That is, an engine rated 1000hp was nominally rated at 1000hp for continuous duty at sea. And, it had to be proven and tested able to supply 3000 hp, fully three times the nominal rating, in combat conditions.
From the navy's point of view this made complete sense. The continual duty rating is what would keep the ship running indefinitely. The combat rating was called "Hell, it doesn't matter if the engine blows up in two hours, as long as it keeps us alive until this fight is over."

Sort of like the engines built for Indy cars: They develop roughly 10x more hp per cubic inch than production cars. But, they were built to endure the 500 miles at Indy, plus 200 more miles for the practice runs and a small safety margin, and it was expected that if the engine didn't blow up after 700 miles--you had built it too damn heavy and heavy isn't fast.

Or the old A4 (aka "Stevedore") engine, a slow-turning gasoline engine that typically shipped with an air restrictor plate in the intake. Remove the plate, and you'd get 50% more power immediately. But the Stevedore wa built to run forever, as they've made a reputation for doing, by turning at slow speeds with much less load than they can really handle.

I can't really say i disagree with Mercedes. I fully agree with a highly educated prof I had the pleasure to meet who once said "the gasoline is the cheapest part of the engine". Now, if there was only a way to run those stinky diesels on WVO and route the exhaust through the galley for some decent fried chicken.<G>

These days...engine makers won't talk philosophy to end customers, like eveyrone else they are afraid they'll scare away the morons with money, or besued by the "lesons"--those who don't have enough money to be morons yet.

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Old 18-02-2008, 10:39   #32
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These days...engine makers won't talk philosophy to end customers,
One of the biggest changes (I purposely am not calling it an advancement)in the industry is the lightweight high power offerings. Yanmar, Volvo etc. Because leisure boating is unlikely to clock up more than say 200Hrs/yr, having high power in a small lightweight footprint is a blessing. But in commercial application, it is a curse. There is a commercial Whale/dolphin watch operator here that clocks up commercial hrs and has to replace his Volvo each year. Now he finds that acceptable because he has to get paying customers out to the spots quickly and then chase the animals around and then hike it back quickly for the next trip. So lightweight and high power is essential and built into his operational costs. But a commercial fisherman doesn't want teh expense and down time associated with replacign an engine each yr. He wants to have a big lumbering slow reving Diesel that he doesn't have to touch for maybe 5 to 10yrs. And even then in some cases, they just want to change the oil.
(please note last coment was a joke)


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