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An Overview of the MAN 900 HP V8 Common Rail Marine Diesel

MAN 900 Horsepower common rail V-8 marine diesel engine

MAN's 15 Liter V-8 900 CR (common rail diesel) is a light-duty diesel engine intended for motoryachts, lightweight fishing boats and patrol craft.

MAN's 15 Liter V-8 900 CR is a light-duty diesel intended for motoryachts, lightweight fishing boats and patrol craft that will operate up to 1000 hours a year and at full load up to 20 percent of the total engine hours.

True to the nature of common rail technology, this MAN marine diesel boasts compact dimensions, a relatively light weight, impressively strong acceleration and miserly fuel consumption. Even better than its eyebrow raising performance, the engine is downright user friendly. For example when the cylinder block and heads are as cold as a stone it starts instantly. It doesn't care what the weather is doing. It just fires. Then once started it doesn't smoke. It doesn't smell. It is easy on the ears. That's the thing about this new breed of man marine diesels. Common rail offers all the benefits of a diesel and at the same time they've shed some nasty habits.

For those scant few souls who might be in the dark, this new common rail technology is a simple concept. Unlike traditional fuel delivery systems, a common rail system flows fuel to all of its injectors via a single tube. This flow tube pulls double duty as a fuel reservoir, holding within itself a volume sufficient for big bursts of acceleration. With this reservoir in place the bank of injectors doesn't have to wait for the lift pump to catch up to the throttle valve position. The fuel is already there knocking at the front door, waiting to be fired into the combustion chamber. So naturally it follows with common rail acceleration comes on stronger, much stronger. In ten years our grandkids won't believe us when we tell them that in our day diesel engines used to be slow to get up to speed.

Common rail also means electronic controls. As such, an array of sensors monitor vital signs, things like ambient air temperature, coolant temperature, engine load and throttle position. Those variables are compared to an electronic database that directs the flow of fuel through the injectors. A computer algorithm decides exactly how the fuel pulses; the precise volume of fuel; and the timing of the fuel pulse relative to the rise of the piston in its bore. Once again the net result is blisteringly-hot acceleration, brutally powerful horsepower and clean emissions. In a word, common rail brings a particularly efficient burn of fuel.

As one might expect from such a formidable marine power package, the MAN 900 hp V-8 is turbocharged. That means hot gas scavenged from the exhaust header spins a turbine that force feeds air into the combustion chamber. The extra volume of air transforms any engine into a giant killer. More air available in the combustion chamber means more fuel can be injected and burned. The more fuel that can be burned the greater the number of BTUs that can be converted from petroleum into raw, bloody horsepower.

You should also know that with this new MAN the amount of turbo boost varies, depending on rpm and engine load. This flexibility-in-boost-pressure lends the big diesel particularly high torque at low rpm, but without shamelessly slurping fuel. Obviously, it's the high boost at wide-open throttle that builds maximum horsepower. But low speed torque means there's power at virtually all usable throttle positions.

Four valves per cylinder are also part of the MAN equation. Simply put, they allow a huge volume of air to flow into the engine. It's like a sweet, old song whose words you have memorized. The greater the volume of air available to mix with diesel fuel and help light it afire, the greater the horsepower produced at mid to maximum rpm.

Remember how earlier in this story we mentioned how the exhaust emissions that emanated from common rail engines were exemplary clean? Point of fact, lowering emissions was the genesis for the development of common rail technology. With restrictive emissions regulations pending worldwide all of the engine builders saw the handwriting on the wall. They researched, they developed. Ultimately common rail is better for the environment and better for boating.

Finally, you might find it interesting to note Rudolf Diesel's wunderkindenfirst took form a century ago at the MAN facility. You remember Herr Diesel as the de facto inventor of the diesel engine. Since those halcyon days MAN diesels have powered motor vehicles, ships and electrical powerplants with more than 600 million horsepower. Today one of every two modern ships plying the proverbial Seven Seas is powered by an MAN diesel. Its pleasurecraft engines include I-6, V-8 and V-12 configurations from 205 to 1500 horsepower. The company maintains a global service and dealer network.