WEBVTT - Is it true that a diesel engine can operate underwater?

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<v Speaker 1>Welcome the brain Stuff front House stuff works dot Com

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<v Speaker 1>where smart happens him Marshall Brain with today's question, is

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<v Speaker 1>it true that a diesel engine can operate underwater while

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<v Speaker 1>a gasoline engine cannot. You sometimes see military vehicles running

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<v Speaker 1>in extreme conditions, and these conditions can include deep submersion

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<v Speaker 1>during a river fording. Creating a vehicle that can run

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<v Speaker 1>submerged is a challenge. In order for any type of

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<v Speaker 1>combustion engine to run, it must have a source of

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<v Speaker 1>air and it must be able to release exhaust gases.

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<v Speaker 1>If the water is not too deep a few feet, say,

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<v Speaker 1>the exhaust castes can take care of themselves because they

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<v Speaker 1>are under pressure. The air intake is usually the problem.

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<v Speaker 1>As soon as you submerge the air intake, the engine

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<v Speaker 1>can no longer get air and it will stop running.

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<v Speaker 1>You can get around the air intake problem by adding

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<v Speaker 1>a snorkel. Military humvees often have a snorkel attached and

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<v Speaker 1>it allows them to submerge in up to five feet

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<v Speaker 1>of water. In order to handle submersion like this, the

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<v Speaker 1>engine and the rest of the vehicle must be waterproofed. However,

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<v Speaker 1>so your question changes into is it easier to waterproof

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<v Speaker 1>a diesel engine than it is the waterproof a gasoline engine.

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<v Speaker 1>To waterproof any off road vehicle, there are lots of

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<v Speaker 1>different things to think about. For example, any electrical devices

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<v Speaker 1>like the instruments, the engine control computers, motors for fans,

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<v Speaker 1>windshield wipers and so on, lights, battery, et cetera. All

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<v Speaker 1>have to be sealed. Second, any venting for things like

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<v Speaker 1>the crank case, the differential and stuff like that must

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<v Speaker 1>also be sealed or vented at the same level as

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<v Speaker 1>the snorkel. The fuel tank must be sealed invented appropriately,

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<v Speaker 1>and any chamber or crevice that can fill with water

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<v Speaker 1>must of a drain. Assuming that all these other things

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<v Speaker 1>have been taken care of, and assuming that the engine

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<v Speaker 1>is waterproof, then the vehicle can run under water. In general,

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<v Speaker 1>it's easier to waterproof a diesel engine than it is

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<v Speaker 1>to waterproof a gasoline engine because the spark plugs and

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<v Speaker 1>ignition system and a gasoline engine are complicated when you

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<v Speaker 1>get them wet. These components run at high voltage, and

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<v Speaker 1>sealing them is harder, although it's not impossible. A diesel engine,

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<v Speaker 1>on the other hand, has no ignition system See how

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<v Speaker 1>diesel engines work at how stuff works for details on that.

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<v Speaker 1>If the diesel engine has a mechanical fuel pump for

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<v Speaker 1>the injectors and a mechanical transmission, there's also no engine

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<v Speaker 1>control electronics to worry about. These features can make a

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<v Speaker 1>diesel engine relatively easy to waterproof. That's why most military

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<v Speaker 1>vehicles that ford rivers or run submerged have diesel engines.

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