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Speaker 1: Welcome the brain Stuff front House stuff works dot Com

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Speaker 1: where smart happens him Marshall Brain with today's question, is

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Speaker 1: it true that a diesel engine can operate underwater while

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Speaker 1: a gasoline engine cannot. You sometimes see military vehicles running

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Speaker 1: in extreme conditions, and these conditions can include deep submersion

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Speaker 1: during a river fording. Creating a vehicle that can run

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Speaker 1: submerged is a challenge. In order for any type of

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Speaker 1: combustion engine to run, it must have a source of

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Speaker 1: air and it must be able to release exhaust gases.

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Speaker 1: If the water is not too deep a few feet, say,

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Speaker 1: the exhaust castes can take care of themselves because they

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Speaker 1: are under pressure. The air intake is usually the problem.

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Speaker 1: As soon as you submerge the air intake, the engine

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Speaker 1: can no longer get air and it will stop running.

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Speaker 1: You can get around the air intake problem by adding

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Speaker 1: a snorkel. Military humvees often have a snorkel attached and

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Speaker 1: it allows them to submerge in up to five feet

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Speaker 1: of water. In order to handle submersion like this, the

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Speaker 1: engine and the rest of the vehicle must be waterproofed. However,

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Speaker 1: so your question changes into is it easier to waterproof

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Speaker 1: a diesel engine than it is the waterproof a gasoline engine.

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Speaker 1: To waterproof any off road vehicle, there are lots of

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Speaker 1: different things to think about. For example, any electrical devices

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Speaker 1: like the instruments, the engine control computers, motors for fans,

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Speaker 1: windshield wipers and so on, lights, battery, et cetera. All

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Speaker 1: have to be sealed. Second, any venting for things like

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Speaker 1: the crank case, the differential and stuff like that must

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Speaker 1: also be sealed or vented at the same level as

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Speaker 1: the snorkel. The fuel tank must be sealed invented appropriately,

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Speaker 1: and any chamber or crevice that can fill with water

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Speaker 1: must of a drain. Assuming that all these other things

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Speaker 1: have been taken care of, and assuming that the engine

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Speaker 1: is waterproof, then the vehicle can run under water. In general,

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Speaker 1: it's easier to waterproof a diesel engine than it is

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Speaker 1: to waterproof a gasoline engine because the spark plugs and

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Speaker 1: ignition system and a gasoline engine are complicated when you

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Speaker 1: get them wet. These components run at high voltage, and

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

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Speaker 1: on the other hand, has no ignition system See how

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Speaker 1: diesel engines work at how stuff works for details on that.

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Speaker 1: If the diesel engine has a mechanical fuel pump for

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Speaker 1: the injectors and a mechanical transmission, there's also no engine

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Speaker 1: control electronics to worry about. These features can make a

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Speaker 1: diesel engine relatively easy to waterproof. That's why most military

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Speaker 1: vehicles that ford rivers or run submerged have diesel engines.

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Speaker 1: Do you have any ideas or suggestions for this podcast?

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Speaker 1: If so, please send me an email at podcast at

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