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Old 25-07-2013, 09:45   #1
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Engine Room Cooling

Which is more effective in cooling the engine compartment: blowing air in or sucking air out?
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Old 25-07-2013, 09:59   #2
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Re: Engine Room Cooling

Out. You want to be able to direct the hot air by blowing it out to a specific outlet. Blowing cool air in allows the hot air to escape anywhere including the living space.
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Old 25-07-2013, 10:05   #3
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Re: Engine Room Cooling

+1

sucking air out allows directing the hot air where you want it, and keeps it out of accommodation spaces, smells too.
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Old 25-07-2013, 10:15   #4
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Re: Engine Room Cooling

Mount a blower directing air out as high in the engine compartment as practical. This will remove the hottest air and will allow cooler air to infiltrate the compartment.
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Old 27-07-2013, 13:19   #5
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Re: Engine Room Cooling

Ideally you want both, with a slight positive pressure maintained. Depending on the size of the engine compartment and how easily fresh air can get in, too much exhaust blowing can lead to inefficiencies as the engine (which is really also an air pump) is slightly starved of combustion air. You don't want negative (in relation to the atmosphere) pressure in the engine compartment.

On a small sailboat aux engine, this may have zero practicalities but it is very relevant on larger power-driven vessels with large displacement engines.

If you have room and means to do it, have one blower drawing fresh air in and another blower as far across the space as practical, exhausting air out.
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Old 27-07-2013, 13:37   #6
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Re: Engine Room Cooling

With a passive air in-take to the engine compartment, I notice no change in engine performance when the compartment's exhaust fan is turned on. Lesson: don't short-change the air inlet.

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Old 28-07-2013, 07:48   #7
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Re: Engine Room Cooling

Greetings and welcome aboard the CF, slochner.

Engine Room Blower
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Old 28-07-2013, 08:12   #8
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Re: Engine Room Cooling

I agree with the "both" camp. Circulating air is much more beneficial IF you can set up the engine compartment exhaust easily. If not than an exhaust should be used. Whatever you choose, be sure and get a continuous duty fan. Chuck
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Old 28-07-2013, 10:31   #9
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Re: Engine Room Cooling

fresh air inlet always below the engine compartment,
evacuation of warm air from the top

but also: the diesel engine air consumption is huge,
are the air ducts sufficient?
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Old 28-07-2013, 11:14   #10
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Re: Engine Room Cooling

Quote:
Originally Posted by bil56 View Post
... the diesel engine air consumption is huge,
are the air ducts sufficient?
Approximate consumption of combustion air for a diesel engine is
0.1 cu m of air/min/brake kW (2.5 cu ft of air/min/bhp) produced.

See Caterpillar’s excellent Engine Room Ventilation guide
http://www.toromontcat.com/powersyst...EBW4971-03.pdf
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