Engine Room Cooling

[slochner]

Which is more effective in cooling the engine compartment: blowing air in or sucking air out?

[Tim R.]

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.

[Sailmonkey]

+1

sucking air out allows directing the hot air where you want it, and keeps it out of accommodation spaces, smells too.

[teneicm]

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.

[Watermann]

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.

[markpierce]

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.

[GordMay]

Greetings and welcome aboard the CF, slochner.

➥ http://www.cruisersforum.com/forums/...tml#post473899

[AnchorageGuy]

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

[bil56]

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?

[GordMay]

Originally Posted by bil56

... 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