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![]() "Terry Spragg" wrote in message .cable.rogers.com... Use the blower for safety before starting your explosion machine. After it starts, it will suck air much faster than any vent fan can. A 454 cubic inch engine running at 3000 RPM and wide open throttle would consume 394 cubic feet of air per minute. That is roughly what a standard 4" bilge blower will move. Turn it off. Do not pressurize the engine compartment, especially if you have a leaky exhaust. Leaky exhausts are bad no matter what. Most bilge blowers draw air out of the compartment, not force air in. A flame arrestor metal filter grille on an engine room exhaust vent driven by engine vacuum seems a good idea, needing only a vent into the engine combustion intake. What? You use a flame arrester to prevent a flame front in one area (generally a small enclosed space) from spreading outside to a larger area. Like the carburetor intake to the engine room. Where are you exhausting this engine room to that you are trying to protect? Plan on driving this boat through an explosive atmosphere? A sufficiently strong "Intake air leak" will evacuate any but the most catastophic exhaust leak into the engine compartment. I have no idea what you are trying to say here. Considering that the volume of exhaust gases is an order of magnitude greater than the amount of intake I don't see how you can make such a claim. Engine air intakes are noisy, and require a dust filter Never seen a dust filter on a boat. , so go a little further and build an intake muffler filter box. The air intake noise is nothing compared to the basic machinery noise of the engine. If noise is a problem, silence the entire engine room! Place any such vent as high as possible in the engine compartment, in case of flooding. Provide a watertigh closure for submerged running, if you are fitting a schnorkel. Dust filters? Submerged running? Are we talking about boats here, or off road vehicles? I have equipped vehicles so that they could wade across rivers and keep running, but it isn't easy. It is not nearly as hard if you have a diesel. On a gas engine you will have ignition problems long before you have water ingested by the carburetor. If you are talking about prolonged operation the starter and alternator will need a lot of attention as well. Use the leakage of air into the engine compartment as a cabin heat circulation function, for instance, by placing the hot water radiator in the bow. Fresh ventilation air could be drawn through a heat exchanger incorperated into the engine compartment ventilation / combustion air intake filter, to improve efficiency in the heating If you desire cabin heat, you will be much better off installing a heat exchanger with a circulation fan and recirculating the cabin air through the heat exchanger instead of constantly drawing fresh (cold) air into the cabin. It is generally unwise to have any air passages between the cabin and the engine compartment. The heat exchanger might accept cold water for air conditioning, which could be cooled by a keel radiator pipe. When it's 130 (F) out, sea water temperature air will be blessedly cool by comparison, and won't eat up much power. I have never been any place that was 130 (F). Where do you boat that gets that hot? Most of the places that I do freqent where it gets what I consider to be "hot" the water temperature, at least on the surface, gets to be 75 to 80 degrees. Some will say you should try to be safer with a tight engine box. Don't ever depend on a tight engine box alone for protection from fumes and fire. You certainly want to have isolation between the engine compartment and the cabin, but I have never heard of making the engine compartment itself air tight. Such a design certainly wouldn't be legal in the USA. Rod |
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