Improved Performance and Effeciency
In the quest for better performance and fuel economy I have a question. I have a 42-foot Navigator with Volvo TAMD 63 318 hp diesels. Would it be worth the time and money to run a 4-inch duct from the side of the hull and dump fresh air on top of the air filter box? I was also thinking of adding 100 cfm inline fan to assist in the air flow. Good or bad idea?
Larry Olund
Pleasanton, CA
Fresh air, the cooler the better, is beneficial to the operation and efficiency of any internal combustion engine, diesel or gasoline. Engine manufacturers often provide specifications regarding the temperature of the “combustion” or “inlet” air in both absolute and relative terms. That is, how hot can the engine room be, which is where the engine draws its air from, and how high above ambient or outside air temperature. The cooler, and denser, the air being used by the engine for combustion, the more efficiently it operates. Many automobiles do this, drawing air through a duct from the grill, hood or wheel well, using what’s often referred to as cool air induction. The concern with ducting directly to the intake is the possibility of water finding its way through this same duct. While diesel engines love cool, clean air, they don’t run well at all on rain or seawater. Thus, your duct design would have to preclude any possibility what so ever of water ever making its way through that duct and to the engine’s air intake (some duct mechanisms include a dorade or baffle to prevent water from flowing to the intake).
Using the inline fan to force air through the duct to the engines may be beneficial; however, most in line fans are not rated for continuous duty. Using a large, continuous duty fan to provide cool air to the entire engine room is the favored approach as opposed to ducting air directly to the engine’s inlet. Ideally, the engine room air temperature should be no more than about 25°F above ambient (some engine manufacturers specify as little as 16°F for this figure, so you may want to check with yours), and cooler is always better. Finally, the pressure in the engine room should be just slightly positive, which ensures that the engines always have enough air to breath. If it’s too positive, fumes from the engine room may be pushed into the boat’s accommodation spaces and if it’s too negative, the engines will starve for air, consume more fuel, run smoky etc. Getting that balance just right isn’t easy, that’s why company’s like Delta T Systems produce equipment designed to monitor and supply just the right amount of air to keep the engine room cool and at the right pressure.
Steve D’Antonio, PMM Tech Ed