Modern Boatworksby David S Yetman
A treasure chest of information, ideas, projects, and maintenance hints for the hands-on boat owner, Modern BoatWorks is novel in that it covers a wide variety of topics, including mechanical, electrical, communications, and maintenance information. It is not just another do-it-yourself text, although it includes some DIY projects. Its purpose is to stimulate, inform,… See more details below
A treasure chest of information, ideas, projects, and maintenance hints for the hands-on boat owner, Modern BoatWorks is novel in that it covers a wide variety of topics, including mechanical, electrical, communications, and maintenance information. It is not just another do-it-yourself text, although it includes some DIY projects. Its purpose is to stimulate, inform, and assist boat owners who have an interest in technology and the hands-on aspects of operating, maintaining, and improving their boats. Many of the chapters of this book started out as magazine articles which were intended to explain some of the newer technologies and their benefits. Others are directed toward helping the reader to use the technologies, or, in some cases, be prepared when they let you down.Modern BoatWorks offers details on improvement projects including the correct tools to use and hints to make the job easier and safer. There are also several chapters on the fine art of maintenance and some suggestions for innovative tools and methods to help take the mess and drudgery out of the tasks.
Even though not all readers will own a diesel engine, install a hatch, rework an electrical system, or need to customize an instrument panel, they will still find valuable information in every chapter. Modern BoatWorks is a potpourri of practical knowledge that will lead to a better understanding of boats in general - knowledge that can be applied in a wide range of situations, help solve a multitude of problems,and enhance the boating experience. The chapters are grouped by a tenuous commonality, but the book is meant to be browsed at the whim of the reader. Enjoy! And remember, the best things in life are afloat. Illustrated.
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- 5.50(w) x 8.50(h) x 0.60(d)
Read an Excerpt
Demystifying Diesel Fuel Injection
Chances are that there will be an exciting, new, high-tech option available on your next new boat: a diesel engine.
Today's turbocharged, intercooled, electronically controlled fuel-injected diesel engines are as different from yesterday's smelly old clunkers as can be. Rudolph Diesel's compression-ignition engine, patented in 1892, was not a universal success despite the appeal of its apparent simplicity and reliability. The major stumbling block was a fuel system that relied on compressed air to blow the fuel/air mixture into the cylinders. It was a crude arrangement resulting in unreliable fuel-to-air ratios, limitations on speed and poor adjustment to the requirements of varying engine loads.
Diesels were restricted to use as stationary engines and power for large commercial vessels for nearly three decades before the advent of mechanically controlled, direct fuel injection. This allowed them to become the force they are today.
In its simplest state, the mechanically controlled fuel injection system, as shown in Figure 1, was comprised of a gear-driven high-pressure pump that delivered fuel through rigid metal tubing to an injector nozzle spraying fuel directly into the combustion chamber. Timing of the injection was pre-set by the pump's mechanical connection to the engine's crankshaft. Later versions were improved by a mechanism that could advance the injection timing in response to increased engine speed, much like the centrifugal advance in an automotive ignition distributor.
The fuel-to-air ratio was determined by the volume of fuel per injection, which was metered at the pump and controlled by a mechanical linkage connected to the throttle. Each cylinder had a dedicated pump plunger, fuel delivery line and nozzle so that the pump for a six-cylinder engine looked like a miniature in-line engine itself.
The in-line injection pump at the heart of this ingenious system was a precisely engineered device whose complexity rivaled that of the engine it served, but the result was so effective that the system, with later advances in nozzle technology, is still in use on some modern engines. It is a tribute to their engineering that they meet current environmental standards, but the writing is on the wall: more restrictive future standards will be beyond their capabilities.
The demand for better performance and reduced emissions has accelerated the development of fuel injection technology. One result is the unit injector, which incorporates a high-pressure pump, injector valve and nozzle in a stand-alone unit for each cylinder. Because it eliminates the plumbing between the pump and the nozzle, it can operate at higher pressure, and its timing can be more precisely controlled, resulting in quieter operation, more power and better control over emissions. The pump plunger in most versions is mechanically actuated by a separate lobe on the engine's camshaft.
There are two basic types of unit injectors: mechanically controlled and electronically controlled. Mechanically controlled unit injectors typically use a complex rotating sleeve valve actuated by a rack or lever to vary the length of the injection pulse. The valve is normally open, allowing the fuel being pressurized by the pump plunger to bypass the nozzle and return to the fuel tank. When the timing dictates that injection is to begin, the bypass valve is closed, and the resulting pressure pulse is forced through the nozzle into the combustion chamber. The volume of the injection is determined by the length of time the bypass valve remains closed. Valve closing is determined by engine timing; opening time is determined by the position of the sleeve valve which is linked to the throttle.
The combination of extreme pressure created by the plunger (often greater than 15,000 psi) and the very small openings in the nozzle tip result in a finely atomized spray of fuel enhancing the efficiency of the combustion process.
The second category, electronically controlled unit injectors, mimic the operation of mechanical units except that the bypass valve is operated by a solenoid as shown in Figure 2. Control of injection timing and volume is completely independent of any engine state or function. Therein lies the key to the revolution in diesel engine technology.
Mechanically controlled systems, regardless of their sophistication, can respond to only two conditions, engine speed and throttle setting, because they are mechanically linked to the engine. Some early applications of electronic control merely replaced the mechanical linkage with a position sensor and an electric actuator attached to the control rod of the mechanical pump. This was a significant improvement because control could be based on conditions other than speed and throttle setting, but it still lacked the flexibility and precision that is afforded by direct electronic control.
The ability to electronically manage timing and volume of fuel delivery opens the door to very precise interactive microprocessor control of the injection system and, by extension, the combustion process itself. Such a system is shown in Figure 3.
Modern controllers, variously known as engine control units (ECU), electronic control modules (ECM) or electronic engine control modules (EECM) are thinly disguised computers that can monitor the input from sensors throughout the engine and its environment. The temperature of ambient air, engine oil and coolant, the oxygen content of exhaust gas, the velocity of intake air, the load on the engine, speed, throttle position and even the speed of a second engine are monitored by the control unit. It processes the information according to its internal program to create output signals that precisely tailor the operation of the fuel injection system to those conditions. Figure 4 is a logical diagram of the system control loop.
Most manufacturers of marine diesels still have a variety of fuel injection systems on their products, with in-line pumps and nozzles on older engines and electronic systems on newer or high-end products. Caterpillar is typical, using four different types of fuel injection for pleasure craft engines. Its 3208 series is still equipped with in-line pumps and nozzles; the 3116 and 3126 use mechanical unit injectors (MUI), while the 3176 and others use electronically controlled unit injectors (EUI). The latest innovation is the hydraulically operated, electronically controlled unit injector (HEUI). Instead of a camshaft to actuate the pump plunger, the HEUI uses hydraulic pressure from a branch of the engine's lubricating oil system. The intriguing part is that the hydraulic pressure in this sub-system could be varied by the ECM, giving Cat control over still another aspect of the process. HEUI was initially available only on 3412E marine engines, but it's slated to become the system of choice in the future.
The electronically controlled unit injector is usually credited with the diesel's current resurgence, but it just opened the door for the real star: the computer. Neither would have reached full potential in diesel technology without the other, but the combination means we will continue to see and benefit from advances in fuel injection and diesel performance. Diesel engines may never be exotic, but exciting high-tech will still apply.
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