February 12th, 2010 by engineering magazines
In a conventional marine diesel engine the power is produced by hot compressed air igniting fuel sprayed under very high pressure into the cylinder head. A marine diesel engine does not use a carburetor to mix fuel and air or spark plugs to ignite the mixture. Instead it employs the pistons to compress the air to 3000 kPa which causes it to become extremely hot and the fuel is ignited as soon as it is injected into the cylinder.
Some marine diesel engines are fitted with a heater plug in the inlet manifold or a glow plug in the pre-combustion chamber of each cylinder to provide additional heat to the combustion air during starting.
Diesel engines are heavier and slower revving than petrol engines but they are also more reliable because they do not rely on external carburetion or an electrical spark for ignition.
Newer engines use an electronic fuel injection system whereby fuel and air are mixed more thoroughly in the pre-combustion chamber before entering the cylinder. This system maximizes power and fuel economy and is also less polluting.
Every boater should have an understanding of how their engine works so let’s start by explaining the mechanical cycles.
Most reciprocating piston internal combustion engines work on one of two mechanical cycles-either the four-stroke cycle or the two-stroke cycle. These cycles designate, in correct sequence, the mechanical actions by which the fuel and air gain access to the engine cylinder, the gas pressure – due to combustion – is converted to power and, finally, the burnt gas is expelled from the engine cylinder.
The Basic Four-Stroke Diesel Engine
From its name, it is obvious there are four strokes in one complete engine cycle. A stroke is the movement of the piston through the full length of the cylinder and – since one such movement causes the crankshaft to rotate half a turn – it follows that there are two crankshaft revolutions in one complete engine cycle.
The four strokes in the order they occur are:
1. Inlet stroke. With the inlet valve open and the exhaust valve closed, the piston moves from top dead center (TDC) to bottom dead center (BDC), creating a low-pressure area in the cylinder. Clean, filtered air rushes through the open inlet valve to relieve this low-pressure area, and the cylinder fills with air.
2. Compression stroke. With both valves closed, the piston moves from BDC to TDC, compressing the air. During this stroke the air becomes heated to a temperature sufficiently high to ignite the fuel.
3. Power stroke. At approximately TDC, the fuel is injected, or sprayed, into the hot, compressed air, where it ignites, burns and expands. Both valves remain closed, and the pressure acts on the piston crown, forcing it down the cylinder from TDC to BDC.
4. Exhaust stroke. At approximately BDC the exhaust valve opens and the piston starts to move from BDC to TDC, driving the burnt gas out of the cylinder through the open exhaust valve.
The Two-Stroke Diesel Engine
The two-stroke engine uses two piston strokes to complete one power stroke and, therefore, fire twice as often as a four-stroke engine. A two-stroke engine is smaller and simpler with fewer moving parts. A two-stroke engine has the potential to produce twice as much power as a four-stroke engine of the same size, however, because of the extra fitting required in a two-stroke diesel engine, for example blowers and governors, they become more expensive to produce. There has been a shift towards four stroke diesel engines which have become more efficient and smaller.
Protect Your Marine Diesel Engine
Protect your engine by avoiding long periods (more than 10 minutes) of idling in a “no-load” situation. This is often done to charge batteries or cool refrigeration but if done repeatedly it will glaze the bores of the engine and cause premature engine failure. If the vessel is in a berth the engine can be put in gear to create load at idle.
All boat owners should have an understanding of basic marine diesel engine maintenance to keep themselves and their families safe on the water.
Read the rest »
January 30th, 2010 by engineering magazines
It has been 114 years since Rudolph Diesel applied for a patent for his new improved engine. It was hoped to replace the gasoline engine but as we can all see that this has not happened. The gasoline engine having just been invented in 1876 was still considered inefficient in fuel consumption and power. An evaluation of each engine’s performance tells a story that is difficult to reconcile with the way things have shaken out in the beginning of the 21st Century. The invention of the Diesel offered the world a far more efficient and effective fuel based engine. It actually provides more horsepower per gallon or liter than a gasoline. This is why diesel engines power our large earth moving equipment, trucks, marine engines, low mileage
cars and now aircraft.
The diesel is a combustion injection engine. Unlike the gasoline engine, air is compressed first and then the fuel is injected into it. The compressed air is hot enough to ignite the diesel fuel without the use of a sparkplug. Diesel engines developed out of the earlier work surrounding two engines; the original diesel design and the solid injection system of Herbert Akroyd Stuart created in his hot bulb engine. This means that the upward stroke of the diesel engine compresses the air to where its’ temperature is between 1300-1650° F. When the piston has reached the top of its’ upward stroke, diesel fuel is then injected, combustion occurs, pressure increases and pushes the cylinder downwards. This motion is transmitted by means of the connecting rods to the crankshaft which itself turns thus transmitting rotating power to a drive shaft which powers ships, cars, generators, aircraft and even motorcycles.
During cold weather, diesel fuel thickens when the wax crystallizes. It becomes a gel and the fuel injection will not easily work. Technological advances have made this a problem of the past. The fuel lines and fuel filter can be pre-warmed, others use a glow plug in the combustion chamber to pre-heat its’ walls, some use resistive heaters in the intake manifold to warm air taken into the combustion chambers and engine block heaters are used in areas like Kansas or Nebraska when automobiles are left in the cold overnight.
Diesel engine speed used to be controlled by governing the rate of fuel through a gear system. Today the use of electronically controlled engines ECM (electronic control module) allows diesel engines to adjust their timing to start according to the environmental conditions of heat and cold, regulate the engine speed in terms of RPM (revolutions per minute) and maintain fuel economy.
Diesel engines may not have beaten its’ chief contender, the gasoline engine, but it has kept ahead in terms of heavy machine and naval engines. It has recently performed outstandingly in the area of remotely piloted vehicle engines, set amazing land speed records for racecars and motorcycles. The diesel engine has improved amazingly in the past 114 years. The use of electronics has given all engines abilities of fuel conservation unheard of in past years. This makes the diesel engine a real budget-winning contender. This year the new 2006, Volkswagen diesel won fourth place in the best mileage evaluation according to http://www.fueleconomy.gov. Diesels may prove to be the green vehicle engine of choice in the future since they have very little carbon monoxide emissions. Catalytic converters and diesel particulate air filters have made diesel engines free from particulate, nitrogen and sulfur oxides. Diesel engines may prove to be the easiest solution to greenhouse gases.
Read the rest »
January 24th, 2010 by engineering magazines
This article will help you to know more about Gas and Diesel. The plus and minus or strengths and weakness of both fuel either gasoline or diesel. This article will discussed both fuel from various aspects such as price, impact on the machine, maintenance etc.
Cost
Due to the high compression ratios and resulting high cylinder pressure in diesel engines, they must be built to withstand a lot more punishment than gas engines. The parts that are spruced up include a thicker block and cylinder heads, pistons, crankshaft, and valves, which can be very costly indeed.
When it comes to the price, gas wins this one by far. Diesel costs a lot more to own than gas, which is one of the main reasons why people tend to choose gas over diesel.
Fuel cost
Diesel fuel is easier to refine, taking less time to get from raw petroleum to final product from gas, giving it a lower price than that of gas. On the other hand, within the United States, diesel is priced the same or just a bit below regular unleaded gas.
“As we head to war with Iraq, President Bush wants to make one thing clear: This war is not about oil, it’s about gasoline.” 
Noise and vibration
Despite many improvements in noise isolation and engine noise technology in trucks over the last 10 years, diesels are still much louder and shake more than gasoline powered vehicles. At idle, the clatter and shake of diesel vehicles are clearly noticeable, while it can be hard to tell if the gas engine is even running.
Cold weather
If you’ve tried to start a diesel engine on a cold day, you know that gas is by far easier to start. Diesels don’t have spark plugs like gas engines do, as the fuel is ignited once it’s injected into the cylinder that is already under pressure. When it gets cold, the air isn’t hot enough to ignite the diesel fuel.
Maintenance
Maintenance on a diesel vehicle is more expensive, thanks to many things including the larger volume of oil in the engine and the fact that fuel filters and water separators must be serviced more often than gas vehicles. Gasoline engines have a bigger advantage due to extended service periods on spark plugs, engine oil, and even antifreeze.
Making that final choice between gas and diesel comes down to what you’ll do with your vehicle and where you live. If you use your vehicle for quick, fast acceleration and rarely ever haul heavy loads, and don’t plan to keep your vehicle past 100,000 miles, you may want to consider buying a gasoline vehicle.
Gas runs smoother, fuel is easier to find, and they are easier to start in cold weather. On the other hand, if you plan to tow, value good fuel economy and plan on racking up a lot of miles, then you’ll want to buy a diesel.
Price is also an important consideration, as diesel vehicles can be a bit more expensive than gas. If you aren’t worried about price, then diesel may be your best bet. For trucks, diesel is by far the superior choice for those who like to haul heavy loads on a frequent basis.
As the last words, I like this quote so much:
“What is needed is an all-out science project to get vehicles off of gasoline, rather than off of the earth.”
Read the rest »
October 26th, 2009 by engineering magazines
Revolutionary advancements to automotive engineering and design have incorporated the use of engine computers to enhance the efficiency of engine operations. Along with the use of electronic engine sensors, computer-assisted engine system operations have established greater engine power and performance perfect for daily driving applications. For high performance driving applications, you can simply employ a cost effective Pontiac performance chip to do just the trick in taking your vehicle’s overall engine performance a level up notch. The chip carries a program that is designed to upgrade the critical factory performance settings of your engine. Aside from that, the incorporation of application tested technologies backed up the dyno-test proven results of the fuel efficiency as well as the performance gains offered by premium performance chips. Souping-up serious power train has never been easier. The secret to enjoying practical and convenient solutions to unleashing your vehicle’s overall level of performance lie on the functionality of a single unit of sophisticated performance enhancing device.
Tuned towards delivering your vehicle’s peak performance and fuel efficiency, the sophisticated and neat technology used in manufactured premium Pontiac performance chip has long been developed to offer greater possibilities to boosting combustion efficiencies. With the help of electronic sensors, it breaks your engine free from the restrictions of critical factory settings for performance. At specified RPM range, the product is designed to meet the exact demands of sustaining smooth operations as specific driving applications. Add that up to the product’s simplest and easiest installation specifications and you simple get pure convenience of continually enjoying the gains of re-establishing the fuel efficiency status of your engine absolutely hassle-free. While it is intended to be wired directly to your engine control unit, the product automatically makes all the necessary adjustments to optimize fuel combustion efficiency. It intelligently improves drivability by simply helping your engine computer keep up with the intensity of engine operations you require so following the course of your driving style will be absolutely fail-proof.
With today’s age of technological advancements, you never will need to crawl under the hood just to upgrade the performance of your vehicle. Back in the days, you need to hope of the best results when fondling with carburetor settings and distributor advance curves just to squeeze more engine power out of the standard yielded output. By combining aggressive fuel and timing settings, plug and play Pontiac performance chip applications eliminates all the dirty works of juicing more power from your engine. By remapping your engine systems for more power and torque, it simply acquires better stance in terms of drivability and fuel economy. Because performance chips are highly advanced car accessories as well as cost effective performance enhancers, chip manufacturers take leverage on more advanced chip features connected with their chips. Whatever type or brand of performance chip you decide to have your ride equipped with, make sure that the product is custom tailored to your vehicle’s specific year and model of application. Otherwise, you might face sever engine computer problems due to imprecision. Finding the best fitting Pontiac performance chip for your vehicle has been made easier as online automotive stores improved the availability of performance chips not just to your country but all over the world.
Read the rest »
October 18th, 2009 by engineering magazines
To effectively reduce the pollution levels coming from your engine exhausts, your vehicle employs a highly efficient Mazda catalytic converter to reduce the toxicity of emission gases. In any internal combustion engine, the use of catalytic converters comes necessary to pass the required emission tests so you can legally drive in any highway or street. Due to the advent of emphasizing the need to address the environmental issues, EPA has already tightened its regulations in limiting the combustion by-products that are released through the atmosphere. As among the forefront innovators when in comes to automotive engineering, Mazda has equipped their excellent lines of automobile with catalytic converters that feature advanced exhaust purification and emission reduction capacities with the company’s standing quest in delivering the best possible fuel economy they could create.
To efficiently facilitate chemical reactions among fuel exhausts, catalytic converters have gone a long way since their power-sapping and pellet-style versions. Now, newer honeycomb converters have been developed to deliver precision flow of exhaust gases while cleaning up your engine from nasty pollutants. Your powerful engine may employ oxidation or three-way type of Mazda catalytic converter. To regulate the toxicity of exhausts, an oxidation converter takes main focus on the carbon monoxide and hydrocarbon contents of gases. As the name implies, this type of converter makes use of an oxidation process to speed up the rate of converting carbon monoxides and hydrocarbons into harmless water vapors and carbon dioxide. The three-way type facilitates an oxidation process similar to the oxidation type. Only, it also takes focus in the reduction of nitrogen oxide levels. The inside shell of the part has BB-sized or Monolithic substrate that serves as effect agents that significantly makes the combustion by-products more acceptable to the environment. The substrate material is plated with thin coating of rhodium, platinum, or palladium to assist or speed up the chemical reactions required to reduce emission levels.Because the part constantly handles harsh working conditions, damages will come inevitable once it has served well and long enough. Broken or rusted out converter body is a clear indication of an already failing part. To have early Mazda catalytic converter diagnosis that is to be followed by timely repair, you must be sensitive enough to the indications delivered by your engine OBD systems. The system makes a great tool in offering accurate and enough information to help qualified service technicians properly diagnose and repair converters during routine checks for maintenance. Because the system is designed to alert you once something goes wrong in the emission control system mechanisms, it could help you optimize the efficiency and service life of your stock converters. In case the part goes beyond repair, you must immediately find new and precision fitting replacement to maintain engine precision and enjoy excellent fuel economy with powerful engine performance. Prolonging the use of an already inefficient converter could cause serious engine damages due to failure and imprecision. A high flow Mazda Catalytic Converter make a great valued investment you can reward your vehicle. Aside from keeping your engine and exhaust clean, the part could yield substantial increases to horsepower and torque so your Mazda ride follows the course of your driving style with no fail.
Read the rest »
July 15th, 2009 by engineering magazines
Try increasing displacement – the more displacement means the more power you’ll because it burns more gas during each revolution of the engine (Not very fuel saving). Try making the cylinders bigger or by adding more cylinders. 12 seems to be the limit.
Modify the compression ratio – You can produce more power by increasing compression ratios. The more air/fuel mixture is compressed the more power it will generate, however the more likely it is to spontaneously burst into flame (prior to the spark plug igniting it). Higher octane gasolines prevent this sort of early combustion. High-performance cars generally use high octane gasoline – because the engines use high compression ratios.
Stuff more into each cylinder – you can get more power from the cylinder, if you can cram more air (and therefore fuel) into a cylinder of a given size. Turbo chargers and super chargers pressurize the incoming air to effectively cram more air into a cylinder.
Cool the incoming air – It get pretty hot when compressing air. You would like to have the coolest air possible in the cylinder because the hotter the air is the less it will expand when combustion takes place. An intercooler is a special radiator through which the compressed air passes to cool it off before it enters the cylinder. Therefore many turbo charged and super charged cars have an intercooler.
Let air come in more easily – As a piston moves down in the intake stroke, air resistance can rob power from the engine. Air resistance can be lessened dramatically by putting two intake valves in each cylinder. Some newer cars are also using polished intake manifolds to eliminate air resistance there. Bigger air filters can also improve air flow.
Let exhaust exit more easily – If air resistance makes it hard for exhaust to exit a cylinder, it robs the engine of power. Air resistance can be lessened by adding a second exhaust valve to each cylinder (a car with 2 intake and 2 exhaust values has 4 valves per cylinder, which improves performance – when you hear a car ad tell you the car has 4 cylinders and 16 valves, what the ad is saying is that the engine has four valves per cylinder). If the exhaust pipe is too small or the muffler has a lot of air resistance then this can cause back-pressure which has the same effect. High-performance exhaust systems use headers, big tail pipes and free-flowing mufflers to eliminate back-pressure in the exhaust system. When you hear that a car has “Dual Exhaust”, the goal is to improve the flow of exhaust by having two exhaust pipes instead of one.
Try making everything lighter – The lighter the piston, the less energy it takes. Lightweight parts help the engine perform better. Each time a piston changes direction it uses up energy to stop the travel in one direction and start it in another.
Inject the fuel – This improves performance and fuel economy. Fuel injection allows very precise metering of fuel to each cylinder.
Read the rest »
Tags: Burnt Gas, Combustion Air, Combustion Chamber, Correct Sequence, Diesel Engine, Diesel Engine Maintenance, Electronic Fuel Injection, Electronic Fuel Injection System, Engine Cylinder, Fuel Economy, Fuel Injection System, Glow Plug, Inlet Manifold, Internal Combustion Engines, Marine Diesel Engine, Marine Diesel Engines, Mechanical Actions, Petrol Engines, Stroke Cycle, Stroke Diesel
