Image
A diesel engine (which was invented by Rudolf Diesel) is technically called a compression ignition engine. The basic principle of a diesel engine is less complex than that of a gasoline engine. No spark plug or ignition system is needed. Unlike a conventional gasoline-fueled engine that relies on a spark from a sparkplug to light the fuel, a diesel uses high compression to cause the mixture to spontaneously combust. This makes the basic diesel engine a comparatively straightforward system that can result in fewer faults with lower maintenance costs than a gasoline engine.
How Does a Diesel Work?
A diesel engine works in a four-stroke cycle – literally four strokes of the piston – consisting of induction, compression, power and exhaust.
Image
First, a piston traps a quantity of air in an enclosed cylinder, then rises up the cylinder and compresses the air. As the air is compressed into a small space it heats up to a very high temperature, of about 600ºC. Diesel fuel is injected under high pressure into the small space. The fuel ignites when it comes into contact with the very hot compressed air. Bang! The resulting expansion of gases pushes the piston back down to the bottom of the cylinder, creating a powerful force which is used to drive a crankshaft. As this happens, the piston is pushed back up the cylinder and the exhaust gases escape through an exhaust valve and then the process or cycle begins again.
Valves
In order to get the air into the cylinder and the exhaust gases out of it, a combination of valves open and close through the cycle at precisely the right moment to either allow air in or exhaust out. When they are closed the valves need to be as tightly shut as possible to prevent the air, mixture and gases from escaping at the wrong moment. Strong springs called valve springs are used to hold the valves closed; the valves are opened by other lever type components called rockers. All the opening and closing of the valves is controlled by a camshaft which is connected to the crankshaft. The correct timing of the valves opening and closing is crucial, as is the gap or clearance of the valves.
Key Components of a
Diesel Vehicle
Image
Aftertreatment system:
This system is comprised of multiple components, which are responsible for filtering the engine exhaust gas to meet tailpipe emission requirements. After the exhaust gas of the engine is filtered through the diesel particulate filter (DPF) and the diesel oxidation catalyst to reduce particulate matter, diesel exhaust fluid (DEF) is injected into the exhaust gas mixture, then reduced to nitrogen and water by chemical conversion within the selective catalytic reducer (SCR) before being released into the atmosphere via the vehicle's tailpipe.
Battery:
The battery provides electricity to start the engine and power vehicle electronics/accessories.
Diesel exhaust fluid (DEF) tank:
This tank holds diesel exhaust fluid, an aqueous urea solution, which is injected into the exhaust stream during selective catalytic reduction.
Diesel exhaust fluid filler:
This port is for filling the diesel exhaust fluid tank.
Electronic control module (ECM):
The ECM controls the fuel mixture, ignition timing, and emissions system; monitors the operation of the vehicle; safeguards the engine from abuse; and detects and troubleshoots problems.
Fuel filler:
A nozzle from a fuel dispenser attaches to the receptacle on the vehicle to fill the tank.
Fuel line:
A metal tube or flexible hose (or a combination of these) transfers fuel from the tank to the engine's fuel injection system.
Fuel pump:
A pump that transfers fuel from the tank to the engine's fuel injection system via the fuel line.
Fuel tank (diesel):
Stores fuel on board the vehicle until it's needed to power the engine.
Internal combustion engine (compression-ignited):
In this configuration, fuel is injected into the combustion chamber and ignited by the high temperature achieved when a gas is greatly compressed.
Transmission:
The transmission transfers mechanical power from the engine and/or electric traction motor to drive the wheels.
Diesel engines have many advantages, but maintenance costs are not one of them. Diesel engines have more complex and expensive intake and exhaust systems than their gas counterparts. And that DEF tank, which typically holds five gallons, usually needs to be refilled at the same time as oil changes. Diesels use a lot more oil and often have two fuel filters. Plus, alternators, batteries, starters, and water pumps can all cost more on a diesel. And because of their weight, tire wear on a diesel will typically occur more quickly than gas vehicles.
Diesel Engines Are Built to Last a Long Time
Consider all the industries that rely upon diesel engines to handle work in this country. Every semi-truck on the road today has a diesel. And cargo ships typically have a pair (or more) of giant diesel engines turning the props. Diesel engines are under the hood of most vehicles used on a construction job site. They are ubiquitous in environments where heavy work must get done reliably—day after day.
Diesel engines last so long because their components have to be more robust than gas engines due to the internal combustion pressures being so much higher. The components that go into manufacturing a diesel engine are inherently more expensive partly because the stronger components are costlier to build. So, while diesels are more expensive (the diesel option box on any heavy-duty full-size pickup truck and it will add roughly $10,000 to the price tag) there’s a lot of value in that initial cost.
But durability is only one factor in the heftier price of a diesel. Fuel injection adds more cost because it must support higher pressures and inject fuel more precisely. And every one of them has at least one turbocharger, which can add upwards of $1,000 to $2,000 to the cost of a diesel.
On the other end, complicated emissions systems to reduce both particulates (soot) and nitrogen oxide (NOx) can really add to the price of these engines. This requires additional components that go beyond a gas vehicle’s catalytic converter including a DEF (Diesel Exhaust Fluid) tank, a diesel particulate filter (DPF), and additional sensors and electronic controllers.
But taking the plunge into diesel brings many benefits, especially when it comes to towing capacity and fuel economy.
Towing Capacity
The jump in capability from a gas- to a diesel-engine truck, particularly in the heavy-duty segment, is enormous. It’s clear these machines can move mammoth loads. Towing capacity is approximately 30 percent greater or more for heavy duty diesel trucks, no matter the manufacturer. Light-duty diesel trucks can generally handle heavier loads, too, but the capability gaps are much tighter.
So why can diesel vehicles tow more? The answer is low-speed torque. A turbodiesel engine is adept at developing a huge plateau of torque that peaks way down low in the rev range. So, when towing a heavy load, the gas engine needs to rev higher to make less than half the torque. Because a diesel’s torque hits so soon, the towing experience is smoother for the driver and lowers stress on the engine itself.
Turbocharging a diesel has another benefit. When you climb in elevation, a normally aspirated engine will lose 3 percent of its power for every 1,000 feet. A turbocharged engine doesn’t experience that power loss because it automatically compensates for the thinner air, pumping more into the mixture.
Fuel Economy
Diesel engines are around 15 percent more efficient than gas engines, and fuel economy improves by about the same amount. Even though diesels do provide an improvement in fuel economy, be mindful that diesel fuel costs on average about 15 to 20 cents per gallon more than gasoline.
If diesel fuel prices are high the great fuel economy may not result in lower costs. However, good fuel economy translates into an extended range. Diesel engines are more efficient when working with a load, too. There is a reduction in fuel economy when a diesel truck is loaded but it’s more, percentage-wise, with the gas truck because the gas truck has to work harder at a higher rpm to move the same load.
Which to Buy - Diesel or Gasoline Vehicle?
Before deciding to plunk down that hefty premium for a diesel engine, make sure you just don’t want a diesel, but rather that you need one. For a lot of towing and/or driving a lot of miles, it may well make sense to go with a diesel. On the flip side, if your daily drives are short and towing is only done occasionally, if ever, then a gas alternative might be better.
Gasoline engines are always cheaper, easier to maintain, and gives you quicker throttle response. While diesel torque feels great and is critical to pulling loads, generally they feel a bit lazier in everyday city driving. While some may be more responsive than others, test drive several models to determine which vehicle and engine combination is right for you.
When talking about heavy duty trucks specifically, keep in mind that while diesel truck's high upfront cost for the powertrain is a disadvantage, at least some of that investment will be recuperated when it comes time to sell to trade-in. Heavy-duty diesel trucks tend to hold their residual value better than their gas-powered counterparts because customers really value that power and that additional towing capability and they’re willing to pay for it.
Image
How Often Should Oil Be Changed in a Diesel Vehicle?
Just like vehicles with gasoline engines, diesels should have their engine oil changed every 7,500 miles according to manufacturer recommendations. That interval can extend out to as long as 10,000 miles or could be shorter depending on the use of the vehicle. If you do a lot of towing in high heat and dusty conditions, a shorter interval is probably a good idea.
Can Diesel Engines be Jump-started?
Yes, but it will take more power than a gasoline engine to start. Since diesels have a much higher compression ratio than a gasoline engine, they are harder to turn over. So additional power may be needed to energize the starter motor on a diesel engine.
If you have any questions on Diesel Engines Last Longer, Diesel Engine Excavator Complete Engine. We will give the professional answers to your questions.