It’s common knowledge that the vast majority of people in the United States are more familiar with gasoline engines than diesels. This is supported by research conducted by R.L. Polk, which found that in 2013, just 2.8 percent of all passenger vehicles registered in the United States (including cars, SUVs, pickup trucks, and vans) operated on number 2 diesel fuel. When opening the hood of a vehicle in the United States, the majority of people anticipate discovering spark plugs or coil packs, not turbochargers and injection pumps. However, these are two very important components found on virtually every diesel engine, which is where the term “turbodiesel” originates from.
In order to have a better grasp of the distinctions between gasoline and diesel engines, we are going to start out by comparing and contrasting the commonalities that exist between the two types. There is no discernible difference between the two power plants in terms of the overall composition of the engine, regardless of the type of fuel that is used (i.e. a crankshaft spinning, connecting rods and pistons moving up and down, air being pumped in, and exhaust being routed out). In point of fact, the fundamental architecture has not changed much at all. However, the process that takes place within the cylinder of a diesel engine is very unlike to that of a gasoline-powered vehicle’s equivalent.
The concepts of “air” and “fuel” are the most useful when attempting to describe the distinction between gasoline and diesel engines. Airflow is the most important factor in a gasoline engine. You are restricting the flow of air. The complete antithesis of this is a diesel mill. The principle behind its operation is to regulate the quantity of gasoline that is fed into the engine; the airflow merely follows suit. As a result, there is no requirement to restrict the amount of air that is flowing in. As a result of this, there is no creation of a vacuum inside the confines of a diesel engine.
For the sake of this discussion, we will depict the movement of air and fuel throughout a contemporary diesel power plant by using a four-stroke, turbocharged, and intercooled diesel engine. New air is drawn into the compressor housing of the turbocharger, which is located on the intake side, and is then compressed in the compressor wheel, which is where boost is produced. This results in the air being denser, but it also makes it significantly warmer.
By passing through a charge air cooler on its way to the cylinder head(s), compressed air may be cooled down before being introduced into the engine (also known as an intercooler). The air-to-air form of intercooler is the one that is utilized the most, and this particular design is essentially simply a straightforward heat exchanger. Along the path that the intake air takes to the engine, the temperature of that air may be greatly reduced by using an intercooler, which does so with just a very slight reduction in boost.
When the compressed air is forced into the cylinder, that’s when things start to get interesting. When the piston is at its lowest point, known as the bottom of its range, the intake valve (or valves) will open, enabling “unrestricted” air to enter the cylinder. This is known as the intake stroke. This differs from an engine that runs on gasoline in two important respects: 1) During the intake stroke of a gas engine, a mixture of fuel and air is sucked in, whereas 2) during the intake stroke of a diesel engine, air is the only thing that is sucked in. Following this, the intake valve or valves will close, and the compression stroke will then start. Because the piston is moving upward, the air that was previously occupying the whole cylinder is now using just 6% as much space as it did before. Because of the enormous pressure, this air is instantaneously superheated to more than 400 degrees, which is more than enough heat to for diesel fuel to ignite on its own. In fact, this is exactly what takes place as the piston reaches the top of its stroke. Before the piston reaches its top-dead-center position, the previously described very heated air is brought into contact with a shot of diesel fuel that has been injected into the cylinder by its corresponding fuel injector at the precise moment that is optimal for combustion to take place. Because diesel engines use the heat generated by compression to ignite the fuel, there is no requirement for a spark plug or other ignition source to kickstart the combustion process (i.e. spark plugs, such as in a gasoline engine).
Diesels can only be as great as the turbochargers that power them.
The final step in the process is the exhaust stroke, which involves forcing wasted combustion gasses out of the exhaust valves, over the exhaust manifold, and into the turbine side of the turbocharger (which is also known as the exhaust side). Because the typical gasoline-powered engine does not have a turbocharger, the exhaust fumes go straight to the tailpipe as soon as they leave the engine. In a diesel vehicle, this is not the case since the turbocharger, which is responsible for propelling fresh air into the engine, actually uses the exhaust fumes that are leaving the vehicle to drive itself. Exhaust gasses are always necessary in order to transport air into the engine using a turbocharger. This is because a turbocharger is comprised of a turbine (exhaust) wheel that shares a common shaft with a compressor (intake) wheel. Both are interdependent on one another. In the following manner, we will outline the significance of the turbocharger: You reduce the amount of fuel going into the engine, which causes combustion to take place. The exhaust fumes then exit the engine, turning the turbine wheel as they pass through. This in turn rotates the compressor wheel, which allows air to be sucked into the engine. You may call it a never-ending cycle. The turbocharger enhances the amount of air that is drawn into the diesel engine, which paves the way for a greater quantity of fuel to be burned off during combustion. This, in turn, improves the thermal efficiency of the engine.