In this article I’m going to discuss the properties of the diesel and gas engines, and compare them to each other. I’m specifically referring to their use in automobiles.
From a distance the gas and the diesel engines seem to do their work in about the same way. A fuel made from refined crude oil is burned inside a cylinder and the hot expanding gasses forces the piston to move. The movement of the piston is then transferred to the wheels through crankshaft, gearbox and transmission.
It’s when you look closer at the two engines that you start to see the differences. Differences in gas mileage, smell, vibrations, price and expected age to name a few.
The gas engine has an ignition system with high voltages, wiring and spark plugs. This is not needed in a diesel as it compresses the air n the cylinder until it’s hot enough to ignite the fuel when injected. In the gas engine it’s the spark plug that ignites the fuel-air mixture through a high voltage spark at the right time.
Another thing that separates the diesel from the gas engine is that gas engines adds the fuel vapor to the air in the intake manifold either through a carburetor or through fuel injection nozzles. The air/fuel mixture is then sucked into the cylinder and is burned the next time the piston passes the compression stage.
The diesel on the other hand sucks clean air into the cylinder and then waits for the piston to compress the air as much as it will go. Fully compressed the air is hot enough to ignite disesel and at that point high pressure nozzles will start to spray fuel into the cylinder. The high temperature of the cylinder instantly ignites the fuel.
The different fuel injection and combustion lets the diesel work more efficiently than a gasoline burner. That’s why diesels have better fuel efficiency than it’s gas burning relatives.
I’m not saying that a diesel engine is better. It’s just different, it has it’s drawbacks too. Diesel engines usually is harder to start in cold and freezing weather. As you may remember it was the hot compressed air that ignited the fuel. When it’s too cold outside the air will never become hot enough to ignite the fuel, and the engine won’t run.
To handle this diesels have something called glow plugs for handling cold start situations. Electricity from the accumulator heats the glow plugs inside the cylinders before you even try to start the engne. That way the fuel is ignited by the hot glow plugs while the cylinder and air is still too cold to do it. A couple of seconds after the engine has started it is usually hot enough to ignite the fuel without the help of the glow plugs and these are not used again until the next cold start.
This is one of the nuisances of having a diesel in your car. The glowing takes from a couple of second to half a minute and can easily lead to stress when in a hurry. You just have to wait until it’s done or the car won’t start. On the other hand if the engine is well done the glowing does not take long and you soon get accustomed to it.
Lets for a second look at the practical differences between the diesel and the gas engine. The diesel engine is large and loud and it produces clouds of black strinking smoke when accelerating. In addition it has a more robust construction because of the high compression is must handle and can usually go twice as many miles as the same size gas engine during it’s life. The heavy duty contruction also makes it expensive when bought new.
Features of The Gas Engine
- More quiet that the diesel
- Better acceleration and higher top speed
- Uses an Ignition System with Spark Plugs to Light The Fuel
- Adds fuel to the air before letting it into the cylinder
- Not as sturdy as a diesel. Lower price but breaks down faster
- Gas readily available everywhere
- Gas Mileage is poor compared to a diesel
Features of The Diesel Engine
- Loud noise, may sound like a truck or agricultural machine
- Slow acceleration (get one with turbo charger, that helps)
- Top speed is nothing to brag about but there should be no problem maintaining the speed limit in most places
- Uses glow plugs to make the fuel ignite when the engine is cold
- Clean air is sucked into the cylinder, then fuel oil is injected
- Engine is simple and robust. Costs more but will run many miles
- Emits black smoke when loading it (like a quick acceleration)
- Can be converted to run on Eco fuel oils
- Has a great gas mileage
If I where to give you advice on selecting either a gas or a diesel powered car I would tell you this: Get a diesel if you drive long trips and can live with the small nuisances of more noise and poor acceleration. Get a gas powered car if you drive less than average or if you just want the comfort at any price.
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