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Posts Tagged ‘gas mileage calculator’

In this article I’m going to discuss the properties of the diesel and gas engines, and compare them to each other. Specifically their usage in automobiles.

Looking at them from a distance both the gas and the diesel engine work in about the same way. Fuel manufactured from refined crude burns in the cylinder forcing the piston to move from the resulting pressure. The movement of the piston is then transferred to the wheels through crankshaft, gearbox and transmission.

It’s when we look at the engines a little closer that we start to notice that there are differences. Differences in gas mileage, smell, vibrations, price and expected age to name a few.

With a gas engine there is an ignition system that uses high voltage electricity with 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.

Also separating the diesel and gas engines is the fact that gas engines mix the fuel vapor with air in the intake manfold before it's entering the cylinder. The air/fuel mixture is then sucked into the cylinder to be burnt the next time the piston strikes.

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. At this time when the air is compressed and hot enough to ignite the fuel, diesel is injected directly into the cylinder (or a small space connected to the cylinder) through high pressure nozzles. The fuel ignites instantly due to the high temperature in the cylinder.

The differences is fuel injection and ignition results in the diesel burning the fuel more efficiently than the gas engine. That's why diesels have better fuel economy than it's gas burning relatives.

I'm not saying that a diesel engine is better. It's different, it has 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.

That’s why diesels have glow plugs that are used when starting a cold engine. Electricity from the accumulator heats the glow plugs inside the cylinders before you even try to start the engne. This way the hot glow plugs ignite the fuel when the air is not hot enough 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. Glowing can take from a couple of second to half a minute and can be quite a stress if in a hurry. You just have to wait until it's ready 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 is large and loud, it emits black smoke when accelerating and is generally regarded as bad smelling by those not owning one. It also has a sturdier construction due to the higher pressures it must handle and thus can often go twice as many miles as a gas engine during it's lifetime. 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
• MPG is low compared to a diesel

Features of The Diesel Engine

• Loud noise, sounds like a truck or agricultural machine
• Slow acceleration (get one with turbo charger, that helps)
• Lower top speeds but can easily reach the legal speed limit in most places
• Uses glow plugs to help the fuel ignite when the engine is cold
• Lets clean air into the cylinder and injects the fuel later
• Engine is simple and robust. Higher price but runs many miles
• Emits black smoke when loading it (like a quick acceleration)
• Easy to convert to using Eco fuel oils
• Has a great fuel economy

If I where to give you advice on selecting either a gas or a diesel powered car I would probably 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.