Are diesel engines more efficient than gas engines?

Small diesel generators sometimes have a bad image. But in my opinion that is just a prejudice. It is a well known fact that diesel engines are the most preferred engines in industrial settings. And that has been the case for a great number of years. There is very much experience with these engines. So you will understand that very important issues like cost, reliability, and efficiency have been thoroughly evaluated. Therefore it will be no surprise to you that diesel scores good at these issues. Diesel is more reliable, more efficient, has a longer life cycle and require less maintenance than engines that run on other fuels. And this is not just the slogan of a commercial, but there are solid technical reasons to back this up.

An important technical issue of internal combustion engines is that a large part of the potential energy from the fuel is converted to heat in stead of useful power. And on top of that some of that power has to be used for cooling the engine to prevent overheating. The temperature of a running diesel engine is much lower than that of any other internal combustion engines, so a greater part of the energy from the fuel is converted into useful power and less of this power has to be used for cooling.

But that is only part of the reason of the efficiency of diesel. Another reason why these engines are more efficient is because the compression ratio. The compression ratio of a diesel engine is 14:1 up to 25:1 and the compression ratio of a gasoline engine is between 8:1 an 12:1. And the higher the compression ratio, the more efficient an engine will be.

Because of the efficiency the cost of using a diesel engine will be less than that of a gas engine. To be more specific: the fuel cost of a diesel generator per kilowatt is 30% to 50% lower compared to a gas generator.

And of course engines require maintenance. And that is yet another reason for the popularity of diesel engines: they require less maintenance and also last longer than gas engines. Partly this due to the lower temperature of the diesel engine we discussed before. But another reason is for the reliability and the lower maintenance cost is the fact that there are no spark plugs or spark wires in a diesel engine. So these parts cannot cause problems will not have to be replaced regularly.

The last prejudice I want to talk about is the fact that many people think that diesel engines are very noisy and smelly machines. And indeed that was true – in the past. But not any longer, because the past decades diesel technology has made great progress. Diesel engines run quieter and less noisy then ever. Better insulation material have been developed (and used). And also the use of mufflers has contributed to the low noise diesel engine.

Considering a turbocharged vehicle? Big kahuna intakes or parallel twin turbo? That’s not important for now if you have a shoestring budget. The first thing you should consider is how fuel efficient is it? Then whether gas or diesel. Read on!

Turbocharging is the method with internal combustion engines to use a vehicle’s exhaust gases to cram force-induced compressed air into the engine. This concept follows the idea that a normal internal combustion engine’s ability to use air to power a combustion cycle is limited to the negative pressure its pistons creates to draw air in from the outside unaided.

However, with the turbocharger, more air mass is forced into the engine, thereby making the engine burn much more efficiently, and hence performs much better.

Comparatively, turbochargers are used more often in diesel engines due to the following characteristics:

-Normal diesel engines are designed to be over-built, helping it withstand higher pressures and heat from the start.

-Diesel engine power outputs are less compared to gasoline engines which require less pressure from turbochargers to produce more power.

-Diesel engines are not limited by the octane ratings of gasoline as diesel engine are designed to pump fuel into its combustion chamber only at the moment of ignition.

-Are proven to be fuel-efficient than diesel engines with no turbocharger. In diesel engines, more air compressed into the engine results in greater fuel efficiency.

Practically, there is little downside to owning a turbodiesel vehicle.

Turbocharged gasoline engines, though, may perform better than turbodiesels but require more consideration for balance and maintenance.

On the other hand, installing turbochargers in gasoline engines have the following caveats:

-Gasoline engines are lighter than diesel engines. Forcing air into engines has the added effect of “overclocking” the engine, increasing heat and pressure above normal specifications.

-Adding a turbocharger to a car is more expensive than buying a car with a stock turbocharger as upgrades to other parts of the car are needed to bear the added heat, pressure, torque and power.

-Gas turbochargers have to take into account the octane ratings and autoignition temperatures of its fuels.

-Gasoline engines spray gas and air into the combustion chamber at the same time it is being compressed. The act of compressing the air with already compressed air from the turbocharger may detonate a low octane gas prematurely.

-Maintenance is high, which limits gas turbochargers to high performance vehicles.

So how can I turbocharge my vehicle more fuel efficient without spending so much more?

Buy a turbodiesel. Hands down turbocharged diesels have the advantage by the price of diesel nowadays, the very design of diesel engines, and the way it saves diesel the more air you pump into the engine! Turbodiesel vehicles have a good resale value so don’t expect rock bottom prices, but expect years of good use from even an old turbodiesel. Best value for money!

Buy gasoline vehicles with turbo already installed. Face it. Unless you’re a car enthusiast, installing a turbocharger in a car will cost you too much!

Buy smaller gasoline vehicles with turbo installed. There are smaller vehicles in the market that sell units with turbochargers to maximize the small size of the engine. Look up units in the Volvo and Saab lines.

Consider alternative fuels. You can use alternate fuels such as a hydrogen-on-demand (HOD) system to supplement a smaller turbocharger and engine tandem. This system creates hydrogen (H2) and oxygen (O2) gas on demand from a water medium to mix with the air and fuel in the combustion chamber for even better performance.

What does a HOD system do?

Hydrogen when compressed and introduced to an internal combustion engine:

-Releases more energy than ethanol-based mixes, maintaining the overall power of the car

-Burns the fuel more completely which gives cleaner emissions

-Raises the octane level of the fuel, preventing knocking, making the engine quieter

-Lowers overall engine temperature slightly

-Requires the engine to use less gas per cycle

Is it safe?

HOD systems generate hydrogen only on demand and are therefore safe. When no electricity is routed through the HOD system, no reaction is generated. No hydrogen is in storage in this system but is kept in medium, which is basically water.

Cost?

Parts are sourced from everyday parts found in hardware shops and basic electronics stores. Total cost for a basic unit can range between $70 to over $200 USD.

What’s offered by most HOD enterprises are plans for do-it-yourself systems, with offers to build the system for the consumer if they so wish. This way the customer can opt to build it himself or to buy a unit once the concept is understood after obtaining the plans to prevent fraud.

Better Fuel Economy: Diesel engines use compression ignition instead of spark plugs to start the combustion process. Using compression as the ignition source, combined with the higher energy content of diesel fuel, provides a much more efficient engine which requires less fuel to operate than a gasoline engine. A diesel engine is also able to operate at peak torque at lower RPM, like you would typically see at cruising speeds, further boosting fuel economy.

More Power: A turbodiesel engine can produce much more peak torque than a gasoline engine of equal size, and maintain peak torque over a broader RPM spectrum.This provides for much more power throughout the operating range, less downshifts for improved fuel economy, and increased payload ratings.

Higher Towing Capability: Due to the stout structure and additional torque of a diesel engine, payloads on diesel powered trucks are much higher than those on similarly sized gasoline V8 powered trucks. If you have something large to tow, a diesel will make the task much easier and provide the best fuel economy possible while loaded.

Aftermarket Support: Diesel powered trucks are receiving much more attention from the aftermarket than gasoline powered trucks due partly to the fact that diesel engines are easy to tune for more performance. Where a few simple bolt on parts may increase your gas powered truck’s performance by 50-75 horsepower, the same parts could take your diesel to extreme performance levels. How does an additional 200-350 horsepower sound? (Based on performance testing of a tuner, cold air intake, and exhaust system; the three most common and readily available engine modifications.)

Driving Experience: If your any sort of automotive enthusiast, or just like a truck that can run through the gears fast, diesel is the way to go. Just remember to hang on once the turbocharger spools, because you will be in for one wild ride. Diesel engines produce gobs of torque at low RPM, which pushes you back in your seat as the truck takes off when you start getting into the throttle.

Engine Longevity: Diesel engines operate at lower RPM and have much stronger engine parts than comparable gasoline engines. This translates into increased engine life, with diesel engines generally lasting up to 2x longer than gasoline engines before needing an overhaul or major repairs.

Cleaner Emissions: New technology has cleaned up the diesel combustion process, reducing the amount of harmful greenhouse emissions and virtually eliminating diesel soot from the exhaust.

Both diesel and petrol are taken out of mineral oil but diesel has better fuel efficiency and lower Carbon dioxide emission. Thus, with respect to the engine concept and combustion process, a diesel engine is more efficient for the same power output. This means diesel consumes lesser fuel. Though diesel is considered to be heavier, it is more efficient than petrol and the engine efficiency is higher by about 20%.

Unlike petrol engines, there is no spark plug-in diesel engine. Ignition of the mixture is achieved by the pressure of air.

Functioning of the petrol engine

1. Suction stroke: When the piston comes down a low pressure is created in the upper part of the cylinder. This causes the inlet valve to open through which the mixture of petrol and air from the carburetor enter the cylinder.

2. Compression stroke: During the upward movement of the piston, the mixture gets compressed causing the inlet valve to close. The volume of the mixture drops to about one eighth of the original volume. Pressure and temperature of the mixture rise enormously.

3. Power stroke: As the piston gets to almost the last part of the upward stroke, the mixture is so highly compressed that its temperature and pressure reaches the maximum point. At the same time an electric spark at the top of the cylinder causes the mixture to ignite and explode. This piston is forced down within the cylinder. This movement is transmitted to the crankshaft through the piston rod. The crankshaft is attached to the car wheel. Hence the movement of the crankshaft is transmitted to the wheel of the car.

4. Exhaust stroke: As the piston comes down to the lower part of the cylinder the pressure inside the cylinder falls allowing the exhaust port to open. As the wheel makes the piston go upwards the waste mixture is discharged.

Functioning of the diesel engine

1. Suction stroke: As the piston comes down air is drawn into the cylinder.

2. Compression stroke:As the piston goes up the drawn air is compressed to high pressure and temperature.

3. Power stroke: At the end of the compression stroke, the air is compressed to the maximum increasing in its temperature and pressure. Now the fuel is injected into the air. Ignition takes place immediately causing the piston to go down. Its movement is transmitted to the crankshaft and to the flywheel and then to the car wheel.

4. Exhaust stroke:As the piston goes up to complete the cycle, the exhaust vapours are discharged out through the exhaust valve.

Advantages of Diesel Engine

It has higher torque
It gives higher power output
It is economical to use diesel as only 70% needs to be spent for fuel for getting the same mileage as a petrol car
Relaxed driving is ensured especially for long distances

Advantages of Petrol Engine
It is cheaper
Maintenance is easier
Engine noise is lesser

The choice between the two is dependent on individual requirements.