Advantages of LPG and CNG in Diesel Engines

The vast majority of diesel engines in service today use solid injection and the information below relates to that system. In the diesel engine, only air is introduced into the combustion chamber.

The air is then compressed to about 600 pounds per square inch (psi), compared to about 200 psi in the gasoline engine. This high compression heats the air to about 1000 degrees Fahrenheit. At this moment, fuel is injected directly into the compressed air.

The fuel is ignited by the heat, causing a rapid expansion of gases that drive the piston downward, supplying power to the crankshaft. In Diesel's manuals, he described the supply of compressed gas into the cylinder to promote the final burn. It is now possible to fumigate the air intake with a small quantity of LPG/CNG.

The now air-gas mixture is compressed as above, and when the diesel ignites, the small quantity of gas ignites as well, causing a more rapid and more complete burn of the diesel. Most diesel engines waste between 30 and 15% of the diesel fuel, so by burning the near total amount of diesel consumed on each stroke, the mechanical effect is to improve the torque curve by as much as 28%.

The net outcome of applying gas into diesel is improved fuel economy via better torque at the driving wheels resulting in fewer gear changes, and greatly reduced exhaust emissions.

Advantages of the diesel engine are numerous. It burns considerably less fuel than a gasoline engine performing the same work. It has no ignition system to attend to. It can deliver much more of its rated horsepower on a continuous basis than can a gasoline engine. The life of a diesel engine is generally longer than a gasoline engine. Although diesel fuel will burn in open air, it will not explode unless compressed.

Some disadvantages to diesel engines are that they are very heavy for the horsepower they produce due to the required heavy design, and their initial cost is much higher than a comparable gasoline engine.

Recommended: Diesel Engine Repair Manuals

Thomas Buses-HDX Electrical System Repair

The electrical system on Thomas Buses vary depending on the model, pictured is an HDX model built in 2004. We are going to change a module that controls the main power to the body and chassis electrical systems. A hoist is handy but not totally required, I had to enlist a grinder with a cut-off wheel to remove the existing bolts.





This unit is called a dual power switch that is mounted on the frame on the passenger side across from the transmission. Since it is exposed to the elements the terminals are exposed so corrosion can develop. Consequently their is a possibility of an intermittent power problem to the lights or engine/trans controls when turning on the ignition.





As you can see the middle terminal is connected directly to the main batteries. The chassis and body battery supply terminals are located on each side while the ignition feed connector is plugged in on the top left corner.
When the ignition is energized a signal is sent to this module and power is directed to both systems. The chassis is the engine, trans. and running electrical while the body electrical is the lighting system.


Here is the module installed on the frame with four fasteners and an insulator between the module and the frame surface. It depends totally on what kind of environment you drive in for a problem to occur with this component. It is very well sealed internally with a hard epoxy type substance.
I hope this article has enlightened you with what to look for when experiencing electrical problems with Thomas Buses.

Diesel Engine- Basic Principles For Beginners

Diesel engine principles are pretty straight forward for the experienced mechanic but what about regular everyday people who have never taken the time to find out more about a diesel engine and how it works?

I am going to explain in layman's terms the basic principles of a diesel engine. WHAT'S THE DIFFERENCE BETWEEN A GASOLINE ENGINE AND A DIESEL ENGINE?...a quick overview.

The first thing you should know is a gasoline engine and a diesel engine are totally different. A gasoline engine is constructed much lighter than the heavier built diesel engine and runs on an air/fuel mixture combined with a high energy spark that is timed to ignite the air/fuel mixture inside each engine cylinder at the precise time creating power and torque [turning force] which drives your vehicle.

A diesel engine uses high compression [intake air that is compressed / squished] into a very small space inside each cylinder causing extreme heat! This is called 'Heat Of Compression' which ignites a very fine high pressure mist of diesel fuel that is injected into the cylinder at the exact time.

So you now know that a gasoline engine needs a high energy spark to run while a diesel uses 'Heat Of Compression' THE FOUR STROKE PRINCIPLE Every engine today runs on FOUR STROKES or FOUR CYCLES- both these terms mean the same.

Here is how the four stroke diesel engine operates. The four strokes are:

INTAKE-COMPRESSION-POWER-EXHAUST.

The pistons, valves and injectors work together in each cylinder in a set sequence over and over.

1} INTAKE STROKE: Intake valves in the cylinder head open allowing pressurized air to enter each cylinder while the piston is travelling downward.{the pressurized air supply is made possible by the TURBOCHARGER which pushes air into the intake system giving the diesel engine a boost of air to keep up with instantaneous injection of fuel}

2} COMPRESSION STROKE: When the piston starts to make it's way back upward the valves close which traps the intake air in the cylinder which allows compression to take place, the HEAT OF COMPRESSION is reached when the piston reaches the top of the cylinder, the diesel fuel is then injected into the cylinder at the precise time.

3} POWER STROKE: After injection takes place an explosion occurs in the cylinder because of the combination of heat and atomized diesel fuel. This causes the piston to be forced downward which produces torque and the horsepower required from a typical diesel engine.

4} EXHAUST STROKE: After the power stroke the piston moves upward once again while the exhaust valves open allowing the previously ignited gases to escape to the atmosphere out the exhaust system.

As mentioned before each cylinder goes through this exact sequence over and over in a set firing order. For instance, a 6 cylinder diesel engine has a firing order 1- 5- 3- 6- 2- 4 This is the order that each cylinder goes by, following the 4 strokes mentioned above.

This sequence has been engineered to allow the diesel engine to run smoothly with no imbalance.

DIESEL ENGINE TRIVIA: Today's high performance diesel engines. Fuel passes through the injector at speeds of nearly 1500 miles per hour - as fast as a jet plane at top speed. Fuel is injected into the combustion chamber in less than 1.5 milliseconds, the same time it takes for a camera flash to go off.

The minimum amount of fuel injected into a diesel engine is one cubic millimetre - about the same volume as the head of a pin. Volkswagen has developed a 1 litre diesel powered car that got 100 kilometres out of .89 litres of fuel {60 miles on approximately 3/4 of a quart of fuel!}

There is much to learn about diesel engines and a ton of information online. If you have ever considered buying a vehicle with a diesel engine you have my blessing!

The extra cost will be to your benefit, so I recommend finding out more about diesel engines before you decide which one to choose.

I hope you have found this information on diesel engines helpful!