Gas for Diesel Engine? Gas-Diesel Theory.
To date, there are two basic ways to install gas equipment (HBO) on the diesel.
The first one is a complete re-equipment for 100% gas supply, for which the engine is thoroughly modernized. Since the octane number of methane, for example, reaches 120, the regular compression ratio of the diesel engine for it is too high, and to avoid detonation and as a consequence, the rapid destruction of the unit, it must be reduced to 12:1-14:1. In addition, the auto-ignition temperature of gas is about 700 ° C against 320-380 ° C for diesel fuel, so it can not ignite from compression and to ignite it, the cylinders should be equipped with a spark ignition system, like in gasoline engines. Of course, such a unit cannot be reworked for diesel fuel.
But there is a simpler and cheaper variant of installation HBO on diesel, based on a combined mode of feeding, actually gas-diesel. Briefly about the principle of Dual Fuel which was used in its time by Rudolf Diesel, the founder of diesel engines: the main fuel here is still diesel, but part of it is replaced by gas – methane or propane. Diesel fuel in this case performs the function of ignition of the air-fuel mixture – because for gas ignition, recall, a spark or ignition discharge is required. The degree of substitution of the main fuel with an additional one depends on the engine load and, in fact, the fuel equipment itself – the original diesel and the installed gas one. Currently, the systems of the world’s leading manufacturers allow replacing up to 50% of diesel fuel in the case of methane and up to 30% – in the case of propane.
Otherwise, the gas-diesel systems do not differ much from the 4th generation HBO for gasoline engines. Hence their main advantages.
The advantages of gas-diesel systems
1) Ease of installation: Equipment sets are universal, suitable for all types of diesel engines with electrical equipment as 12V and 24V, including the most advanced, and does not require disassembly and modification of the power unit, and the transition to the original diesel mode is possible at any time by simply pressing the switch in the driver’s cab.
2) Increased efficiency and service life. Adding a dose of gas increases engine power and torque – with turbocharging, the increase in performance can be as much as 30%. At the same time, the engine runs noticeably quieter and more elastic, and due to the reduced load on the diesel fuel supply system, the service life of its elements increases, especially in the case of the Common Rail direct injection, which operates with variable high pressure depending on just the load.
3) Economy and ecology. Replacement of a part of diesel fuel with gas allows reducing the cost of vehicle operation by up to 20% in relation to the cost of its operation only on diesel fuel. A change in the composition and a significant reduction in the volume of exhaust gases improves the environmental performance of engines, reduces toxicity and smokiness of the exhaust and its particulate matter (soot) content to an extent that allows you to stop using urea solution on units that meet Euro-4 and Euro-5 standards.
Thus, the modification of a diesel engine into a gas-diesel engine makes it possible to simultaneously solve the following problems: 1. reduce costs by 10-30%; 2. increase power and torque by 20-30%; 3. increase the service life of fuel supply system elements (primarily Common Rail systems) and the life of the engine as a whole; 4. reduce the CO, CH and particulate matter content in the exhaust.
And if for the passenger diesel engines with their small appetite and a relatively moderate daily and annual mileage topic gas-diesel is more of pure academic interest, the intensive operated trucks and long haul tractors, daily covering considerable distances, the installation of gas-diesel HBO more than justified from any point of view. And with the rising price of diesel fuel will only increase in relevance.
Conversion of the diesel engine to gas
Gas equipment must ensure the safety of storage, supply and operation of the engine on gas. Cars use methane in a compressed state, and propane-butane in a liquefied state.
When gas is installed on a car, the main type of fuel can also be used. It is interesting to note that the factory power system is not changed when installing HBO. Car is only supplemented by special equipment for gas.
Car owners are satisfied that the car can run on both types of fuel, with both separate and simultaneous supply. Combustion of the fed fuel is the same as that of the car running on gasoline.
What is the essence of this method? The essence is simple – the diesel engine is completely converted to gas. Thus after such intervention it will no longer work on its “native” fuel – only on gas.
In order not to make the aggregate go wrong, its compression ratio is corrected. It makes about 12:1. Only this way the engine can “digest” fuel with a high octane number. Then the mixture ignition system is installed. There are no special mechanisms here. For ignition, regular candles are used, as well as on gasoline engines.
What is the disadvantage of such a modification? Due to the need for a whole set of works, the cost of reinstallation can reach 200 and more thousand rubles. This is dozens of times more expensive than converting a petrol car to gas. Therefore, the savings are highly questionable. Especially since such a motor will reduce power and torque.
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Peculiarities of the diesel engine
The diesel engine has a number of peculiarities of operation, unlike the gasoline engine.
The main differences relate to mixture formation and ignition:
- The fuel-air mixture is formed in the cylinders.
- Air is initially fed into the cylinders, then the diesel fuel is injected.
- The diesel is ignited by temperature or compression pressure.
- A spark is not needed because there is no ignition system.
The design of the diesel can imply: separate combustion chamber and injection.
It is believed that the fuel system of a diesel engine is more complex than that of a gasoline engine. This is because the diesel engine requires precise timing, volume and pressure.
To facilitate a cold start, glow plugs are used. They preheat the air in the combustion chamber. There can be 2 pumps – high and low pressure.
All these features indicate the questionable feasibility of the installation of HBO on a diesel engine.
The installation of HBO on a diesel at the service center
Not all companies specializing in the installation of automobile gas equipment, undertake such orders. Will agree only those who have a certain knowledge, experience in this area and technical capabilities for the re-equipment. And if the question is about heavy machinery, qualified specialists are even less.
On how to choose the right installer, we told here.
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But regardless of the need to install HBO on diesel trucks, passenger cars or agricultural machinery (tractors, etc.), with the proper approach the economic effect will be obvious.
Is it possible to install HBO on a diesel?
Next to the question of whether it is possible to install gas equipment on the diesel engine. If we talk about the design, such a unit is slightly different from the gasoline one.
The difficulty lies in the fact that gas does not ignite from compression. Therefore, the use of a small amount of diesel fuel is provided for.
Not pure gas is fed into the cylinders, but its mixture with diesel, the proportion is 3 to 1. This approach allows to save diesel injectors work and serviceability of fuel equipment.
The essence is the following – the gas-diesel works as the fifth generation GTB. In it, liquid gas is fed into the cylinders. Implementation and arrangement of such a system is complicated and expensive, but there is nothing unreal here.
Gas increases the stability of the diesel engine and is clearly beneficial for trucks and special equipment.
Conversion of the diesel to gas helps to reduce harmful emissions and is more economical.
If there is a desire to save even more money, then you can install methane on the diesel engine. This will help to reduce the percentage of expensive diesel in the total mixture.
Installing HBO on a Diesel Engine
In recent years, owners of fuel-efficient diesel engines have faced an unpleasant Russian reality. Prices for diesel fuel in some regions of our homeland began to steadily catch up and even overtake gasoline prices. There is no economy, the only option to save money on a car with a diesel engine is to install a gas burner on it. Gas prices are not actively increasing, and it always remains cheaper than diesel and gasoline. Driving on gas is 1.5-2 times more profitable.
Equipping a diesel engine with HBO is not as easy as a gasoline engine. There are two basic ways of installation of HBO.
The first option. Re-equipment of the diesel engine for HBO
This is the simplest, but very cardinal option of converting a car or truck to gas as a fuel.
After the installation of HBO it will be impossible to return the engine back to diesel
It will be simply impossible to switch the engine back to diesel. Diesel fuel ignites at 300-400 degrees Celsius, but the gas it starts with 700 degrees Celsius. Therefore, you need to redesign the ignition system, power and other systems.
The modifications will look as follows:
- A set of spark plugs is installed instead of nozzles.
- Gas injectors or metering unit are installed in the intake manifold.
- The compression ratio of the engine is reduced to run on fuel with a higher octane number (propane, butane -110, methane -120). For this purpose, all “extra” metal is removed from the engine combustion chamber and metal gaskets are installed.
The advantages of reprocessing into a gas engine:
- The service life will be seriously increased.
- The engine will produce fewer emissions, its use is not as harmful to the environment.
- The engine will have increased torque and power.
- The engine will run quieter.
- No detonation.
The disadvantages of converting to a gas engine:
- You will only be able to drive on gas.
- Difficulty of tuning and adjustment.
- When installed on a passenger car cylinder will occupy a significant amount of space.
In a passenger car, the gas cylinder takes up a significant amount of space
- There may be difficulties with starting in severe frosts, but this is also typical for a simple diesel engine.
- The car will have to be serviced more often: to drain the condensate, change the gas filter and so on.
The second option. Gas-diesel and principle of its work
Conventional gas equipment is not suitable for use in many modern diesel engines. This is due to the difference of their ignition system from gasoline engines – they work without a spark.
The way out is the installation of a gas-diesel with distributed fuel injection. The engine will run on two types of fuel at once: diesel fuel will be used to ignite the mixture, then the engine will run on gas. A constant fuel balance must be maintained in the engine, and both gas and diesel fuel must flow into it. This process is controlled by various sensors, the electronic control unit of the HBO kit constantly monitors the situation and makes adjustments. It sends signals to the gas injectors and the engine, which provides diesel fuel in turn.
The most efficient type of gas for a diesel engine is methane.
For a diesel engine, the most efficient type of gas is methane
Diesel fuel can be diluted with methane at a ratio of 1 to 4. For rural, rustic and other machinery this is another plus – methane can be obtained from any organic compounds in a very simple way. If you use propane, you would need to burn twice as much diesel fuel. And methane is cheaper than propane. However, in some regions of our country, methane is not widespread, and it will be difficult to find gas stations.
Gas-diesel engines have long been known in Russia. Back in the days of the Soviet Union, they were mass produced for trucks.
Fuel can be supplied by a high-pressure mechanical pump or by a more modern Common Rail system, which meets Euro 4 standards.
- The ability to drive on two types of fuel.
- Even though the diesel fuel will be burned together with the gas, there will be very few harmful emissions.
- Engine life and oil life will be longer.
- No detonation.
- Difficulty of tuning and adjustment.
The gas-diesel engine has both pluses and minuses
- When installed on a passenger car cylinder will occupy a significant amount of space.
- This method is more expensive for installation and equipment.
The price of installing a set of HBO on cars with diesel engines is much higher than on cars with gasoline engines. Installing a diesel engine in a passenger car is almost impractical due to its high cost. But for trucks, special vehicles, construction and agricultural equipment the installation of HBO is a serious way to save money.
Is it possible to install a GTB kit on a turbocharged engine?
A turbocharged diesel engine does not differ from its atmospheric counterpart. The processes in them occur the same. The installation of a turbocharged diesel does not differ from the installation on its atmospheric version.
HBO on a diesel – principle of operation
About how the gas-powered diesel works, it is worth talking about in more detail.
The principle of operation:
- Gas flows from the cylinder to the gas valve.
- Then the gas is purified in the valve filter and goes to the reducer.
- The propane evaporates and the methane expands.
- The gas enters the mixing chamber before the nozzles.
- The gas flows into the combustion chamber. It mixes with diesel fuel and air, after that it ignites.
The electronic control unit is responsible for the fuel supply, receiving signals from regular and additionally mounted sensors.
What is a Diesel-Gas Engine and How It Works
The dual-fuel gas-diesel engine is a power plant, on which the equipment for gas operation is additionally mounted. The operating principle of this unit is the simultaneous supply of two types of fuel into the combustion chamber. The main fuel is diesel fuel, and an additional methane gas. Moreover, diesel fuel is fed in a much smaller volume than usual.
In fact, diesel fuel is a kind of “igniter” for the gas-air mixture. The supply of diesel fuel is due to the fact that the ignition temperature of methane is higher than that of diesel fuel. For this reason, at the moment of compression in the combustion chamber, the methane itself cannot ignite. To ignite it at the intake stroke, some amount of diesel is fed into the combustion chamber.
A dual-fuel gas-diesel engine can only run on diesel, but is incapable of running on gas alone.
Diesel equipment options
Equipping a vehicle for methane and propane is different.
Diesel on methane is suitable mainly for large vehicles because of the difficulty in locating the cylinders. Passenger cars are often equipped for propane, moreover it is liquid, which simplifies its adaptation on a car.
There are two main variants of such re-equipment: full and gas-diesel.
Installation of this option is used when equipping the car for methane. The engine needs a serious modification, after which it can only run on gas.
Methane combustion occurs at a temperature twice as high as that needed for diesel. It needs so much compression, otherwise it won’t ignite at all.
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The compression ratio is lowered and an ignition system is installed for the system to work properly. This is true for both propane and methane diesel engines.
A complete conversion also involves installing a metal gasket under the head. The spark plugs are mounted in place of the diesel injectors, and gas connections are cut into the intake manifold.
After such radical changes, it will be difficult to return the engine to its original state. The diesel will no longer be called a diesel, as it will not be able to run on diesel fuel.
Installation of the gas-diesel
The gas-diesel is very widespread. It is the best option to run on propane-butane. The engine will be able to run on diesel fuel or on a mixture of gas and diesel fuel. It will not be able to run on pure gas.
Gas to the diesel engine is not very different from the installation of conventional gas-diesel.
Working principle of gas-diesel:
- Gas enters the cylinder on the intake stroke.
- Diesel fuel is injected at the end of the compression stroke, after the gas-air mixture is created in the cylinder.
- All this is ignited.
Ways to install HBO
One of the ways can be called radical – modification of the diesel engine for running on gas. In this case it is necessary to cut classical spark plugs into the cylinder head. Since a spark is required to ignite the gas, unlike the diesel fuel, which is ignited by increasing pressure.
If space allows, they replace the injectors or look for another possible place, and the diesel injectors are replaced with plugs. The gas injector system is integrated into the intake manifold. In addition, the compression ratio must be lowered for gas. For this purpose, a gasket between the cylinder head and the cylinder block with increased thickness is installed. Of course, the modification affects the wiring, electronics and fuel system. After all modifications, the diesel engine ceases to be such. In practice, this method is extremely rare.
The diesel engine with integrated HBO is practically the same as a conventional one.
The second way is more practical and cheaper. HBO is integrated into the diesel engine, not different from the similar equipment for gasoline engines. A liquefied mixture of propane-butane or compressed natural gas is used as fuel. And methane is more profitable for the diesel engine, since it replaces up to 80% of diesel in the fuel mixture. The main feature of gas-diesel operation becomes the ignition of the fuel-air mixture of air, gas and diesel fuel from compression. Depending on RPM, load and temperature, up to 80% of fuel can be replaced by gas.
What does HBO for diesel fuel include
The control computer (ECU) is the brain for diesel engines. By analyzing information from the sensors, it forms control signals for the gas and diesel fuel supply.
Diesel gas train set includes cylinder, reducer, multi-valve, gas valve, gas lines and the following parts:
- gas injectors and dispenser;
- mechanism to move the fuel injection pump rack, but the high-pressure pump will need to finalize;
- temperature, timing, crankshaft, gas sensors, some of the original ones are also retained;
- low and high pressure gas filters.
Where to install
Installing gas on a diesel is a complex procedure in view of the necessary equipment. This work should be done exclusively by specialists who understand this issue.
The organization, to which the owner of the car will entrust the conversion of the diesel to gas, must be licensed. The list of necessary works must necessarily include the adjustment and testing of gas equipment.
The duties of the installer include the execution of the necessary papers for registration and further periodic maintenance and inspection.
If you want, you can install HBO on a diesel yourself. However, in this case there is no guarantee of quality, and under doubt remains the safety of the car. Car owners prefer to figure out how to install gas on a diesel independently in order to save money.
However, experts do not recommend installing gas to the diesel in the garage, as qualitatively perform this work will be unreal.
In addition, adjustment is required, which can not be done without a special stand.
What documents are needed
According to TR CU 018/2011, a diesel on gas is considered a conversion.
The provisions of Article 12.5 paragraph 1 of the Administrative Code of the Russian Federation states that using a car without registering the conversion of diesel to gas is prohibited. The registration procedure is carried out at the traffic police.
The following documents will be required:
- Equipment certificates;
- installer’s license;
- diagnostic card;
- Receipt of payment of duty.
Authorized bodies will issue a certificate of conformity and a passport for HBO. It is worth carrying these papers with you in your car.