Which vehicles can be convert to CNG?
All gasoline vehicles: carburetor, injection All petrol, carburettor, injection and multi-point injection cars can be converted to CNG. CNG systems are also available for direct injection vehicles.
Is it possible to install a CNG system on diesel vehicles?
Yes, installation is possible for vehicles with a diesel engine. The system can be installed on all diesel engines, including generators. The DDF (Diesel Dual Fuel) system can be fitted to cars, vans, pick-ups, buses, trucks and tractors.
The DDF (Diesel Dual Fuel) mixture varies according to various parameters: the type and configuration of the engine, its power output and, of course, the age of the engine. Generally, between 50% and 50% of the diesel can be replaced by CNG. With efficient, new-generation engines, this leads to considerable cost savings for the user.
This conversion not only reduces running costs but also lowers NOX, CO and CO2 emissions, drastically reducing unburnt carbon particles in the exhaust, making it an ideal 'eco-friendly' choice.
Finally, DDF increases engine power and torque, prolonging engine life and enabling smoother engine operation by reducing deposits of impurities in the crankcase and consequent oil changes.
Which are the advantages of CNG in comparison to others fuels?
First of all, we can say that the least expensive energy is methane, while the most expensive energy is petrol. The efficiency of the various types of fuel is as follows:
- "Otto cycle" engines (spark ignition) have about 20% lower efficiency (also due to the presence of the throttle, which gives rise to significant leakage losses).
- Between methane, LPG and petrol, which are used in Otto cycle engines, methane has a few more efficiency points thanks to its higher anti-knock power. Methane has an octane rating of 130 and has a slight efficiency advantage over petrol.
- Natural gas is economical.
- Methane is the cleanest operating fuel system burning today. This means less vehicle maintenance and longer engine life.
- CNG vehicles produce the fewest emissions of any fuel.
- Methane produces much less pollution than petrol.
- Petrol-engined vehicles release carbon dioxide into the air through combustion, which contributes to global warming. This is greatly reduced with methane.
What is the impact of the CNG on the environment?
Methane is definitely more eco-friendly fuel among those commonly in use. A clean fuel but above all a ready and reliable, that is, unlike gasoline and diesel is not attained through complicated and expensive refining processes, which will inevitably be passed on to the sales price to the public, but from the beginning is ready to be used as an ecological fuel.
In methane are almost totally absent impurities, such as sulfur compounds, and are absent poisonous compounds such as lead and polycyclic aromatic hydrocarbons and its combustion does not cause significant formation of odor or particulate matter.
With appropriate technology and calibrations, the motors get very low emission levels.
Detectable exhaust hydrocarbons are composed almost entirely of methane, non-toxic and already excluded in the calculation of emissions from existing U.S. law and EU legislation on heavy vehicles.
The favorable ratio hydrogen / carbon of methane results in a production of CO2 considerably lower compared to other fuels. In particular, the reduction is about 20% in comparison with gasoline.
Is special maintenance required for CNG systems and their engines?
To ensure that the system works properly over time, it is subject to periodic checks (e.g. filter replacement) according to a scheduled maintenance plan every 15-20,000 km. These operations are therefore generally carried out by the workshop in conjunction with the regular servicing of the vehicle with particular attention to the ignition and electrical system.
What is the energy yield and power of a converted CNG engine compared to a petrol one?
Running on natural gas results in the following changes: a loss of maximum power of only 10% on maximum torque, which translates into a drop in top speed of only 5%-10%.
The fuel cost savings are due on the one hand to the different energy yields of the fuels and on the other hand to the government's tax policy.
In terms of energy yield, 1 kilogram of methane corresponds to approx:
- 1.675 litres of petrol
- 1,300 litres of diesel
- 2,000 litres of LPG
How much range do you get with an autogas CNG conversion?
To calculate the autonomy of a car fuelled by CNG, it is necessary to know that 1 kg of CNG corresponds about 1.7 litres of petrol and that the coefficient of distance of CNG/petrol is 0.3 (therefore with a 70 litre CNG cylinder the distance covered is comparable to that covered with about 21 litres of petrol).
An example: let's suppose to have a 70 lt CNG cylinder; it allows therefore a distance comparable to about 21 lt of petrol (70 lt x 0,3); let's suppose that the car runs with petrol 10 km with a litre; to calculate the distance, we will have to use the following formula: 70 lt x 0.3 x 10 = (21 x 10) = 210 km of autonomy on natural gas.
The CNG benefits.
CNG for automotive use has interesting physical and thermodynamic characteristics, in terms of quality and cleanliness of combustion and safety of use. The gaseous state of methane and its high speed of diffusion in the air make it easy to obtain excellent carburation even in the initial phases of operation with a cold engine. This circumstance, together with the fact that, compared to petrol engines, methane emissions upstream of the catalytic converter are considerably lower, accentuates the benefits of using natural gas vehicles in city centres, where cold starts, short journeys and slow running in columns are particularly frequent; conditions which do not allow the engine and catalytic converter to reach ideal operating temperatures quickly.
Are the autgas CNG equipment safe?
The use of CNG offers ample guarantees of safety, in many respects greater than traditional fuels.
CNG has a lower density than air, so if it escapes into the environment, it tends to disperse upwards without forming dangerous concentrations or accumulations on the ground.
To test the safety of CNG systems, dozens of crashes and fire tests have been carried out to verify, with the most sophisticated equipment, the efficiency and safety level of systems and tanks. CNG has the highest flash point of all other fuels. Its auto-ignition temperature is, in fact, double (650° C) compared to liquid fuels, and the concentration of fuel in the air for combustion to occur (5%) is much higher than petrol (1%) and diesel (0.5%). These are factors that contribute to significantly lowering the risk of an accident with fire development.
Finally, CNG is not dangerous to health, even in high concentrations, as it is not poisonous.
What safety measures are in place once the CNG system is installed?
CNG tanks are much stronger than liquid fuel tanks (petrol, diesel or LPG) and far exceed the impact and flammability standards laid down by the strictest international standards.
In the event of an accident, a fire is caused in bi-fuel vehicles by the petrol tank rupturing and not by the CNG cylinder rupturing, which is the strongest component in the car.
Each natural gas cylinder is tested at a pressure of 300 bar, which is 1.5 volts above the normal operating pressure (200 bar).
They are also tested at destructive hydraulic pressure; the minimum strength required is 2.25 times the operating pressure (450 bar), although in practice rupture pressures of 580 bar are reached. Finally, for cylinder rupture dynamics, strict international standards require a behaviour known as "leak before burst", i.e. a progressive leakage of gas from cracks in the cylindrical body before the structure fails.
Fusible safety valves, finally, in the event of fire and an increase in temperature and pressure, then allow the controlled escape of gas, avoiding overpressure.
In the event that the on-board piping should break, the overflow safety valve (located on the cylinder valve) prevents uncontrolled gas release.
All these tests of thermal and mechanical resistance mean that CNG cylinders are by far the strongest components on board the vehicle, including structural parts.