Retrofittment

The process of converting a car to run on LPG is fairly demanding and requires a good knowledge of automotive systems in general to accomplish.* Raghav LPG offer kits that include all the needed parts to perform the conversion. Retrofittment without the necessary know-how  or spurious parts may lead to non optimum performance and safety hazard. Although LPG is very safe as an automotive fuel, if the system is not installed correctly, there can be safety problems.

Example dual-fuel conversion system

The first step is choosing a tank. Most conversions are dual-fuel conversions, meaning you won’t be replacing your old fuel system, you’ll simply be adding a second. As a result, the LPG tank will take up some of the storage space in your car, usually in the trunk.

Tanks come in “Torroidal” or “capsule” form. Capsule tanks generally have more capacity, but will take up more space in your car. Torroidal tanks are designed to fit in the spare tire well of your car. They are smaller tanks, and you’ll have to refuel AUTOLPG more  frequently. The tank is covered with Multivalve.

Multivalve

Multivalve is the most technical product of any Gas kit. As its name indicates, it has multiple functions to perform. It allows filling of gas in cylinder up to maximum 80% of water capacity of tank. It allows controlled release of gas. It indicates level of gas in tank. It prevents any excess flow of gas due to any leakage. Its Thermal fuse helps in release of gas in controlled manner in case of any calamity.

Once the tank is bolted in, a filler valve is mounted to enable filling of autp LPG. The ideal location is one that requires minimal piping to connect to the tank. The fuel lines themselves are copper tubes, which offer a certain amount of flexibility when the lines are routed. The tank must be connected to the fill point, and lines also have to run along the underside of the car up to the engine.

solenoid valve (LPG valve in the above diagram) should be installed on the fuel line in between the tank and the engine. This valve cuts the flow of LP gas when the car is running on petrol and when the engine is shut off. It also has a filter built in that removes any dirt that may be in the fuel. A few modern vaporizers have inbuilt Gas Solonoid in them (IBGS). Even in that case, an additional filter should be used.

The next major component is called a regulator, also referred to as a vaporizer. This device performs one of the functions that a carburetor handles in a petrol engine — it uses heat from the car’s cooling fluids to vaporize the LPG into gas form. Another safety check occurs at the regulator, as well. It includes an electronic circuit that cuts the flow of gas if the engine stops or stalls. The regulator is usually smaller than a regular carburetor, so finding space for it in the engine compartment is not a problem.
The other part of a carburetor’s function is handled by a mixer mounted in the intake manifold. The mixer takes air from air filter and vapours of LPG from vaporizer. It has vehicle specific design to ensure optimum mixer of LPG and air.

The system must then be wired into the car’s electrical system, allowing for a functioning fuel gauge, as well as proper automatic switchingbetween LPG and petrol. (along with a dashboard-mounted manual switch). There must be connections to the car’s ECU so that the engine controller can adjust for different fuel settings.

Cars with MPFI (multi point fuel injection) will need an electronic emulator. When the car is operating on LP gas, the fuel injectors will not be sending any information to the other sensors in the car — this may light up the “check engine” light and give incorrect diagnostic readings. The emulator fakes the proper signals so the ECU can operate properly.
Conversion kits come with more detailed instructions, but this is a basic overview of what needs to happen in a dual-fuel conversion.

*Disclaimer: This is not be used as a guide for an actual LPG conversion. It is intended as an overview of the process and not a set of instructions. Unless you are authorized in automotive fuel systems and electrical systems, you are strongly urged to have the conversion performed by a professional. All conversions should be done, tested and approved by a professional with experience and authorized for retrofitting by concerned RTO.

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Safety and Storage

LP gases are actually quite safe in comparison with other fuels. Propane has a high ignition temperature, about 850-950 F (450-510 C), compared to about 495 F (257 C) for petrol. This makes it less likely to ignite spontaneously.

Also, the tanks used to store LPG are stronger than Petrol tanks because of the pressure needed to keep the LPG in liquid form. This makes on-board LPG storage safer than a typical Petrol tank — it is more resistant to rupturing in the event of a collision. Special safety valves and cut-offs function of multivalve increase the safety factor.
To store LP gas safely, there are some guidelines. It’s important to remember that an LPG tank is never really empty. When the tank is filled, most of the LPG is under enough pressure that it is in liquid form. But at safe pressures, not all of the LPG is liquefied — a small amount is in gas form, filling up the rest of the space in the tank. As more LPG is used, the pressure decreases, leaving less LPG in liquefied form and more LPG gas filling up the remaining space.

Hence, Tanks should only be filled to roughly 80 percent capacity. Changes in temperature can change the pressure inside the tank. If you were to fill your tank to 100 percent on a cool, cloudy day, and then leave your car out in the sun the next day, the increase in temperature would cause in increase in pressure within the tank that could cause it to fail without that 20 percent headroom.

Video courtesy Shell Gas

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