When it comes to LPG (Liquefied Petroleum Gas) conversion systems, there are two main options: traditional and sequential. A traditional system dumps gas into the intake manifold, while a sequential system supplies gas separately to each cylinder in measured amounts. Think of it like comparing an engine with a carburetor to one with multiport fuel injection.

Converting a vehicle to run on LPG requires a deep understanding of automotive systems and should only be done by a skilled professional. Many manufacturers offer conversion kits with the necessary parts, but it's important to find a local workshop with experience in LPG conversions to ensure the job is done safely and correctly. Most conversions are dual-fuel, meaning the original fuel system is retained and a second system is added.

When it comes to LPG storage, there are two main types of tanks available: "torpedo" and "donut" shaped. Both are used in traditional and sequential systems. Regardless of the system or tank type you choose, it's important to work with a reputable professional to ensure a successful LPG conversion.

What is a Traditional System?

This is an older system of LPG car conversion which controls the injection system manually. Some of the important parts of the traditional conversion system are the regulator, the solenoid valve, and the mixer. 

The solenoid valve is installed on the fuel line between the tank and the engine. This valve cuts the flow of LPG when the car is running on petrol. Also, when the engine is off. It also has a filter built in that removes any dirt that may be in the fuel.

The regulator, much like the carburettor in a petrol engine, uses heat from the car's cooling fluids to vaporize the LPG into gas form. 

The mixer takes information from the car's sensors and then controls the amount of LPG that flows into the cylinders.

The system is wired into the car's electrical system, this allows for a functioning fuel gauge and automatic switching between LPG and petrol. 

As there is no computer control over the flow of LPG into the car’s engine, an even flow of LPG mixture enters into the combustion chamber and burns with the help of the sparks generated by the spark plugs fitted in the car’s cylinder head.

What is a Sequential System?

Sequential systems are the most appropriate type of LPG conversion for vehicles built after 1999. Kit costs have gone down. The systems’ set-up is now considerably easier with an experienced installer.

The sequential system injects LPG as a vapour for each cylinder, very close to the inlet valves. The LPG ECU works with the petrol ECU so that when switched to gas the engine is run as it was designed to be run. 

The sequential system is completely automated. The engine does not stop once gas runs out. If the gas is run out, it will automatically shift LPG to the petrol system.

Traditional System vs. Sequential System - Summary

Traditional System

Advantages:

• Older conversion system--tried and tested

• Simple system

• Easy to install
  

Sequential System

Advantages:

• Newer conversion system

• The Electronic Control Unit (ECU) helps the system stay tuned perfectly

• Better performance

• Accurate fuel consumption

• The car behaves like running on petrol

• Fuel efficient 

Disadvantages:

• No computer control system

• More fuel consumption

• Lower performance than a sequential system (as much as 10-15%)

Disadvantages:

• Harder to install than traditional systems

• Takes longer to install 

• Tuning needs to be performed by an authorized skilled technician

Traditional System vs. Sequential System - Details

Check engine light

Traditional System

The check engine light will likely be on. 

Sequential System

Cars with an electronic injection system have an electronic emulator. When the car is operating on LPG, the fuel injectors will not be sending any information to the other sensors in the car -- this will light up the "check engine" light. The emulator fakes the proper signals so the ECU can operate properly.

Does the type of car or condition of the car matter?

The Traditional system was designed for cars with carburettors.

The Sequential system is a modern LPG conversion system. All the multipoint fuel injection systems or indirect injection system cars can convert to LPG with it. Its system is similar to the petrol injection system, which is why its performance is similar to regular petrol.

Fuel consumption

Traditional systems earn approximately 10% less mileage.

Sequential systems provide similar mileage to petrol.

Tuning

Traditional systems are manually tuned. It's easy to tune for any technicians who are used to CNG tuning. 

Because it is tuned manually, regular checking of engine spark plugs, ignition coil, and the air filter is required.

Sometimes the system slows down the engine performance and misfires if the tuner is not skilled.

Sequential systems are computerized tuned with auto-calibration. This helps to read accurate ECU injection timing and ensuring the engine required fuel injection. This tuning automatically checks petrol ignition time and sets LPG ignition time accordingly during tuning, thus the system consumes less fuel. There is no frequent manual tuning required. 

However, a Sequential system is harder to tune or calibrate because it can only be accessed or tuned by the authorized person. The tuner needs to know the fuel system well.

LPG waste

Traditional systems waste fuel due to their continuous supply to the engine. It just has a single injector (mixture) for gas supply fixed by the adjuster. The wastage of fuel or the unburned fuel goes back through the air filter which causes backfire or misfire.

In the sequential system, this will never happen if the engine plugs are good. Since it provides just the amount of gas required to the engine cylinder/combustion chamber.

Control

Traditional systems have no electric controlling system. Its fuel tuning and operation system is controlled by the gas pressure. Because of this, the Traditional system gets less performance and mileage.

Sequential has an electric controlling system. Its fuel tuning and operation system is computerized. Because of this, the Sequential system gets better performance and mileage.

Performance

With a Traditional system, the car will lose power. Due to continuous misfire or backfire that hamper crankshaft position sensor, airflow sensor etc. Also, the engine compression can go down. Furthermore, it’ll take more pressure on the acceleration paddle when a customer drives on ramps or rocky hill roads.

Potentially provide approximately 10% less performance.

Modern LPG conversions suffer no noticeable loss of performance. Engines will run smoother and be slightly quieter. A driver cannot know without watching the indicator light if it's running in LPG or petrol. 

Shake and misfire

In Traditional systems, there’s a likelihood of misfires. When an engine misfires on acceleration, it’s not only bad for the engine, but it can be particularly alarming for everyone on the road.

In Sequential systems, there is no misfire or shaking due to the modern injection system.

Final Thoughts

Which is better for the engine?

Using LPG, in general, is better for car engines, as it reduces carbon build-up during the internal combustion process. It produces less carbon overall when compared to petrol--the buildup which manifests itself in emissions and the waste starts to coat engine components.

Eco Mode

Many of the new vehicles have multifunction modes like “Sport” and “Eco” modes. There is no noticeable change in performance in the respective modes when running on LPG. Many users mentioned a quieter smoother ride on LPG. 

How much can I save using LPG?

This is the reason why most people in Bangladesh convert their cars to LPG.

As it is a liquefied petroleum product, so the burning of the LPG and petrol produces the same energy. The LPG conversion will reduce engine wear. LPG burns cleaner than petrol. These deposits are very abrasive and can contribute to engine breakdowns. The oil and spark plugs will also last longer. The price of the LPG is almost half of petrol, though it produces the same energy, at half price it can save you almost 50%. Due to the system losses and different chemical combinations, the real-world saving is around 40-45%.

We have systems that can be installed on all kinds of vehicles. Contact our workshop to find out which kind of installation is best for your vehicle.