What type of system is best for a given engine?

The two key decisions about an LPG conversion kit are the type of front-end system and the size and shape of the tank(s).

The various front-end systems are described below.

Sequential Gas Injection

Multipoint Sequential Gas Injection Systems (SGIS) are the most appropriate type of LPG conversion for vehicles built after 1999. Earlier vehicles with a plastic inlet manifold should also have this type of conversion. Kit costs have reduced and set-up of the systems is now considerably easier. The sequential system injects LPG as a vapour for each cylinder, very close to the inlet valves. The gas ECU works with the petrol ECU so that, when switched to gas, the engine is run as it was designed to be run (except for the change of fuel).

The system offers slightly improved economy and performance (when compared with induction systems) and eliminates the possibility of spit-back.

1. Gas ECU 2. Gas injectors  3. Filter/shut-off valve  4. Vaporiser  5. Pressure sensor  6. Pressure balance  7. Changeover switch  8. Manifold nozzle  9. Water temperature sensor  10. Gas temperature sensor  11. Multivalve  12. Tank  13. Filler  14. Vapour filter

Induction Systems

This type of system is the simplest type of LPG conversion carried out. Suitable for all types of vehicle built before 1999 (except those with a plastic inlet manifold), the system introduces gas to the engine in vapour form through the inlet manifold. When switched to gas, the way the engine runs is controlled by the LPG system.

Open-Loop Induction Systems

Older, carburettor vehicles and early, injection models that do not have a catalytic convertor can be converted to an open-loop system where the LPG reducer and power valve are used to control the inlet of fuel into the engine. This is the simplest and cheapest solution. However, with the addition of a lambda probe in the exhaust, the system can be upgraded to closed-loop operation, with all of the benefits described below.

Closed-Loop Induction Systems

Later petrol-injected vehicles have catalytic converters and require LPG systems that use a slightly more sophisticated management system that reads the oxygen sensor in the exhaust. This then controls fuelling using a stepper motor, to give the most efficient fuelling at all times, resulting in better fuel economy and better throttle response.

Diesel LPG Conversions

Diesel engines can be converted to run partly on LPG, partly on diesel. Since the diesel engine has no spark plugs, the only way the LPG can burn is if diesel is used to ignite it. So diesel is always used. The addition of LPG gives a more complete burn of the diesel and can result in a reduction in the amount of black smoke emitted from the exhaust, which is often associated with diesels. More significantly, it increases the power from the engine.

Typically a ratio of 30% LPG to 70% diesel is possible. No adjustments are required to the diesel injection system and fuel savings come from the fact that throttle openings are lower due to the greatly increased power. The way the extra power is used has a direct influence on the fuel economy.

If you drive at the same pace as you do when running on diesel alone, the addition of LPG will allow you to use a smaller throttle opening. This means that the load on the engine is the same, but the amount of diesel used will be less. Many of our customers report savings of 20 to 30% in fuel bills. The older, mechanical injection engines tend to give greater savings than the newer, more efficient, electronic injection engines.

If you decide to use the extra power, the load on the engine will be higher and, at large throttle openings, the engine will burn the normal amount of diesel in addition to the LPG. Thus, your fuel bill may well be higher than when using diesel alone.

Given the above, it is difficult to predict how the use of LPG will affect fuel bills in the context of the diesel engine.

The Tinley Tech diesel LPG conversion kit is intended for use by owner-drivers rather than commercial users, where drivers tend to drive hard.

Care must be taken to avoid feeding in too much LPG as ADDING TOO MUCH LPG MAY DAMAGE THE ENGINE. Tinley Tech cannot be held responsible for damage caused by incorrect tuning.