Chosing your Installer
Most people make the mistake of contacting several installers within their immediate area and simply ask them to quote a price for their particular vehicle. It is fair to assume that more often than not they will not chose the cheapest quote, or the dearest but quite often the one in the middle. Using this method presumably makes them think they are not choosing the worst installer or being over charged by the dearest.
In my experience, whilst quoting customers over the phone I have found that most have not got a clue about the different types of LPG systems available. They do not know the difference between single point or multi point, closed loop or open loop, sequential or non sequential or what is the most suited to their type of vehicle.
Most are quite simply interested in obtaining a cheap quote not realising how much an error at this stage might cost them in the long term.
A vehicle manufacturer will have spent millions of pounds and thousands of hours on developing the vehicles petrol engine management system to perfect driveability, performance and good emissions. What is even more amazing is the LPG installer is now expected by the customer to take a universal off the shelf LPG kit, fit it to the vehicle and deliver similar results.
When obtaining quotes some customers seem to suddenly become experts in choosing which installer and which system to chose whilst some have no idea in reality the difference between good and bad.
Installations do vary from vehicle to vehicle but the major difference is not the LPG tank size and location but what goes on under the bonnet.
The tank fitment varies from vehicle to vehicle but should not prove too much of a complexity to the majority of installers, this involves competence, pride and engineering skills. What really changes from vehicle to vehicle is what goes on under the bonnet and that which integrates with the cars everyday complex engine management system.
What is worrying is that anyone can overnight become an official and insurance approved LPG installer. Unfortunately, to become LPGA approved does not mean that the installer has had to come from a motor vehicle background or prove his knowledge and understanding of how engine management systems work. As long as a minimum installation standard has been met in accordance with LPGA safety guidelines then anybody can become approved.
As some customers have found to their expense, if a complaint is made to the industries governing body, the LPGA, they are only able to check if the system has been fitted with its safety guidelines and not how the vehicle performs. How well the LPG system has been fitted as apposed to how badly the vehicle runs are the main concerns of the LPG Association. So, now you see, choosing an installer who is approved by the LPGA is no guarantee that they are able to make your vehicle run perfectly well on both petrol and LPG.
The following is a guideline of what questions you should be asking and observations you should make.
• Does the installer come from a motor trade background and able to prove previous business involvement of repairs to motor vehicles.
• Is the workshop immaculately clean, i.e. no oil on the floor, wing and seat covers being used, the workshop lighting should be good, heat in the winter and cool in the summer, giving staff ideal working conditions.
• The minimum equipment requirement should be a 4-gas analyser, 2 channel oscilloscope, European and Asian scan tools for reading the vehicles OBD data (on board diagnostics), 2 or 4 post vehicle lift, smoke test machine, multi meter and sensor simulator tester, on the road AFR (air fuel ratio) test equipment for 4 wheel drive vehicles (if only a 2 wheel drive rolling road), ignition output and coil KV test equipment, LPG injector flow test bench, dynamic compression tester, petrol injector flow test bench also fuel flow and fuel pressure test equipment.
• Are the installers contactable out of normal hours?
Conversion Gallery
Here is a selection of some of our conversions.
LANDROVER DISCOVERY 3 V8 HSE
VAUXHALL CORSA 1.6 SRI
MERCEDES C180 K
MERCEDES 230
AUDI A8 SE 4.2
Diahatsu Terius
Honda CRV
Toyota Estima Aeras
Audi A8 4.2
BMW X3
Porsche 911
Subaru Legacy Type R B4 Spec H6
Volvo V70 2.4
.JPG)
.JPG)
.JPG)
Vauxhall Vectra 1.8
Honda Jazz 1.4
Range Rover 4.2
Subaru Impreza 1.5
Toyota Landcruiser Amazon 4.7
Vauxhall Zafira 1.8
Mercedes S430
Volvo V70 XC
Jeep Cherokee 4.7 V8
P38 Range Rover 4.4
.jpg)
.jpg)
.jpg)
Alfa GT
Porsche Cayanne 4.5 V8 Turbo
BMW 645 Ci
Skoda Octavia FSi
Nissan Murano V6 3.5L
Bently Flying Spur W12 Twin Turbo 6.0L
Landrover Discovery Series 3
Three of a number of tank options available
Vauxhall Astra 1.4L
Talking Technical
Explaining the different types of conversions
Single Point
The single point conversion is called such as it has one single point of gas entry into the vehicles engine. The basic kit comprises of an electronic means of switching the gas on with a switch and fuel gauge inside the vehicle, a reducer sometimes called a vaporiser and a mixer. The mixer is installed in to the inlet tract as close to the throttle as possible, it is designed to draw varying amounts of gas vapour into the inlet stream dependent of the air flow passing through it into the engine the mixer is linked to the reducer using rubber fuel hose.
The reducer is mounted inside the engine compartment this part converts the liquid from the tank into gas vapour in a controlled manner dependent on the required gas demand. As the boiling point of LPG is approximately – 42ºc, the LPG boils from liquid state to a gas state inside the reducer, doing so the LPG takes energy from its soundings and freezes the reducer, so for this reason it is connected in to the engine cooling system and this keeps the reducer from becoming frozen.
The basic electronic system switches on and off the petrol along with safety solenoids that are fitted on the tank and in the engine bay .More advanced systems utilise microprocessors to aid in fuelling the engine correctly. Fuel enrichment under high demand and fine emission control can be achieved by referencing sensors in the engine management system and then by altering the state of a device fitted between the reducer and mixer, this mechanically alters the flow of gas in to the engine.
Microprocessors can also be used to emulate the petrol injectors and lambda sensor signals to stop ‘Check Engine lights’ and adverse rough running when returning the vehicle back to petrol. There are drawbacks to these systems, among which power loss and ‘Blowbacks’ are common, as the mixer is a restriction in the induction system the maximum flow of air can be reduced, which in turn leads to a loss of maximum engine horse power. Blowbacks are caused when the premixed air and fuel in the inlet manifold ignites before it has reached the combustion chamber, this creates a powerful shock wave that can cause severe damage to inlet manifolds, air filter housing and MAF sensors.
Single Point Kit Made By Zavoli
Multipoint vapour injection
Multipoint systems differ from single point systems as in they introduce the gas into each cylinder individually. These kits comprise of an electronic switch with gauge, an LPG Electronic Control Unit (ECU), reducer, injectors and nozzles.
The reducer on an injection system works slightly different from single point. They takes liquid gas and convert it into a vapour by boiling the gas, they are also connected to the engine cooling system to stop them freezing, but these reducers are designed to maintain a set gas pressure to supply the injectors with fuel under pressure so that it can be injected, these regulators are also tapped into the manifold so that the pressure difference between the regulator output and manifold pressure remains constant.
The injector nozzles are installed into the inlet manifold, one into each cylinder port of the engine, these are fitted as close to the inlet valve as possible, in some cases straws are inserted into the manifold to ensure the delivery of gas is at its optimum. The injectors are attached to the nozzles via small bore flexible fuel hose or attached directly to the nozzles themselves depending on the type of kit, the injectors are electronically operated by the LPG ECU, early type of injectors incorporated a stepper motor design, stepper motors are like electronic taps, the ECU can open and close the stepper motor which opens and closes the tap, this increases or decreases the flow of gas allowed to pass through the injectors.
The other later types of injectors are operated like petrol injectors where as the injectors have electromagnetic coils around the injector. When these coils are switched on by the ECU these become magnetic and draw up the inside parts of the injector allowing the fuel to pass through it. When these are switched off the injector closes as they are spring loaded. The time the coils are on controls the amount of fuel injected.
The length of time the coils are switched on varies from 2-25 milliseconds (1 millisecond is a thousandth (1/1000) of a second) depending on the required fuel demand and opened once for 2 revolutions of the engine. The LPG ECU controls fuel by referencing sensor signals from in the vehicles engine management system and additional sensors fitted, these varies dependent on the kit manufacturer.
The ECU is programmed with a fuel map, where adjustments can be made against engine speed and engine load, the systems also run in closed loop, this is achieved by referencing the lambda sensor in the exhaust in which the output signal is related to the engine air fuel ratio being rich or lean, the ECU in some conditions will then ‘Trim’ the fuel according to this signal. On vehicles fitted with a catalytic converter running in closed loop is required to keep them functioning properly.
Sequential fuel injection
Sequential injection is the latest generation of Multipoint systems. The kits are designed to follow the petrol injection system exactly and allow the engine management system to control the gas system.
The kits comprise of an electronic switch with gauge, an LPG Electronic Control Unit (ECU), reducer injectors and sensors for the engine coolant temperature, LPG temperature and LPG pressure.
The kit fits exactly like the earlier injection systems but it is very important for the injectors in this kit to have to be the later type of injectors, like petrol injectors that have electromagnetic coils around the injector. The reason for this is that the kit works by taking the individual pulse to each injector and passing it trough the LPG ECU, when running on gas it emulates the petrol injector and switches off the real one to stop petrol entering the engine, it also measures the opening time for the petrol injector, and buy refinancing a programmed map, it determines how long the gas injector needs to be switched on for to give the engine the equivalent amount of LPG.
Because the gas vapour pressure and temperature alter in normal working conditions the kit uses sensors that monitor the alterations and adjust the opening times accordingly. If the petrol ECU switches off an injector for safety the LPG ECU will see that the injector has stopped opening and also stops the opening of the equivalent LPG injector.
As the LPG ECU acts as a signal converter to the gas injectors, with the correct sized injectors, reducer and ECU map the petrol ECU is completely fooled and does not produce check engine lights. It also remains mostly in control of fuel enrichment and emissions control.
Alisei Sequential Injection Made By Zavoli
Direct Injection LPG conversion kits
Direct injection engines have fuel injectors mounted inside the combustion chamber and this creates new obstacles to over come. As the injectors are mounted inside the combustion chamber they require fuel to pass through them to keep the injector tips cool, which stops them getting damaged, there are also issues with recognition of the injector pulses as the technology used for operating them is different from a standard petrol injector, because the fuel pressure is much higher, along side this the fuelling of the engine is not solely controlled by varying opening times of the injector but by varying the pressure of the fuel at the injector.
As each system is slightly different the kit manufacturers build kits together that are made to fit only one engine type and must be matched to the engine code, the kits are mostly based on sequential injection kits but the main difference are the LPG ECUs. These ECUs are designed to read and influence the high pressure injectors and extra fuel pressure sensors so that the correct translation can be achieved and run the vehicle on both fuels simultaneously tuned to give maximum fuel efficiency and cost saving whilst protecting the direct petrol injectors tips from damage.
Liquid Injection
A Liquid injection system works similarly to a petrol-injection system, liquefied fuel is pumped out of the tank to a fuel pressure regulator and to the injectors. The system comprises a LPG fuel tank with an integrated pump, a fuel pressure regulator with a pressure sensor and safety valve incorporated in to it, Liquid gas injectors and the LPG ECU.
As the system is similar to a petrol injection system, the fuel is pumped out of the tank to the regulator with the excess fuel being allowed to return to the tank, this creates a steady, pressurised supply of fuel to the injectors. The injectors open allowing the liquid gas to enter the inlet manifold at which point it turns to vapour. This has a cooling affect on the charge entering the engine which in itself is beneficial to the running of the engine as an engine performs better with a cooler more condensed air fuel mix.
The ECU controlling the injectors can operate like a standard multi point system using load sensors and a pre programmed map or like a sequential injection system where by the ECU translates the petrol pulses to the LPG equivalent and using the additional sensors for correction.
Tank options
There are several options when it comes to choosing a tank and the choice is made by comparing what we are able to fit to the vehicle to the customers needs.
Single or 4 Hole tank?
Each LPGA installation must have tanks that meet certain criteria in its construction and valves used, each tank needs to have an outlet connection with an electronically operated safety flow shut off valve, a overpressure blow off valve and an electronic gauge interface filling point connection that only allows the tank to fill to 80% for LPG expansion.
The outlet connection has a safety flow shut off valve that is controlled by the LPG Electronic system so that it is only open when the vehicle is running on gas and the engine running. The over pressure valve is needed because as temperature of the gas in the tank changes its pressure alters. If in extreme circumstances the pressure exceeds 27 bar the valve opens and releases gas vapour to bring the internal pressure lower.
The filling point connection has an internal valve that closes when the tank is at 80% capacity, this is done to leave a small air gap for the gas to expand during the summer months. The gauge interface is made by using a float inside the tank which is connected to magnets that pivot behind a non-magnetic brass plate inside the tank, this allows for the fitting of an electronic pick-up to be fitted outside the tank that can pick up the position of the magnets, this method is favoured as the tank is a sealed pressurised vessel and does not require the need to get wires inside of the tank
.
The 4 hole tanks have one gauge valve, one blow off valve, one fill point valve with fill stop and one outlet valve with electromagnetic cut off. A single hole tank incorporates all these on one valve, the benefits of a single hole valve is cost it is by far the cheaper option were as the 4 hole tanks has a more accurate gauge, faster filling and higher flow output high demand vehicles.
Cylinder 4-Hole Tank
Cylinder or toroidal?
Cylinder tanks can be fitted inside of a vehicle or underneath larger 4X4 vehicles, toroidal tanks also called doughnut tanks are most often used in the location of the spare wheel, this can be in the boot floor, under the boot floor or even stood on its end in a boot. Tanks fitted inside the vehicle must be fitted with an air tight box that is vented outside the vehicle so in the event of a leak the gas vapour is vented outside the vehicle
Toroidal Single Hole Tank
Valve Saver Kits
When running vehicles on LPG the low carbon content effects how the valve wears in the cylinder head, vehicles that have hydraulic lifters, self adjusting valve clearances, automatically adjust for this and can run for over 100,000 with out issue, vehicles that can't self adjust must be fitted with additional kit to coat the valves to reduce this wear.
Flashlube is a delivery system designed to introduce a concentrated Lead Replacement Additive formulated to minimise Valve Seat Recession , there are two types of kit available, the first uses a bottle with a micro filter, tap and drip glass, this is mounted under the bonnet and connected to the engine with a brass jet, the vacuum in the inlet manifold pulls the oil through the system, the flow rate is adjusted by using a small tap and using the drip glass counting the time elapsed between each drop of fluid.
For forced induction engines and high capacity engines there is an electronic system that uses a bottle and a pump with a small electronic control unit that is connected in to the LPG injector wiring and is then pumped in, depending on the design of the inlet manifold either one jet can be fitted in a central point for even distribution, or multiple jets so that each cylinder gets even dosage of fluid.
Fuel Saving Chart
The UKLPG has kept a record in recent years of the prices at the pumps of LPG and petrol as published by Fleet News and petrolprices.com. Based on these national average prices the actual savings per year by running on LPG are higher than ever.
| year |
LPG |
petrol |
LPG as % |
Annual Savings |
| 2004 |
38.46 |
80.13 |
48.0 |
£576.00 |
| 2005 |
39.88 |
86.98 |
45.8 |
£667.00 |
| 2006 |
44.53 |
91.94 |
48.4 |
£652.00 |
| 2007 |
46.71 |
93.96 |
49.7 |
£639.00 |
| 2008 |
56.00 |
107.75 |
51.9 |
£679.00 |
| 2009 |
52.00 |
99.15 |
52.4 |
£613.00 |
| 2010 |
63.00 |
116.63 |
54.0 |
£680.00 |
Annual savings based on 15,000 miles per year at 38 mpg