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Which LPG Conversion Kit do I choose?

Introduction

This page is an attempt to provide an overview of LPG conversion kits that are available in the UK market place. It does not list them but rather discusses the technical merits of the different approaches of different manufacturers. I try to be unbiased and in that spirit will link to some of our competitors, something you'll not normally find on the web!

We must have an idea of what we are looking for -- a good kit is one that has all the components working in balance to produce the end effect of an efficiently fuelled vehicle with minimum change in performance to gether with improved emissions and no side effects.

The detail

The last ten years or so have seen some big changes in the UK LPG conversion industry. Single point (mixer) systems are now very rarely used and reserved for old pre multi-point petrol injection vehicles. With the influx of eastern european immigrants there has been a corresponding influx of LPG injection kits from those countries. The result is that where there was less than ten kits to choose from now the choice is probably in excess of 30. Good for the end user in that the competition forces the price down but not so good in that the individual installers who chase the cheapest kits do not build expertise in any particular kit.

Lets look at the kits, they all work! Front end kits can be categorized by: country of manufacture; vapour or liquid injection; electronic control unit; make of injectors; make of vapouriser; cost. The back-end is usually categorized by: 4 hole or single hole; cylinder or toroidal. Already we have a bewildering array of possibilities. For the purpose of this discussion I'll forget about the back-end and concentrate on the front-end kits also because of their relative rarity at the moment I shall not include liquid injection kits, therefore we will consider only sequential vapour injection LPG conversion kits.

If we categorize by country kits fall into one of three groups, Dutch, Italian and others (mainly eastern european) and conventional wisdom would have it that the quality descends in the same order. I have no evidence that this myth is true but suspect it has grown out of clever marketing in the past by the Dutch manufacturers. When installed correctly on an average car the difference in performance between Prins, BRC & Stag for example is unmeasurerable. We should consider other ways to differentiate between LPG Conversion kits.

If we categorize by Electronic Control Units (ECU) again we end up with three groups. This time we have kit manufacturers who make most of the components in the kit including the ECU for example Ultra-Gas, AG & Landi (group A in table 1). Also there are a large number of kit manufacturers who make the mechanical components and buy in the electronic expertise, e.g. Romano, Tartarini, OMVL and Bigas all use AEB electronics(group B in table 1).This group can further be broken down into those that design and make their own injectors(group B1 in table 1) and those that buy in injectors(group B2 in table 1). Finally there are the kit manufacturers who make the ECU and supply it with bought in mechanical components e.g. AC Stag and Tamona(group C in table 1). We could perhaps add a fourth group, the people who buy in almost everything, badge the components and sell them as there own e.g. Elpigaz , but I think this group should be in a category of its own(group D in table 1).

Table 1

Group ECU Injectors Vapouriser Tank Examples Comment
A Yes Yes Yes Yes Romano As far as I'm aware Romano are the only company to manufacture all of the components.
Yes Yes Yes No Ultra-Gas, AG, BRC BRC sometimes uses other injectors
Yes No Yes No Prins Uses Keihin injectors
B1 No Yes Yes No

Bigas,Emer,

OMVL

ECU firmware tailored to particular injectors.

Emer use Valtek injectors which is part of the same group of companies

B2 No No Yes No Zavoli when using Matrix
C Yes No No No AC Stag, Tamano ECU mixed and matched with Injectors and Vapourisers
D No No No No Elpigaz .Everthing is branded.
This is a first stab at classification, please let me know about errors and improvements.

When all components are made in house (group A) it is a good assumption that everything is compatible and will behave accordingly.

When an injector manufacturer uses an bought in ECU (group B) you can assume that the firmware has been adequately adapted for those injectors and that once again everything is compatible.

In the case of Groups C & D the possible permutations of Injectors and vapourizers with the ECU must create doubts about compatibility issues. This is exasperated by this group tending to be the cheapest kits and hence the natural reaction of sourcing cheaper injectors in the mix and match. Because of the different combinations of components in use, suppliers in all honesty can not be expected to carry out the strict emission test that are a feature of the complete kit manufacturing procedure.

The above is a summary of the strategies of various groups of LPG conversion kit manufacturers now lets take a look at the two key components, the ECU and the injectors. All ECU's work in a similar manner in that they take the petrol injector signal and modify it for the gas injectors hence allowing the petrol ECU to sill be in charge of emission control. They all work but their sophistication varies. Cheaper more basic ECUs while they work OK on older vehicle my have problems coping with the more complex requirements of more modern cars. The more expensive ECUs will employ newer technology and possible inter-react with the vehicles ECU via the OBD socket. This inter-reaction allows for fault code diagnostics and adaptivity to long term changes.[ I'll do a plug here. -- An example of technology advancing is our Romano ECU. it has OBD connectivity, self sensing injector cut wires (the order does not matter), built in petrol pressure emulator and software very similar to AEB to help migration from AEB ECU's]. While the latest OBD ECUs will work on older vehicles it is overkill and some manufactures have produced "cut down" versions that do not have the OBD connectivity.

The injector are the most important mechanical part of a LPG conversion kit. All manufacturers strive to produce injectors that are compact, easy to install, fast, quite, tolerant of impurities in the gas (dirt), serviceable etc. They also need to be produced is differing sizes to cope with different engine sizes and power. They all achieve this to a greater or lesser extent, the cost being a good indicator. As an example lets consider two injectors that we supply (I know i said it is unbiased but i can compare these with some authority). The Ultra-Gas injector is a rail type injector similar to basic valtex injectors and costs about £10 per cylinder, it is not easily serviced since a re-calibration is necessary however it is cheap enough to be considered a disposable part. The Romano injector at about £40 is individual hence facilitating optimum positioning,fast, quiet and easily serviced if needed. It is designed to be tolerant of dirt and as far as I know is the only gas injector that does not require a vapour filter. How do you choose between them? Does quality win over cost? The same comparisons can be made of other system e.g. Prins and Lima.

Conclusion

The conclusion is that there is no easy answer to which LPG conversion kit is the best for you. There are many considerations besides the technical and cost issues.The proximity of a good UKLPG approved installer my be more important than the make of the LPG conversion kit that he fits. The backup from the UK importer may be high on your list of requirements (make sure they are members of the UKLPG).

LPG conversion kits are no different to other commodities, you pay your money and take your choice. Higher cost does usually mean higher quality but be carefully at the top and bottom extremes. The top priced conversions although probable of a high quality do not always justerfy a significant price difference and similarly at the bottom end of the scale a cheap conversion usually means some corners being cut and that is often in the components being used. mintLPG offer a range of kit that cover the whole spectrum for budget to premium quality conversions, all at reasonable prices.

 

[note. As part of my research for this page I have studied several internet sites that are offering LPG conversion kits and spare parts. Some seem to be vastly over priced when compared to the prices of the official importer. Even some ebay prices are too high. Always check prices with the official importer.]

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Some links:          
Romano mintXI Ultra-Gas AEB Vialle Prins
Elpigas AC Stag Europegas/Oscar KME Magic Tamona
Matrix Keihin Tartarini eGas BRC AG
Valtek Emer Rail OMVL Bigas Landi