Why are Direct Petrol Injection engines unsuitable for conversion to LPG?


For a change, the reason is quite simple;


Engine manufacturers are tending to move their petrol injectors away from their more traditional position (close to the end of the inlet manifold), placing them directly into the cylinder they are meant to be fuelling instead. This change has a beneficial effect on Emissions. Naturally, the tips of direct injectors are heated up when placed in the flames of cylinder combustion. This isn't normally a problem as the petrol being squirted through the injectors keeps them cool.

Problems arise when the engine is converted and the petrol injectors are turned off. The cooling effect of the petrol being injected is lost and the injectors will overheat as a result. Eventually, the petrol injector tips will be damaged, and may even melt. Whatever happens, eventual failure of the injectors (and therefore the petrol system) is inevitable.

One way to get around this problem is to keep the petrol injectors cool by making the petrol injectors work for some of the time that the engine is running. This mixture of both fuels (Dual Fuelling) has to be done with a high degree of accuracy, the ratio of petrol / LPG mix being different for any given engine load or RPM. At present, it isn't possible for installers to accurately set-up this Dual - Fuelling facility with the LPG kits available. LPG Kit manufacturers are having to develop dedicated software for each and every enigine or model, which costs a lot of money and takes a lot of time. The result is that there are only a very small number of dedicated, car specific Direct Injection kits available (Dec 2008) made by our suppliers Romano and BRC.

Whilst the LPG Kit manufacturers are playing 'Catch up' with Direct Petrol injection technology, it is the policy of GO LPG and other professional installers not to convert Direct Injection engines unless a specifically produced kit is avialable for the model.

If you have a car with such an engine and want to get it converted, contact us to see if the job can be done.

Steven P. Sparrow BSc (Hons)

December 2008

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