I have heard that some engines, converted to use LPG / Autogas, are wearing out exceedingly quickly.
Apparently, the LPG strips the oil coating from the valve stems and cylinder walls, causing very rapid wear. It seems that some LPG converters are now being very cautious about which models they convert, and are advising existing owners to revert to petrol only.
Is this a common problem with LPG conversions?
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Ford has advised against LPG conversions of all its engines except the old 2.3 litre twin cam four which has harder valve seats. The company did make a special LPG head with hardened valve seats for the 1.8Zetec E as fitted to old Mondeos, Escorts and Focuses, but that raises the cost of the conversion.
HJ
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It's like all these things. New ideas come about, everyone gets all excited, and it's only after a period of time that the cracks start to appear. I know some gas guys are developing direct gas injection because of problems having an inlet manifold full of gas, which can backfire and blow the airbox apart.
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Injection kits are already available and are used on high-performance and high-efficiency engines with cats etc. The simple venturi bleed into the air intake is OK as long as the mota doesn't have a huge plenum chamber and does not have a wide range of fuel flow.
LPG backfires do happen if the unit is poorly tuned but the installation of a one-way valve with presssure relief skirt aka "Fart Flap" will protect the airbox but, most importantly, the air flow meter.
The protection of valve seats is not done by oil. Valve seats, in older engines, are protected by the lead oxide from the combustion of the leaded fuels. This lead oxide is white/pink and can be seen in any exhaust manifold from an engine running on leaded. This lead oxide layer remains for many months after stopping use of unleaded and this explains why symptoms of valve seat recession don't appear immediately.
It is widely known that the Mondeo engines are not suitable for LPG conversion. Many manufacturers offer OEM conversions (Volvo/Vauxhall) - I wonder what they do to their valve seats?
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Friend of mine with 2.5V6 Vectra wanted a LPG conversion but was refused by the local outfitters as they had had significant troubles with these engines after conversion. 4 cylinders fine though apparently...
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