Bifuel or not? This is the question…Part 1


Santa promotes natural gas © by Dvortygirl

In this period of expensive fuel, I suggest again the question of convenience or not to switch to gas. Whether it’s
natural gas or LPG, the car is registered as an original bi-fuel or it is transformed , the advantages are many: savings on supplies, reduced emissions and always the ability to drive. What I am going to do is a list of the main concerns, of even greater concern, which can be in
dealing with such a choice.

I state that since there are no incentives in Italy for scrapping or eco-incentives, and I say that any form of sponsorship has been made ​​to support the only alternative (and who knows for how long) to gasoline, and I am not versed in the issues type of Transport White Paper, Protocols
on CO2 emissions, etc … I’ll try to be as comprehensive and clear as possible dividing the discussion into two parts in which I will address some motoristic concerns.

Hotter and drier combustion damages valve seats and heads

It’s important to know that in the combustion of air / gas mixture in the combustion chamber temperatures increase from 12 to 15 degrees. LPG is a gaseous fuel, thus has no lubricant and coolant action on valves and valve seats In addition, there are no gas substances used in gasoline (benzene, toluene, etc. …) that washes up on the valves and valve seats, creating a veil of protection over them and amortize it to beat on the seats of the valves being closed, thereby mitigating the effect of “hammer”. Every 15-20,000 miles, depending on the use of the car, there is a variation of the opening and closing of exhaust valves at the expense of the exchange of heat in the combustion chamber.

If the valves are not self-regulating, i.e. not automatically adapt to this change, the car needs maintenance, valves registration  in order to maintain the qualities of handling and reliability.

The maintenance varies according to materials of construction of valves and valve seats.

1. If the car is equipped with self-adjusting valve requires no maintenance, and if the materials of construction of valves and valve seats are
made of steel. The motor efficiency in the gas operation is higher than when running on gasoline or diesel fuel.

2. If equipped with valves and register plate glass and steel building materials, requires valves registration every 45/55.000 miles depending
on the use of the car.

3. If equipped with valves and register plate glass and not steel building materials, requires valves registration every 20/25,000 miles
depending on the use of the car.

Burning clean and free of deposits makes the cylinders so smooth that the rings can no longer be required and a
higher consumption of oil

It ‘true, but the increase of oil is irrelevant (surely a minor drawback of the problem of some FAP or DPF filters in diesel engines)

The coils break down more easily for the heat derived from the combustion gas

Depends on the car and the position of the coils, even in this case a car ready to dual power has certainly more secure than the other.

Traveling with the fuel tank under 1 / 4 is a risk for burning the fuel pump;

Just keep ¼ of gasoline in the tank over two months and replace it with fresh gasoline as unleaded fuel, if not used within this time it decomposes and can cause damage to the fuel pump and injector. Avoid using gas reserves with the light turned on because the fuel pump may deteriorate. Even in switched gas, pump works to circulate the fuel in the injectors and let them cool.

To be continued … for more discussions please let me know your point of view, thanks

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  1. Mike Wattam says:

    You have highlighted the ‘heat’ issue, yes this is true. The development of high control over the petrol combustion process suggests that the VM’s may have taken the opportunity to reduce the specification/cost of valves and seatings and local evidence shows that LPG-fuelled engine maladies particularly in the valve area are much more prevalent on very modern petrol engines than previously.

    Some of the LPG conversion suppliers have introduced a metered-drip oil supply system at added cost to protect the valves/seats but the jury is out as to whether these are any more than a cosmetic accessory.

    With the best will in the world, LPG conversion kits don’t have the benefit of extensive VM test programmes and in my experience are therefore less than reliable and as they are always ‘fail-safe’ will shut off for minor reasons.

    VM’s can build engines to withstand the heat reasonably successfully e.g., Volvo, Ford, (at greater unit cost) but both have ditched LPG due to the lack of public fuelling infrastructure in most countries, and – dare I say it – withdrawn government subsidies on each vehicle registration. This year in particular when the consumer is looking to minimise costs, LPG has taken a very serious sales ‘dive’.

    With the cost of conversion (now only after-market) becoming quite high, the initial investment means that LPG systems take a longer time to the ‘break-even’ point, possibly well over 100k but this period is being pushed out further and further as the original 50% price differential between LPG and petrol is now only 40% and the price gap is still reducing. Then factor in the 10-20% reduced mpg on LPG too……

    There is an additional technical factor now creeping in; petrol engines are resolutely heading towards direct injection of petrol, when those engines are run on LPG it seems to kill the petrol injector nozzles with the result you can’t start the darn thing.

    Other technological advances such as lean-burn, sophisticated engine management for economy and so on, mean that it is becoming progressively more difficult to integrate an LPG system into these engines/cars.

    Then there is the warranty problem; VM’s will not honour engine warranty when an after-market LPG kit is fitted. Therefore engine problems will be up to the user to fund and with parts bills maybe over 2,000 Euro plus not inconsiderable labour, alternative vehicle hire and contingent liabilities, engine problems on a newish vehicle can be very expensive indeed.

    Finally there is the environmental issue. Before CAT converters were used, the LPG exhaust gas was VERY clean but with all the latest technology petrol and diesels are now almost as clean. And the cost per mile of diesels has got down to that of LPG!

  2. ezio says:

    thanks Mike,you’re so detalied, I will ask you about VM, forgive me but I don’t understand and I cannot answer the way I would.
    see you

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