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15207 Views 26 Replies 11 Participants Last post by  elmo40
Anyone looking into ordering the 3.7 Ti-VCT V6 with the propane prep package.

Here in Canada a complete conversion costs about $4500 to $5500. This is for a dual conversion gas/propane. Vehicle is reported to run equally well on either fuel. Propane costs about 40% less then gas. It would not take long at this rate to pay for the conversion.

If anyone is planning a conversion I would be interested in any information regarding conversion companies, systems, costs and procedures.
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Gas has an octane of around 87 and needs a compression ratio in the 9s to extract the energy efficiently. CNG has an octane of 130 and needs a compression ratio in the 12s to extract the energy efficiently. Propane has an octane of 110 and needs a higher compression ratio higher than a standard gas engine to run efficiently you will see a loss of MPGs and horsepower. With CNG conversions you see a loss of horsepower (10-15%) and loss of MPGs (~12% city / 7% highway).
My 2 cents on this great subject....

I think most internal combustion engines become more thermally efficient as the compression ratio is made higher. However, it's the fuel's octane rating that limits how high the CR can be made otherwise the engine knocks due to detonation or pre-ignition of the fuel. I like to look at from the standpoint that higher octane fuels allow spark-ignition (SI) engines to have higher compression ratios. And higher CR makes engines more thermally efficient. Obviously engineers also have to worry about pollution in addition to power/fuel efficiency.

The Ford 3.7L V6 has a compression ratio of around 10.5, which seems about average by modern standards. With gasoline direct injection some modern engines have considerably higher CRs.

Regarding lower power, I'm under the impression that comes about in part due to the gaseous fuel reducing how much air the engine can breath during intake stroke. And if so, that may make it less powerful without being less efficient.
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