You may want to rethink the idea for the following:
Propane = 91,000 BTUs
Gasoline = 125,000 BTUs
So by using propane you have reduced the efficiency of internal combustion
by 27% or 34,000 BTUs.
Propane or LNG will reduce your engines HP on an average of 40% because of
the thermodynamics in the combustion process and reduced BTUs.
So if you got 15 MPG you will now get around 6 MPG.
So if you had a 20 gallon tank with gas you could travel 300 miles.
With a propane fuel system 20 gallons will get 120 miles per tank.
The difference of 180 miles so you would fill up your tank 2.5 times more
2.5 x $ 1.75 = $4.38 In reality at $3.00 a gallon for gas you would end up
spending $1.38 more per gallon.
If you do it yourself the propane conversion costs would be about $2400.00
So what appears to be a savings is not just smoke and mirrors
On Sat, 8 Jul 2006 06:22:11 -0400, "Coasty" <uscg_ret at comcast dot
You are way off on most of this. While it is true that propane has
less energy than gas, (20 to 30% depending on whether gas is E10 or
pure and more energy than E85) you will simply pure more to get the
same heat input. Propane is a excellant motor fuel and burns cleaner
than gas (cleaner than natural gas in a motor too) and with some kits
it actuallys make more power on propane. Proapane has a little
different burning curve and requires a bit more spark advance than gas
to do its best and engines that do poorly with it are not properly
timed. (like if they are tuned for low octane fuel) Also propane has a
very high octane (110+) so if you want to you can raise compression to
12 to 1 or higher with no fear of knock even towing and in the process
get even more power and MPG. If you get sav 15 MPG on gas, you should
get about 11 to 12 on propane in a stock engine that is properly timed
and it you mod the engine to higher compression to take advantage of
propanes octane, you will get near the same MPG as you did with gas on
a stock engine because of improved thremodynamic efficency. WHile it
is also true that you have to install a heavier fuel tank to hold
propane, it only weighs 4lbs/gal vs 6.5lbs/gal for gas which offsets
the weaight of tank and there is not problem towing with propane other
than finding it for fuel.
I ran a fleet of converted gas engines to propane in the 70s and mileage was
poor along with power. A 360 engine would only deliver 145 HP from it's
280HP after conversion. You can help as you said by raising the compression
however BTUs do not lie and there is a big difference between propane and
The conversion was done at the factory by the manufacturer and it did not
matter if it was a Chevy, ford or dodge they were poor. The only good thing
we could get 300k out of an engine and when torn down it was whistle clean
unlike gas engines. At that time we were getting 5K between oil changes.
On Sat, 8 Jul 2006 18:31:43 -0400, "Coasty" <uscg_ret at comcast dot
You can a very poor conversion because like I said it cam make just as
much power or more IF done correctly. Check out link below and I have
another one when I find it that covers conversions to GM 8.1 in med
duty trucks and they make more HP and torque on propane than gas after
dual fuel conversion. People do bad conversion and then blame the fuel
when it is the method that is bad.
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