Quote:
Originally Posted by orbywan
Thanks for the thoughts slowmover but I'm not sure you understood what I was referring to. I'm talking about injecting small amounts of propane in the intake while driving down the road. It is claimed that this improves combustion efficiency (of the diesel fuel), reduces emissions, and improves mpg by anywhere from 5 to 20%, depending on who you're talking to.
Several of my class A 40 and 45 footer customers swear by it, citing improvements of 8 to 15%, and say it improves power noticeably also.
My brother has a 2002 F-350 7.3 pick up that now has propane injection added. He says his mpg went up 15 to 20% depending, and the added go is very noticeable in his lighter vehicle.
So anyway, one more thing to add to the list. Yehaa.
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Oh, I understand. Perfectly. One is still paying a BTU price per measured volume which the engine consumes. The price differential between diesel and propane is what makes or breaks the conversion. Propane has a lower price, but a reduced BTU content as well. Nothing magic happens as a result of propane injection, the engine just doesn't demand as much diesel as before.
Thus my comments about wanting to "stretch" the diesel onboard. If one can come up with a reasonable, conservative prediction about "increased mileage percentage with propane injection" then the available propane capacity can be seen in a new light.
Propane = 91,500 BTU/gl $2.80
Diesel = 139,200 BTU/gl $3.80
If one ran the truck on straight propane, the gallon count would
rise to perform the same work. Propane has only 2/3's the BTU content as diesel, but the price differential [per EIA, today] is that propane is 3/4's the cost of diesel.
So, X-amount of diesel takes me a certain distance. Y-amount of propane
when combined with diesel extends my range to ??
At the end of those miles I have covered Z-miles at what combined fuel cost?
It's all in the price differential. Is the $1 enough to jusify the lower BTU content of propane and associated conversion costs?
If the benefit of increased propane capacity can be put to good use beyond increasing the "reach" of a stated amount of diesel, then the conversion cost nears being moot. That's as close as I can get it to "work".
And this is before we take into account potential detonation damage which gaseous fuel injection can cause. So, let's assume that the highest, best use of propane as motor fuel "additive"is under fairly light load, level terrain conditions.
One should also look at water/methanol injection systems (SNOW PERFORMANCE) as they are a bit easier to live with, and may provide a similar benefit without a number of drawbacks. I am not saying "superior" by any means.
An RV and extended driving range via propane injection may be a very good combination.
That is what we can say about it at this point, not that we will see increased FE.
From another tack: This is similar to a big solar installation, IMO. If I can "boondock" (without water, gas, electricity, sewer) for an extended number of days -- let's say I can extend my stays without other inputs from 3-ights to 10-nights -- I am seeing a benefit. A refrigerator that runs on propane as well as either 12V or 120V inputs allows choices to run other power demands. A big solar installation, backed by a bigger propane installation, gives a maximum of electric or direct fossil fuel "range" given adequate battery capacity. That I can also use the extra propane to lower diesel burn is in the same vein where
best I keep as much diesel in reserve as possible is operative.
Note: for non-RV'ers one can figure that a night at a campground with "full hookups" costs $40. While extended stays of one week to one month can be as low as $10/night, one is best in figuring the conservative higher cost for planning purposes. Choices, therefore, about how much money to spend in operation can have a large bearing on the capital expense of outfitting or upgrading the RV proper where time & miles can show a reasonable payback period.
Thus, the FE benefit of propane injection will vary from okay to non-existent, but the ability to
choose from a variety of onboard energy sources may well make it a worthwhile expenditure for an RV where propane also powers generators, stove/ovens, water heaters, refrigerator/freezers, lighting, etc,
and a mere increase in propane capacity and some extra equipment of fairly low cost, size and complexity not only increases current run-times, but extends vehicle range as well can be seen as an easy addition.
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