Aero RV Belly Pan(s)

[slowmover]

Propane works "best" when the fuel price differential is great enough that the reduced amount of energy per liquid measure is offset. These days it is not much of a mpg gain in re fuel cpm. Utah, I think, has a very low price. Other areas of the country not so much. On the other hand propane is easy to find, tanks are cheap, and the tech to make it work is straightforward (be very careful nonetheless) in comparison to CNG.

I do like the idea of an additional fuel, but the tradeoff of reduced storage space may not be worthwhile. On a Class C perhaps it would be possible to fit a much larger propane tank of standard RV spec. Again, it would have to be weighed against extra diesel tankage. Both fuels are stable (diesel treated), and a reading of a commercial backup generator page the other day (BALDOR) was making the point of diesel having some advantages over gaseous-powered generators long term. Were your RV mine I would be looking to the Ford truck enthusiast forums to see who has done what with the 7.3. IMO, it's a fair amount of expense for a small benefit, unless,

1] One foresees difficulty in obtaining diesel under some scenarios, where maximizing liquid fuel is beneficial given that a gasous fuel is already aboard. And,

2] Where additional propane capacity is seen as being good for the use of the RV as in a rally or event where a ton of cooking and lighting is needed for big groups outdoors, etc; i.e., the Orby-C is the support vehicle).

If these two items dovetail then further investigation of costs and trade-offs is worthwhile as best I can see.

For what it's worth, I flip back & forth on wanting an all-diesel travel trailer, or adding propane tankage to the truck that the trailer have additional propane for current appliance mix and uses (beyond stretching out the diesel). The latter approach appears cheaper at present. Plus, I'd be able to add a lighter weight ONAN propane versus large/heavy diesel-powered generator (4k or larger to run A/C) to the truck bed more easily than modifying the trailer.

This link to RV Salvage yards in AZ might uncover a horizontal side-fitting tank to retrofit. See Manchester Tank, I'd want a 100# tank (11.5/gls) as a place to start.

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[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.

[drmiller100]

I have a 99 ford superduty with the 7.3 turbo diesel.

I've run a Jody Tipton (DP Tuner) chip for over 150,000 miles on it. I can switch between 4 tunes - Stock, 40 horse, 80 horse, and 120.

It is a documented fact by myself and MANY others the 40 horse gets better then 10 percent better mileage in basically all conditions over stock. Sometimes it is as much as 15 percent.

Further, under light loads at highway speeds the 80 horse tune gets an additional 5 percent.
In no conditions does anyone see better then 20 percent improvement, but 15 is pretty common.

Jody and others believe the additional mileage is because he is injecting the fuel at higher pressures for better atomization, and is injecting it sooner for advanced ignition timing.

I suspect the propane is doing the same thing - it is causing the ignition event to happen faster for more efficiency.

Under NO circumstance should you EVER run DP Tuner tunes with propane without discussing it with Jody.

My point is I think you could buy the 40 horse tune from Jody for a couple of hundred dollars and have all the benefits of propane with none of the hassles.

[orbywan]

Thanks DR, I'll call Jody and discuss this with him, that sounds like an interesting possibility.

[slowmover]

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.

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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[orbywan]

OK slowmover, my mistake, sorry. I'll let you know how it turns out.

[slowmover]

Originally Posted by orbywan

OK slowmover, my mistake, sorry. I'll let you know how it turns out.

No mistake at all, please. I hadn't thought it through in re RV energy storage and the benefit of extending the range of the rig, not just its' appliances, so allow me the thanks in putting it all down in one place. (One place for now, as I am in negotiations on another trailer so this is close to heart as I will be living full-time in same for an extended future and expect to have a thread or two at some point). Besides, KamperBob might show up and kick over my assumptions with the headstart he has on me in experience and long consideration.

Orbywan, you've doubtless got the single cool motorhome I am aware of as the FE changes are real, the quality of the work appears high, and the benefits reduce every category of time/mile expense by reducing the fuel burn of the main powerplant. Most moho's are just a way of doubling and tripling the cost of the exact same space and capacity of other RV combinations. Your well-chosen, used, altered Class C is breaking ground in what, for groups, could be a sensible choice (where a separate vehicle is deleted in favor of bikes, motorcycles, etc).

As I wrote above, when a suitably altered moho arrives, it can -- as with disaster scene vehicles -- provide energy and other inputs to basic shelters or tents for a fairly large group of people. The RV catalogs have all kinds of "extend-a-range" propane appliances driven off of a main tank on an RV at quite a distance. It can also pull a trailer with still more energy/food/water containers. This may not be on your list, but your inquiries bring up new thoughts in others. Why I so much enjoy the Orby-C story.

I'm genuinely looking forward to see how you tackle solar at some point, if that is on the list of considerations.

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[orbywan]

Thanks slowmover. I haven't gotten far enough with the aero mods yet to dive into solar. I do a lot of camping in the Arizona mountains so it is high on the list.
OK, aerohead told me about a guy who built a diesel pusher trailer to assist in locomotion of an electric VW. That's pretty far out there. You can read more about it at http://www.mrsharkey.com/lpg.htm. Sorry, I'm at a show in Calif and don't have my notes on how to make an uptown link to that site so you can just click on it. Here's an excerpt:

"Introducing LPG gas into the combustion air intake of a diesel engine acts as an accelerant, promoting the even burning of the diesel fuel, and more complete combustion, resulting in more power being produced. Many web pages and forum posts will call LPG a "catalyst" but this is not correct, as LPG creates no change in the molecular makeup of either the air or the diesel fuel.

Propane by itself resists self-ignition inside a diesel-fuel compression-ignition engine due to it's high flash point and narrow fuel-to-air ratio. During the compression stroke, the air/LPG mixture is compressed and the temperature is raised to about 400°C, not enough to ignite the LPG, which has an ignition temperature of about 500°C. In the small concentrations that LPG fumigation uses, the LPG mixture is not rich enough to be overly flammable and is more difficult to ignite. When the diesel fuel is atomized into the cylinder under high pressure, it immediately self-ignites (diesel ignites at about 385°C.), and causes the LPG to burn as well. Since the LPG is in mixture with the air, the flame front from the diesel spreads more quickly, and more completely, including igniting the air/fuel mixture which is in contact with the cylinder walls, which are cool in comparison to the super-heated air inside the combustion chamber. Much of the cleaner burning of the fuel is attributed to this ignition against the "cooler" components of the engine, and accounts for raising the percentage of combustion from a typical 75% for a well-tuned diesel engine running on pure diesel fuel alone, to 85-90% with the addition of LPG. Obviously, this more complete combustion also gives a nice boost in power, with an accompanying increase in fuel economy and reduction of pollutants."

I want all that to be true because it has good implications for my project, but I'm curious if anyone has any documented info that supports or defeats this?

[slowmover]

There are links to sites tied to diesel pickup truck enthusiast threads. There may be some in moho site threads. Mainly the experience of members with LPG component system vendors. There is less about any problems with combustion so modified (engine mechanical timing, injection timing, etc) as experience in time/miles is not well-defined in terms of climate, terrain, load and use; more anecdotal than is strictly reliable.

Much dates from 2008 when diesel prices skyrocketed. Less since then.

A couple I've saved:

Dieselbombers

Dieselplace: CNG (as reference)

DIY at Cumminsforum

Two vendors:

dieselperformanceproducts

Ecodiesel


My feeling about this has been (as above) that increased propane capacity has it's own benefits for an RV, and that perhaps the use of LPG as a main fuel extender while running the flats is a lowest risk proposition for a well-monitored engine.

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[orbywan]

Thanks slowmover, I'll check those out. Can't wait to get these mods done and get out there and enjoy the weather.