Gas efi vs propane

Discussion in 'Alternative Fuel Forum' started by cdqat1432, Jan 18, 2013.

  1. cdqat1432

    cdqat1432 LawnSite Member
    Male, from Youngstown, Ohio
    Messages: 138

    We all know that a propane fueled engine is cheaper to run than a carbureted gas motor but what about efi? Efi is maybe 1000.00 more but the conversion is going to run at least 500 with the state incentive. With the fuel economy of gasoline efi would it still pay off? Can we do an efi propane? Probably big bucks.
  2. ToddH

    ToddH LawnSite Silver Member
    Messages: 2,214

    I am sure Propane is injected but you will not see the same power
  3. DR J

    DR J LawnSite Member
    Messages: 34

    Yes, KOHLER has a liquid LPG injected motor and a vapor injected motor, they were just put on the market. Now all we have to do is wait and see which manufacture is going to use them. To learn more about method may look at a website maker of alt fuel sys for vehicles. To answer your ? yes you can convert an efi engine. One problem, no epa approved sys yet.
  4. The Swamp Fox

    The Swamp Fox LawnSite Member
    Messages: 77

    I am preparing to launch my own solo lawn/landscape maintenance operation, and as an efficiency nerd I came across this thread while searching for an answer to this question myself. Since this thread is now six years old, I thought I'd post my findings here as a follow-up of sorts for other lost souls who may have this same question.

    This mock EFI vs. Propane ROI article
    by Green Industry Pros covers most of the base calculations. IMO there is no definitive answer, as the price per gallon of the propane and gasoline available to you can sway the calculation significantly either way. I've outlined my findings on some of the base considerations below.

    EFI Engine Upgrade Cost
    I'm considering a 52" John Deere QuikTrak stand-on mower (Model #652R) as my primary mower. The base price for the unit with the 23.5 HP Kawasaki FX730V was $10,276 vs. the 20 HP ECV740 Kohler Command Pro EFI at $10,579. So the EFI upgrade costs $303.

    Propane Conversion Cost
    The Propane Education Research Council (PERC) rebates for lawn mower propane conversions are still available in the amounts of $1,000 for new mowers and $500 for conversions done on used mowers. There are several disclaimers in the fine print, however:
    1. Mowers must exist on the list of eligible makes/models
    2. Mower deck size must be 36"—72"
    3. Used mowers must be model year 2012 or newer and have less than 250 hours at the time of conversion
    4. Mowers must be set up for exclusive use of propane
    5. Conversion kits must be EPA-approved
    6. Rebate is limited to 25 mowers per person per year
    My two local John Deere dealers quoted me roughly $1,300 for the required propane conversion kit for a QuikTrak 652R with a Kawasaki FS730V engine. The kit comes with all required components other than tanks, and includes install. So out-of-pocket cost for the conversion after rebate will be about $300 — comparable to the EFI upgrade.

    In addition to the cost of conversion, you'll also have to factor in the cost of obtaining the required propane tanks, which are not cheap. If you're a large operation, you may need to consider the setup cost of a bulk filling station ($$$) as well.

    Fuel Efficiency Comparison
    Most commercial lawn mower manufacturers claim their EFI engines can reduce fuel consumption by 25% compared to the comparable carbureted model. If the industry average is 1.3 gph for a carbureted engine, an EFI unit would lower that to 1.04 gph.

    In all of the reading on this topic that I have done, consensus seems to be that carbureted engines converted to run on propane will consume approximately 20% more fuel due to the inherently lower energy content in propane. I asked my local small engine repair shop mechanic for his take on this, and he confirmed that the dozen or so lawn mowers and generators he's converted use about 15-20% more propane than gasoline.

    For a true case study, reference the test that LawnSite user Thunderthud ran back in 2011 pitting a Scag Turf Tiger 60" EFI vs. a Scag Turf Tiger 60" with an OEM propane kit:
    • EFI — .99gph
    • Propane — 1.21gph
    I am unclear on whether the propane-powered Scag Turf Tiger in the above test was an EFI or carbureted unit, but the numbers would appear to indicate that it is about 20% less efficient so an EFI unit would seem likely, as a carbureted unit should be about 45% less efficient overall.

    Operational Cost Comparison
    This is where the rubber meets the road. In my area, propane bottle fill is priced at $2.49/gallon whereas the current average price of 87 unleaded gasoline is hovering around $2.75/gallon. Let's take a look at annual fuel cost, assuming weekly mower usage of 20 hours/week x 30 weeks/year (600 hours). In order of lowest to highest:
    • Gasoline (EFI) = $1,716/year (600 hours x 1.04 gph x $2.75/gal)
    • Propane (EFI) = $1,865/year (600 hours x 1.248 gph x $2.49/gal)
    • Gasoline (carb) = $2,145/year (600 hours x 1.3 gph x $2.75/gal)
    • Propane (carb) = $2,331/year (600 hours x 1.56 gph x $2.49/gal)
    In this scenario, gasoline EFI beats propane in every scenario. Propane EFI beats out carbureted gasoline, but not by much. And we didn't even factor in the fuel excise tax savings which we can recover from the price paid for gasoline at the pump, which probably means that all forms of gasoline win in this scenario.

    But there's one caveat here that can completely flip the above results on their head — the current local price for bulk propane is only $1.14/gallon. So if you have a 500 gallon residential heating tank at home and if your propane supplier will allow you to install a "wet leg" and fill your own propane bottles, there is a $1.35/gallon savings available for propane. Re-running our calculations above:
    • Propane (EFI) = $854/year (600 hours x 1.248 gph x $1.14/gal)
    • Propane (carb) = $1,067/year (600 hours x 1.56 gph x $1.14/gal)
    • Gasoline (EFI) = $1,716/year (600 hours x 1.04 gph x $2.75/gal)
    • Gasoline (carb) = $2,145/year (600 hours x 1.3 gph x $2.75/gal)
    In this scenario, going the bulk fill route with a propane EFI engine saves $862 annually per machine compared to gasoline EFI. A carbureted propane unit saves $1,078/year over a carbureted gasser.

    You'd obviously have to still factor in infrastructure costs associated with propane operation, such as the initial cost of obtaining propane bottles and a bulk fill station, but the numbers don't lie. As mentioned at the start and as demonstrated above, whether gasoline EFI or propane is the better option will mostly depend on the price of each commodity in your area.

    Hidden Propane Savings
    There are some not-always-obvious potential savings when opting for propane over gasoline. Here's a list from my notes on the topic:
    1. Reduced maintenance (no more carb teardowns; longer oil change intervals)
    2. Less engine wear, resulting in estimated 25% longer engine life
    3. No loss of fuel due to spillage, leakage, theft
    4. No need for Sta-Bil or other solutions to combat fuel staleness
    5. Propane tank size may enable longer run times between refueling
    6. Elimination of trips to refuel mowers at the gas station
    7. Additional hours of operation possible during ozone-protection days
    8. Marketing advantage for low emissions / green operation
    If you couple propane mowers with battery-powered handheld equipment, you can double up on savings in a few additional ways:
    1. Eliminate the need to purchase portable gas tanks and spouts
    2. Eliminate the need to purchase trailer racks for hand-held equipment — other than for convenience — as they can be safely stored inside your tow vehicle
    Propane EFI Availability
    When it comes to efficiency and lowering operational costs as low as possible, coupling EFI technology with propane seems to be the best of both worlds.

    That said, all of my local dealers were of the opinion that propane and EFI technology were incompatible, and that EFI engines could not be converted in EFI form to run on propane. To this point, I've found that all propane conversion kits currently available are designed only for carbureted models, and are therefore incompatible with EFI engines. I have yet to find one that is.

    I was excited to recently learn of the Kohler Command Pro Propane EFI engine which was released in fall of 2012. I thought perhaps this would be the ultimate power solution for my new fleet. Unfortunately, as of the date of this writing it appears that this engine is only available on one or two ZRT models:
    These are larger than my desired deck size of 52", and I have yet to find an EFI Propane engine available in a stand-on ZRT. I would LOVE any and all information on any additional mower make/models available with propane EFI technology, or conversion kits which are EPA-approved and are compatible with EFI gasoline engines.

    Does this unicorn yet exist??

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