Home Power Prius, dual fuel

Discussion in 'Gen 2 Prius Accessories & Modifications' started by Garett Churchill, Aug 1, 2021.

  1. Garett Churchill

    Garett Churchill New Member

    Joined:
    Aug 1, 2021
    6
    0
    0
    Location:
    San Diego, CA
    Vehicle:
    2007 Prius
    Model:
    XLE
    Hello,
    Brand new to the forum. Having read a few pertinent threads I have decided that this place is exactly where I need to be!

    by way of introduction, I'm 51yo, and have worked as an electric sign contractor, fluorescent lamp manufacturer and am now in industrial electronics. We make induction heaters at Fluxeon. I'm good with electric, fabrication, and plumbing--pretty much everything needed for this kind of endeavor.

    I have a 2007 Prius.

    OK, so there are a number of threads on using the Pirus for home power. I plan to use it with the traction battery voltage and a high voltage inverter, integrated with a small-ish solar installation and a small-ish battery bank. The weak link is, basic energy. It's not convenient, cost-effective, or certain in the face of a crisis that you just unplug and go fill up the gas tank. I want to use natural gas as the fuel.

    NOT looking to run the vehicle exclusively on it, though. I only want to use natural gas while the car is in the driveway and plugged into the house. so, no high-pressure tanks and pumps needed or desired.

    is there a straightforward way to just pipe in natural gas to the fuel line? thinking of a 3-way solenoid valve that would sense when it's plugged into the house and flip it over to nat gas. simple circuitry involved there, nothing fancy.

    number two concern is, would standard residential pressure be sufficient, or would I need a small compressor? (think rotary vane or maybe diaphragm, not piston.)

    number one concern is, of course, would it work at all? is there an aftermarket kit that does all of this?

    all information and insights are welcome!
     
  2. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    14,574
    10,257
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    I guess my first question would be whether the same injectors at the same injection pulse width would flow an appropriate amount of natural gas. Maybe by adjusting a pressure regulator carefully enough you could get it in the ballpark, and the ECM's ability to learn a fuel trim (within ±20%) could do the rest, but things might be a little ungraceful right after switching from one fuel to the other.

    At least when stationary the car doesn't generally throttle up above maybe 4 kW output or rev above idle speed, so maybe it would be simpler to regulate the natural gas supply to cover those conditions than it would be if you wanted to cover the whole range of normal driving conditions.

    The conditions at the intake ports are negative pressure, so my first guess would be that you can get the needed flow at residential pressure or below, but that's just a guess.

    You could use Techstream to see what your current injection pulse width is on gasoline, at idle and when charging the battery in Park, and then experiment with an identical injector to see how much natural gas it delivers at the same pulse widths and various pressures.

    How tight are you with your insurance agent?

    Got a plan to prevent mistakenly driving the car away while the natural gas line is attached?
     
    #2 ChapmanF, Aug 1, 2021
    Last edited: Aug 1, 2021
  3. Another

    Another Active Member

    Joined:
    Jun 22, 2021
    555
    113
    0
    Location:
    Naples, Florida
    Vehicle:
    2007 Prius
    Model:
    Touring
  4. Garett Churchill

    Garett Churchill New Member

    Joined:
    Aug 1, 2021
    6
    0
    0
    Location:
    San Diego, CA
    Vehicle:
    2007 Prius
    Model:
    XLE
    I think the bigger problem is that the car will want to regulate the flow of fuel. I am many things, but not a car mechanic... But I do know a couple. :)

     
  5. AzusaPrius

    AzusaPrius Active Member

    Joined:
    May 27, 2020
    885
    423
    0
    Location:
    Apple Valley
    Vehicle:
    2010 Prius
    Model:
    IV
  6. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    14,574
    10,257
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    Sure; it'll do that by regulating the number of milliseconds each injector is open for it's cylinder's intake stroke. The ECM knows how much liquid gasoline at 43 psi will flow through the injector per millisecond, and it knows how much gasoline makes a stoichiometric mixture with how many grams of air, so it can calculate how long to hold the injector open. It can trim its calculation by up to 20% either way if the oxygen sensor reading after combustion says it wasn't spot on.

    So your mission would be to look up what's the corresponding stoichiometric ratio for natural gas to air, and figure out what gas pressure will push that much gas through the fuel injector in roughly the same amount of time as for the right amount of 43 psi gasoline would flow. If you are able to supply the injectors with gas at that pressure, then the car's normal modulation of the injector pulse width will probably be able to get you the mixture you need.

    However, sitting here in my armchair, I haven't any idea what "that pressure" will turn out to be, and the answer could determine the practicality of the idea.

    The thread linked in #3 is interesting, but different in a couple of ways:

    • It uses liquefied propane, not natural gas. (From my limited-experience with natural-draft water heater burners, LP requires both a higher pressure and a smaller orifice compared to NG.)
    • It is designed for use under actual driving conditions.

    Again, I'm hopeful that your plan to use NG only when stationary might simplify some things. The controller for driving might need an extensive 'map' of injector timings to cover the whole range of engine RPM and power output. As you will only need to cover the idle to roughly 4 kW range and only roughly idle RPM, possibly something less elaborate will suffice.

    Their system needs to vaporize the liquefied propane, whereas your natural gas is already gas.

    They use separate injectors for the gaseous fuel. It would be nice to find a simple way to get the car's existing injectors to flow the appropriate amount of NG ... but maybe the characteristics are just too different, and it doesn't work out.

    Interesting project!
     
  7. Garett Churchill

    Garett Churchill New Member

    Joined:
    Aug 1, 2021
    6
    0
    0
    Location:
    San Diego, CA
    Vehicle:
    2007 Prius
    Model:
    XLE
    Thank you for those links! I bought the Red Bullet valve, and thinking seriously about the lithium traction battery. I had planned to have a small battery in the house that the charge controller would cycle, but this new Prius battery has more capacity, higher discharge rate, and a 2 year warranty. plus it will make driving better. :)



     
  8. Garett Churchill

    Garett Churchill New Member

    Joined:
    Aug 1, 2021
    6
    0
    0
    Location:
    San Diego, CA
    Vehicle:
    2007 Prius
    Model:
    XLE
    wow, 43psi would almost certainly mandate a diaphragm or better compressor. doable, but not ideal. I tend to gravitate to overly complex plans, and then whittle down to something that works and that's something I can afford....

    I wonder about feeding the gas into the carburetor would work? (sorry, that was a bad joke. ;) )



     
  9. Garett Churchill

    Garett Churchill New Member

    Joined:
    Aug 1, 2021
    6
    0
    0
    Location:
    San Diego, CA
    Vehicle:
    2007 Prius
    Model:
    XLE
    also bought the capacitor spark plugs.
     
  10. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    14,574
    10,257
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    The car's fuel pump produces about 43 psi, but that's what it takes to force a liquid (that we weirdly in the US call "gas") through the injectors.

    Your mission would be to find out what pressure would be needed to force an energy-equivalent amount of natural gas (an actual, you know, gas) through the same injectors in the same amount of time.

    Maybe it would be high, maybe not. I haven't tried to back-of-the-envelope it.

    The joke part was that there even is a carburetor, right?
     
  11. Garett Churchill

    Garett Churchill New Member

    Joined:
    Aug 1, 2021
    6
    0
    0
    Location:
    San Diego, CA
    Vehicle:
    2007 Prius
    Model:
    XLE
    there may have been more than one joke in there.... ;)

    there is more than one way to figure this out, but the easy way will be to give it the ol' ''college try''. :)
     
Loading...