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  1. #1
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    Anyone here with any experience building engines for CNG?

    Anyone here done any work on or build engines that run on CNG? With articles like this, which I have agreed with for years and been preaching it, I'm wondering what it actually takes to build a motor to run on CNG.

    http://www.cnn.com/2012/02/29/opinio...html?hpt=hp_t2

    We had a couple of cars on campus at the University of Tennessee that the classes before me built as senior design projects, to run on CNG but I wasn't involved in those. My class built a diesel-electric hybrid suburban for the Future Truck competition, no CNG experience.

    I don't think it would be all that hard to take an existing vehicle and modify it to carry the correct tanks and have a fueling port on it to run CNG but, I don't know the fuel's characteristics that would dictate how the engine is built, such as required compression, combustion chamber pressures, timing curve, flame speed, gasket and seal material required, etc. I work in the natural gas industry as an engineer so I know most of the information as far as requirements to resist corrosivity of the gas in the metals and gasket materials but, I don't know if those materials I'm used to working with are even available for car engines on a readily available basis when it comes to items such as head gaskets, intake gaskets, etc.
    "If we can prevent the government from wasting the labors of the people, under the pretence of taking care of them, they must become happy." Thomas Jefferson

  2. #2
    Hmmm.......I'm sure I could find something around here to convert.......

  3. #3
    Rolling Scrapheap colombiapunk's Avatar
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    I've been considering this with the wheeler. CNG or Propane, it seems like a good idea, CNG has a few perks over propane too.
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  4. #4
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    Quote Originally Posted by Xtremjeepn-Cole Ford View Post
    Hmmm.......I'm sure I could find something around here to convert.......
    I was thinking the same thing. I just happen to have a few connections to the gas company that might help me get tied to the meter for a filling station at my house too.

    Quote Originally Posted by colombiapunk View Post
    I've been considering this with the wheeler. CNG or Propane, it seems like a good idea, CNG has a few perks over propane too.
    I've done Propane and know what that takes, hence my questions about CNG. Propane has some odd characteristics that sparks my questions about CNG. Timing curve specifically.

  5. #5
    My V10 dodge has a Propane set up on it already. I certainly wouldn't be against experimenting with that truck.(not like you could make it get worse mpg)

  6. #6
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    Quote Originally Posted by Xtremjeepn-Cole Ford View Post
    My V10 dodge has a Propane set up on it already. I certainly wouldn't be against experimenting with that truck.(not like you could make it get worse mpg)
    The problem with propane on a standard gas motor is that propane has a vastly different timing curve and wants tons more compression to take advantage of it. Propane has a very high octane value/rating and the timing curve needs to be extremely advanced right at idle and climbs steeply with rpm, then is almost flat after that. Nothing like a standard gas curve, all due to flame speed with a proper mixture.

    I have a special MSD ignition box at home that I got for the purpose of creating that timing curve on my buggy but never installed it.

  7. #7
    Rolling Scrapheap colombiapunk's Avatar
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    I've got the MSD box and timing control for on the fly retard and advance, but if I do it I'm going to have to up my compression ratio a ton. CNG has the same issues from what I've googled.

  8. #8
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    The other problem you have is that Propane isn't cheap or as widely distributed as CNG. Back about 6 or so years ago when I was running it, it was going for about $3.50/gal. CNG can be had cheap at the meter at most houses if you install a legal filling station/connection.

  9. #9
    That is why I'm not running the propane set up. Not cheap enough any more.

  10. #10
    also you will have to have a compressor setup to fill the tank at your house, not sure how cost prohibitive that would make the whole thing either.

  11. #11
    Camp Cook Geek cheftyler's Avatar
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    Quote Originally Posted by mbx400 View Post
    also you will have to have a compressor setup to fill the tank at your house, not sure how cost prohibitive that would make the whole thing either.
    I would guess the compressor is built into the "filling station" thingy Camp was talking about, but I don't know shat about this stuff, just interesting to learn.
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  12. #12
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    Quote Originally Posted by mbx400 View Post
    also you will have to have a compressor setup to fill the tank at your house, not sure how cost prohibitive that would make the whole thing either.
    If your consideration is to only do this for one vehicle in your lifetime, yes, the extra couple of thousand dollars required to set up a filling station is cost prohibitive. If you believe the article and my preaching of CNG being the bridge energy to get us off foreign oil, consider using it a very long time and it paying for itself.

  13. #13
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    A few years back, when CannonBall and I were driving buses, we had several that were converted to CNG. If memory serves me right, they were older Cummins 6BT's with minimal (if any) modifications. These were not the newer computer controlled versions. Besides the Obvious (tanks, regulators, etc.), I remember one of our mechanics telling me they took care of it as it was a regular diesel.

    That said, the power out of those things was absolutely miserable, especially if they were running cold and/or the tanks were low. It turned me off to the whole CNG thing.

    FYI: There's a CNG filling station (or, used to be) at 30th & Baseline.
    I don't wheel, nor do I pretend to.

  14. #14
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    Quote Originally Posted by Mack View Post
    A few years back, when CannonBall and I were driving buses, we had several that were converted to CNG. If memory serves me right, they were older Cummins 6BT's with minimal (if any) modifications. These were not the newer computer controlled versions. Besides the Obvious (tanks, regulators, etc.), I remember one of our mechanics telling me they took care of it as it was a regular diesel.

    That said, the power out of those things was absolutely miserable, especially if they were running cold and/or the tanks were low. It turned me off to the whole CNG thing.

    FYI: There's a CNG filling station (or, used to be) at 30th & Baseline.
    That is similar to the experience a lot of people have with Propane because the engine isn't specifically sent up for that fuel. I need to do some real research into this because I might want to start building a CNG motor for our 4Runner and convert it in another 50K miles or so if I can make it run correctly and fill it at the house.

  15. #15
    Camp, I work on and in the natural gas field, and specifically the engines. I have built and worked on everything from the industrial single cylinders, through the common GM engines up to Cat 3516 engines.

    The industrial diesel designed engines (the Cummins 8.3, and the Cats) use specific cams for NG and don't run over 1300 rpm. But on the gasoline designed GM 350's, 454's,& 502's, we just used RV cams and ran up to 2200 rpm. All timing was fixed at 30 degrees. Anything less than 25 or over 38 would loose HP rapidly. So timing range is narrow.

    The only problem with LPG or CNG is it will take a 350 HP engine and only make 150 or less. When I had propane on a scout with a 345, a forklift size tank would only last 25 minutes. I sold the system only after using it a few times.

    I believe that CNG would be very worth it on a very light, small displacement computer controlled engine in a low altitude flat geographic location, but I think on a heavier rig in this altitude you would run out of fuel fast. Probably LNG would be a better option, but then you eliminate the convience of filling off your house meter.
    My name is Daniel. I pretty much do what I want.

  16. #16
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    Thanks for the input. LNG brings in a whole other host of problems that include extremely high pressure and extremely low temperatures. Running on NGL would be fun but, the "nasties" in the NGL's makes it not terribly safe for civilian handling. There are a number of CNG vehicles running around Denver, mainly owned by the gas companies. I know both Encana and DCP have them as I've seen them in the parking garages down here. I've never gotten to drive one but, perhaps my wife can beg her way into getting us into one, she is an accountant for DCP. I was told range wasn't a big issue on the cars we had on campus at UT but, filling was only available on campus. I remember one of them specifically being a Dodge Intrepid but, I know there were a few more cars on the engineering campus as well.

    I think there are ways to get good power out of a specificly built CNG engine. I know I made very good power out of my 351W that I ran on propane but, it was built for it. Fuel consumption was a little greater than it would have been on gasoline, but not horribly so. There is a lower BTU value to LPG than gasoline so, you have to use more fuel to get the same power unless you can burn it more efficiently, which is what I was doing, just not enough so to make up for the BTU difference. As those that ran with me at the time, mine ran a little rich and smelled like a "rolling BBQ"

  17. #17
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    I drive a CNG F250 for work. Its got the new 6.2l gas engine. There is no noticeable difference between gasoline and CNG as far as power or driveabilty go. My commute to work one way is about 80 miles and it uses 3/4 of a tank of CNG to do that. I cant remember how many gallons the CNG tank holds. The tank is in the bed and is the size of a cross box. I share the truck with a co-worker and we dont use the cng much because its way out of our way to fill it with CNG. It turned out nice looking on this truck though because its a 2011 and they put the fill nozel where the urea filler should have been in a diesel.

  18. #18
    I have a 2009 CNG work truck that I had built at fuel Tec here in Denver. Noble, Encana, Williams and couple other companies have been building a couple trucks over the last 3 years and fueling station in Rifle.

    The conversion is about 10g and mine is bi-fuel, but there is a 75% tax credit to build this truck. Least there was. I believe it is now about 50% tax credit.

    The kits are based on the engine block family. They have to be EPA certified kit. Once an engine block is approved and best tests, you can buy these kits and install.

    There is a computer that plugs with the trucks original computer. They swap the injectors out and run the plumbing. The truck starts in gas mode every time. Once the truck is running and warm the computer switches the truck over to CNG one cylinder at time until all cylinders are firing CNG. Takes about 2 seconds. You dont feel a thing.

    I have hit the hills and towed with my truck and I don't feel a difference.

    I can drive to Junction and half way back on one 20 gallon CNG tank.

    I can explain more during work tomorrow if this thread keeps moving.
    Holding firm with Cash...Waiting for next build to come to me.......

  19. #19
    The U.S. Dept of Energy has a really nice web site about a variety of alternative fuels. They show station locations for different fuels and describe characteristics of the different fuels and some incentives. It's at: http://www.afdc.energy.gov/afdc/
    Dig around there - they have a lot of info plus related links.
    Jeff
    2000 4Runner with rear e-locker, front ARB locker, supercharger, 285/75R16 MT/R's, 3" lift, custom bumpers, rock sliders, 1/4" aluminum skidplates

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