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How does a CNG/Diesel engine work???

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  • How does a CNG/Diesel engine work???

    Just curious. Can anyone explain to me how a CNG/Diesel engine works. Since there is no spark plug, I am assuming it uses both fuels at the same time????? If so, what is the ratio? I am thinking about putting a proposal together for the pencil pushers at my job since we use hundreds of gallons of diesel fuel daily and was wanting to figure how much money could be saved. I assume this is possible, since my city has a new garbage truck coming that runs on cng and have seen other vehicles that are Diesel engines running on CNG.

  • #2
    Re: How does a CNG/Diesel engine work???

    Bi-fuel diesels DO run like that w/o spark plug, as the diesel injector still acts like the spark plug to get the explosion going, and the CNG is there to make the burn hotter, but you CAN also run dedicated CNG in a diesel platform, but the modifications required are much more extensive, including, but not limited to, installing a spark plug system to make it work. Industrial diesels are good candidates for this since they come with higher compression and heavy duty components for durability. And there ARE big conversion companies who take common industrial buses diesels and such and they convert them to dedicated CNG for city buses and stuff. It is not cost effective for the small end-user guy to do a full dedicated CNG conversion though. Only large fleets ever get considered for that.

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    • #3
      Re: How does a CNG/Diesel engine work???

      Check out this picture: http://www.dieseltruckresource.com/d...70&postcount=9

      This is what the guy quotes off that page: "On a side note , cummins DOES build engines with spark plugs.
      CNG powered engines:"


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      • #4
        Re: How does a CNG/Diesel engine work???

        boomr, I would contact Cummings-Westport to see if they can provide you a White Paper that has all the pertinent data you'll need for your proposal. You may also contact your Clean Cities Coordinator and your local AQMD to assist you. This is what they do.

        You'll find a link to the coordinators list in the Clean Cities forum.
        [ATTACH=CONFIG]temp_4586_1441434431016_578[/ATTACH]

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        • #5
          Re: How does a CNG/Diesel engine work???

          There are many ways to run a diesel cycle engine on CNG. If you run with spark plugs, you lose the higher compression effeciency of the diesel. Because NG will not ignite by compression alone, something is needed get the fire burning. I used to own a couple of large 50 year old generator sets that were bi-fuel capable. The engines were rated at 2880 hp and were started as a pure diesel. When inlet air temperture reached 165 degrees and the engine was at 50% load, NG was injected into the cylinder from an additional intake valve. At the same time, diesel fuel injection was reduced to 10% "pilot fuel"--the remaining 90% of the fuel was NG. These engines ran very clean compared to diesel but still had (they were 2 cycle) high NOX emissions. Cummins is working very hard with Westport technologies to build a totally NG engine that doesn't use pilot fuel. In the Westport design the gasous fuel injector has a glow plug type tip that will ignite the fuel when it is injected into the cylinder. It works .

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          • #6
            Re: How does a CNG/Diesel engine work???

            Originally posted by boomr View Post
            Just curious. Can anyone explain to me how a CNG/Diesel engine works. Since there is no spark plug, I am assuming it uses both fuels at the same time????? If so, what is the ratio? I am thinking about putting a proposal together for the pencil pushers at my job since we use hundreds of gallons of diesel fuel daily and was wanting to figure how much money could be saved. I assume this is possible, since my city has a new garbage truck coming that runs on cng and have seen other vehicles that are Diesel engines running on CNG.
            Talk to Tom at Tulsa Gas Tech ther in tulsa. He worked on a project called Co-fueler that does the mix

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            • #7
              Re: How does a CNG/Diesel engine work???

              People are beginning to formulate a natural gas and diesel blend called GDIESEL. There is also aftermarket kits which supplement the diesel fuel with natural gas in the intake when the intake suction increases beyond a certain point. I am looking for the latter myself for a Cat 3208 powered school bus.

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              • #8
                Re: How does a CNG/Diesel engine work???

                I been running a dual fuel International truck diesel/CNG now for well over 200K miles. Things to note/ consider

                1. The higher the CNG blend ratio i.e. 70% CNG 30% natural gas the more tendency to detinate. especially under loads
                2. High blends ratios also cause extremely high EGT's again especially under loads.
                3. The obvious the more CNG blended in the more you offset you diesel consumption and hence the more savings
                4. Range always remains an issue with the size of CNG tanks

                With all of the above in mind I like to run my truck at a 25% blend, I also have a system shutoff at a predetermine EGT temp. Long term savings for this vehicle has been 33% because there is a cost to CNG after all. My truck holds 42 GGE's of CNG and at 25% it allows me 850-1000 miles range plenty for long trips and to make the next CNG station. However I find myself turning up the blend whenever I'm in Utah as stations are plentyful
                sigpichttp://WWW.CNGMOTORS.COM
                SAVE TIME. SAVE MONEY. SAVE THE ENVIRONMENT.

                2003 Hummer H2 bi-fuel
                2000 GMC Yukon XL bi-fuel
                1999 International 4700 dual-fuel
                2007 Chevy Avalanche bi-fuel

                FMQ2-36 Fuelmaker w/ 24 GGE cascade

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                • #9
                  Re: How does a CNG/Diesel engine work???

                  Hello, I am new here and looking to learn more about the diesel conversion process in view to an investment in a new company working on this. Who are the most experienced and biggest converters of diesel engines now? Aremost of them using a blend like you are talking about? Who are the leaders in the pure cng or dutiful conversions?
                  Many thanks for your time in answering my questions,Michael

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                  • #10
                    Re: How does a CNG/Diesel engine work???

                    I meant to say "who are the leaders in the pure cng or DUAL FUEL conversions". thanks

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                    • #11
                      Re: How does a CNG/Diesel engine work???

                      This company has extensive experience in stationary diesel/NG power generator systems (where there is little regulatory red tape). They are working on vehicle applications for dual-fuel on-road and have some good traction outside of the US.
                      http://www.americanpowergroupinc.com/

                      They are a subsidiary of GreenMan Technologies (OTCBB: GMTI)
                      http://www.greenman.biz/greenman-technologies/

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                      • #12
                        Re: How does a CNG/Diesel engine work???

                        hello I had been banging this idea around on a TDI VW site for some time. have 9000 views and 180+ posts on it.
                        It is being done now. With kits on larger trucks. My plan was to use my CNG kits I use on my CNG VW BI-FUEL Turbo's
                        Beetles.

                        most of the diesel kits do a kind of blend thing.it is on or off set up mostly for a cruising speed thing. I had worked out a CNG Fogger system that I build and use on all my kits and adapter it to the TDI and control the diesel flow of fuel. My plan is to set up to work the whole driving range. I would do a 50% split CNG/Diesel to start with and work it to 80% if it do's not blow it up.

                        I found the VW TDI crowd very tough to show how this will work. When i get some time and backing I will finish it.
                        I find Building my CNGVW turbo Bi-Fuel Beetle a lot easer to sell.When there done the are all ready sold.
                        here is my post on the TDI site

                        http://forums.tdiclub.com/showthread.php?t=262819

                        here is a guy that did it to TDI VW TDI
                        http://forums.tdiclub.com/showthread.php?t=278427

                        Bob Mann
                        http://www.CNGVW.com

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                        • #13
                          Re: How does a CNG/Diesel engine work???

                          Do you know anything about TGI's "The GFD Dual - Fuel system for diesel engines?

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                          • #14
                            Re: How does a CNG/Diesel engine work???

                            We plan to convert our diesel engine based agricultural tractors to CNG.
                            Kindly note that these agricultural tractors need to take care of lots of loads, during their work time.
                            Can CNG converted tractor take care of the loads ?
                            Has anyone else experimented or tried to use CNG kit on tractors before ?
                            Regards.

                            Omar S Chaudhry
                            Managing Partner
                            GASOLINA CNG Station
                            Lahore, Pakistan
                            Cell : +92-321-4001299
                            Email : omar@digimart.com.pk

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                            • #15
                              Re: How does a CNG/Diesel engine work???

                              The basic diesel tractor can be converted to CNG but it is VERY expensive, requiring a full engine disassembly and replacing several major internal components (pistons) and modifying the cylinder head. You will also have to design the intake throttling system and ignition system, plus fit a different turbocharger.

                              Another problem you will encounter is fuel storage, there is not that much available space on a tractor to fit CNG tanks.

                              I have converted several diesel CI engines to Spark Ignition and the results were not always successful.

                              Franz

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