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Gas engine running on Veggie oil - need help

  1. Nov 8, 2009 #1
    Before I get flamed for this, I am not running a gasoline engine directly with normal fuel oil or veg oil- I made a gasifier.

    My gasifier is lame at the moment, but is just for testing purposes. It consists of a small fuel reservoir, suspended several feet up, then it flows down through about 50 ft of steel tubing which sits inside a stove that is red hot. The tubing itself also gets red hot. After the stove, the tubing comes out, and has a cooldown phase, with 5 feet coiled in a bucket of water.

    After that, the tube goes into the air intake of my little 4 stroke gasoline engine.

    I currently have no throttle, just as much oil drips down the tube.

    My QUESTION is, how strong is gasified oil? I have talked to people who have built wood gasifiers, and say to use 50% wood gas and 50% fresh air for the stoic mixture, but my engine seems to run far, far leaner than 50% "oil gas".

    PS If I get past this, I have a v8 chevy truck just begging for some nerdy modding.
  2. jcsd
  3. Nov 8, 2009 #2


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    The main difference between a diesel engine, which readily runs upon recycled food oil, and a gasoline engine is that of ignition method. A gas engine has to have a high enough octane rating to eliminate pre-ignition. I don't know that such an engine can ignite and utilize any kind of oil, no matter how preheated it is. A diesel runs such high ratios that the heat of compression initiates ignition of the air/fuel mixture. The glowplug is just for starting.
    I guess that the answer to your question depends upon the octane rating of your gassified fuel and the efficiency of the delivery system. Propane, for example, has a higher octane rating than any available pump gas, but you have to have a specialized carbeurator setup to use it. Aside from the mixture, the ignition timing has to be altered to make it efficient.
  4. Nov 9, 2009 #3
    OK, this oil is not "pre-heated", it is "pre-gasified". What is being sprayed down the engines air intake is a white gas that burns extremely well.
    When I light the end of the tube with a lighter, the gas burns as if it was propane. The little engine seems to run extremely well, even with only primitive fuel metering.

    I've already done the WVO in a diesel truck "thing", I think it's cooler to run a gas engine on WVO, even at a power reduction...
  5. Nov 9, 2009 #4
    What do you mean by how 'strong' is vegetable oil?

    Also after extended running, take the engine apart and inspect it. The reason SI don't tend to run very well on ex food oil is a large build up of particulate matter. Diesels already dewl with this problem. It may or may not be a problem for practical application, and there has to be some way of solving it.
  6. Nov 9, 2009 #5
    What I meant is how potent the gas is, as in the gas from wood or garbage needs 50% stoic mixture, whereas my gasified oil seems to run well at a very lean mix.

    I can not find any research on gasified oil.
  7. Nov 9, 2009 #6
    The stohiometric burn can be calculted from fuel composition, which needs the chemical formula for the fuel.

    I suspect research on SI engines using vege oil is pretty rare. I've never heard of it being done before. They ussually use it in CI engines.

    I think atm your best bet is a 'suck it and see' approach. Just record all the data you can yourself. Research has to be started somewhere.
  8. Nov 9, 2009 #7
    Thats what She said

    I guess I'll have to test myself, but I was hoping to start with better information, I work in an old garage, not a top of the line science lab.
  9. Nov 9, 2009 #8
    Some of the best things came from a man with a hammer in a shed.

    Ok you wount be able to get lots of telemtary, but any data (even anecdotal) is a start.

    If you manage to find a fuel flow rate that works 'best' that gives an idcication as to completeness of burn. The next step would be to try to measure exhaust temperatures.
  10. Nov 9, 2009 #9
    Actually I was planning on measuring exhaust temps from the beginning, as soot can easily be cleaned out by removing 6 bolts, melted piston or valves not so much.

    This stuff burns a lot cleaner than you'd imagine. I have to say I'm very suprised that more people have not tried this. In a real life implementation, exhaust could be used to gasify the oil, maybe with a supplemental burner for starting and low load conditions.
  11. Nov 10, 2009 #10

    Ranger Mike

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    i been down this road before. i bought a diesel New VW beetle used...it now gets 44 MPG and i could add a chip to up it another 2 to 3 MPG...and I have all the stuff to convert it to veggie oil...i can tell you the following:
    expect 10 percent less MPG with Waste Vegatable Oil (WVO)
    winter is a real problem..the WVO must be heated to at least 140 degree befroe injecting into the combustion chamber. this requires a heat core ( electric or using radiator coolant, and heat coil mid chassia and one just before the injector pump
    there must be a seperate fuel tank for WVO and the diesel starts up on diesel , GETS TO OPERATING TEMPERATURE, before the WVO is introduced via switching valve system.
    finally the WVO must be purged before the diesel is shut down of risk lock up of injectors and pump (WVO whe nit cools is a wax like mess)
    also the WVO must be dewatered and filtered to about 10 micron so as not to ruin the pump and clog the injectors. this requires a heating device and i use a centrifuge to further dewater the messy WVO. ther is also a large grey area regarding legality of operating a WVO om the public highway but this is for other discussions that i personally dismiss once we again hit $ 4.00 a gallon fuel...just listen to the news to find the sell price a barrel of oil is selling for and devide by 33 to get the cost of a gallon of gasoline...
  12. Nov 10, 2009 #11
    I've been down that road too. What I am talking about is not running WVO in a diesel, but turning diesel/ veg oil/ heavy oil into a flammable gas, and burning it in a gasoline engine.
  13. Nov 10, 2009 #12
    Tbh i'm very surprised it isn't detonating when the spark is introduced.

    Try removing your spark plug and see if you still get a bang. (you may not due to relatively low compression)
    The low compression ratio will be destroying themal efficiency.
  14. Nov 10, 2009 #13

    I realise that by reading this, immediately it sounds like I'm trying to make a diesel engine from a gasoline one- this is not the case. Once the oil is gasified, there is nothing "oil" about it.

    The gas made from it, is best described as a "white fog", you can fill a bucket with it, but it is easily blown out by blowing on it. It acts and burns exactly like butane, only you can see it, and it stinks sorta bitter. (I tried to not inhale any, I was warned by someone smarter than myself that it is no good...)

    When the engine is running, exhaust is always perfectly clear, leading me to believe that it is burning nice.
  15. Nov 11, 2009 #14


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    You will need to condense the gas out of the generator and start from there. Do you think that you are running the engine on vaporized oil? Not likely. It is a decomposition product. You must isolate it and run that through an engine to determine the energy density.

    I have heard of using Calcium hydroxide and high temperature to generate C8 compounds for gas engine use. Something you might try...

    Calcium hydroxide = mason's lime

    Expect a lot of ash...
  16. Nov 16, 2009 #15

    I'm thinking about doing the same, but with waste oil instead as I have a lot of that. My primary concern is with the oven carbonizing the oil, eventually clogging the tube. Is there any evidence of carbonizing? Another concern would be the octane rating of the gasified product, whatever it is made of. You are not going to know if that's a problem until you put a load on the engine. You can try experimenting with the timing and see what you can get away with. Finally, I would be concerned of contaminates in the gasified product. If it was wood gas, obviously it would need a filter. For peanut oil, it might be clean. Try running the gas through a filter and see what gets trapped, if anything.

    Have you tried not cooling the gas in the tube and cool it with the intake air?

    When leaning the mixture out, I would check for knocking, engine responsiveness, and engine temperature.
  17. Nov 16, 2009 #16
    Edited to remove rubbish information, see Brewnogs post instead ;)

    Why do you want it to run as spark ignition instead of compression ignition anyway?
    Last edited: Nov 16, 2009
  18. Nov 16, 2009 #17


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    I understand what you're doing, in fact I'm currently putting together some engineering plans for pyrolysis and syngas engines. Ignore the comments about octane and cetane number, these don't apply for gaseous fuels. For traditional gaseous fuels in an SI engine, methane number is the best indication of knock resistance. However for gases weak in methane but rich in hydrogen and carbon monoxide, the model falls over. Your first step is to get a gas sample analysed, let's see what's in it and then we can build up an idea of what you're likely to get. Failing this, an idea of exhaust emissions (NOx and O2) will help things, and failing that, a measure of air fuel ratio.
  19. Nov 16, 2009 #18

    I want to run it in a spark ignition engine for these reasons:

    1. Gasoline vehicles are cheap to come by; My old chev 1/2 ton 1990 might fetch 1500$ if I sold it, why not do something useful?

    2. I love diesel vehicles, I own a ford 7.3 liter powerstroke truck, but realistically, diesel trucks are not just laying around for the taking- they are either completely destroyed, or still worth decent cash.

    3. Diesel vehicles are mostly limited to larger trucks. Asides the jetta, there are really no diesel cars, meaning selection is limited. If I can make this work on a V8 gas truck, 4 cyl sunfire should be possible for someone with a puny budget.

    4. If I can get this to work, I can market an E-book and become a millionaire! You know, 90% off, but only if you order RIGHT NOW!!!! LOL, just kidding.
  20. Nov 17, 2009 #19


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    Before you go down the gasifier route, why not just buy a european Diesel? Ten a penny round here, pretty much every car on the motorways here are Diesels.
  21. Nov 17, 2009 #20
    I don't know where you're from, but here in canada, diesel cars are rare.

    Another reason to use a gas vehicle: I've been down the diesel engine WVO route, and it takes a while to actually begin using WVO instead of diesel, you need to wait until everything is all warmed up. You also need to switch back to diesel before you shut it off, for up to 10 minutes, to prevent leaving any veg oil in the lines or injectors.

    On a vehicle mounted gasifier, how i picture it with the gasifier tubing in the exhaust, a supplemental burner (either diesel or propane) would burn to start the vehicle, or possibly idling in cold conditions, meaning you could take even a small trip and still spend way less than gas or diesel at the pump.

    This is how I visualize it working, anyways.

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