My gasifier wont work

we made a gasifier for engine system. we can light our flare but our engine won’t work? our fuel was mix of rice husk and coconut shell.

What kind of gasifier did you build?


And please: what type of engine are you try to gasification gas substitute fuel?
The original engine’s designed fuel? Gasoline? Propane? Methane? Diesel?
Spark ignition?
Compression ignition?
Number of engine cylinders?

Steve Unruh


A picture is worth a thousand words. Please send pictures or a detailed description of gasifier, engine and gas/air mixer at engine. Are you trying a mix of wood gas with other fuels or straight wood gas? We love puzzles.


we are very grateful to hear you sir(s) your concerns and suggestions. We made the engine run by adding cooler after cyclone filter and another filter unit to eliminate vapor and tar. I hope this case helps a lot to those who are willing to make their own gasifier for engine.


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sir it’s downdraft gasifier. i included the picture below.

we used gasoline engine sir

i also uploaded the picture below. we only use pure wood gas.

Your pictures show much details.
Tee-valve engine fuel-gas to air mixing.
Hopper fill cone indicates you are using a fine dense particle/pelletized fuel stock.
High produced gas-out; and low-in air speaks volumes too.
The tee rod handle as the grate shaker.

From here to operator learn/train you will have it much easier by converting this pull-rope engine to some kind of electric starting.
Initially continuous cranking over you will be too fuel-gas rich and air starved. Will not want to start.
As you engine continuous crank, air will be sucked in blending until an engine running mixture is achieved.
Since this IS a generator set. It can electrically charge up a starting battery. So no outside energy cheating is going on.

Now that you do have the engine-genrator running. Electrically load it down as much as possible. You are trying to engine fuel-gas demand pull UP your gasifier temperatures into their maximum conversion efficient ranges.
Once that is achieved your produced tars HC’s will be into fuel-gas converted and your supplemental filtering will not be needed. Very wasteful; expensive in materials and time, to have to slave at tars filtering.
Once you start paints heat discoloring you will know you are finally at good gasifier internal temperatures.
We’ll know too.

Steve Unruh


Hi B,

Been looking thru the details on this picture:
My suggestions and remarks:
1: Modify the gas hose from the gasifier to the generator, nominal size DN25
2: Your blower is able to create vacuum to produce gas, thru your gasifier, but your vacuum needed is high since you have rice husks and small material as fuel., try to have your blower, or a second one , near the end of the hose towards your generator.
3: install a vacuum gauge on the outlet of your gasifier, to measure / compare the gasflow

Turndown ratio, aka the ratio in your gasifier between minimum and maximum, is very sensitive, AND the small generator even more… So, maker sure that your blower meets the quantity at the same level as your engine would ask @WOT, to compare flare / gas quality.
Many builds do get a great flare, with an heavy blower, but starve down on the lesser vacuum from the engine.
Rule of thinking: smaller is more difficult to balance then big… ( air/gas mixture against power output/ starting capability )

Start your testing with running your generator on gasoline first untill warmed up, then switch to the use of the gasifier/ starting with the gasifier

If your engine does run, it doesn’t mean that power would be available, put a dimmer between a resistive load and a watt meter, this to check on your power outlet.

Use a step by step approach and observe every single outcome,

My few cents to your nice build…


I see NO lid on the hopper. Do you have some way to stop air from entering through the hopper? I don’t see the air inlet either. Are you running this as a FEMA??? TomC


Hello cedie ali,
Welcome to DOW.
First, let me say your workmanship is very good. A neat job. I presume you have flanges on the inside of the shells to bolt the covers to. I don’t recommend ears, they are too hard to make the covers air tight.
Some of my comments may not apply to your design, that’s why the request for more inside info.
With the startup fan running and the single handle valve closed, you light the fuel from the lower pipe near the the bottom of the outer shell (I presume). The gas then exits the large pipe near the top of the outer shell (double walled I presume). The gas then enters the side of the cyclone on a tangent and the particulate matter drops down into the cyclone base and the gas is then pulled out of the top of the cyclone to the fan and pushed out of the fan to the flare tube.
When the gas flares suitably, the valve is opened and the engine vacuum pulls the gas through the system. At this point I would presume that the flare pipe is closed off (air tight), otherwise you get a great reduction in pressure through the nozzles (killing the high temp needed for the oxidation zone) and worse yet the gas becomes diluted with too much air. Also at that point, the air and gas mix becomes somewhat explosive.

Now, how does the gas get through the filter? I don’t think it can. In my unit the gas enters the bottom of the filter and is pulled up through the medium and exits the top of the filter. You could replace the tee at the filter with an elbow and push the gas into the bottom of the filter and draw it up through the filter medium with a second pipe just at the top of the filter and then feed it to the carb.

Another point of contention is the hopper top. It must be sealed airtight to maintain the air velocity through the nozzles in the oxidation zone. If the air velocity through the nozzles is too slow then the temp won’t get hot enough to fully oxidize (complete combustion) all the fuel into CO2 and H2O. It is the CO2 (carbon dioxide) and H2O (water vapor-steam) that gets turned into CO (carbon monoxide) and H2 (hydrogen) in the reduction zone to fuel your engine. At this point the density of your fuel (very little air space between particles) becomes a problem if you’re relying on heat circulation to help dry the fuel, which in my case is 1" to 3" blocks of wood with lots of space between pieces.

You may also want to consider putting a tee in the line with a jar,etc just before the carb valves to catch any moisture in the gas before it fouls the spark plug. Guess how I found that out? Yup, wet spark plug! I pulled on that rope until I was blue in the face and my language was even more blue. Have you heard our term “swearing a blue streak”?

I (and others) would like to see a drawing(s) of the interior workings of the burner so we can more adequately address your concerns. I hope this helps out.
Check out my build in the Small Engines section at “My first small engine run” for some pics of how I built mine. Good luck. Below is the general concept I used. You’ll see some differences on my site, but it’s still the downdraft concept.
Good luck, Pepe

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wade made the gasifier run. but someones asking us about electrical efficiency. how can we calculate it? thanks for you all.

A post was merged into an existing topic: Saman’s gasifier project

Hi B
You can find good information about efficiency in this site