Reduction zone?

This is my first attempt at a gasifier, and basically I’m scared of screwing it up. In the FEMA manual it says I’ll need about a 16" x32" + to run a 350. My question is, does the firetube need to be necked down into a reduction zone? Or would it be better to maintain the 16" at the bottom?


Which would e better?

Welcome to the site Matthew.
There are many of us on here that have tried a FEMA gasifier. Many have ruined engines in doing so. The problem is because it produces tar. My best guess is because the air coming in isn’t preheated. Matter of fact, it’s cooling the wood down before the jets and just can’t get hot enough to make the thermochemical reaction needed to make engine grade gas.
There’s good news for you. Wayne has figured out a gasifier with all kinds of preheated air and has logged in 100’s of thousands of miles.


Also a hearty DOW welcome Matthew.
The primary problem with the F.E.M.A. design is it is a “floating zones” system. Without zone defining air jets; without a constriction all-gasses-must-flow-through zone defining area as you use a FEMA it will zones-float making too much wet, sooty, tars laden produced gasses.

Your picture shows well you are willing to cut, grind, Fab and weld. This is good. You are a NOW-DOer. This is even better.
Actually there are at least three broad ways to woodgas produce for a 350 CID Chevy engine.
Mr Wayne says his DID begin as a FEMA base. Then added air jets. Then added air pre-heating/firetube cooling system. Along the way added-in a soots-dropper/heat-exchanger. Refined out a parallel pathways cooling rack and natural-stem “hay” filtering system.
Really need to buy the book to see all of the devilish-details including engine controls.

Another way would be a S.E Werner/JohanL./Dutch John ash-slope shielding, modified “V” hearth system. These following the well proven out 1940’s-1960’s bases. These have very well proven out zones fixing air-jet nozzle rings, constrictions positively defining the oxidization to reduction zones boundaries. Realistic/proven ash handling grating systems. And more. Again with proven devilish-details work-arounds.

A third way . . . . ha! I’ll let the charcoal-teer’s chime in on their black-magic.

All ways . . . here is where it begins. Your availability, capability to get/make, size process and dry the actual wood fuel.
Without that you ain’t ever going anywhere.

Please show your woodpile now. Or declare your wood species intended. Can you get/process enough to support an at least 2 pounds of wood per mile habit?

tree-farmer Steve unruh


Indeed. Even with your wood gas producer, charcoal making is important. You can not live without your gut, like wise, a wood gasifier can not live without clean charcoal properly sized. Make it and fill above the nozzles.


Thanks for the replies! Sounds like everyone really recommends Wayne’s book, so I’ll probably be picking up a copy of that. Are there any other books that are recommended?
As far as wood goes, I have an unlimited supply of cottonwood, so many branches that it’s a nuisance. I can pick up 6 cords of pine out of the forest per year. And finally I work in construction, which hopefully will provide me with tons of scrap, already in chunks. I have a wood splitter, and a couple chainsaws. I will have to build a chunker at some point. Sorry, I don’t have any current pictures of the woodpile.

Thanks for the advice! Very much appreciated!


Go to the library section of this thread. All sorts of information on sizing the nozzles, restriction, reduction and others that come from early Imbert designs. ( there are many variation to the" Imbert". TomC

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Being Grean at this as I was .it was way more than with the knowledge in varies designs feats too build from. the book covers operator choices on finding problems ahead of time.OPERATION AND MAINTAINANCE THE OTHER 75% ANDERSTANDING THE SYSTEM. And just and all around good book too have in your library.I highly recommend the book,

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