Merits of gasifier styles

Moved from Joni’s build thread to it’s own topic… - CS


Hello Joni,
Your comment here; plus something KristijanL said about the WK’s having minimal below restriction capacity has had me viewing back WK construction videos.
He said that on the WK’s the reduction took place in their above restriction char-pot.
Then I reviewed back all of my books charts for the below restition specifications.

I see now why you consider the old systems two zone types with the dividing line as the restriction.
Meaning yours is not rigidly divided.
So . . . floating zone above the restriction, eh?
With yours and the WK’s below the restrictions as having essentially a char-saver grate system.
Ahhh. I see now.
My Doulas Fir wood is actually a spruce with very low charcoaling capability and all char must be used up in the gasifier to created the needed thermal and chemical conversions.
No possibly of char harvesting from my fuel wood.
Steve unruh

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I thought restriction was there to increase the temperature, so more gas was produced but above all to burn off tar?

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Yes - but to actually concentrate the heat and the flows.
More gas produced - maybe, but only by more complete char conversion.
Burn off tars? Absolutely not. Tars must be oxidized/burnt up in that air jets areas where you have the free oxygen. “Oxygen restricted” (starved) down in the reduction zone is what must occur!

So must the reduction zone always be below the restriction as has been done in the past??
It seems that Joni’s later systems; WayneK’s; and I think some of Kristijan’s systems are now saying NOT true.
Pure charcoal gasifier systems have expanding and contracting oxidization and reduction zones depending on draw loading.
These particular woodgas ones are allowing now this too. Mostly above the restriction.

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Steve, I’m not 100% convinced.
I think this one has to do with heat recovery as well.
With a WK you still tune the gasifier with the size of the restriction to prevent making tary gases.
Yes, the restriction sits low and there may be no oxygene left at that point. BUT, what I think happens is, concentrating the remaining heat, will turn remaining tars solid or to soot if you like, which we know how to handle.
Also, there are some oxygene set free with the reduction process that may have something to do with it, but that’s a WAG.

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Right, and we’re back to where we’ve been so many times before :smile: Vehicle gasification process can’t be properly explained because it works so differently depending on load.


Hmm, I think I should stop reading the old books, it seems that everything I read is not true.
In my books, it seems that the limitation is the deciding factor whether you should get tar in the engine or not. (unless something crowded)
So then I can put in greater restriction, without the tar amount increasing to the engine?


Jan, the books have great information in them. But how many of them talk about a WK design? None using W K letters. But it is there in the different pages of the books in the principals of how the gasification prosses works. Your unit is unique the way you built it is one of a kind. The same with Jo’s, and everyone else that have built their own gasifer. They are all different, but the same in what they are supposed to do and that is gasification of wood to charcoal or just straight charcoal, or a mixture.
Question on your unit, Have you tried the charcoal mix in your fuel like Kristijan has done? This is a safe to see if you need to open up your restriction. If it performs better, then open it up a little more.


JanA on the Premium side of the DOW WayneK made up a down sized WK unit to put on a smaller engined gasoline farm tractor.

He made nesting stacked restriction plates. Uncertain what would work the best.
5" (~125mm); 4" (~100mm); and 3" (~75mm). It ran fine once he got everything beds settled in with the initial smallest 75mm plate.
He fished down and pull out the 75mm plate then leaving the 100mm plate in place.
He said working the tractor no better power. So he dug out his bed pac and put back in the 75mm plate to be safe. THEN hand restacked his bed. The same day after working and shutting down; he then had two valves tar up bending the push rods on his next starting up.

I wish you could read this incident in his own words.
It was not the restriction size so much as his disturbance of the char bed. His analysis.
The char bed above the restriction up to the air nozzles.
He freely admits that he fouled it up. He should have ran longer to establish a natural forming char bed before his shutting down.

And this is why many of us are saying quit looking for a magic dimensional solution.
Run your system harder; hotter; longer for your better performances.

The dimensional windows for acceptable performance are wide and not rigidly defined.
The operator techniques are unique. And allow very little variance.
Steve unruh


Yes I agree Steve, you can have the perfect gasifer build, and all set up correctly but if your charcoal bed is not established correctly it can allow tars to slip through and not convert the tars to good gases to be burned in the engine. This rises the Question: Where does the charcoal bed begin. I say it All begins in the hopper and works it self down to the nozzles, then to the reduction plate. From there it established on down to the grate, or if there is grateless to the bottom of the gasifer. The charcoal bed is a prosses that has to always replace it’s self to work. This is why fuel sizing and types of fuel for the gasifer being used is so important on some types of gasifers. It is in there designs. Lets take Imbert gasifer it seems to have this have this built in it’s design. But a modification to the nozzles will change this. Other things the size of fire tube and length is another factor. Preheating air and how much, hopper sizes, condensation tubes, tar collection gutters. it just goes on and on. It comes back down to the 25 % build and 75 % operator or learning how that gasifer unit works and it’s limitations.


Thanks @SteveUnruh.
I’ve talked to Cris, about premium, but can not become a member where I live, I thought i could be member without the book would work.
Wayne’s tractor, could it not have been tar after the gasifier, which was pulled when the 75mm plate was inserted into the gasifier, and the heat increased?
I look at my car, the tar remains and haunts long after I got a hang in the hopper.
This is how the grille looks like I have after the filter, since I have had hanging and cone in the hoppern, and then the pipes looks simular i think.
Edit,Oops, I’m ruining your thread sorry.

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Fantastic talk here guys! Great marriadge of theory and experiances.

Steve, l agree with you saying that the tars MUST oxidise in the uper part of the gasifier, to give clean gas. At least the vast majority.
However, the reaction is not instant and requires some help.
3 things make reactions happen faster, heat, time and stirring (turbolence). Thats basic chemistry. So, if one parameter is reduced, tho other one or 2 must be increased for the same resault.

We can only increase temperature to a point so thats limited in a wood gasifier. Plus gasification is endothermic so we loose heat fast.
We can increase time and thats what a WK does, along with a slight taper of the charbed and thus velocity increase.

A lmbert goes all the way speed and stearing. If you will, a WK is a slowcooker, cooking food till in falls apart, but a Imbert is a Smoothie blender :smile:
From the nozzles down, heat starts to fall so in order to keep the gases flowing at the same speed, the diameter needs to be gradualy lower, hence the restriction. But it comes at a price of more drag and restriction heat-suffering, plus potentialy heat losses.

Bob, spot on on the answer to “where the charbed starts”!

To shortly summarise what l see when l think “perfect gasifier”:

  • A WK is great by it self but takes a lot of space, weight and skill to make. So, we take that away and only keep its geometry; air jets and a bit of taper towards the end. Put away the finned hevy duty firetube and rather invest in better insulation. A WK with its fins does just that anyway, conserve heat but not trugh insulation but recirculation. Works but costs in weight…

  • then, to decrease the size/volume of a true WK we either need to increase the temperature or turbolence. Turbolence comes at a cost of drag and is not optimal. So, boost the temperature!
    Harvest as much of the energy from the gas via heating incomeing air, but thats still not enaugh. We need more heat!
    So, we borrow the heat from the system that has too much of it. A charcoal gasifier :wink:
    Its just as simple as that. Add just 10% by volume of charcoal in the wood fuel and you have increased the max output of the gasifier by at least 20% while still maintaining or probably increasing the idle capability. The charcoal allso “lubricates” the wood chunks in the hopper, making them flow nicely and prevent bridges.

I know charcoal making is a pain to most. But, look at it this way. How much wood does one burn per year? For me it was about 6 cubic yards l think… 10% of that by volume equals to 250 pounds of charcoal. Thats about 17 55gal drum retorts worth of charcoal. Comes at 1 barrel every 3 weeks! Think about it. Every 3 weeks throw junk wood that cant be gasified in a barrel, light it, cool it and mix with your wood chunks and you got your self a vastly mproved motor fuel. Or, with a simple 2 cubic yard kiln like my Kursk, only ONE kiln of charcoal per year is enaugh to make a world of a difference.

Let me just point out here, this is not intended to “invent hot water” or “meake Waynes gasifier better”. Mr Waynes gasifiers work perfectly for what they are made for. I am ameing more to sedan/car/small vehicle appliances.


Well said!
Thanks for the detailed explanation of gasification.
I am with you we have to come up with a good gasifier that can be built lighter and work on small cars and suv’s.


Yes Kristijan, very well said. I need to say this again charcoal is not hard to make. I like to sit around a fire in my back yard. I have made hundreds and hundreds of pounds of that stuff burning wood in a steel fire ring with a steel bottom. When I am done for the evening or day time cooking out side, I put it all into a steel barrel with the brand pieces of wood on top and cover the barrel air tight. This larger and smaller chunks of charcoal is perfect for mix with or wood after you remove the ash from the charcoal. The wood that was not turned to charcoal is my start wood for my next fire.
One other thing Kristijan knows is the charcoal also absorbs water and tar vapor and it then it goes through and makes Hydrogen fuel. This is a great plus in any gasifer, it also traps tars in the hopper or bunker like a sponge as it is heading into the hot hot hot lobe of hell because on the nozzles adding air. Then the changes really start to happen the speed of frequency is increasing the restiction opening that everything has to go through causes the frequencies increase to incredible speeds and vibrations that causes the molecular changes that happens. An example is like what is happening in your microwave oven but at a very much higher speeds, vibration, and frequency, and holding this to a point is where the conversion is done. Your tars are change converted, your CO2 is now being stripped of oxygen, Methane gas is there, H2O is now H2. All these things are happening at different nanoseconds of times contiinuelessly in the firetube of the gasifer. It now starts to cool, the frequencies, speed, and heat have done their job as the gases move trough the charcoal bed cooling.
Turbulence is the frequency, speed, heat, and friction in the gasifer firetube. They all work together not being separate from one another.
A loose charcoal bed will change everything not enough charcoal mass, and to tight charcoal bed with much ash changes it also. The rection open has be be just right for this to work. The engine has to idle and the gasifer has to make no tars and hold it heat of operation and at the engine operating highway speed no over pulling of the gasifer or heater effects which burns up your gases you just made also this is related to you charcoal bed reserve at the grate or grateless gasifer.
The point is this, you can get a little more out of your gasifer, to a point by just adding charcoal with the wood. And it is easy to do.
I call it my Rocket Fuel mix.


Hi guys,
I have not seen all of you vaunted WK and do not understand why to burn coal for wood gasifier, but I know one thing for sure, that if you do it and you have the feeling that it worked well then something is wrong. That is, somewhere something needs to be changed and altered …
I will tell you a little secret - a good system should produce good tarless gas on any fuel, be it lumps, sawdust, or branches …
And if you are happy with “rocket fuel” then alterations are needed … :woozy_face::dizzy_face:


Hi Joni, have you watched Wayne’s video of him, dumping a bucket of water soaked wood with water still in the bucket into his WK gasifer? And then driving on down the road show his friend that you do not have to use dry wood? This is very impressive for the amount of water that went into the hopper or bunker.
On the flip other side. I can go down the road with just wood and drive at top speed 75 mph or 120.7 km and not over pull on my gasifer or turn it into heater mode. And pull over and let it idle for a while and then take off again no problems. At 75 mph this is with my foot almost to the floor with the throttle pedal 90 %. Or I can mix up my Rocket Fuel mix and do the same and not have my foot all the way push down on the throttle pedal. About half way down 50%. I have never tried to go up to 80 mph using this fuel mix. The 75 mph freeway is 60 miles from where I live. The roads here are 60 mph. I do not like tickets by the police. Lots of fun and SWEM Driving on wood gas. Yes?
There is no need to change the WK gasifer it drives just fine with wet wood dry wood and charcoal mixed in wood. I wonder if it would drive on wet charcoal only in the gasifer hopper. I just like to experiment that’s all.
It is fun.

How do you mix rocket fuel? Wood, charcoal, wood ,charcoal, or wood and charocoal on top? Would be interesting to try.

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I have to agree and disagree.

It is not my intention to say our wood gasifiers dont work. What l want to say is any good working wood gasifier will work even better with a bit of charcoal mixed in. Big difference.

Normaly l wuldnt change a prooven sistem but l was forced to. Unlike you, l had to build my sistems in the trunk. Imagine you have to build a gasifier hearth 30x40x 27cm tall and it must stay cool to the touch and power a 2.3l engine… good luck doing that with raw wood! So l had to get creative and discovered some interesting stuff in the mean time.


Hi Jan, there are a few ways to do it. If your wood is above 18% moisture content I will pore the charcoal on top of my feed bag of wood. Mix it 1/2 bag of wood to 1/4 charcoal. 3/4 of a bag is all I want to lift into the hopper. I have also put wood in the hopper after light it and put charcoal in the center of the wood about the same ratio. Every gasifer is different. Kristijan will probably give you his mix ratio.
Just play with it. My charcoal is popcorn size and larger. I have used the charcoal out of my gasifer after screening the ash out of it. The smaller charcoal will fall right down in between the wood pieces. It also gets rid of the sticky tar.
I look at this way, the gasifer made all of this good charcoal why throw it away. Just use It for more power it makes Hydrogen when it has moisture in, and it will absorb tar vapors and uses it to make more power. It is a win win.

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I have read and re-read.
I will be asking AdminChris for a topics split out, separation.
Do realize it is just past mid-night his time. He is a young family man. So expect an 8-12 hour delay for this request.

Some said here is pure information gold. A shame to delete and lose this.

But some said now cannot help but be offensive to Joni who has now through ten systems already evolved to a bumper mounted small car lightest weight system.
Something a WK with it’s heavy walled “tub” core firetube can never be.
Jodi to join the Premium side for full WK information, and system lay outs, discussions and operating feedback instructions it is just a matter of paying for the Premium membership.
Ukraine not an EU member there are no restrictions onto you.
No magic to the WK system.
Just an answer to a different set of goals; originating in a different part of the world; offering different possibilities.
So even with the information I’d say you would never build a WK. Too big. Too heavy. Far too many weld lines for your tastes.
And without coming here USA or Canada never understand the needs. Or why any such system would evolve. Be seen as so far the best driving solution for us.
You have a different goal sets. You do not have access to light weight pick up trucks with relatively huge, high torque, low RPM engines.

Same-same for me. I just do not have cost effective access to charcoaling hardwoods. To charcoal. Depend on DIY charcoal is an unrealistic fantasy for me.
Ha! So I make do just fine with the low carbon, but fast, fast, combusting; low, low ash Douglas Fir wood that I do have readily and cheap. Just as all North Pacific coast folks here have for the last 170 years.
Popping, snapping, too rapid outgassing, and pitchy as it is to wood stove with.
And a very sooty wood to gasify with.


maybe this will seem offensive to someone, but the situation I got into is very similar to the case when a buyer arrives at a car dealership on a Bugatti Veyron and asks the manager what he wants to buy a new car, since the one on which he arrived already a little outdated. And the manager replies to him that he sells a 1985 Volkswagen specifically for such clients and if you buy it, you will have a lot of knowledge and even more new technologies than you already have … Instead of saying that nothing new has been done yet …
It’s the same with you. I don’t mean to offend anyone, but the DOW site is just a store that sells WK☹️

I think that you shouldn’t dwell on this and you need to move on … This is what I think about it.