Nozzles for Charcoal gasifiers, part 2

Okay, i gave the carb a bath in some gasoline, poked out all the holes i could get to, and put the whole thing back together the way it was when I got it. (except one extra bolt that i am still not sure where it came from).

To test I used a shop vac which pulls 950W out of an outlet on 122volts, and heater with 2 settings: 650W low, 1400W high.

Running on gasoline the generator wanted to idle at like 3800RPM and was putting out about 140v ac with no load. So yeah, voltage regulation is … spotty. Anyway, I plugged in my loads, and recorded the wattage and the voltage as I upped the load.

800W - vacuum cleaner - 117V
1300W - vacuum cleaner, heater on low - 111v
1700W - vacuum cleaner, heater on high - 103v

At that point I called it good, because 103v is already a bit too low, I think. It seems like the fact that RPM and voltage are linked, you would be very hard pressed to make this thing just stop dead in its tracks. As you load it down more, the voltage drops with the RPMS, and the lower voltage reduces the wattage of your load. Resistive loads wouldnt care, but more sensitive equipment might not like it.

So, I think I would call its effective wattage somewhere around 1300W on gasoline. Seems like I will be lucky if I can get 650W out on woodgas? My current setup seems to top out around 450, so I feel like there is room for improvement.


Carl it seems that your not a million miles off the max you could really expect on charcoal anyway , so you may as well play a little trying to get more out of it advancement and water drip could help a lot , but in the mean time keep a look out for a larger output generator ,maybe one you can buy for spares or repair just to keep the cost down .


This is what I use to adjust my generator. As the generator loads down, the Hz may change. So I adjust the generator to the load that’s needed, always matching as close to 60 Hz as I can.


Rule of thumb, for every .006 of an inch you shave off a key and turn a flywheel you pick up about 1 deg of timing.
But that is a rule of thumb and you need to measure and test with a timing light.

You can use loctite but a better way is to lap the flywheel to the crank shaft with some fine valve grinding compound and lap until you have good contact between the flywheel and the crank.
Torque properly with a torque wrench.

Do both and you will not need the key at all

All kinds of really useful ignition related stuff here.

One could run two ignitions.
One for gas ( the stock ignition ) and a modified automotive high output ignition for wood gas

There is room under all clone and Honda flywheels to add a pick up coil and disk to trigger it


Well, I’ve been out here reading DOW stuff all week. I’m sure I haven’t even scratched the surface if the knowledge that you folks have put out here. Since I got my little simple fire running the 13hp generator last weekend, I have been all over making it better. Now I’m looking at upgrading the nozzle. So, from what I’m reading, my simplest replacement for an open ended 1 inch pipe would be a closed ended pipe with vertical 4 holes in it. Is that right guys? I plan on using 1 inch black pipe again. I had no idea airspeed and hole diameter was so critical. I just assumed that I needed to get the same volume of air out that was comming in. I guess I need a little advice on hole size for this nozzle. Or at least someone to show me the math. Tha.ks again for putting all this info out there.

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Hey, good work on getting the generator up and running! Koen made a spreadsheet that one can use to calculate nozzle airspeed based on displacement, which you can find here

The displacement and RPM are the most critical numbers in the top section, dont worry too much about the other ones for now (and treat your results as a decent estimate).

I could not find the original chart that he is referencing, but here is a version of it that I have marked up a little. The spreadsheet gives you the air rate in Liters/sec, so to make heads or tails of this chart, you need to convert that number to Cubic Meters/hr (I.E. Multiply by 3.6)

It took me a long time to figure out what this chart was saying, but it basically shows the percentage of the CO2 that is being converted into CO up the Y axis. Each line is labeled with the nozzle size that generated that resulting curve. (if anyone can find where this was originally posted, I will link back to it, as I recall it had some explanatory text that went along with it) What I took this to mean was that with my setup (using about 5 m^3/hr) a nozzle of 3.1mm would give me 92% conversion, and a nozzle of 12.7mm would still be like 88%

So, is nozzle size then actually that critical? After looking at this chart I am inclined to believe it is not. Anecdotal evidence seems to back this up, as many sizes have been tried with good success. As the nozzle size gets smaller, you get higher conversion efficiency, but you also create more restriction, which forces the engine to work harder to fill the cylinder with woodgas. (this is what one of those other values in the spreadsheet is trying to account for, I believe) I suppose there is a sweet spot somewhere in there, but without the means to measure the quality of the gas being produced, its pretty hard to find the true peak. Generators have the nice feature that you can see how much load they will put out, and that lets you at least approximate the quality of your gas.

Now, all that being said - if you want more power from any given setup, you are going to have to start thinking about water drip. I think there is a pretty recent thread on that topic that might shed some light. Keep up the good work!


Thanks for all the great information and the in depth explanation of what’s going on in that spreadsheet.

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Just back from Rwanda. Here is a picture of our nozzle. Tungsten Carbide sand blast nozzle screwed into a stainless reducer tipped up 45 degrees.

Cargo trike.

Unfortunately we won’t get to finish this until next February.


Welcome back Bruce , such a shame you will have to wait nearly another year now to get the trike finished and up and running .
I have yet to start running my old system yet due to a very sunny summer so solar has been taking care of my battery charging needs , and i am still hunting down items for building another gasifier to use up those 3 new tungsten nozzles , by the way your nozzles look way longer , where they from the same supplier as the ones i got ?


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The tungsten carbide is that little crown-shaped piece on the end. It is the same size that I sent to you. The big piece is a thick stainless steel 1" F to 3/4" F reducer that I picked up somewhere.

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Ah i see ,Bruce is there a reason behind screwing into stainless steel adapter ? i was just going to screw it directly into the fitting and hope for the best , but i guess it will get the heat away from the iron fitting and give a little extra length into the gasifier

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I want to use 1 inch pie for my external plumbing, so I needed a reducer for the TC nozzle. I had this massive SS piece in my junk. It just kind of fell together and gave me the right length for my 12 inch diameter reactor. There is a better picture of this setup at post 191 above. I was planning to seal the nozzle threads with high temp ceramic paste, but I don’t know if that is necessary.

I’m looking forward to getting some reports from your winter usage to see if we are on the right track with this. I hope to try this TC nozzle on something this summer, but nobody that I know of gives the kind of real world testing that you do.


Hi Carl:
The interesting chart you are referring to is the “Conversion Ratio versus Air rate for various nozzles diameters.” is figure 67 @ page 73. Belongs to: Small scale (20-100 HP) gas producer-Engine systems (Edited 1984). Normally know as G.A.T.E. (German Appropriate Technology Exchange).
Authors: Kaupp/Goss.
The author refers that this info was based on “The Gas producer for motors vehicles”. Institution of engineering, Australia Journal, V14, # 4, 1942, pp 81-93.
The next following picture (table 2 @ page 74) in this same manual is also very interesting, because it give a 3.2 mm diameter Nozzle Temp depending the Air blast velocity (mts/sec).

Eddy Ramos (Argentina).


Carl suggested I document my experiences with nozzles in my Toyota Corolla gasifier, particularly to show my results with horizontal air entry versus vertical air entry to the reaction zone of the SimpleFire updraft-style charcoal gasifier.

The first photo shows the original side air inlet 1.5 inch stainless steel pipe nipple nozzle with a stainless steel sheet metal shield after about 20 miles. This pipe nipple was mounted horizontally. I replaced that with the Lettinger style nozzle shown in the same photo after it had been used for about 65 miles. This nozzle is made of a 1.5 x 12 inch schedule 80 steel pipe nipple used for steam applications. It screwed in place of the side entry nozzle, but functions as a vertical nozzle with the holes facing up toward the gas outlet at the top of the reactor.

stainless nipple nozzle and Lettinger Nozzle

Below is a close-up of the Lettinger nozzle after 65 miles.First close up of Lettinger nozzle 65 miles

I had the holes drilled larger in the Lettinger nozzle and reinstalled it. Then after 128 more miles this is what it looked like:

I did not notice any deterioration. Here is a close up of it:

I had the “bright” idea of trying to lower my reaction zone by going back to a side entry nozzle similar to the first one, but with a one inch pipe and a heavy floor flange on the end to protect it. Here are two view of it before installation:

Here are two views of the results after only about 15 miles. The most deteriorated part was facing up toward the gas outlet with an accumulation of slag at the bottom.

Lesson learned for me: Unless there is some cooling method employed and/or material which can take the high heat, the side entry nozzle is not likely to last long in the updraft gasifier. the nozzle will fare better if the gas is taken off opposite the direction the air is entering the reaction zone. I have decided to stick with Kristijan Lettinger’s design.

Others have pointed out that the durability of Kristijan’s design is due to the mass of metal surrounding the holes and the accumulation of slag on top of the pipe forming a protective coating for the pipe which separates the pipe from the glowing charcoal.

One disadvantage with this nozzle design is that it is difficult to monitor the temperature by the color of the glowing charcoal, because you can’t see it clearly from the air inlet, but as Kristijan has pointed out, by examining the accumulation of slag vs. ash at clean-out time, you can determine whether it has been running too hot or cold and make the necessary adjustments for future operation. If I remember correctly, a lot of slag formation indicates a high heat situation. I remember the first time I removed the Lettinger nozzle, there was virtually no slag. The last time there was nearly an inch of slag formation on top of the nozzle. Hope this helps.


Thank you for sharing Steve. How thick of a wall on the pipe do you use? Can you look inside the pipe when it operates? Mine was glowing dull red (barely noticable) when the gasifier was cleaned and it was completely dark when some ash formed.

Allso, to be honest l expected the plate to deteriorate quite fast but NOT nearly as fast as it did! There realy is hell in a charcoal gasifier.


For your style nozzle, I am using a 12 inch long, schedule 80 steam pipe nipple. It is about 3/16 inch thick and 1-1/2 inches inside diameter. I can look inside the pipe and see the charcoal glowing above the nozzles enough to tell that all the nozzles are working. I may have noticed the pipe glowing once. When water hits it, it boils away almost instantly, so it’s hot.


Thanks for sharing this info. It really show how “hellishly hot” the oxidation zone of a charcoal gasifier can get. I am curious about the amount of square inches the four holes in the Leitinger nozzle has compared to the side nozzle? Does this create a restriction or is the air velocity increased with no loss of gas volume. With out a vacuum guage, I guess it is hard to tell. Did the toyota run better on one nozzle design versus the other?
Gary in PA


Gary, The four holes in the Leitinger nozzle were about the same area as the one inch pipe with flange on the end. I think the inside of the “one inch” pipe is actually about 1-1/8 inches. I haven’t noticed any problems which might be due to a restriction, and I have not done any vacuum tests to compare the different nozzles. I got similar results driving with both nozzles. Of course, I didn’t travel far with the flange nozzle. Also, during that time I was having a miss-firing problem when the engine was under load which I fixed with new spark plugs after changing back to the Leitinger style nozzle.


I guess its time for me to let the cat out of the bag.
For those who couldnt make the Argos event this year,I tried out an aluminum nozzle for the charcoal simple fire gasifier. My theory is that the aluminum,with its cast fins would disperse the heat outside the gasifier faster than it could absorb it. Inside.

I ran a 5000 watt generator. Using exhaust gas recirculation and water drip it ran great for about half hour without melting the nozzle. The generator started acting up at that point. Spark issue we think. Then we connected the gasifier to a larger 9000 watt generator which was not ser up for egr, and succeeded in melting off the end of the nozzle. So, prelimonary tests show that it could work.
Ive ordered a new ignition module so when it arrives ill test it some more.


Useful info…

Advantage very hot spark,
Add a second trigger and you can use one for retarded timing to start or gasoline and one advanced to switch too for gengas

And I am in aw of the casting work,

Could you recreate that part in copper?