Adverse effects of charcoal gas on engines

I have run charcoal gas through a Honda GX340 engine for a few hours. It’s taken only that amount of time to freeze up the throttle and choke. While the steel and aluminum parts don’t appear to be affected, a copper plate I fashioned was severely corroded.



So a few questions:

What is it in the gas that is responsible for this? Looking for this on the site, some have suggested H2 and others sulfur compounds. I am leaning towards sulfur.

Has anyone found a way to mitigate this? I would try and spray some oil into the carb, but I need to be able to use the engine-generator on gasoline at a moments notice. That means leaving the air filter assembly on it.

Has anyone tried filtering the gas through limestone as has been suggested?

I worry now about the intake valve in the engine sticking in its guide. I don’t often see these issues raised so I’m wondering if it’s just something I’m doing wrong. Any advice would be welcome.


We talked about this subject a while back here.


The condensate is very acidic. Try to add more filtering to drop it out so it cant reach the engine.


I put limestone (gravel) in my filter and it helps condense water and keep the other filter material (planer shavings or straw) out of the condensed water. I never considered that those rocks might have any other effects but acid would react with it and produce carbon dioxide.

I doubt the amount of CO2 would be a lot but I should save some of the condensed water next time I run mine and check the pH. I have a jar to collect the liquid from my cooling pipes and more usually collects in the filter so I would have liquid before and after it has contacted the limestone.

I had tar on my choke plate and a stuck intake valve but that was from trying raw wood. Other than moisture and dust, I haven’t noticed any adverse effects from running good charcoal. That was supposed to be why the “dark side” is easier than a WOOD gasifier. Easier to build and, as long as the charcoal is good, no tar problems.

I’m curious what other replies you get from people with more charcoal experience. I kind of remember something about certain woods having salt or something else that was a problem.


Matt, its alkaline not accetic.

JO once had a throtle plate completely disintigrate and be eaten by the engine. We investigated the situation and found out certain brasses are not compatible with woodgas.

Problem is that the zinc "disolves " out of the alloy, leaveing only brittle copper behind. It will do the same to aluminium.

You will probably need to change the axle and plate unfortunaly, to a stainless one. Thats what JO did. Steel shuld be just fine in the engine, but its became common practice for me now to always squirt a shot of oil in a engine at shutdown, if l dont intend to run the engine for a while.


These are very helpful replies. They suggest several things to do.

It sure does look like condensate is reaching the carburetor. Mitigating this moisture is probably the first thing to do. I like the Brian’s idea of using rocks. I do find moisture in the bottom of my final filter. If full of rocks, maybe more would be trapped. Depending upon the pH, perhaps a counteracting chemical could be mixed in.

I have been toying with the idea of making a better radiator. My water cooled nozzle set me to thinking of a shell and tube heat exchanger for the gas. I have a lot of old copper tubing and I thought I could use that for the heat exchanger. The problem with that now is the corrosive action of the gas on copper, I’ll have to use stainless instead of copper for the tubes. But if I could lower the temperature of the gas further, more moisture would fall out.

Here’s a crazy idea. If the temperature of the gas was then raised, say from 50 to 100 degF, the moisture might be kept from condensing out in the carb. If the gas was at 100% relative humidity before heating, it would drop to about 55% relative humidity afterwards. Normally, I would want a cooler more dense mixture of gas (more energy), but a roughly 9% drop in density would be acceptable when weighed against the protection of the engine. Or maybe I should just heat the carb? :thinking:


marty, after running a motor, while motor is hot yet, we open our secondary air start valve,( what is very close to the throttle block), so moisture, that is eventually there, can escape…
without moisture chemical reactions can happen less…
eventually also take out the spark plug that moisture can escape from the combustion chamber…
it seems that our horse hair filter also absorbs umidity…horse hair is known for this ability…
can be dried after use in the sun or near the stove, and when too dirty can be also washed and reused.
a certain volume of this filter catches a lot of fine dust (what can eventually provocate chemical reactions combined with umidity)…on my red bear mower i will make a larger filter volume…
tone takes sheep wool…


Before I started venturing into manufacturing my own throttle plates or whatever, I’d consider adding a propane adapter and forgoing the gasoline altogether. Originally had minor issues with throttle sticking after running WG on my Generac generator but I had already converted it to propane and just quit running gasoline no further problems. Could eliminate the gas carb altogether but instead just leave the thing wide open and use the wood gas ball valve to feed the air for the propane. Propane conversion for that generator was $230 dollars in 2011. I bought a 4500 W dual fuel generator last year for under $500. I can see no reason why a person couldn’t make their own conversion kit for less that a hundred. Propane has storage life, gasoline does not.


Now that is a really interesting proposal Tom. :thinking: I did a quick calculation and at current prices here, the cost of propane BTUs is about 72% that of gasoline. I assume that equal amount of BTUs in each fuel translate directly into the same amount of shaft horsepower. That would give quite a significant savings in fuel cost. And I like the storage life benefit.

I can get a propane dual fuel carburetor for a GX390 engine from China for only $27. But what was your conversion like? How do you regulate rpm’s without a carb throttle plate?


I just checked the pH of the condensate from my charcoal gasifier. Didn’t really change the color of the pH paper at all so maybe very slightly acidic but basically water.

Both before and after the limestone gravel was the same. Your condensate might be different. I’m using mostly softwood charcoal with a little bit of hardwood charcoal mixed in.

My cooler is made from electrical conduit and the filter is made from a 20 pound propane tank so all steel. It will eventually rust out but they were all scrap that I had laying around.

The rocks do condense a lot of moisture. Previously I had a lot of moisture making it to the engine and it decreased the power a lot. I’m sure I still have some moisture getting through but have noticeably more power with the cooler and dryer gas. I’m still working at trying to use drier charcoal and getting the gasifier tuned so less moisture is in the gas right out of the gasifier but I still get condensed liquid in the water trap after the cooler and in the filter.


Here’s an edited copy from page 44 of the FEMA book that’s in the forum’s library that you can download.

carb from fema book

Propane should be able to be fed in where I marked wood gas but you would need to control the flow somehow. I’d assume the dual fuel carburetor kit has some way of doing that but I’ve never even seen one of those. Wood gas (or charcoal gas) would use the engine suction to draw it in but the propane would be under pressure.

I feed my charcoal gas through the original carburetor so it uses the same throttle plate as running on gasoline. I only have a valve to control the air mixture. Mine uses a PVC ball valve but the homemade butterfly valves should work especially for the throttle linkage because it would be easier to move so should be able to be rigged up to the governor although I haven’t tried it yet.


Propane or liquefied petroleum gas contains much less energy per liter than gasoline, Martin, you have given an exact value, but I can serve here with the work effect on the crankshaft of one or the other fuel, I have used LPG in my cars for more than 10 years and I can say , that the consumption in liters of one or the other fuel per 100 km is approximately the same. Mr. Steve could explain it well, well, if I try to express my thoughts,… the first difference is the complete gasification of propane and good mixing with air, which ensures complete combustion, with gasoline there is almost always some incompletely burned fuel. Another difference is the octane number, where propane has a higher one, so it can work in an engine with CR 1:13 without detonations, which enables a better effect, the third better feature is that propane contains more hydrogen atoms that burn into water vapor, which gives a large expansion, so with a smaller filling of the cylinders with a combustible mixture, we get the same torque on the motor shaft as with gasoline with a larger amount. Maybe I’m wrong somewhere, I hope Steve corrects me.

I added propane on my Fergi, I can say that it is a great combination with wood gas. Starting a propane engine is very easy and when wood gas begins to enter the engine, it is possible to easily and quickly reduce the proportion of propane and shut it off instantly or add it if necessary, but wood gas is definitely the “law”.


Yeah, it happened back in 2017 to my 1.8l VW Rabbit pickup after about only one year of everyday driving. Reason - too much moisture due to unsufficient cooling.


Thanks Brian for checking the pH and the diagram of the control valve. That’s interesting that there was no strong reaction. I will definitely try the rocks.

Tone, thanks for the practical aspect of using gasoline versus propane. Since there is less energy in propane on a per liter basis, but you are using about the same number of liters, that is a great benefit for going to propane. I think I will try to refine my calculations to take this effect into consideration.

And thank you Jan-Ola for the photos and explanation for the damage. It looks like cooling and getting the moisture out of the gas is key. I think I’m going to explore a new heat exchanger.

This feedback is making me more confident that a solution is possible.


Eventually I want to build a carburetor like this.

He says this is from the FEMA plans. The same guy has another video with A much stabler woodgas carburetor but he said in the comments:

This design works well but I really liked the simplicity of the first design I did with just the PVC pipe and a few threaded rods along with the fact there are no special brass parts that have to be purchased so I went back and corrected the first design and now it works great too. I wound up adding some rubber bushings to the side adjustments along with using wing nuts that could be used to keep things tight enough to stop the baffles from slipping but would still allow you to reach down and make the carburetor adjustments when needed.

My thought is to turn small engines that have bad carburetors (mostly from the ethanol fuel) into wood/charcoal gas only. Should be a lot of small engines cheap or free that probably only need a new carb or converted to wood powered.

Oh, I went back and looked at your first picture. Mine was way worse than that.

I cleaned it up and am still running it. This was a combination of tar, too much water, and probably some charcoal dust. It stuck the intake valve open which was when I discovered this problem. Hard to tell from a picture but I’d just try cleaning the one on your carb up and work at getting the moisture condensed out before it makes it to the engine. If it is corroded too bad, maybe build a new plate from a piece of stainless steel obtainium.


Ahh, Flash001USA. He’s the guy that first got me interested in gasifiers. Then I found DOW. I haven’t seen this video though. Pretty cool.

Yeah, I’ll try cleaning up the carb. Then I will try getting the moisture out as you suggest. If the carb holds up, maybe I’ll invest in a propane carb. I think Tom’s idea of going to propane makes a lot of sense.


I made some more calculations that makes propane as a fuel source look much better than gasoline. Here in Chile we pay about 1300 CLP per liter of gasoline, and 20500 CLP for a 15 kg tank of propane.

Since a liter of propane weighs 0.583 kg, a 15 kg tank has 15/.583 = 25.7 liters in it.

That is 20500/25.7 = 797 CLP per liter propane.

If as Tone reports that he gets the same output from a liter of gas or a liter of propane, the cost of running on propane is 797/1300 = 0.61 or 61% that of gasoline. Wow.

I don’t know for sure, but as in other countries Chile may be adding a road use tax on gasoline that makes it more expensive over other fuel sources. In the States, you can run No.2 fuel oil used for heating to power diesel vehicles. Fuel oil is much less expensive than diesel because of all the road use taxes put on diesel. But heaven help you if a cop pulls you over and finds red dyed fuel oil in your tank!

My father-in-law used to run a saw mill powered by a diesel generator. He used to run fuel oil in it till they told him he wasn’t allowed. Never mind the engine was stationary. I guess a diesel engine is a diesel engine to the libtard powers that be and fuel oil is meant for furnaces.

Anyway, propane is looking really good.


Excellent short listing of reasons Tone.

I hope I do not lead astray from this topics ongoing talk.
I had set tup a whole topic titled the “Needs and Usage of Inert Expansion Gasses In IC Engines”.
MartinS. and others . . . the usage of laboratory fuels BTU’s is worse that worthless if their usages are to make shaft power in engines. ANY engines. Tone re-stated just a few of the actual in-engines fuel use factors.
Still skeptical, eh?
O.K. The engines using the the most energy dense of hydrocarbon fuels by weight, by volume still have sucky efficiency conversion use of that fuel. Even after 180 years in improvements and developments.
Fossil coal fueled steam engines.
External combustion has too much heat made energy transfer losses. Piston steam must rely on primarily heat made expansion pushing with decreasing pressures.
Internal combustion engines have compact, contained, make heat, then heated gasses rising pressure pulses.
You in-cyclinder only need the quick heating burst to quick expand the working pressure gases. ALL internal gases are heated becoming the expansion gasses working to push the piston.
Another topic I had set up: “IC engines will beat any external combustion engines”
A balanced combination of good quick T&P bursts, then reset, repeat; will always beat an unbalanced T&little-p in steam and Stirling engines.

Early IC engines were ran on powdered fossil coal dust. Far too dirty and abrasive all bottled up inside.

Take BTU’s and other Lab-burn fuel energy comparison and throw them out of any discussions with practical make shaft power usages.

Steve unruh


Giorgios hint is also important. Any “agressive” gas needs water as a medium to do any damage to anything. I have tryed puting the gas in the engine hot lately, so far so good. But l cant give you a number of how much power is lost, if any. Doesent feel like it.
Filtration is easyer and no corrision on the carb. Problem might, however, apear if the gasifier makes “wet gas”. In this case there is no cooler and condensation so all the moisture will dilute the gas as steam. But its my firm belive and l stand by it strongly that a good gasifier shuldnt have any water left in the gas after the grate.


Hello, fiest time commenter here, hello everyone, this threat topic is my worry of why i will not try it in an engine because I dont know mechanics for cleaning carbs or cylinder heads sadly. That is my next step but if i can research here and avoid cleaning carbs or engines, A ok by me. Much preffered.

I have a filter idea of pipe going into bottom of filter drum > wood chips on bottom, hay layer (or horse hair as Giorgio suggested may work) sawdust over, wall insulation next, zeolite bag (i found some for kitty litter deodorizers) arund top pipe for outgoing gasses to take out sulphur, Steel wool and copper flakes to take up corroding mixed within drum,

After the filter drum i was thinking of running past a tube of snow ice melt (calcium chloride i think it is) which works as humidifier and I have seen a guy on youtube who bubbles his gas from a digester through ceramic pellets i believe.

Anyways, Just wondering if this (throwing everything including the kicthen sink way) would be a for sure way that is for a cleaner enegine. Because I’d rather clean 5 filter drums a month than 1 engine a year.

Sorry for lots of words here but this has been a years long thought for me. Thank you.