Proper mixing of air and woodgas

I was reading a post in another forum by Doug Williams of Fluidine about woodgas burners for heating purposes and he made the following statement:

“What I can tell you about producer gas combustion, is that if not completely mixed before ignition, the CO will enter the high temperature flame without igniting and revert to soot and CO2”.

That statement got me to wondering whether that would hold true in engine use too. It would seem that slow low pressure burners for heating purposes are quite different from the higher speed and compressed fuel/gas mixture in engine use, but IF complete air/fuel mixing does NOT take place in engines, could it possibly have that same reversion effect? The soot we talk about in our oil changes we might attribute to inadequate filtering but could it also be inadequate mixing of air and gas? What do you think?

Don M


I believe that most of the dirt in oil is from incomplete combustion. New cars that recycle exhaust into the intake causes contaminates as well.
It has been a few years since my schooling and I can not recall the exactly what the fuel converts too when incomplete combustion happens.
I prefer older engines that do not dump extra fuel into the exhaust too burn in the catalytic converter or recycle back into the intake stream.

As far as woodgas engines go, most of the soot is thought to be carried in with the gas, some of it burns in the engine, and some winds up in the oilpan. Some reversion may be taking place as well. The only way to know for sure would be to filter it all perfectly and see if the oil got dirty.

“What I can tell you about producer gas combustion, is that if not completely mixed before ignition, the CO will enter the high temperature flame without igniting and revert to soot and CO2”.

Hey Don,

Do you think the same thing is happening on a LP stove if the air is not adjusted correctly? It really soots up the ole frying pan!

Yes Wayne, I think it is. It is also like holding a piece of glass down on a candle flame and see the soot build up. I guess my real question here is - what are we doing or how are we designing the mixing stage of air and gas to ensure complete combustion. Who was it a while back - John Wells? -that cut down a freon tank above a carburator with cyclone type inlets to swirl the mixture in hopes of a better mix? I never looked close at propane powered carb setups, but I imagine they face the same issues there.

Don M

Hi Don. Both my deceased lawn mower and Ranger have as good a mixing chamber as you can get(cyclone).
The lawnmower would get it in the oil but very very little in the intake.
The Ranger gets it in both. It’s because I pull a lot harder on the Ranger that has a lot less filter per HP.
I have the room to double my filter and I probably should. It’s a small pickup and I do fill up the bed sometimes. It’s a balancing act of operating system/useable truck.

I believe everyone’s flare pic’s are shown under 5" of column. If we could crank them up to 20"+ that vehicles accelerate on, we would probably see some carbon blowing through.


Would 20" WC look something like this?

Right on Wayne!! That’s what i’m talkin about!

You can see the carbon takes longer to burn than the gas(of course). I believe that under pressure and heat that it still gets consumed. (We should look at our exhaust manifolds to see if i’m correct.) So the oil probably gets dirty from the intake and compression stage.

From my automotive text book

“When there is enough Oxygen in the mixture, CO2 is formed.” “CO emissions are caused by a lack of air or too much fuel in the mixture” “CO will not occur if combustion does not take place in the cylinders. Therefore the presence of CO means combustion is taking place.” “CO emissions are a good indicator of rich air-fuel ratio but Not a lean condition.”

IMO - Carbon in the combustion also causes spark knock. It glows red hot and when the fuel is added it ignites. Not noticed much with the newer vehicles partly to due with the timing always being adjusted by the computer.

I can see too much soot or contaminates when too much fuel to air ratio is occurring.

With Wood Gas -

What is the proper fuel to air mixture for combustion?

In “Gas-Engines” It says " 1 part gas to 8 parts air".

Would this change with compression?

Are those of you with meters able too read this? If so what range are you running in?

I know that those of us used to carbs, are probably able to tell when an engine is lugging or working smoothly, so it would not be necessary to know.

I don’t intend to steal your thread Don; I thought this was along the same lines as your question.

The ideal mixture (from what I’ve read) is a 1.1:1 air/gas mixture, slightly favoring the air. The O2 meters you can buy are calibrated for gasoline, and so you need to run slightly leaner than that. Wayne keeps it on the very furthest edge of the visible scale. With wideband sensors you can get a more accurate reading.

I don’t have the sensor yet and yes I’ve been setting it by ear, and by performance. It’s worked out fine, but you do end up “lost” sometimes, not having a reference point. I intend to get a gauge installed. They’re around $20 at AutoZone.

i don’t think there are too many car engines now a days that are set to run at 8/1… more like 14/1

on a stationary its easy, use a tach for highest rpms and a way you go… I know Max gasman has commented about an automated mixing valve before on the woodgas group… maybe some thought needs to be put into that for ease of operation.

The O2 meters are not calibrated for gasoline. They read the left over oxygen in the exhaust. It doesn’t matter what fuel you are burning.
I run the same stoichiometric ratio either way.
I love having a gauge on the Ranger. It wasn’t needed for the mower.

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I installed an O2 sensor on the Prehistoric Van and read it with multimeter. Still not sure what to make of it, though.
Also, I made one of Max Gasman’s mixers, but it isn’t automated. The wood gas goes tangentially in one side of a cylinder and the air goes in the opposite side. They spin around together and then shoot down another tube into the manifold. Does the automated version run off the O2 info? And, really, how do you really know if it all mixes properly???

Current gasoline engines are at 14.7:1 ; although they do swing up & down at times.

The 8:1 comes from a wood gas book. It is referring specifically to wood gas engines needing the mixture at 8:1 (air to wood gas) for complete combustion.

I just lean mine out until the engine seems to miss fire then make it a bit richer. The air fuel gauge is all the way lean way past 17 or 18 to 1. I can do this only after the gasifier is warmed up and the char bed is flowing nicely. I say a minimal amount of carbon in my exhaust header pipes and no build up.

At 8 to 1 air to fuel ratio our calculations for nozzle size and velocity would be way off when we were always told to use 50/50 air/fuel wouldn’t it?

hi for what it’s worth last may we had a power outage lasted for 10 days i ran my china hybrid for 6 days until i melted the choke it was just 16 gauge steel but my gen exhaust was powder white or grey no soot at all my intake did have a trace a soot on the filter but was far from plugging i have it filtered really good it has a water bubbler, fiberglass filter, radiator, water trap then a final fiberglass filter befor the air filter
I only ran it 6 days but my oil didn,t look bad at all

Hi, I am new to the forum here however have been involved with bypass filtration and oil testing for 16 years, more concentrated last 4 years. I by no means mean to stir the pot only contribute with science and practical facts. I have helped many folks go 8 times further with oil changes while running cleaner oil. For a true read of actual soot and not good ole boy look at the stick and “Feel” it use CCECO lab, Or some other reputable lab.

Soot is sub micron and fuel dilution, oxidation, nitration and varied ISO code and lowered TBN forms conglomeration. With proper oil testing you can have scientific results actual hands on. I have a fine micron bypass filter in my dodge caravn 286,000 miles -Oil per ISO code and reports runs many times cleaner than oil pours out of bottle. The filter I use functions to .5 micron and is a bypass filter. bacteria is 3 micron, Soot is sub micron and because of many factors will conglomerate, I have tested oil that to the eye and "feel looked like it needed to be changed, but because of fine micron bypass filter after testing it was proven the oil was actually many times cleaner than it was at install and soot was in a acceptable range.

Without testing is like letting a doctor bleed you with leeches and do a blood report. Today we get our blood tested and look for all types of things, Oil testing should be done especially for scientific purposes of wood gas and its effects on engines. Establishing a trend is paramount and could show us all types of neat things. I use Noria Corp for all lubrication and filtration data, very good resource. Science mixed with common sense could make some real neat projects fly. I have enjoyed very much reading these post and seeing what innovative folks have done.

Rather than reinvent the wheel I am look forward to the most functional plans. Heat sensors make good sense and limiting soot and crud into the engine makes even more. I am sure my use of premium grade synthetic oil( I like amsoil and mobil one because of the chemistry-the additives and high TBN resist things like fuel and soot-thus you do not loose viscosity) and use of our CCECO fine micron bypass filter, will make the wood gas device work well.

steve, by bypass filter is that a centrifuge? i have found that a company makes a standard replacement filter that uses SS screens down to 1 micron that you can clean and reassemble then install with out buying another filter, i plan on running a centrifuge bypass filter, along with the primary recleanable SS screen 1 micron filter, the centrifuge im about to purchase is able to be dissasembled and cleaned aswell (so i dont ever have to buy another stinking oil filter lol) also is it likely i would see 20k miles oilchange capability with this sort of set up? ive been reading some very conflicting info on oil change intervals with centrifuges.

edit, i reread the thread and found my answer. 8 x 5k miles is pretty sweet :slight_smile:

@ John, no, Max gasman’s system uses vacuum