How to calculate gas consumption for any engine?

I would like to share a method for calculating the volume of gas consumed by an engine running on wood …
I do it very simply - I look at the passport data of the engine, and taking into account the drop in power, I take as the indicator of gas consumption in cubic meters per hour, the indicator of its power in kilowatts … :joy: That is, if the engine power on gasoline is 85 kW, then its I will build a gas generator based on the Imbert table for a line approximately corresponding to a gas consumption of 80-90 cubic meters / hour …:grin:

Who has any thoughts on this matter?


Hello Yevgen!

There is a formula we usualy use

(Displacement in liters) x (rpm/1000) x 3 = volume of gas in L/s

This is at Wide open throttle

3 is the const that takes to a count that every second stroke sucks gas (4 stroke), 75% cylinder filling ratio…


So, in the case of my Mercedes.

2.3l x 2.5(1000rpm) x 3 = 17.3l/s at full throtle


well, and it turns out the gas consumption … Immediately I ask a counter question: why are we taking such low rpm?; why the filling of the cylinders is 75 and not for example 95?
Don’t you think it’s strange that my Opel with a 1.8 engine eats more than your 2.3. my gas generator is made at a flow rate of 90 cubic meters per hour and yours is 62.2


why do all modern builders of gas generators substitute 3000 rpm in the gas calculation formula ??? After all, this is wrong! :woozy_face: I understand that the formulas are 100 years old, but we use them for modern engines, and taking into account the fact that those engines for which the formulas were made and derived from technical data could not give revolutions above 3 thousand even on gasoline … … Can’t the pickup engine now reach 5-6 thousand rpm ??? Gentlemen, I think it’s time for your formula to be scrapped … :woozy_face:

Your formula is outdated trash !!! :joy: It’s time for her to go to the trash can.


Friction of the induction system.

Hmmm— Yes, this is such an exact science that we should be working to at least 3 decimal places

Pete Stanaitis


Yes but do you drive your Opel at 5 or 6 thousant rpm all the time? The formula is designed for REALISTIC drive conditions not what you can do “in theory”.

Every engine is different. My Chevrolet liked to run best at 3200 rpm on woodgas. Any less and it was preety much dead. So, l put 3.6 in the formula.

My Mercedes had most power on 2500rpm on woodgas. Cruiseing rpm was 1700-2000. Anything more wuld give litle to no more power and just burned more fuel. So, l put that a slight exess in, 2500rpm.
The engines are allso geared different originaly. My Mercedes in 5th gear got under 2000rpm at 100km/h. My Seat reaches 100kmh at 3500 rpm!

As for filling ratio. We put 75% instead of 95% because 95% is just a wet dream :smile: thats realisticly not possible even on petrol with fuel injection, unless you turbo charge.

And with higher rpm, filling ratio decreases drasticaly! So thats one of the reasons why you dont want high rpm on woodgas!

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I agree that I don’t need 5 thousand every day, but even on gasoline such revolutions are almost never used, nevertheless they are in any car … What you described with driving on wood, I expected from my first systems , but time has passed and now I need a good reserve of power, which I do not need every day, but I still need it, I do not want to drive a truck at a speed of 70 km / h without being able to quickly overtake it. I hope you understand what I mean, so in such cases I shift to a lower gear and step on the accelerator and … Of course this will not be possible with a 3000 rpm gas generator …


I understand. But can you guarantee the gasifier can then make good gas at idle? And will the idle keep the gasifier hot enaugh for a smooth takeoff?


I perfectly understand what you are talking about, and I already had this even on the GJ-9.0 version and this is not a problem.


The below video may show what Kristijan was referring to. This is a 25 min idle with a smooth take off at the end . The gasifier was able to keep the heat for long period without any throttle up.


I think we have already come close to opening a new topic “gas generator GJ-9.0” :roll_eyes::thinking:


Why is it that some of fence posts seem to be curled over, along the drive?

Hey! Mr. Wayne, are we there yet??? TomC

Hi Pete,

The real life numbers are even lower :wink:

Hi Joni,

The whole . real , sience, is based on Law’s of Physics, math and logic.
Feel free to challenge me on some details or on the entire topic of gasification.

The formula, mentioned by Kristijan, might be strange, but nevertheless quite accurate to use for basic design.

There is a lot of good info available on the internet and even on Youtube on how to understand an engine…

Let me give you one example, kinda based on my experience with your type of engine.

Consumption on straight road, 90 Km/hr
6 L/ 100 km gasoline

ad the air under normal conditions to get perfect lambda:
4.5 Kg gasoline + 66.6 Kg air
= 71.1 Kg mixture @ 25ºC = 56880 liters mixture for 100 km
engine running at 2600 RPm for 67 minutes to have 100 km = 174200 rev’s= 156780 liters physical displacement.
equals effective volume displacement of 36%

Physical displacement vs real displacement is a huge difference even in average its less then 0.7 @ wot

Valve overlap, Valve timing, temperature, pressure in the intake system, filter restrictions…

Enjoy the next clip


one for diesel


compression ratio

Bore Vs Stroke


Hi All,
I did check. And all but one of these videos K.V.L. so helpfully put up when viewed in CC mode can be text language switched from English scrip to French, Czech, Russian, Slovenian, Swedish, Ukrainian and many others using the gear shaped tool icon.

I haven’t yet watched them all. So still unanswered to me are the now out there for over 15 years the double overhead camshaft engine with on-the-fly timing adjustable camshafts. Toyota/Lexus engines this was ~50 degrees on the exhaust and ~30 degrees on the intake.
So . . . woodgas has a bright future for anyone learning to hack cam twisting systems.

And this explains why the ignore by most stationary gasifier guys on this topic.
We mostly have pull-out removable restriction plates. Allowing for inside opening changes and height changes with stacked ring spacers. Screw in and out air nozzles that can be changed out for opening and length protrusion. And BensBookSystem builds the air nozzles changed from 10 to 5; with 6 to 9 nozzles stepped in between.
So although only 15 to 1 one in one set up. With others the total range can be a spread of 4X that. The below restriction plate reduction tube volume changeable too with inside diameter and height lengths too. Grate grid changeable too of course.
Our costs for this is system size and weight. Not a big deal with stationary.
And the larger in-pickup bed units do much of this pull-out, drop-in adjustability too. The larger trailer towed also.
These systems you do not calculate. Best guess set up 1st. Adjust in for better. Ain’ no big deal.

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When you calculate taking the lowest you could never reach the highest. I mean you could never hit the accelerator and reach max power. If you calculate using the highest it would be available when you need to accelerate but may have loses when you are at minimum.
I think there must be an AVERAGE… I think you and the приятелями are right based on your own work and this case may need a study

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