The common recommendation that I’ve found on a number of sites for natural gas and propane is about 20% closer plug gap. That seems to work well on CO. I will start listening for the “cracking” sound.
Bruce
Hi, Bruce!
Closer gap, are you (they) refering to gasoline as a starting point?
I have no reference to gasoline, but the reference in the Audi service book, which is not consulted in this matter yet!
The reference to the “wartime” gap was a reality in those days, with weak ignition coils and bad insulation on all hightension cables, bad condensers in the primary circuits, and you name it…
Accumulators dipping the tensions when cranking made it worse.
DC Dynamos could not keep up with the frequent fanning…
Now in the Audi, I made a series of gap settings from 0,3 mm upwards to 1,0 mm, 0,1 mm at a time.
There was still some “cracking” at 0,6 mm.
The refered sound is exhaust sound.
1.0 mm was giving absolute wonderful sound and power results.
All flags “clocked” in “downwind” to the incomming gas-mix stream!
Max
1 Like
Hi Max,
Yes, gap for gasoline as starting point. Nothing beats actual tests with empirical results. Thanks for your test data.
Bruce
1 Like
Hi, Bruce!
Drawing a conclusion from this, seems to be:
The richer (heat value) the fuel-mix has, the smaller the gap is used.
Acheived firefront speed seems unimportant in this comparison…
as long as the compression ratio stays under ~14:1.
Gasoline 0,8 – 0,9 mm / woodgas 1,0 mm.
Max
I guess my progression to the smaller gap suggestion for charcoal gas had a few leaps of logic. I first noticed that old charcoal gasifier instructions recommended .012-.015 spark plug gap, then I came across propane and natural gas instructions recommending a narrower gap. Heat value of propane is twice that of natural gas per volume, but 20% narrower gap is recommended for both fuels. I assumed the spark gap had something to do with gaseous fuel vs atomized fuel. Natural gas has over 3 times the heat value of CO per volume. I assume air fuel ratios figure in here somehow so we should compare stoichiometric mixed fuel per volume not just the heat value of fuel gases per volume. Max, hold my hand and lead me through the heat value spark gap issue comparing gasoline to wood gas to CO. How might compression ratio and modern ignition systems affect optimum spark plug gap?
Bruce
Hi, Bruce!
First, those charcoal instructions have a definite “ring” of wartime accumulators and DC dynamos on 6 Volt…
Low compression ratios, little compression heat, damp gas, if not in Australia… …
Right?
Then, you are on it; it is the heat value of the gas mix and not the fuel heat value as free-burning.
High calorie value gas needs much air, low heat value gas needs less air; this reduces the difference of various gas-mixes.
How about this: The less nitrogen in the mix, the larger the spark gap?
See what you find!
Modern ignition systems have modern maintaining systems to keep accumulators well and alive, less susceptible to dip at cranking and failing.
Max
2 Likes
If you are having trouble sensing the small pressure changes you need and using that “push” to drive a valve:
A $4.00 Arduino Uno, a $10.00 servo and a $14.00 Freescale MPXV7002DP differential pressure sensor will do it easily and reliably.
Pete Stanaitis
3 Likes
you probably also need a roll of aluminum foil to protect everything from electro magnetic interference from the engine.
I would try the MPXV7007DP instead it has a wider pressure range and higher operating temperature range. Plus I think they might have discontinued the 7002, and they are the same price.
It is too bad the silicon diaphragm versions won’t work.
Yeah you could map the signal to a pot and have full adjustability 
Hi! Pete, Sean, Matt.
Yes, if sensitivity gets you sole! Now a full regulation range within 0.5" WC is good enough for proper and smooth operation. Why then expand the range of service needs with electronic gadgets?
If you start without any electricity available where is the advancement?
By the way, start up does not need any prebalancing for minute intake flows; the twin-flap dispensing makes that with help of the sucking vacuum… INSTANTLY!
Max
Looks great Chris! Those bearings will probably never wear out.
Mr. Max.
I’m trying the mechanical approach first for a couple of reasons but I still believe it will work with the electronics. Without the electronics our engines won’t start anyway.
It is possible to build an engine with minimum of electronics. May not be legal for the road but I wouldn’t tell if you don’t.
2 Likes
You don’t need ANY electronics.
3 Likes
Hi, Arvid!
Stationary- and small boatmotors run excellently with magneto ignition. So does many tractors too… with the “sportsman” handcranking.
Needs to master the mixing ratio at very low flows, which means precision twin flaps for dispensing.
Additionally, a small manifold vacuum bellow, diaphragm or cylinder to do the flap opening overcomming a spiral when reaching a preset vacuum.
Handgas setting only restricts how much the twin flaps are allowed to open!
This way the precondition of gas flow by gasifier overpressure or ventilating does not affect the desired mixing ratio by the twin flaps!
Otherwise, no problems, besides manual ventilation.
Gas mixing (dry) does not need electrical gadgets.
Max
Here’s a few important sounding questions from a newbie with no experience: doesn’t the woodgas from the reactor vary in “strength/quality” as well as “amount/quantity”? I.e. Weak gas after coasting down a long hill would have a different fuel/energy density, even if it has the same vacuum/water-column and cubic-volume-per-minute flow rate of gas, as richer gas from a gasifier running at peak temperatures/flows? Wouldn’t that inherent difference in fuel/energy density of the gas, which is not directly tied to gasifier vacuum/flow, cause discrepancies in the fuel/air ratio, needing adjustment?
Would a pressure-differential mixer such as this be able to account for that needed adjustment?
3 Likes
Nope. If you’re making weak gas, this won’t account for it. Nor will it compensate for air leaks in your plumbing.
It counts on the fact that, once the gasifier is up to temperature, the gas quality is relatively constant.
3 Likes
Hi, Brian!
Yes, this question has been debated over 100 years!
in every woodgas book!
No one is comming downhill from the Himalayas, anyway… so if the motor goes well with its gasifier system on idle for 15 minutes and more, there is just a little “noch” moment in the retaking of driving power, when the land is flattening out, or a new uphill is about to be “taken”.
With a manual gearbox you can use the motor for pumping more gas than the idle gas need, by swiching off the ignition and giving a little foot (pedal) gas. That is called motorbraking…
Perhaps too modern vehicles also will make a mess with all kinds of shutdown-functions when they are deprived of current?!
Hope you can circumvent that!
If you reed the books, you will learn, that a hearth after heavy drafting can produce an excellent gas, because the steam boiling in the silo pushes out through the hearth, and no air is comming in with nitrogen, which normally will dilute the burnable parts of the gas by ~1:2!
If this goes too far, the motor can be suffocated by the lack of secondary oxygen (air).
This is typical with T-mixing, where the mixing ratio (air/gas) happens above the common throttle.
In this case, the high succing-vacuum is under the common (for both gases) throttle.
Above the common throttle and the succing vacuum you have the two (freely compeating) entrance routes of free flowing gas and air.
This “competition” is under normal power conditions a place with a swift flow-through, and in consequens of that, you have flow resistances in both entrance-routes.
With this flow-through, you can balance the flowresistance between the routes with the traditional hand-regulated air-flap.
That is the traditional way to set the mixing-ratio.
But, when the gasgenerator is pushing out more gas than needed, the mixing ratio is upset, as the t-mixer is dependent on setting the flow resistance equal in both arriving routes (legs).
When the gas is flowing into the T-mixer without succing, it is impossible to balance the “flowresistances” and the air/gas ratio!
…
This will not happen with the twin-flap dispenser, because it is setting and controlling both arriving air and gas routes’ flow resistances independent of which “mood” the gasifier happens to be in!
Pushing or resisting…
The twinflap dispensing is dependent on the always
equal flow areas and equal pressure drops
over both flaps — from cranking to modest high power levels.
At WAT level the twin flaps are no longer the dominant resistant for flow control, so the flow routes for air and gas have to be made absoutely identilcal from the sampling points for the flow routes to the dispensing flaps, and to the swirl mixer.
Sampling points for the membrane, which regulates the arriving air pressure according to the arriving gasflow pressure, when there is a definite pressure drop in the gas line.
Max
1 Like
Hi! Pete, Sean, Matt and Marvin
Yes, if sensitivity gets you sole! Now a full regulation range within 0.5" WC is good enough for proper and smooth operation. Why then expand the range of service needs with electronic gadgets?
If you start without any electricity available where is the advancement?
By the way, start up does not need any prebalancing for minute intake flows; the twin-flap dispensing makes that with help of the sucking vacuum… INSTANTLY!
Max
Just as an update I got the bearing and shaft in and it will not be good for this. Very rough movement and it would hang up in places. Pretty low quality. Back to looking for something else.
1 Like