Lately I’ve been working on adjusting the ignition timing (pre-ignition). I have a Suzuki Maruti distributor on my Fergi, which is equipped with a centrifugal and vacuum regulator, which change the ignition timing. The Suzuki distributor is designed for a high-revving engine (up to 6000 rpm), so the centrifugal regulator does not significantly affect the ignition timing, but because the Fergi engine reaches a deep vacuum, the vacuum regulator changes the ignition timing a lot. Now that I have a vacuum gauge in the intake manifold, I can see that the vacuum regulator is not working optimally. The ignition timing starts to increase at 0.1 Bar and at about 0.3 Bar it reaches its maximum deviation (it shifts the ignition by about 30°, maybe even more). What’s going on? If I set the distributor so that the engine has max torque at full throttle - 0.1 Bar, then I hear knocking at 0.2- 0.3 Bar, but if I set the ignition for vacuum 0.3 Bar, there is no real power at 0.1 Bar. I will try to replace the spring in the vacuum regulator, so that the operating range would increase slightly (0.1 -0.5 Bar)…
So you don’t get any knocking at full throttle but you do knock at lower rpm?
I know they had problems with swirl chambers, and pre-chambers with knocking, in my books.
Jan, I want to say that this vacuum regulator operates in too narrow a vacuum band, which does not satisfy the optimal ignition advance setting for a wood gas engine.
Wood gas is no joke, it is a powerful fuel, but it has its own characteristics, to which we must adapt the engine’s operating mode.
My intention is:
- to change the effect of the centrifugal regulator, which must operate in the range from 800 to 2500 rpm (in fact, the distributor rotates at half speed and this must be taken into account)
- to change the effect of the vacuum regulator for the range from -0.1 to -0.5 Bar
I find that the engine reaches maximum torque - power when it operates at the knock limit, well, the ignition distributor must provide this in all operating ranges
Ok, how much earlier do you think the ignition needs to be on an engine that is around 14-15kg in compression?
At the moment I cannot give exact data on the ignition advance angle, which is measured in degrees of the main shaft position,…
According to experiments and a rough estimate, an unloaded engine (vacuum pressure -0.5 Bar) should have at least 30° of ignition advance at low speeds (1000 rpm), which would increase with the speed, so at 2500 rpm it would increase to 40°. A fully loaded engine (vacuum pressure -0.05 Bar) should have ignition at 1000 rpm 5° - 10°, which increases with the engine speed and reaches at 2500 rpm approx. 15° - 20°.
I may be wrong, please correct my thinking (Mr. Wayne, Goran, JO, Jakob,…)
Hello Tone
On the for-gasoline distributor ignition vacuum timing advance the typical advance is INCREASED by higher manifold vacuum as a fuel use economy device.
At a normal naturally aspirated engine loaded condition the manifold vacuum decreases so the timing is NOT vacuum control advanced so as not to created pre-ignition/ pinging.
Now just to add confusion it became commonplace to have dual motion distributor vacuum controls with two input source lines.
One side to advance for fuel use economy.
The other side to pull back advance to prevent in cylinder high pressure made nitrous oxides emissions. The control source for that actuation somewhere under the edge of the throttle valve.
The internal springs centering. The two vacuum sources overriding each other at different made conditions.
Some actually did not pull for actuation - but pushed.
Ha! Ha! I’ve in vehicles hand pumped for on the fly changes - economy challenging.
Or used a vacuum can (like for old windshield wipers) with tubing and little plastic aquarium valves to timing trim for quick jaunts up into our mountains. This on emission feed back carburetors to on-the-fly driving enrich; or enlean.
You bet. Get creative. For response of changes you may have to increase the diameter of the diaphragm area. Look at natural gas control valves. Or propane control valves.
Regards
Steve Unruh
Or maybe Arduino plus many sensors. Electronic engine controls can be very precise, and can allow you to really understand engines.
Rindert
SteveU point out some good stuff here.
Timing advance / vacuum advance/retard could easily be mixed up, easy to think in the wrong direction, there are some different systems out there, where the 1980s systems, exhaust control, is the worst. As SteveU points out there are “double vacuum” systems, and a variety of places where vacuum is “taken” under carb=normal inlet manifold underpressure.
In venturi: more vacuum when throttle opens.
Special “pitot” tubes=more vacuum with more flow.
And worst: combinations of two or all three of these, controlled by electrical, thermo, and other types of valves, and vacuum modulators. Sometimes a distributor which looks the same, only one number in serial difference could work totally wrong. There are Bosch distributors, fitting, looks exactly the same, where vacuum advances in one, retards in the other, just by how the diaphragm link is placed. (Been there, done that…)
And progressive vacuum regulators… looks the same, just a little elongated cylinder between diaphragm housing and the dist. this cylinder contains another spring, and a plunge piston, counteracting the diaphragm.
A real “djungle” of things to take in acount.
I once got a classic distributor tester from a shop school, i gave it away to a “racing” guy, because it took to much space, i really regret it today…
SteveU may remeber these? A “box” on four legs, with a round degrees scale, adapters and holders for different distributors, and a special scope where one could read out advancing/retarding at different speeds, and be able to shift springs in the centrifugal advance, and see results. There was a hand operated vacuum/pressure pump with a gauge for testing. And about 6 or 8 heavy binders with settings for various distributors.
Ofcourse this could be done with a good timing light, a 360° protractor disc, and tachometer and vacuum gauge.
Yep. My professional experiences too Goran.
In the mid-1970’s as an early 20’s something I got my first job in a true full service auto electric company. They were still using a top of the line SUN brand classic distributor machine. For decades the best of shops for premium tune-up’s it was remove the ignition distributor from the engine; clamp it in and spin it up strobe light checking the mechanical and vacuum advance curves against charts. Then rebuild or replace the distributor.
Problem. We could no longer get the parts to repair or rebuild. The “remanufactured” units would often test worse than the original take-out unit.
Became a relitvley unimportant then. The challenge was trying to sort out the many control lines and inline vacuum delay valves affecting engine drivability. Nothing was position polarized. ONE reversed little bi-colored in-line valve could ruin your day.
Then the thing became expensive engine analyzer machines. Lots and lot of probes; sensors; hoses and lines to hook up for a menu directed full spectrum diagnosis of state of health.
Service was too time consuming and expensive. Folks did not want to be told bad news. They just wanted their vehicle to run like it used too. And that was not a woo-woo tech-solve. But a manual clean, adjust . . . sometimes by-pass . . . always a make-work any which way. Legal or not. The big expensive analyzer machines got pushed back into corners collecting dust. Hand-helds gave you the to-the-point specific, that you needed.
Past a low $$$ in repairs and here USA they’d just go out and finance a newer vehicle anyways. You never, ever got the pay for diagnostic. Only component replacing.
Ha! Ha! I am so American. Aged into my 40’s after ONE tow back home I am done with that vehicle. Don’t want spend any more time or money into it.
S.U.
I am attaching a link that talks about the ignition distributor, but all these ignition systems are adapted to engines that run on gasoline, but we need such a system adapted for the “engine fuel” wood gas or charcoal gas.
We can see that the ignition distributor has about 15° of effect with the vacuum regulator and 15° with the centrifugal, so a total of 30°. The question is, is this enough for wood gas? According to the reports I have read here, this is not enough, because some of you (Mr. Wayne) have a system installed for manual correction of the ignition advance while driving, which is controlled from the cabin.
To summarize some facts:
- I have an ignition distributor that changes the ignition angle by 30°, if I know that the engine does not reach more than 2500 rpm, then this angle of change is probably sufficient and will meet the needs of “wood gas”
- wood gas can withstand slightly higher temperatures during compression compared to gasoline, so the CR of the engine can be up to 1:13, but at this compression pressure the temperature of the gases rises very much (more than 400°C), well, such a mixture of wood gas and air should not be ignited too early, as this causes a rapid increase in temperature and pressure, which triggers detonation (to approx. 500-550°C) … this means that the ignition must be carried out almost completely at the top (5° - 10° before the top), when the engine is rotating slowly and the vacuum is -0.05 bar
- when the engine starts to rotate faster, the throttle is at max, it starts in the vacuum in the suction line increases (resistance of the gasifier, gas cooler, filter,…) and at 2500 rpm it is approx. - 0.15 bar, in this state the centrifugal regulator should increase the ignition angle by ?? (10°) and the vacuum regulator by ?? (5°) is this enough?
- the vacuum regulator must operate in the range of -0.1 to -0.5 bar and proportionally change the ignition angle by 15°, is this good for wood gas?
This afternoon I took some time to make changes to the ignition distributor, I replaced the springs on the centrifugal regulator (I tested it with a cordless drill, which reaches 1600 rpm, the max deviation reaches about 1200 rpm) and added a screw for adjusting the vacuum regulator (the original has a small adjusting screw, but it has very little travel and is difficult to access, so it is not possible to make adjustments while driving).
I also did a test drive, the feelings are good, I get more power at higher rpm, it works well even at low rpm
Tone, I once asked Kristijan how many hours a day Slovenia has. We have only 24. I bet you have at least 48, or more. Impressive work you do.
Thank you JO, I haven’t done anything so impressive, I write and think too much, I don’t do enough. How true is the saying of wood gas users, which contains the number 75%,… I hope I have reduced this number a little, I don’t dare to state my current figures, because I don’t know what awaits me,… 
Tone, you are way ahead of us others.
I also wonder how many hours a day Slovenia has?
Even that i know the secret to work 25 hours a day, i don’t make 10% of what you do…
It’s not how many hours there are in a day. It’s how many minutes there are in a hour and I think that’s variable according to age. My hours are about 15 minutes long now unless they come between 2 and 4 am while I’m laying in bed staring at the ceiling.
fine and useful arts, tone!!!
I’ve been very busy lately, no time to ride Fergi, well, today he got some work in the field,… I almost forgot what a pleasure it is to ride on wood gas. After I made the settings on the ignition regulator, it works like a song,…
I have a few fields that I cultivate in a crop rotation, that way the soil can breathe and pests can leave the area, well, weeds and grass need to be mulched to enrich the soil with nutrients, at least that’s what I think…
The hard work was done by Fergi today, transporting the excavator to the location where I had deposited the sand, and then 5 heavy loads of sand uphill, approximately 15 m3, I still can’t believe how little wood is needed to do such a difficult job.
Tone, that’s exactly what I’ve been thinking. I remember before woodgas I was dreaming - what if a basket of wood (15-20kg) could take me into town (15-20km). To my surprice I noticed half of it takes me there - and back.
My hoppers sometimes last 1.5h puttering around home in the woods. Only a couple times a year, on longer open road trips, they last sligtly less than an hour and I could wish for more. But I can live with that.