ya matt you could be right . the old way was with the vacum and weights . but i am not sure any more with the new electronic controls. i have heard different things maybe the enginers dont even know any more for sure there has got to be a way to make it work on different fuels but that requires to change timing as the fuels burn at different rates. sorry to bother you but i was picking your brain maybe for the answer. you seem to be working in that direction.
I was an ASE certified tech
If you watch this video around the 14 minute mark when I am trying to start this machine you can see the DRO of the AFR meter read the mixture. If I would have been paying attention to it I would have started the machine up faster. But when you do video you can lose focus on things.
Matt,
It has been my understanding for some time that data from the knock sensor allows the engine to take advantage of better (more stable) grades of fuel when it gets them by advancing the ignition timing. Is this true? If so then it would seem likely that this type of engine would adjust its own timing when it encounters woodgas.
Rindert
No the sensor in the fuel tank determines this. Most cars after 2000 have a sensor to detect alcohol in the fuel. Other than that, this is the reason you have an O2 sensor, the MAP, MAF, TPS AIT and engine temp sensor all work together to get to get to a base line timing and injector pulse. Then if the O2 sensor is un happy the ECM will compensate. The knock sensor is there to protect the engine and nothing more. It is to prevent detonation and destroying your engine. Anytime you have predentination this is not good.
As you open the throttle the manifold pressure will drop, and retard timing. Id need to examine how the signal in produced from a map. I would assume as vacuum pressure is increased the signal will increase. So higher vacuum would be a lower signal. If thats the case you could install a voltage divider to reduce your MAP signal to increase your timing.
Edit: might just be the flex cars that have that sensor.
ya you mean the flex cars have the senser for alcohol the older cars dont care or cant read it. they have a pressure senser in the tank. for wood gas you need to retard the timing more before top dead centre as was said a couple of day ago i think it was kevin could be wrong but on the forum we were told he could get 4000 rpm out of his car with wood gas by retarding his timing to 45 degree before top dead center this is the reason we are wondering how timing is retarded with ECM i think you just answered the question you said manifold pressure drops the timing will retard… also you said if the O2 senser is un happy the EMC will compensate… if this is true to retard the timing you would change the map senser voltage. up to retard divide voltage to increase timing. am i right or is this back word ???
I think so. in that article I posted, it says when the throttle plate is idle position, the manifold vac pressure will be higher. Then when you hit the throttle it opens and lowers the pressure, retarding the timing. So I think you could add the voltage divider or get a higher bar sensor. All sensor read 0 to 5 volts. If you change to a higher range this will change your timing. Just look up 1 bar, 2 bar, 3 bar on up to even 5 bar sensors. dont really matter who makes it. If you can OEM that is the best way, but you can get them with wiring pig tails and just re wire in place of your old one.
The O2 sensor I dont believe will effect timing but will change injector pulse. There is a set parameters or an operating range its supposed to work in to accommodate different fuel grades.
Look up how guys are adjusting timing when boosting their cars. This is how they are doing it by changing out the MAP sensors.
thank you that may be what we need to automat the fuel change problems .
It is called a flex fuel sensor. It is inline usually by the fuel filter. Apparently GM vehicles that have an E85 option are prewired for it, there just isn’t a sensor attached, nor are the fittings in the fuel line.
Apparently you can use something like an HP Tuner that changes the timing tables based on MAF sensor input. And quite a few more tuning options then I thought was available for a cars via the computer.
Hi Rindert, Matt,
OBD2 with the knock sensors does exactly that, within some limits…
I am using this to my advantage in my setups with the TukTuk and the TaTa cng pickup.
I had to work on the ecu mapping ( to explore the limits ) a bit, but it was doable and the mechanics behind it works fine…
I am also using , for teaching myself a few tricks, an Haltech elite 2500 ECU.
They have some great teaching video’s, let me show this one, for the knocksensors and what you can do with the ecu ( ignition learning mode )
Many things can be done nowadays, if we stop thinking inside the box… actually, a few of us, including me, are living outside the box… 
To Matt: DRO’s are indeed utmost important, even when your engine is not running… The DRO gives an exact status and subsequently a program rule that fits that certain DRO status.
Ad an ECT sensor and a TPS to the Carburetor controller, adjust the flap position for cranking when cold and of you go… program connect your O2 sensor with the TPeS from your gas pedal and MAP sensor and create an acceleration mixture … ( more rich to accelerate and lean when idlle… )
So much you can do, play around, with modern ECU and gasifiers…
The best source for learning is DOING, not having someone around that say “can’t be done”
I am still living my dream to be the fastest driving on wood ever 
Enjoy the clip
I may in the future write my own ECM code. I am already on the way with the electronic AFR auto adjust. I could very easily add a sensor to read crank position way in advance of TDC and set a delay based on RPM I could use the flywheel as an exciter ring to determine this. Then use a MAP sensor to adjust timing depending on load. I dont really need the TPS on the small engines the vacuum load should be sufficient.
Edit: I could use a servo to control the throttle plate. I can then use it as both the throttle control and also as the position sensor.
Here is a video of a guy using a tuner. He is using the knock sensor to set his parameters. What needs to be understood here, is the parameters have nothing to do with the knock sensor. He is using the Knock sensor as an aid here. In the video he is physically listening to his engine. He is basically re writing the map curve of the ignition timing to the ECM.
Ive never ran a tuner software, so I assume he is changing a delay variable that is set to a particular state through out the range of MAP sensor input.
ECM sees a voltage input from the MAP sensor and then links it to this “delay mapping” As the map sensor detects a load " less vacuum" this delay is lengthened retarding your timing. These are the variables he is changing.
Maybe this is where some confusion is coming from as they are using a knock sensor to detect knock telling them they are too advanced. But the variables that are being tuned here have zero to do with the Knock Sensor. With the Knock Sensor the only thing you could change is how it retards your timing if pre-detonation is detected other than that it is static input.
Also something else that maybe confusing some. Is when we are talking about mapping the timing curve. The word mapping has nothing to do with the MAP acronym for manifold absolute pressure.
In the code they are mapping one range to another range set to create custom variable. So this case the 0 to 5 volt input signal from the MAP sensor; the code is taking that full range and re mapping to another that can be customized by OEM or by you.
Matt, Koen,
There are sooo many ways to build a tach. Back in the day I taped a hall switch to a plug wire and ran the signal through a LM2907, freq to voltage converter. One could also hijack the signal from the crank position sensor or look at the ripple coming from the alternator. The list goes on.
Anyhoo. I have sometimes thought that a Cam Position Sensor would produce a lot of useful data that the CPS cannot. Your opinions?
Rindert
You can wrap a wire around a plug wire as well.
right, create a little transformer.