Originally Posted by
cathurga
Joystick, that is unbelieveable! Not doubting your claims/research, but that is probably the most counter-intuitive thing I have ever seen regarding an ignition curve! Retarding the timing at start or high idle is a common practice in many engine applications, but I dont think I have ever seen this in our applications. Its WEIRD. It could be that as per truckrcers findings, that the sensor was bombed, giving you those results?
The reason I raise my question is that I have an OSGF40 that is behaving weirdly. I dont have the original ignition module, and am trying to match a standard ignition to the engine, but cannot find an area of comfort to get this engine to run properly. I suspect that there are some carb issues that may be contributing to my frustration, but I have also heard that the ignition module was purpose built for this engine, and may have odd curves. In some forums, people have said that there is NO spark during low rpm, and requires a speedy starter in order to get the ignition to fire. Some say that OS didnt want people handstarting them in order to avoid injury, so they cut spark at hand starting speeds, yet I have seen videos of people handstarting them
The sensor is not placed where it could be set easiy at 28Deg BTDC so perhaps there is some truth in it. When using an NGH 38 ignition module, with sensor as close to 28Deg BTDC it runs, but battles a bit. I tried it at the stock sensor setting, and I got BIT...bad.It was firing after TDC and would rotate and smack the back of my fingers before I could get them out the way! At 28Deg BTDC my Align starter, with the throttle opened slightly, would NOT rotate the prop past the compression stroke!
Truckracer, would it be possible to share your published findings, or provide a link....if its public info?
To the OP, my apologies once again, I am going to find a suitable place to move the topic so that I dont derail any further...
First, good idea about moving some of this info to its own thread. These were and still are good discussions and too important to be hidden away in a thread where the info will never be seen.
Regarding OS ignitions, I have zero experience with these so would have no comment on them at all.
Regarding Joystick's findings and published curves. He is spot on and most everything I have read that he published about these ignitions has been accurate. That I found something different in some cases is meaningless as I tested different examples of ignitions with different sensors, etc. Had we had the opportunity to work together in the same place at the same time, I'm sure we would have found the same results from the units tested. I never published any curves as I didn't have enough data to publish a pretty curve of the various timing curves and only tested enough to confirm the sources of the problems and the parts of the curve I was interested in. When testing sensors, I had use of a scope from my old workplace but didn't think at the time to take a picture of the waveform. This had clearly confirmed the double spark or double trigger problem as the magnet passed by the sensor. I don't remember if it was Joystick or not but someone published that waveform image later on. I found and confirmed the problem in multiple cases and moved on. I no longer remember all the threads I participated in but they were in two or three different forums with RCU and FG being the most active. By the way and another point, on the A-02 ignition, the timing curve exhibits a bit of hysteresis as the curve is a bit different as the engine accelerates than when it decelerates, maintaining more advance at a given RPM during deceleration. This might account for why some engines have a hard time settling into a steady idle on throttle down.
Again, overall I was satisfied with the A-02 RCexl ignitions if they were fed adequate voltage and had a decent sensor that played well with that version of the ignition. If these two conditions were met, they didn't exhibit kickback during starting by firing too soon, they didn't have excessive retarding that made starting very difficult, they ran smooth and the advance curve was acceptable. Too little retard for starting or excessive retarding seems counter intuitive as you say but both conditions could and did happen if the necessary conditions weren't met. Regarding rough running, I'm sure many people have blamed this condition on carburetor problems when the problem was actually ignition related. Also interesting, most of these problems didn't exist with the A-01 ignition and most of the so called bad sensors that caused the serious double spark problems with the A-02 ignition would work just fine with the A-01. The A-01 ignition had a reputation for not liking higher voltages (It might overheat or exhibit shortened lift) so many people chose to run it at the lower end of its voltage rating. In complete contrast, the A-02 seems to run better with a voltage in the middle or higher end of its voltage rating. Strange stuff but interesting for people like me who like tracking this sort of thing.
Again, none of these comments are intended to bash any product in any way. I am an active user of these products. I recommend them and am thankful we have them to purchase.