Pulse point is somewhat advanced from actual 'mist' point, and as reiterated by our 'Reg' or was it 'Simon'?; different strobe manufacturers callibrated differently...
For example:
My Early Sun strobe that later became Snapon/AVL was callibrated to be attached to the fueline near the pump outlet with a correction chart for use near the injector. Remember several degrees are added on for line length, increasing for higher rpms.
I think the later versions were callibrated for use near the injector [I think] but I've seen no evidence that Snap-on did anything other than reduce the output terminals on their control boxes 
My freq counter and advance box actually had a terminal for output to a chart, and another output described as "Not needed yet" 
Mark, You actually have a good (and valid) point here. I have been following the variations in measured (by pulse sensing) timing with some interest, as it seems by far the best method to optimize any given engine. However, I had more or less accepted that each engine would have to be tested for a baseline, then an optimization curve created from there by experimentation. This curve would then allow for repeatable use of the measured timing after any work or changes. I'll add more on this below, but for this discussion, I think that the difference in placement or calibration of the sensors may account for some of the difference between different peoples readings. Also, fwiw, I am not sure that Mike's Or marks engine running at 13 degrees would run the same as mine (400000 km, all original, yes injectors too i think) would run at 13 degrees. I suspect compression numbers will make a significant difference in the engine's optimal injection point, as lower compression would (i think) cause a slower burn.
Mike, I am somewhat local to you. If I found my way round your way, any chance that you could hook me up and give me a timing reading on my jetta. I dont expect a freebie, but I'm thinking more like side job (or beer) than an hour of shop time, if you know what I mean.
Back to the timing numbers. If I can measure the actual pulse in the injector line, then I am correcting by design for any changes in timing caused by injector break points, etc. Using a predicted break point based on pump piston travel will require that I (try to) predict the change caused by injectors, or other changes. This would be (perhaps) doubly difficult in the case where injector break pressures are not 'to spec' but the outlet check valves are either 'to spec' or to a different spec. In any case, if I can determine that the engine in my car runs best with the pulse timer showing 14 degrees at idle for a baseline, then any changes I make from that point forward could be reset to 14 degrees 'baseline' at idle, and all other adjustments made from that point. I feel that this would be especially helpful when one is messing with anything that affects the pumps timing systems, including fuels, timing system, internal pressure, etc, as well as the aforementioned break pressures. Any thoughts?
Topic: pulse time AAZ? (Read 3225 times)
