Is this a wasted spark system?
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Inside Look At An Engine As It Runs!
- Thread starter weekendrider
- Start date
angus67
Welder's penetrate deeper!!
Real cool
jabcb
XS650 Enthusiast
Neato video!
Its a simple Briggs & Stratton flathead engine like you might have on a lawnmower.
It has a combo magneto ignition + flywheel that is attached to the crankshaft.
This produces a wasted spark because the magneto & crankshaft are rotating at the same speed.
Its a simple Briggs & Stratton flathead engine like you might have on a lawnmower.
It has a combo magneto ignition + flywheel that is attached to the crankshaft.
This produces a wasted spark because the magneto & crankshaft are rotating at the same speed.
Good demo of the flame front progressing.
Yup a wasted spark, just as found on most 4 cylinder bikes.
Suck, squeeze, bang, blow, repeat... Yup. All four cycles illustrated. Great vid, especially to those who never really got the concept. Thank you, Weekend.
Indeed, and there's even more learning available in that video.
For instance: in the video you can easily see the progress of the flame from the spark plug across the combustion chamber. The "speed" of that flame front is constant for a given fuel - no matter what RPM the engine is running.
Thus, for the flame front to consume all of the fuel at a higher RPM and provide complete and consistent combustion, the spark must happen earlier in the cycle - and THAT is why engines need spark advance systems: to change the timing of the spark according to engine speed.
For instance: in the video you can easily see the progress of the flame from the spark plug across the combustion chamber. The "speed" of that flame front is constant for a given fuel - no matter what RPM the engine is running.
Thus, for the flame front to consume all of the fuel at a higher RPM and provide complete and consistent combustion, the spark must happen earlier in the cycle - and THAT is why engines need spark advance systems: to change the timing of the spark according to engine speed.
angus67
Welder's penetrate deeper!!
It would be interesting to see the difference of different grade fuel. It would clear alit of confusion of how fast 87 octane, compared to 92 and how that affects combustion
Indeed it would!
I'm not an expert in fuels and combustion, but as I understand it, each fuel has a "characteristic" flame front speed and so each one will have an ideal timing setting for a given engine and combustion chamber shape. The problem for OEMs is to build engines that can work on all the various types and compositions of fuel all over the world - espeically in the days of relatively primitive carburettors and ignition systems which did exactly the same thing regardless of the fuel being used. It is actually much simpler now that engines have electronic closed-loop controls that constantly monitor the intake and exhaust conditions and adjust spark and fuel injection timing to ensure optimal combustion, fuel economy and emissions performance.
I posted the query for those not familiar. The video clearly demonstrates firing on an exhaust cycle similar to the later firing sequence on the electronic ignitions of the XS650 (does not apply to points ignition.
I think the firing position was to re-enforce the integrity of the top plate. Had he placed it the middle or more directly over the combustion chamber the damage may not have demonstrated well. But may have a better example of the combustion (ahh umm what do they call it) kernel?
Last, I think he would have had better ignition with the alcohol if he reduced the jetting. He was drowning the cylinder?
I think the firing position was to re-enforce the integrity of the top plate. Had he placed it the middle or more directly over the combustion chamber the damage may not have demonstrated well. But may have a better example of the combustion (ahh umm what do they call it) kernel?
Last, I think he would have had better ignition with the alcohol if he reduced the jetting. He was drowning the cylinder?
Could be - it sure looked pretty wet in there when he was on alcohol.
Pete
Pete
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