I'm not understanding why this happens. I'll I can get is that somehow lean F/A allows for ignotion before the intake valve closes, and the flame shoots up the intake runner to the carb.
I'm not understanding why this happens. I'll I can get is that somehow lean F/A allows for ignotion before the intake valve closes, and the flame shoots up the intake runner to the carb.
Ever use an Oxy/Acetylene Torch and turn the oxygen up too high causing it to pop. Not enough fuel to continue a burn for the amount of oxygen present.
Ever use an Oxy/Acetylene Torch and turn the oxygen up too high causing it to pop. Not enough fuel to continue a burn for the amount of oxygen present.
Ok, but why does that make a flame blow up through the carb, and make it a sound as if some fired off a .22 right next to my ear? What I'm not understanding is why there is, what appears to be, a small explosion coming out of the carb.
I'm not understanding why this happens. I'll I can get is that somehow lean F/A allows for ignotion before the intake valve closes, and the flame shoots up the intake runner to the carb.
Super lean a/f ratio can and will light off with the slightest amount of ignition source.Most likely source would be a glowing carbon deposit acting like a glow plug in a diesel engine.In theory..no backfire can enter the intake tract with the intake valve closed..but this is with timed spark.All bets are off if there is a secondary source of ignition prior to intake valve closing.An issue commonly known as preignition...a burn inititiated prior to timed spark.Thats my take on it..I am sure there is much more involved tho.
Ok, but why does that make a flame blow up through the carb, and make it a sound as if some fired off a .22 right next to my ear? What I'm not understanding is why there is, what appears to be, a small explosion coming out of the carb.
That changes things somewhat.If you a/f is correct and not super lean...the exhaust side comes into question.If the exhaust valve can not dump cyl pressure..the residual gas waits for the intake valve to open..reversion occurs and the hot end gasses attempt to shoot geese out of the air.
Very lean mixtures have a very slow flame speed. So, when the intake valve brings in fresh charge, there can still be some burning gas in the cylinder.
Very lean mixtures have a very slow flame speed. So, when the intake valve brings in fresh charge, there can still be some burning gas in the cylinder.
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