Spark plug fires Once per Revolution ?

hal

LawnSite Fanatic
Location
Georgia
Should be every other, one fire stroke, next exhaust stroke.
Google it, there should be some animations about it.
 

hal

LawnSite Fanatic
Location
Georgia
I looked it up too, thought I may have misspoke, but I always thought it fired every other stroke.
 

hal

LawnSite Fanatic
Location
Georgia
Well you learned sumtin every day (sometimes)
 

rlitman

LawnSite Silver Member
Location
Long Island
Spark plug fires every rev.
But cylinder ignites only every 2 revs.
It's called wasted spark ignition, and is used in may cars as well as small single cylinder engines.

I did. Apparently there’s disagreement.

I always thought once in small 4stroke .
How would you get that to work? The magneto is driven by the crank shaft, not the cam shaft. I suppose it may be possible with EFI, since you need a cam sensor to control fuel timing as well, but I haven't had my hands on any small EFI engines yet.

Should be every other, one fire stroke, next exhaust stroke.
Google it, there should be some animations about it.
Yeah, that's the problem with so many textbooks. They tell you the important principles, but skip the details they consider unimportant for purposes of simplification.

Wasted spark ignition fires a spark through the exhaust stroke. In automobiles, it's done by firing a spark through pairs of cylinders that are opposed in their timing (this pairing causes other issues, because the spark polarity is different in each) at some time around TDC.
 

knox gsl

LawnSite Fanatic
Location
knoxville, tn
It's called wasted spark ignition, and is used in may cars as well as small single cylinder engines.



How would you get that to work? The magneto is driven by the crank shaft, not the cam shaft. I suppose it may be possible with EFI, since you need a cam sensor to control fuel timing as well, but I haven't had my hands on any small EFI engines yet.



Yeah, that's the problem with so many textbooks. They tell you the important principles, but skip the details they consider unimportant for purposes of simplification.

Wasted spark ignition fires a spark through the exhaust stroke. In automobiles, it's done by firing a spark through pairs of cylinders that are opposed in their timing (this pairing causes other issues, because the spark polarity is different in each) at some time around TDC.
I had a Saturn years ago that had 2 coil packs on a 4 cylinder engine. It fired 2 plugs at a time.
 

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