Engine Basics, Spark
#1
Engine Basics, Spark
I got a pretty basic engine question, what triggers the spark plugs to fire?
I understand the magneto generates the power. On the flywheel there is a contact patch that trips the trigger coil. The flywheel turns equally with the crank, the cams only turn 1/2 the speed of the crank. For every 2 rotations of the crank there is only 1 combustion stroke. So that means for every 2 crank rotations the spark plug only fires once, but that would also mean that flywheel would trip the trigger coil twice to generate 1 spark. Is the CDI responsible for when the spark is delivered. If the CDI is responsible, then how does it know if the piston is in the compression stroke or the exhaust stroke, technically they are the identical position just 360* off.
Please point out any errors I made to help me better understand our motors.
At least on a distributor you can physically see how it works! And its running off the cam gear so there is no 2:1 stuff.
I understand the magneto generates the power. On the flywheel there is a contact patch that trips the trigger coil. The flywheel turns equally with the crank, the cams only turn 1/2 the speed of the crank. For every 2 rotations of the crank there is only 1 combustion stroke. So that means for every 2 crank rotations the spark plug only fires once, but that would also mean that flywheel would trip the trigger coil twice to generate 1 spark. Is the CDI responsible for when the spark is delivered. If the CDI is responsible, then how does it know if the piston is in the compression stroke or the exhaust stroke, technically they are the identical position just 360* off.
Please point out any errors I made to help me better understand our motors.
At least on a distributor you can physically see how it works! And its running off the cam gear so there is no 2:1 stuff.
#2
Engine Basics, Spark
Have you been reading my mind?
I've been wondering this for the last 6-mos. Have asked a few people and none have the answer.
I've put a few cams in and never have I had the issue of it not firing because the piston was on the exhaust stroke and I had the cams set with th lobes inward.
I gotta think it is firing every TDC but, I'm know expert.
I've been wondering this for the last 6-mos. Have asked a few people and none have the answer.
I've put a few cams in and never have I had the issue of it not firing because the piston was on the exhaust stroke and I had the cams set with th lobes inward.
I gotta think it is firing every TDC but, I'm know expert.
#4
#5
Engine Basics, Spark
Originally posted by: Sandaholic
That pretty much sums up my question, actually I think it fires a few degree before TDC. But what device makes it fires every other revolution?
Originally posted by: COUNTRYJOEGLASS
It fires every other TDC.
It fires every other TDC.
How does it know which revolution to fire on?
I've never heard of anyone having to rotate the cams because they put the engine together on the exhaust stroke?
#6
Engine Basics, Spark
Originally posted by: DuneMe
I've never heard of anyone having to rotate the cams because they put the engine together on the exhaust stroke?
I've never heard of anyone having to rotate the cams because they put the engine together on the exhaust stroke?
#7