(Yet Another) Electrical Question

[Ak Sourdough]

To answer the non electrical part of the question, the engine will stop on the compression stroke of whichever piston is coming up when the flywheel no longer has enough inertia to overcome the resistance of compressing the air in the cylinder. The highest compression will be at the top of the cylinder, so it will very likely always stop near the same piston location.



If you mark the crank pulley every time the engine stops there will only be 2 marks on the pulley and it will look like it only stops in 2 places 180 degrees apart. Each mark will be the compression stroke for cylinders 1 and 4 or 2 and 3. Being a 4 stroke engine it takes 2 revolutions to make a complete firing cycle, 720 degrees. 1 and 4 will have the same mark, but fire 360 degrees apart, same with 2 and 3.
Clear as mud, huh?

[ericr]

Originally Posted by Ak Sourdough

To answer the non electrical part of the question, the engine will stop on the compression stroke of whichever piston is coming up when the flywheel no longer has enough inertia to overcome the resistance of compressing the air in the cylinder. The highest compression will be at the top of the cylinder, so it will very likely always stop near the same piston location.



If you mark the crank pulley every time the engine stops there will only be 2 marks on the pulley and it will look like it only stops in 2 places 180 degrees apart. Each mark will be the compression stroke for cylinders 1 and 4 or 2 and 3. Being a 4 stroke engine it takes 2 revolutions to make a complete firing cycle, 720 degrees. 1 and 4 will have the same mark, but fire 360 degrees apart, same with 2 and 3.
Clear as mud, huh?

oh that is pretty clear.....but next, explain why the firing order is 1-2-4-3 instead of 1-2-3-4

[Sparky]

That’s not an electrical question

The middle pistons (2 and 3) rise and fall together. So 3 can’t follow 2 in the firing order, it has to skip to 4.