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Old 10-15-2004, 12:04 PM
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Firing Order Question

I was having one of my random thoughts, and i wondered why vehicle firing orders are the way they are.

for example

GM has 1-8-4-3-6-5-7-2

1 2
3 4
5 6
7 8

that just bounces around the motor. It would seem more symetric and balanced if it was something like

1-4-5-8-7-6-3-2

or

1-8-7-2-5-4-6-3

why are they set up the way they are. I know there are cams out now that change the firing order so 5 & 7 dont fire in sequence.

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Old 10-15-2004, 02:54 PM
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Crank throws

Doc here

If I understand your question properly, The reason is because the rotating assembly is balanced in the LEAST objectionable amount of vibration and wear by weight, and F.O. So that the firing pulses are offset by each other. For each action, there should be an equal and opposite reaction...so to speak.

Heat is another factor to...

To point out an example , the 80's Buick had 2 flavors of 231 v6's, Even-fire and odd-fire...one ran like a V6, and was smooth, the other developed a bit more punch but was a "Vibrator"...and a parts wearer...


I suppose in theory, you could set up the engine in ANY fire order you wanted, provided your rotating assembly was weighted accordingly, the cam followed suit,and the pulses were all balanced..but it would probably be costly...

Doc
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