Quote:
Originally Posted by jamesqf
I don't see why any engine designer would do that. You want to make the engine run smoothly, which means spacing the firings at equal intervals. 1 & 4 might be at TDC at the same time, but one should be on the compression stroke, the other on exhaust.
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Straight fours fire in pairs every 180 degrees, but due to the
difference in piston speed between the pairs most modern straight fours also use a
balance shaft. Straight sixes fire in pairs too but don't have this problem because
they can fire every 120 degrees, so the fastest pair speed, even though there is still a slowest pair, is offset by the third pair moving a some speed in between.