So, last evening and this evening I’ve been spending my free time watching this two-part series on how to reassemble a classic FIAT 500/FIAT 126 engine (yes, I am obsessed enough that I’m watching 2 hours of video on reassembling the engine for a car I don’t even have yet :P):

I didn’t clue in until now, but I noticed something as he installed the pistons - the crankshaft - the pistons don’t move in opposite, but move together with a counterweight opposite!


This boggled my mind! Now, I know how engines work, but I don’t know a lot about the design side of this a common design for small, inline two-cylinder engines? I always thought one would fire and then be travelling down as the other was travelling up to it’s firing point, this way they would be balancing each other out without needing a counterweight (and as it is an even number of pistons, it would run smoothly...right?)? The way the 500/126 engine is designed, both pistons are travelling together even though one is on it’s firing stroke and the other is on it’s exhaust stroke...very odd to me!

Anyone else find this an odd and interesting engineering choice? The more I research and learn about these little cars, the more enamored I become! :)