Can anyone explain why with the 500s when you have a horizontal cylinder as in the Giardiniera that the flywheel requires an out of balance weight as opposed to a balanced flywheel on the rest of the 500 range with the vertical cylinders ?
It is the same with the Fiat 126 Bis water cooled as opposed to the standard 126 air cooled engines.

Just a guess, but if the engine is organised so that the weight is furthest from the top of the pistons when the pistons are at TDC it might be to assist balancing, which in the vertical engine has the natural assistance of gravity at that point.

Just a guess, but if the engjne is organised so that the balance weight is at its greatest distance from the tops of the pistons when they are at TDC, this would assist where gravity naturally helps in a vertical engine.

fiat500 said:

Just a guess, but if the engjne is organised so that the balance weight is at its greatest distance from the tops of the pistons when they are at TDC, this would assist where gravity naturally helps in a vertical engine.

Click to expand...

I see where you are coming from but my feelings are that with the sort of rev range you have even on a standard engine that gravity would not come into play.

Just guessing here but I imagine it helps offset the horizontal forces of the pistons firing, which would otherwise create a constant 'push' on the car to one side? A car can absorb vertical forces through the suspension, but not so much horizontal forces. Think about a scenario where your passengers jump up and down while you are driving, in a small car it would be irritating but not unduly dangerous. Now imagine they are widely jumping from side to side.... Not good!

like I say, just a guess....

Roger that may be a good guess and gets my vote so far. Because you do have two cylinders both thumping in the same sideways direction, different to any horizontally opposed engine that would balance out.