Firing order

Because, in the case of classic 1342:

That doesn't explain why it isn't 1234.

"Tom Del Rosso" wrote

The reason they don't just fire "one end to the other end" is balance.

Feel free to build you own engine, and make it fire "consecutively" using normal numbering (have fun as your engine shakes the car to pieces), or get a felt pen and number your cylinders any way you like. :-)

In theory you could make a cam and crank to do that but in practice the crank would be huge to restore any workable harmonic balance.

I don't see why, but thank you to all. I have to read up and think about this.

That helps balance the engine. Otherwise the engine would act crazy, might not be firing right too.

Relies on the crankshaft: flatplane or crossplane And control of engine balance.

It does, if you care to look. Some thinking is required.

It's simple. it's not possible to balance the crankshaft in most engines to do that and still have an engine that fit's into a vehicle. Take a simple 4 cylinder. The crank throws have to be 90 degrees off from each other to maintain balance. Then you need to balance out the rocking coupled frequency from the firing order. If you don't the vibration will quickly destroy the engine.

On a V engine you have 2 cylinders on each crank throw. So you have cylinders 1&2, 3&4, 5&6 each sharing a throw. Number one is at TDC but number two is already past TDC and heading down the bore by the time number one fires. Impossible to have them fire in sequence.

There are some engines out there that have a sequential firing order, but the crankshafts have split journals and generally they are not capable of much power output because of the crank design.

One cylinder up to 16, 24 or more, engines fire on only one cylinder at a time. Most of them anyway. Batteries do not have electricity in them either