Boxer engine - I don't understand the ignition
 

Hi all,

Just a random question that popped in my mind and I can't figure it out.

I used to have a VW t3 Westfalia. This was powered by a 1.9 petrol water cooled boxer engine.

Once I changed the coils, cables and the rotor (is this the correct English name?).

Anyway, point is, there was a specific order for the ignition cables, cil 1, 2 3 and 4.

BUT! If the engine is a boxer.. should cilinder 1 and 2*fire at the same time?? They share the crank.. so they both hit the high point at the same time.

And when cil 1 and 2 are on there lowest.. cil 3 and 4 should fire.

So, how come that there is a firing order ?!
I searched online and read Wikipedia. They state that the firing adds to the smooth operation, but not how it works.

Thanks for explaining this to me!

Alex

As all four strokes, it only needs to fire every second time the piston is on top.
When piston 1 and 3 is on top cylinder 1 fire, next time they are on top cylinder 3 fires and so on.
Remember that the cylinders work together in pairs but the valves do not. So cylinder 1 is in compression stroke (right before ignition) when cylinder 3 is in exhaust stroke (exhaust exits cylinder)

It doesn't matter if it's a boxer or an inline engine.

http://www.aa1car.com/library/4_cycl..._injection.jpg


Note, to add some more confusion:
On two cylindered boxer-bikes you fire both sides every time pistons are on top. (but of course you only get explosion on one side, it's very hard to ignite exhaust...).

God that I didn't think of that! The cilinders are on the high point at the same time but at different stroke...

Jeez I feel stupid! :eek:

Thank you so much!