A while back I found this picture on the web, in a different form. It was black and white and had a bunch of numbers printed all over each picture. I know how these things work and I could not follow it using this format.

 

So I copied it and removed the numbers and backgrounds. I added colors. So there are two pieces of data that can be seen now.

 

First is that the rotary is a 4 Otto cycle engine. It has all 4 strokes. The two TDCs are on different sides of the engine. The two BDCs are on top and bottom of the engine.

 

TDC = minimum chamber volume.

BDC = maximum chamber volume.

 

Note also that the top of the engine runs cold and the bottom runs hot. The bigger the difference between the halves, the greater the distortion and loss of power.

 

If you sit number 6 behind number 3 you can see some of the ignition system problems the designers had to overcome.

 

The old distributors looked like walkaways from the Rube Goldberg funny farm. Now there is no distributor, but the same problem is still here. The modern ignition, distributes the trailing ignition timing but uses a double ended coil or, two coils fired at the same time on the leading plugs. Both leading plugs fire at once and the system is called a lost spark system, because one of the plugs is firing so late that the chamber is in the exhaust cycle, so that spark is wasted. The other end of the coil is firing the front chamber at the correct advance point. A coil for each plug is an advantage.

 

But this only works on the leading plugs. The computer must still distribute the trailing plugs. In picture 2 you will notice that the trailing plug (the top plug is the trailing plug) in that chamber is in front of a new charge that is way far away from TDC or 22 BTDC, so lighting it would destroy the engine. So, you can light the trailing plug in the front housing (3) but not in the rear housing (6).

 

Just for the fun of it.

 

Lynn E. Hanover