This image I know represents timing , after bottom dead center , before bottom dead center, bottom dead center, as well as top dead center and before and after.

I'm having trouble grasping the whole picture and what everything represents. Why only certain numbers are showing and what they mean.

I've tried to understand and read it quite a few times, maybe it will take me writing notes on the picture labeling everything to help me see what everything means.

Any help appreciated, just hate to never understand the heart of what makes a rotary a rotary.

Attachment 493592

Straight lines show where the timing is on respect to the housing and the rounded lines coming from those points shows the timing with respect to the plate. The straight lines will tell you what the timing is for a port that is on the housing, i.e. peripheral ports and the rounded are for side ports since they are covered and uncovered by the side of the rotor and not the apex seal.

Blue lines look to be the intake opening timings and the other color are the closing timing. Try to think of it more as the port being covered by the rotor and then seeing where the apex seal is on the housing for the actual timing number. Once you scallop the rotors then this will get even more confusing as the rotor is no longer a nice radius when it comes to covering the port.

A degree wheel on top of a rotor that is spinning in the housing will make the easiest way of showing the timing.

So the end of the lines are the rotor tips and the line from end to end is the side of the rotor?

I do alot better with visual and reading but that pic is hard to conceptualize.

Hey

the original image was from rotary illustrated .com and if you ran the mouse over a variation selections it would highlight the port shape of different plates and engines

you could see the change from one to the other in terms of open and closing edges
.. the image in its original format makes things much simpler to grasp

.. there are some errors ( or rather some omissions of some port variations from other markets )
so you have to take that in mind when making blanket statements about porting of one series engine to another
ie.. s4 turbo engine in some markets gets a larger primary plate port ( earlier open )
.. this may be because of local laws for cat service life or for internal passive EGR in preference for the external system