Rotary firings

[ChrisBourk at aol.com]

In a message dated 98-09-17 17:57:41 EDT, you write:

<< This is a copy of something I posted some time ago, based on my experience
 and documentation on hand for both my '87 normally aspirated (that's Mazda
 for non-turbo) and my '93 twin turbo.  I hope this helps.
 
 Most Mazda rotaries (i.e. almost all) have 2 rotors (13B or the earlier 12A)
 not counting triple rotor Japan-only and racing engines (20B and 20G), or
 even the few 4 rotor beasts you won't find on a street.  According to my
 documentation, you get one rotation of a rotor per 3 turns of the eccentric
 shaft (piston engine fans read: crankshaft) with 3 faces per rotor, which
 give you 120 deg between pulses per rotor or 180 deg per turn of the e-shaft.
 Due to the long, narrow cumbustion geometry, there are two plugs per rotor -
 the leading and trailing plugs.  The trailing plugs are above the leading
 plugs; roughly at 2 o'clock while the leading plugs are at 4 o'clock.
 Trailing plugs are fired by individual ignition coils (in the 13B-REW of
 the 3rd gen twin turbo) or ignitors (earlier 13B), while the leading plugs
 are tied to a single coil or ignitor as waste fire.  Timing at idle is fixed
 at 5 deg ATDC leading and 20 deg ATDC trailing, while at crank it is fixed
 at 5 deg BTDC (both?), and variable everywhere else (on a 13B-REW).
 
 Andrew >>


This is true,

Christopher