I have started this project some years ago however I am still working on the ignition, the injection being controlled by the other oem ecu of the biturbo.
There is my wiki page about this project and others on odd fire engines.
The biturbo engine is a V90deg 6 cylinders, odd fire, with 30° offset so TDC are 30°-90°-30°-90°... crank angle and firing is 150°-90°-150° ... .
Triggers are 3 pairs on the crank pulley, 10deg before each TDC, an a pair on the cam pulley. That cam pair "enclose" a crank pair.
There are 2 ecus one Weber IAW (6803 processor 64k rom) to control injection, one Marelli Microplex (6803 processor 64k rom) to control ignition and boost (knock)
Since it was my first experience, I wanted to work out a soft transition from the OEM ecus to Vems in order to keep my car running and to be able to easily return to oem. This implies to keep the same oem triggers.
If you follow the oddfire links, you know that Vems offers a solution for odd fire. In short, you choose coil type, camsync and you filter one crank trigger out of 2, so there are only 6 triggers per revolution (4pi), each 120 deg apart, but there is a trick: you delay each second spark by 30deg
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Does it work ?
On the bench, if you input Vems with the z012 VT trigger signal every works good, except a full revolution delay (4pi and more) before Vems send the first spark. You catch this issue by increasing the level of the trigger signal from zero.
My first install on the engine keeps the DIS and I was able to switch between Vems and Microplex. (I have copied the oem ignition map on the Vems map).
On the road -> no change
On start up -> sluggish
On the top graph you see the Vems triggers as the engine is already started by the Microplex (a quarter of a turn).
Below, Vems starting the engine.
Next I did a full ignition install, using Bosch 3x2 wasted spark coil. Indeed one can pair cylinders so that one cylinder is TDC fire and the other beginning admission (30deg)
-> The engine did not start (bang) or can start with 35 deg spark advance during crank
with such config
http://www.vems.hu/files/MembersPage/Maserati/v3.3_u003856-A-2012.08.01-19.18.13REF2.vemscfg++++++++++
What I understand !.
I believe that Vems computes the time of the next firing from the time interval (Told) of the last 2 triggers (120° apart).
Let the starter cranks at 300rpm. When started with the Microplex ecu, the engine reaches 800 rpm quite fast say in 600deg (5x120) So the speed increase of 100 rpm each 120deg phase.
Hence after the first fire, speed has increased by 30% (100rpm) at the next 120 deg trig. Which means that this 2nd trigger is 30% or 36 deg sooner than expected (or more in the case of firing with the 30deg spark delay)from Told.
So at best the startup is messed up, at worse, with wasted spark, the paired cylinder is ignited at 60 deg on admission (30+36 - 7 advance)...
