Rotax 914F Engine and M880
Posted: Wed Nov 17, 2010 1:45 amI have been using the M880 to control several development engines for the past 3 years.
I have successfully implemented the M880 for a single rotary / turbocharged single rotary / 2-stroke single / 2-stroke dual cylinder.
However, I am facing a new challenge now: The 4-stroke 4-cyl Rotax 914F aero engine.
My problem is the 914F ignition system. The engine is configured as a dual-redundant 4-cylinder wasted spark:
a. 2 CDI modules (module A fires the 4 cylinders top position at 26 deg. BTDC / module B fires the bottom 4 cylinders at 22 deg. BTDC.)
b. 4 dual-post coils (wasted spark).
c. 8 spark plugs (each cylinder has a top and a bottom plug with a 4-deg spark offset).
Question: How can I configure the ignition system for using a dual waste spark with a 4-degree offset?
If I define it as 8 individual cylinders – how can I arrange them in 2 sets of 4 (fire every 180 degrees instead of 90)?
Note: Rotax actually designed the 4-deg offset mainly for eliminating knocks. The Rotax 912 engine which is not turbo-charged, does not include this feature.
I have successfully implemented the M880 for a single rotary / turbocharged single rotary / 2-stroke single / 2-stroke dual cylinder.
However, I am facing a new challenge now: The 4-stroke 4-cyl Rotax 914F aero engine.
My problem is the 914F ignition system. The engine is configured as a dual-redundant 4-cylinder wasted spark:
a. 2 CDI modules (module A fires the 4 cylinders top position at 26 deg. BTDC / module B fires the bottom 4 cylinders at 22 deg. BTDC.)
b. 4 dual-post coils (wasted spark).
c. 8 spark plugs (each cylinder has a top and a bottom plug with a 4-deg spark offset).
Question: How can I configure the ignition system for using a dual waste spark with a 4-degree offset?
If I define it as 8 individual cylinders – how can I arrange them in 2 sets of 4 (fire every 180 degrees instead of 90)?
Note: Rotax actually designed the 4-deg offset mainly for eliminating knocks. The Rotax 912 engine which is not turbo-charged, does not include this feature.