Discussion: Wasted spark on leading & trailing plugs, rotary
Posted: Sun May 05, 2013 10:04 pm
I was just having a chat to wheeler_express and he told me that a few guys run wasted spark coils hooked between the leading and trailing plugs on their rotaries.
I explained that wasted spark usually works because one plug is sitting in highly ionised exhaust gas which is effectively a short circuit and thus effectively a ground (very low resistance).
My thoughts are that if you fire the same wasted coil into the same cylinder at the same time, the Voltage requirement could be doubled, or at least raised due to having two high impedance gaps to jump.
Also, your spark energy will be split across both plugs and neither will get full heat.
My advice was to use two single post coils per rotor, each with an independent ignitor, and each of those with an independent ignitor driver. Then you've only got the CPU to blame/fail, the rest is duplicated completely. Application is planes, btw.
I'm interested to hear others thoughts on this. Shoot holes through my theories, go right ahead!
Fred.
I explained that wasted spark usually works because one plug is sitting in highly ionised exhaust gas which is effectively a short circuit and thus effectively a ground (very low resistance).
My thoughts are that if you fire the same wasted coil into the same cylinder at the same time, the Voltage requirement could be doubled, or at least raised due to having two high impedance gaps to jump.
Also, your spark energy will be split across both plugs and neither will get full heat.
My advice was to use two single post coils per rotor, each with an independent ignitor, and each of those with an independent ignitor driver. Then you've only got the CPU to blame/fail, the rest is duplicated completely. Application is planes, btw.
I'm interested to hear others thoughts on this. Shoot holes through my theories, go right ahead!
Fred.