Hi Jeff,
It appears the primary coil resistance can typically range
from 0.8 – 1.4 ohms for an ignition coil. So picking 1 ohm as a
nominal value. The stabilized current flow for one coil would be
13.8 /1 = 13.8 amps – not too surprising for what is almost a dead
short. But, we know the coils are not on continuously - fortunately.
IF all four coils were on continuously they would draw 4 * 13.8 = 55.2
amps.
Steve Bose provide me some ignition data from the EC2 which
indicated that at approx 3000 rpm the period between firings is 20 msec with a
dwell (on) time of approx 3.7 Msec. So that gives a duty cycle of approx
3.7 / 20 = 0.185 or 18.5 %. That indicates for a single coil a DC current
flow of approx 0.185 * 13.8 = 2.55 amps.
Taking that 0.185 * 55 = 10.175 amps as the outside
limit on the total current for all
four coils. Now this is a DC resistive analysis
approach. The time it takes for the current to build in an inductor,
building and collapsing magnetic fields and their effects would indicate
somewhat less current flow than this purely DC resistive type analysis.
I found some information at the MSD (ignition) forum where
the company replied to a question stating their “Blaster Coils”
drew approx 1/2 amp average per 1000 rpm when used on a 4 cylinder
engine. So if we applied that to the Renesis coils at 3000 rpm, we would
have 1.5 amps each or a total of 4*1.5 = 6 amps at 3000 rpm. Now, not certain if that
relationship holds linearly for the higher rpm or not. Probably drops off
a bit due to less dwell time to charge the coils – but that is
speculation on my part.
So I would say that Al’s 6 - 8
amps sounds right to me.
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
http://www.andersonee.com
http://www.dmack.net/mazda/index.html
http://www.flyrotary.com/
http://members.cox.net/rogersda/rotary/configs.htm#N494BW
http://www.rotaryaviation.com/Rotorhead%20Truth.htm