Paul and guys,

Does anybody know how many amps the smart coils pull when charging?

I have an idea and this information would be helpful.

Kevin Alderman

RX8 coil. Over 7 amps with 5 V applied to the trigger. That is all
my power supply could handle. It reduced the PS 12 Volts to about 6
volts with 7 amps If you leave it connected it will shut down. They
are designed to be "on" for only 4 ms.

You need a real low impedance power supply or a 12 volt battery to
make them work.


I'll let you know tomorrow as I have a motor cycle battery back at
the house. I am at the hangar now.

Paul Lamar

Next question- with the knowledge that a constant 12v across C and
B, the coil will charge and eventually overheat. Can the coil charge
for 4ms, then sit for another short period before being triggered?

Or will there be a spark as soon as the field collapses from the
input voltage drop?

The answer will have an effect on the timing.

Kevin Alderman

With computer chips less than a buck I would not surprise me if it
shut off if an attempt was made to keep it on for more than about 4
ms.

I have no way of knowing with out doing a lot of analyses testing.

In any case as far as I can tell it takes an EFI system to control
them.

I want to make a simple ignition and carb fuel system so it takes
less than 5 or 10 years to install a rotary.

Besides I would not be a bit surprised if the RX8 flooding problem
was not mitigated by a simple CD ignition. It has the proven ability
to punch through fouled (AKA shunt resistance) plugs.

The other thing about CD's is they will work up to 11,000 RM  or
higher which a smart coil will not. The RX8 coils are on the bleeding
edge of inductive coils at 9000 RPM.


Paul Lamar


Paul, here is what I have in my head- (dont laugh at what is in my
head, its stuffed so full of stuff like this it isn't even funny)

For about 50$ or so I can use a small atmel board and an LM1815
Variable reluctance board and program it using a few other components
diodes, transistors, etc. to read the stock CAS sensor every time
both sets of teeth produce a signal. The programming would simply
calculate the rpm (or probably read simple table), and from that
calculate the amount of time needed to get in the 4ms dwell, and then
let the CAS fire the coil. The coils will fire every time they get a
trigger event from the CAS, except for the first time which will be
before it charges. So with that information, we only need to
calculate dwell as a time interval that precedes the next firing
event based on the last firing event. So, we read a firing event, and
in the 180 degrees anticipate the next event, charge the coil 4 ms
before it needs to fire, and when it fires turn off the charge until
next time. For those that have a stock CAS with 2nd gen coils or even
later coils, this should be a cost effective way to add spark at a
fixed timing advance and be reliable. A couple of connections, a
small box, add a carb and go flying. An alternative might be to read
the CAS 180 degrees ahead of firing and delay the firing based on
RPM. This way there would be more wiggle room for timing advance
adjustment based on RPM. Would be more code- might be version 2.0. If
I read the rpm off of the bottom teeth, and let the top teeth trigger
the firing, it shouldnt be too difficult to get it to work. If we
start adding retard and advance, it will get progressively more and
more complex as we go. To provision for a turbo would mean reading
MAP and retarding the timing with boost.

I need to go get a couple of rx8 coils to try it out and run some
tests on them. I have 2 sets of 2nd gen coils so I can experiment on
those as soon as I get back from a short trip I have to take this
week. It probably wont turn out quite that simple, but I think that
it will work. If it works and is reliable, then someone could buy a
junkyard engine, add a carb, use the factory CAS or hall effect
sensor and coils and be running much easier than tuning an EFI.

Kevin Alderman

Sounds like a plan that will work. I just got some $4 LM1815 and they
look good. Not as good as a hall effect but the best for a VR sensor
due to the zero crossing feature.

My ultimate goal is to have the rotary engine run with no electrical
system dependence. Just like a Lyc or Cont. with mags.

The outboard-motor/motor-scooter ignition system will do that. If one
had a low wing, a cowl tank and a hand pump you could keep the engine
running with a failed electrical system. I had a failed electrical
system at night one time in the C182 going into Las Vegas right after
an annual. The mechanic forgot to tighten the alternator belt tension
lock nut.

BTW High wings have lower accident rates due to fuel supply issues.

I'll trade 4 RX8 coils for two waste spark 2nd gen coils.

Paul Lamar

--

I will trade you the waste spark coils for the rx8 coils. I will send them out today before I leave on my trip in the morning.

Redundancy is never a bad thing.

In my Viking I remember picking it up from annual, filling her up with gas and taking off. And when my gear wouldnt stay retracted and I had very little hydraulic pressure, staying in the pattern and landing. Turns out that if you remove and rebuild a retract cylinder, you might need to add a bit of hydraulic oil too. :) The mechanic apologized, and it turned out well, but....

Kevin Alderman

Thanks for the coil swap Kevin.

Paul Lamar