Tracy Crook wrote:
I reviewed the article and was very impressed with the knowledge and
understanding of CDI displayed by the authors. The design is
excellent
from
an electronics engineering standpoint and it could be triggered
directly
by
the EC2. Keep in mind that three of them would be required for a
13B
or
six for a 20B. But, before anyone decides to use this thing,
please
read
the article. Especially the section on Applications (pg 4). If
you
truly
understand the tradeoffs and still want to do this, have at it.
Tracy Crook
rws@altavista.net
www.rotaryaviation.com
Why just three units and not four Tracy? I was thinking of one coil
per plug and not using the very heavy stock Mazda coils.
I read pages three and four Applications again and I don't see what
concerns you on this. The rotary is basically like a four cylinder
with two plug firings per rev. (Each rotor fires once per rev, each
rotor
as two plugs). Are you referring to lead dressing?
BTW Jim Mederer at Racing Beat is using one MSD unit per plug on his
900
HP
turbo three rotor. I suspect MSD's are something like this unit.
Paul Lamar
Well, I already had my say on the subject so I'll just quote the article
which sums up my position pretty accurately.
Paragraph 2 under Applications reads:
"Nor do we recommend using this CDI on any car with an engine
management
computer. We take the attitude that the factory designed ignition
system
will always be optimum for that particular car."
The reasoning behind this is a long subject so I won't go into it now.
But,
if anyone can point to some evidence why the stock coils (86 - 91, not
the
earlier RX7 system) in combination with a good engine management
computer
(EC2 or otherwise) is not adequate, I'll be glad to revisit the subject.
The only reason I would consider using this CDI (or any other) is if I
were
going to use high boost (> 12" Hg.) or run at engine speeds greater than
7000 rpm, neither of which I would recommend in aircraft applications.
Still, I would not condem anyone for wanting to try CDI, after all, they
call them "experimental aircraft" for good reason. I said you would
need 3
CDIs on the assumption that the stock coils would be used. If you want
to
use one coil per plug, yes, 4 would be needed. When choosing coils,
pay
particular attention to another point made in the article. A CDI
imposes a
greater stress on the coils than an inductive setup. Choose high
quality
coils. The CDI in the article is easier on the coils than the CDIs of
old
but still wallops them pretty hard (and often!)
Tracy Crook
rws@altavista.net
www.rotaryaviation.com
Here is why I think it might be rewarding. I don't think Mazda explored
the
super lean option in the second gen cars. Perhaps we can run it even
leaner
than you have already explored. Here is some of the results of some of
Klause's
work with a multi spark CDI system. He calls it a plasma ignition system.
Paul Lamar
Klause is not lying but he is using the "Straw Dog" method of salesmanship.
Note that the chart compares his ignition to magnetos. Compared to an
aircraft magneto, ANYTHING would look good. Aircraft magnetos and their
anemic spark are the reason why aircraft plug gaps are in the range of
.017 - .019". A lean mixture doesn't have a prayer of igniting under these
conditions. Show me some comparison data to a good inductive ignition
system. If the CDI looks significantly better, I'll start producing those
things tommorrow! (not kidding)
Tracy Crook
rws@altavista.net
www.rotaryaviation.com
I don't think that data exist Tracy. This is why we call them experimental
airplanes :-) Have you forgot already? :-) Seriously the main thing
we should worry about is the engine does not quit.
Paul Lamar
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