Here are a few charts from Heinz Heislers book Advanced Engine
Tech and others. The first chart shows that; as the fuel
air ratio gets
real lean and the pressure lowers in the combustion chamber
at high altitude the voltage required to fire the plugs
goes up.
Klaus has exploited this situation to lean his engine out
at high altitude and improve the BSFC to remarkable levels
by increasing the spark voltage. He has achieved as much as
100 MPG at 130 MPH and 60 MPG at more reasonable cruising
speeds.This is a piston engine where the spark plugs are
at one end
of the fire and the piston is at the other end.
In our case we have a moving combustion chamber where the fire
travels along side the spark plugs for quite some time.
IMHO We want
the spark plugs to continue to fire for as long as the unburned
and burning mixture is still present moving past the
plugs. That takes
8.3 ms at six thousand RPM cruise RPM. See chart 2.
A capacitor discharge ignition system is very good at firing
spark plugs fouled with 100 LL but it only fires for .2
ms. Even
an inductive system (Chevy LS1 coil) or stock Mazda ignition
only fires for about .8 ms.
IMHO NO WHERE LONG ENOUGH FOR WHAT WE NEED!
IMHO we need an ignition system to fire for 8.3 ms or 300
degrees.
TEN times as long. MSD makes a multiple spark capacitor
discharge ignition system widely used by Mazda rotary
engine racers but it only works up to 3000 RPM. After
that it
is "one strong spark" says MSD. Not enough in IMHO. This
is why
I am doing a m.s.d. ignition system with several pre-charged
capacitors fired in rapid sequence by a cheap single chip
computer.I hope this is a break through in improving the
BSFC of
the rotary engine. I think it is worth a try.
Patent applied for :)
--------------------------------------------------
This is the range of rotor positions I intend repeatedly
firing the spark
plug. Mostly the leading plug (lower plug) as one does
not want to risk
igniting the mixture in the following chamber.
Paul Lamar
Good going Paul. We need the long duration. Will be very
interesting.Sure wish we access to the Mazda factory
development notes and a supplyof
the three sparkplug rotor housings the Mazda factory
built for the R26B
LeMan's engines to improve efficiency.
Steve Beckham


Steve,
Heck I would just like to be able to buy factor P-port
housings for a
reasonable price!
2 plug or 3 I don't care.
Paul,


I think the long spacing idea is a good one. The only
concern that I have
is actual
spark duration. Modern coils and CD ignition may improve
things there. At
Kawasaki
in the 2 stroke era there were many single-spark CDIs. We
found that the
super short
spark duration was a problem when lighting lean mixtures.
Kawasaki had
tried surface
gap spark plugs, which had no side wire. The business end
of the plug
looked like a little
target with the center electrode as the bullseye,a
ceramic stripe andthem
the case
of the plug outside that. the surface gap plugs didn't
work well because
they carbon
tracked easily and then there was a conductor for the
spark to jump
through. Later
the choice was a standard plug with an incredibly large
gap, around .100
inches!
Surprisingly this worked well because there was plenty of
voltage to fire
the gap, and
with the long (length) spark they were more likely to
actually hit someof
the mixture
molecules! The large gap standard plugs with single shot
CDI lasted tothe
end of the
2-cycle era. If the duration of the spark can be improved
you will have
better results
when firing the lean mixtures we want to run to improve
BSFC on the
rotary.


Bill Jepson
Bill, regarding your note about problems associated with
firing lean
mixtures with short duration CD, we experienced the same
problem withlean
mixtures and found the inductive worked much better all
round. Ourengines
were tuned for lower rpm peak power. I think the factory
used a custom
electronic CD with their LeMans engine. One of the file
reference books
shows a CD ignition in the ex-Le Mans three rotor 1986
IMSA GTO beforethey
later switched to the four rotor for GTO. But it appears
the factory was
using CD for these engines even before going to the three
sparkplugengines.But longer duration inductive system
worked better for our engines.
Steve Beckham


Steve,
As Paul and many others among our group have said, many
thanks forsharing
your wealth of experience with rotary installations.
Can't beat hands on
experience. Getting back to the CDI vs Conventional
ignition, the rotary
is a unique case because the spark plugs can't protrude
into the chamber
at all. Since the sliding seals prevent that I would
think that a plug
that presented the electrodes as close as possible would
be best. I read
that VW was experimenting with a no-side-wire plug and a
pointedprojectionon the piston to fire to. I don't know
if they ever used it inproduction.
The spark actually jumped to the piston. I thought that
this type ofsystem
would be perfect for the rotary. The plug could be closer
to the rotor
without a side wire and the long spark would be perfect
to ignite the
lean mixture. Having the plug closer would even bump the
compression a
little. Just thinking out loud but it seems like a possibility.
Bill Jepson


We always removed the spark plug washer to move the plug
closer.Works great. There are washers available from Mazda.
Skip
Skip did you use no washer or the substitute washer from
Mazda? Any
measurable difference in performance or other, such as
different carbon
patterns on rotor at disassembly?
Steve Beckham
Steve, We took the washer off. It was a drag race
application. The gain
was only measurable at the track clocks. We thought we
had a secret
performance gain, then we found that Mazda Speed offers
washers to
move the plug in or out.
Skip


Steve,
I'd like to say some more about the spark plug issue. The
spark plug
washer trick did not have any effect on charged cooled rotaries.
In fact
is was a negative effect. Don't know why that was. What did work
is we
changed from a 14mm spark plug to a 10mm spark plug and gained
some real
hp and torque. Ten to twelve hp on a single rotor. There is a serious
leak when the apex seal goes over the hole or any hole in the
rotor housing.
So the smaller the hole the better. I'd like to reduce the
Mazda. I don't
know why they don't. Just about every mfg has gone to a smaller
spark plug.
Skip
-
That is only for the trailing plug Skip.
There must have been something else going on with the Rotamax.
Paul Lamar

Hi Paul and group,

Paul do you have a good picture of a housing with 3 spark plugs
hole/location.Thank you

Marc Joseph

It's on the front page of the web site on the four rotor.
There are two blue spark plug boots and one black
spark plug boot just above it. The black boot is the third
spark plug. Worth about 2% on power and 2% lower BSFC.
Hardly worth the effort.

Paul Lamar