Colin,
Indeed, my KR2 has got a very special electronic ignition, which I call
"solid state". And believe me, this has absolutely nothing to do with
standard electronic ignition as you know it.
Let me try and explain.
It is a very simple set of components that "reads" the ignition timing
with a magnetic sensor, and triggers the ignition coils with a relay.
Period. So, it has got absolutely no software in it, in any form
whatsoever. It is only a handful of plain and simple electronic components
that react to a magnetic impulse.
How does it work?
There is a tiny steel mass clamped to the crankshaft. Around the
crankshaft, you have small magnetic sensors (roughly half the size of a
matchbox) that react when that steel mass passes by (for one of my two
ignition systems, the steel mass is a 4mm grubscrew that protrudes by
about 3mm... so we are talking very small mass, here!). As for the exact
operation principle, I believe the magnetic pick-ups create a very small
magnetic field, and react when that field is disturbed, although I am not
too sure about that. Then, the magnetic pick-up triggers a relay, which in
turn triggers an ignition coil, which in turn fires two spark plugs (the
coil has got two output wires).
Now, the idea is that each of these magnetic pick-ups takes care of two
cylinders. I mean, it triggers two cylinders at the same time each time
the magnetic mass passes by, and therefore, once per revolution f the
crankshaft. These would be the two cylinders that are at opposite times of
the 4-stroke cycle, and therefore, offset by one full revolution of the
crankshaft. So, for a given cylinder, one turn out of two, the system will
fire the cylinder at the correct timing. The next turn, the cylinder will
be fired at the wrong timing, but that will be during the exhaust phase,
so this will have no effect whatsoever.
If your engine is a two cylinders, a single pick-up will do. If your
engine is a four cylinder, then you will need two pick-ups, offset by
180°. A six cylinders will take three pick-ups, offset by 120°. And so
on...
It doesn't get more reliable and more simple than that.
So, what's the beauty of the system? Well, I see many.
- It runs on the crankshaft, not the camshaft, so you don't have to worry
about gears, or build mechanical interfaces
- It runs from the outside of the engine, so no ports
- It has no mechanical contact whatsoever, so no friction, no breakage, no
slippage, no nothing;
- It is set once and for all. Bolted in place, zero maintenance except for
checking the condition of the electrical contacts.
- It has an extremely low parts count, and very few failure modes.
- It costs peanuts, because it comes straight out motorcycle junkyards
And here comes the one-and-only drawback:
- It needs electricity to run, so you have to make sure you dont' lose
both your alternator and your battery.
The only sophistication in the system is the advance-retard mechanism.
This system will give you less advance at engine start, and a constant
advance thereafter. How does it work? Very simple again. The steel mass
can move for a certain angle ( it has a mechanical angular travel), and is
held in the "start" position (low advance) by a spring. As soon as the
engine turns, the strength of the spring is overcome by the centrifugal
force of the rotating crankshaft, and the steel mass moves towards its
normal position (ful advance) and stays there for as long as the engine
runs.
Let me add that I did not design that system. It came with the engine when
I bought the plane. But I was so happy with it that when I upgraded the
engine (you see, I became power hungry), I replicated it, and introduced
more redundancy (two spark plugs per cylinder).
As far as I am concerned, the track record is 400 fligh hours on the
previous engine without a glitch, and about 3 flight hours with the new
engine, still without a glitch.
So, I'm a believer.
Serge Vidal
KR2 "Kilimanjaro Cloud"
Paris, France
"AVLEC" <av...@telkomsa.net>
Envoyé par : krnet-boun...@mylist.net
26/12/2005 16:48
Veuillez répondre à KRnet
Remis le : 26/12/2005 20:07
Pour : <brokerpilot9...@earthlink.net>, "KRnet" <kr...@mylist.net>
cc : (ccc : Serge VIDAL/DNSA/SAGEM)
Objet : Re: KR> Corvair ignition
Colin, if you had the oppertunity to see the system in Serg's plane, you
would see how simple it really is. You literally just remove it from the
donor motorcycle and install it on the motor of your choice( any motor,
any
number of cylinders. By just seperating the power supply to the seperate
ignitions, you end up with a totally seperate ignition system for every
two
cylinders (for odd number of cylinders just leave off one of the plug
leads). In the case of a VW I doubt that you would be able to stay in the
air with two cylinders but with the corvair 3100 that I should be getting
soon, if one of the three independant ignitions should fail I would be
left
with the equivalent of an out of tune type IV VW to take me home! That
system in Serg's
plane has done probably in the region of 600 hrs + without as much as a
hickup. It also needs zero maintenance except to check the electrical
connections now and then.Thats reliability in my book! It even has
centrifugal advance!! It
doesn't get much simpler than that.
Regards
Dene Collett
KR2SRT builder
South africa
Whisper assembler
See: www.whisperaircraft.com
mailto: av...@telkomsa.net
----- Original Message -----
From: "Colin Rainey" <brokerpilot9...@earthlink.net>
To: <kr...@mylist.net>
Sent: Sunday, December 25, 2005 02:42
Subject: KR> Corvair ignition
> Dene
> If you are going to go to that much trouble with the ignition system,
when
there is very little faults with the original system, and a Petronics
electronic update from either Summit Racing or Clark's Corvairs will
eliminate any other normal failure. Modern electronic ignition systems do
not just "quit" as in days gone past, if it is a quality system.
>
> You can use an external GM crank sensor, or cam sensor, and install a 3
tiered trigger system, then have 3 GM late model capacitive coils which is
what they use on the Aerovee VW engine, and trigger each one individually,
hooked up to the 2 companion cylinders so that one is firing on the
exhaust
stroke while the other is firing on compression stroke. The only problem
with that type of simple system is it is fixed timing, unless you figure
out
how to incorporate an ignition module. Since caps, rotors, and normal use
distributor shafts don't fail in use suddenly, but rather deteriorate
slowly
over time, a pilot will notice they are wearing out before failure.
Therefore, that is ALOT of engineering to go through for very little pay
off, and will definitely hurt peak performance.
>
> Most sudden failures of ignition systems today are actually systems that
have been ignored, and driven with for some time, until the vehicle will
not
operate any more. From my observation here, KR pilots are ALOT more
conscientious and will abort takeoffs and determine the problem, instead
of
flying anyway, and "worry about it later" attitude.
>
> If it makes a difference I will be flying behind a single ignition
system,
of electronic type, and vacuum advance distributor, and expect with
regular
maintenance and attention to have the same reliability as I have in my
driveway...
>
> Merry Christmas from our family to yours, including our "new baby boy"
Zeus, a 2 pound miniature Doberman/rat terrier mix.
>
> Colin Rainey
> brokerpilot9...@earthlink.net
> _______________________________________
> Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp
> to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net
> please see other KRnet info at http://www.krnet.org/info.html
>
_______________________________________
Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp
to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net
please see other KRnet info at http://www.krnet.org/info.html
