Thanks, Mark. 28 degrees is the figure I remembered from the original
builder, who had built the engine at sea level (Port Elisabeth, South
Africa). Although that was with the 2.0 liter, and the new one is a 2.4.
It is currently set at 25 degrees, which was fine for Johannesburg.
Something funny, though. My engine has solid state dual electronic
ignition, taken from 1980's Japanese motorcycles. This type of ignition
has sort of magnetic pickups, that are rigged to the crankshaft. There are
two pickups, opposed by 180 degree; each one fires once every crankshaft
revolution, and triggers one coil; the coil has two output wires, and
fires the two opposed cylinders simultaneously
In order to be able to start the engine, the system also has a
mechanical, centrifugal advance / retard compensation mechanism. Once the
engine turns, the centrifugal force fights against a spring, and the
advance comes back to normal. I love that ignition system, because it is
so reliable (solid state), so simple to install, so simple to set (just
turn the support plate, and so affordable ( scrap from old motorcycles
comes very, very cheap).
The only construction difficulty was to make the ignition dual redundant
(which is not really required, anyway). For that, a second set of magnetic
pickups is installed. In my case, this second set is installed at the
propeller end of the crankshaft. A mere grubscrew is used as the magnetic
mass.
Now, when we installed the new engine in Johannesburg, we took great care
to synchronize the front and rear ignition as well as possible. The result
was great. You could hardly hear the difference between front and rear
ignition. So, when I started the engine here in France, I was puzzled to
see that there now was a big difference in noise and RPM. I thought that,
somehow, one ignition system had moved.
Until I realized that one ignition uses small diameter spark plugs. This
did not make a noticeable difference before, because the mixture was very
lean...
Serge Vidal
KR2 ZS-WEC
Paris, France
"Mark Langford" <n5...@hiwaay.net>
Envoyé par : krnet-boun...@mylist.net
2005-01-07 03:42
Veuillez répondre à KRnet
Remis le : 2005-01-07 03:41
Pour : "KRnet" <kr...@mylist.net>
cc : (ccc : Serge VIDAL/DNSA/SAGEM)
Objet : Re: KR> Timing for a VW engine
> I have a 2.4 liter VW engine, Great Plains type. I have to re-time my
> custom-made electronic ignition. The reason is that I set up the engine
> first time in Johannesburg, altitude 5300', but the aircraft is now in
> Orleans, altitude 300' or so.
I haven't seen an answer to this, so mine may be all you get. I'd set it
to
28 degrees of total advance at wide open throttle, or above the RPM at
which
it stops advancing.
Mark Langford, Huntsville, Alabama
see KR2S project N56ML at http://home.hiwaay.net/~langford
email to N56ML "at" hiwaay.net
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