503 Engine Guage Installation

jfranklin

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Apr 27, 2012
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Location
Lakewood
Does anyone know if the Rotax 503 DCSI came with the gray wire for the engine rpm output? Mine does not seem to have one. My MGL E-3 Engine Monitor installation instructions say that the engine rpm input needs to connect to this gray wire.
 
Got the answer

Got the answer

Found the answer on the Rotax Owners Forum. Here it is for those who are interested.

I could be wrong here, but I don't think the older single ignition breaker point systems had the grey wire. If you have breaker points rather than the newer solid state ignition, the MGL tach can be hooked up. I believe you can hook the tach wire to the wire between the coil and the breaker points. This will pick up the firing pulse. Since the rotax fires at the top and the bottom of the stroke, you would have to program the tach so that two pulses equals one RPM. The MGL is programmable to work with just about any combination of pulses. Basically, you would be hooking it up like an older automobile tach. If you go to the MGL website, I'm pretty sure they have schematics showing how to wire the tach to a breaker point system.
 
Jim,
I am don't know about other systems, I can only speak about mine.

Mine is as well a DCSI but with electronic ignition.
My engine only has the 2 yellow AC output wires and one brown ignition kill wire.
When researching the wiring, I discovered that mine is not a Ducatti ignition, but instead it is a Nippon-Denso.
This system also does not have the Grey wire tach output...
I think I am going use a coiled pick up wire around one of the spark plug wires as my tach signal.
It should work fine.....
If anyone knows of a different way I can do this, let me know....
d
 
You could also use the signal from the yellow lighting coil output wires to derive a tach signal. It would take some experimentation, but I believe you'd have to pick off the signal between the alternator and the rectifier/regulator, rectify the sample through its own diode, and probably run it through a limiter to clamp its maximum voltage to the limits of the tach.

You'd also have to determine how many poles the alternator had, and use that as a divide-by number in programming the tach.

If you used a full-wave rectifier in the tach sample, you'd get twice the number of pulses per-revolution as the number of alternator poles.
 
503 engine guage

503 engine guage

you can use a lighting coil tach on any rotax engine but if you have a ducatti system you do need a tach for ducatti ignition or it will read higher than it should. the bosch point and the nippondenso cdi both use the same tach, it don't need a regulator to work, with the bosch point system you can use the yellow wires or the green wires but you should stay away from a breaker point type tach because while they work ok they can fail and short out your ignition and you get to practice a dead stick landing for real.

Norm
 
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