In a message dated 6/5/2003 5:21:56 AM Pacific Standard Time,
andy@europa-aircraft.com writes:
>
> I should just qualify Mark's statement about the factory demonstrator having
> a 'similar problem' with regard to mag drops. The 914 engined demonstrator
> exhibits a larger mag drop on one mag relative to the other but both are
> within limits (300 rpm and 150 rpm difference). This is normal on the 914 as
one
> mag runs all upper plugs and the other all the lower plugs. Due to the
> geometry of the cylinders, when one of the plugs ignites the mixture, it
> results
> in a different flame path to that of the other, hence the difference in mag
> drop.
>
> One of the factors that should not be ignored is to check the balance of the
> carburettors. A mis-balance could result in one bank of cylinders or even
> one cylinder causing the problem. We shall investigate this on Mark's engine
> before anything else.
>
My carbs were off balance by quite a bit - my cable end securing nut came
loose (non Rotax Europa supplied) and after I did that, the engine ran much
smoother - except the mag drop and missing are even worse (I think it is
progressing down a bad path all by itself). I was getting a difference between
#3 and #4
at 2000 RPM of about 175 degrees - also a difference between 1 and 2. That
has evened out, but I am still getting very rough running on single mag
operation.
The timing is also different on the 914 between A and B. It is 22 and 26
degrees.
Dave
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