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Richard Carlisle · Guest

My EGT's are all of a sudden not behaving. Maybe someone here has had the
same problem. Here are the details...

I changed props from a 66" PF A model 3 blade to a 70" PF F model 2 blade.
I set the prop for 6300 on the ground. This gave me 6600 in the air but the
EGT's went to 1300.

I landed and reset the prop for 6200 in the air. The EGT's were better but
still a whisker hot. One was trying to creep past 1200.

I landed and raised the needles by one notch. When I tried it again, there
was no difference in EGT. During that flight, I noticed the RPM drop 150
RMP. I added some throttle to bring it back to 5500 and 5 seconds later,
the rpm went to 5650. I reduced throttle to bring it back to 5500 and it
was fine for the next 15 minutes until landing. EGT's were about 1175-1200
during that flight.

I took off again and just after takeoff, the rpm went from 6200 to 6350. I
throttled back to 6000 and climbed to 2000ASL then throttled back to 5500.
This time the EGT's were 1150. They did not try to creep up towards 1200 as
they did before.

None of this was happening until I started fooling with the carbs. Jetting
is as Rotax specs it for a stock 582 and the engine runs good. Actually, it
ran better before I raised the needles, but the EGT's were too high. After
raising the needles, the engine seemed to run rougher, but they are in slot
#3 which is where Rotax spec say they should be.

Is it possible that the EGT probes were drilled in the wrong location and
the EGT numbers I'm seeing are inaccurate? Does anyone know the exact
measurement for the probes from the head? Any other ideas?

I also noticed a .7GPH decrease in fuel consumption at the same speed and
RPM by going to the new prop. I think this is because the new prop is more
efficient than the old one. This seems to have something to do with the
EGT's. The more pitch I add to the prop, the better the EGT's are.

I've always been pretty good at tuning these things, but this one has me
baffled.

Thanks for any insight.....Ross

bob evinger · Guest

My initial question would be what do the plugs look like? I've had probes
that were indicating that I was melting the pistons only to find out that
the probes were the problem. If the plugs look like they are running the
right mixture it may just be the gauges. Could be that you were running a
little richer than you thought before, maybe.

bob

On Tue, 28 Oct 2003, Richard Carlisle wrote:

Jim Williamson · Guest