Careful, long and complicated story. Dive in it on your own risk.
The general understanding, or at least my limited knowledge, seems to be that
the
turbo only starts charging over 100%. However, i had a problem earlier in the
week. Outside temperature was -15 C and the plane had been washed in the warm
workshop. Started the engine after about 10 minutes outside, and waited for
the oil to be 50 C. All indications were normal. Then i put in more power, and
noticed that the second half of the throttle control did not do anything. The
engine would not run faster then 35400-3600 rpm. Stopped the engine and took
the cowlings of to check that the throttle levers on the carbs were operational.
They were.
Back in the workshop i checked about everything i could think of. Found nothing.
Noticed that the TCU opens the waste until half throttle, and closes it again
when moving the lever to full throttle. This on a non running engine. Had a
look at the log in the TCU and noticed that the waste gate had been doing the
same with the engine running. Yesterday took the plane out again, and had
another
run. OAT -5C. Now full revs could be reached, problem gone.
The TCU log now showed up to full waste gate opening, and opening already
started
at 3600 rpm. Interesting was, that closing the throttle a bit from high revs,
opens the waste-gate further. Have a look at the attached log. I assume now
that the intake side of the turbo had been frozen, so that the turbo would not
run during the first attempts.
Just a condensed, frozen droplet on the impeller is probably enough for that.
During
the heat up run, air at very low temperatures could keep the ice there,
even if the other side of the turbo is hot.
I also assume that if the pressure in the air box not rises if the waste gate
opens,
the TCU starts closing it again. Too much assumptions probably :-)
Comments please!
Regards,
Jos Okhuijsen
Visit - www.EuropaOwners.org
Attachments:
http://www.europaowners.org//zfiles/02081620_135.txt
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