Thanks Peter for your pearls of wisdom (and Roger Mills).
I had been thinking of incorporating Jon Tye's lower cowling ducts (G-PTYE)
to alleviate this problem and have now decided to do so (correction, already
done). It consists of a large vertical vent (like a back to front NACA)
about 12 inches behind each radiator to draw hot air out of the front end of
the engine compartment. This in turn should reduce the under cowling
pressure sufficiently to allow my cold air inlet scoop to function.
Another common mod is to use spacers about 1cm thick between the fuselage
and the base of the lower cowling to increase the gap at the bottom. It adds
quite a considerable extra area for extraction. The factory Europas also use
B&Q alloy door vents in the area beneath the silencer box - which also
prevents the cowling from getting burned (radiation from the silencer box)
Jons reckons the ducts are very worthwhile. I believe Graham Singleton used
a similar arrangement (but then he moved the radiators too)
The only drawback may be that the cockpit NACA vents could draw in warm air
instead of cold (OK in the winter maybe).
Has anyone else used this mod (Jon's that is). Incidentally it is a very
easy mod to do and only takes a day to complete - less if you use polyester
resin (which the engine cowlings are made of unlike the rest of the a/c).
One last thing - the reason I did not use the factory (or anyone elses)
plenum box is because I have an early 912 engine which has a large (9x6x4
ins) box containing the ignition coils which has to be squeezed into the
engine compartment as well as everything else.
----- Original Message -----
From: "Peter M. Davis" <pdavis10@compuserve.com>
Subject: Europa mods
Hi Carl,
As I read you E-mail, your inlet scoop has no plenum chamber. As I
undestand things, any cooling problems that have arisen with the Europa
seem to have been caused, not by lack of inlet area for the radiators, but
by lack of outlet area as the under-cowl area achieves a positive pressure.
I have done the cold air plenum mod. and one of my mental queries was 'will
this affect the cooling as pre-mod the carbs were taking quite a bit of air
out from under the cowels?'
As things have turned out, I have not noticed much difference, although I
did not do enough flying last summer to be able to make a realistic
assessment.
However, if you are introducing air into the undercowl area without any
control, in the form of a plenum chamber which will prevent the air from
adding to the under-cowl pressure, then you could exaserbate any cooling
problems.
Just a thought from a totally unqualified guy.
Regards,
Peter
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