Message text written by "Bob.Harrison"
>The complete absence of a myriad of coolant pipes to leak and indeed so
be likely to swamp the intake breathing air supply of the engine must be a
huge benefit.<
Whilst liquid coolant adds complexity it has advantages over air cooling
particularly in the case of overall efficiiency. Liquid coolant controls
cylinder head temperature more accurately allowing leaner mixtures to be
used resulting in lower specific fuel consumption. This was proved very
dramatically on the round the world Voyager aircraft which only completed
its circumnavigation because of the specially liquid coolant modified
Lycoming which improved the fuel consumption by about 10% over the
equivalent air cooled engine. Even Porsche (a long time advocate of air
cooled engines) has finally moved to liquid cooling. Their motivation might
have been for emission reasons but this is yet another reason to go the
liquid cooled route.
The case to which you refer was unfortunate and hopefully not likely to be
repeated due to the recommendations that have been made (ie using at least
80% glycol and ensuring that the overflow bottle has a sufficiently large
vent). I think it was also unusual to get leaking coolant swamping the
engine particularly as the carburettor air is now drawn from outside the
cowl. With all the hours achieved on Rotax powered Europas (and other
aircraft for that matter) it would be reasonable to think that this was a
one-off.
>It must be expected that the aft cylinders will obviously run hotter than
those forward so the simple remedy is to feed some dedicated cooling air
direct to No's 5 and 6 .If your installation actually need the temperatures
reducing<
Not such a problem with liquid cooling.
Nigel Charles
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