Hot Air

[Bryan Cotton]

[Skippydiesel]

Still hoping for someone , with experince, to comment on the advisability/effectiveness of exit air vents in top/rear or side/rear of cowling.

Where have you placed your vents & why?
How big are your vents? & did you start with smaller & incrementally progress to what you have now?
How effective are they? ie what were your under cowl temps before and now after modification?
Any other advice/observations

NOTE:

This is for INFLIGHT not parked.
My engine is a Rotax 912 - carburettor air inlets top of engine, near firewall (sucking hot air)

[Skippydiesel]

Have decided, there being no responses to my enquiry/question, discretion is the better part of valour.

I am not going to cut any holes in my cowling, for the moment. Instead I am going to ;

Fit a Gates PN 28091, automotive concertina aluminium 40mm hot air pipe/duct, on each side of the engine, to take (cool) ambient air from each front air scoop, back to the carburettor cone filters. This will require no modifications to the cowling/engine/airframe.

If the above has no beneficial effect, I plan to use the same aluminium pipe running from the vicinity of each carburettor, down to the cowling exit air hole. The hope being that a venturi effect may "suck" the hot air from the upper firewall area, which will then be replaced by cooler air. Again no modifications required.

If there is no substantial reduction in undercowl temperatures, I will go back to the idea of cutting a small( 20mm) exit air hole above each carburettor. If there some reduction in air temperature - I will progressively increase the hole size, up to a maximum of 75 x 50mm rectangle. This is the size of readily available hardware store, louvred aluminium vents.