I've been doing lots of reading on old threads related to addressing cooling problems. I'm a bit confused by two seemingly contrary mods people do to help with CHT cooling. The lower cowl exhaust tunnel as it comes from vans is cut off squarely in-line with the firewall. Some people suggest cutting the edge of this tunnel back (towards the nose) to open up the exit area. At least one pic I saw showed the cut angled back, so instead of being parallel to the firewall the is cut angles down and forward (so that the bottom of the tunnel is forward of the firewall).
Others talk about extending this exit tunnel back behind the firewall under the airplane, so smooth out the exit airflow - the theory being that air spilling down the firewall is getting in the way.
Am I understandign these two options correctly? Cutting the tunnel is certainly a *much* easier mod and can be done incrementally. It also provides more room for the exhaust pipes. I don't care if I lose a knot's worth of speed... is there any otehr reason not to cut this exhaust tunnel on the lower cowl a bit shorter (so it terminates forward of the firewall)?
Others talk about extending this exit tunnel back behind the firewall under the airplane, so smooth out the exit airflow - the theory being that air spilling down the firewall is getting in the way.
Am I understandign these two options correctly? Cutting the tunnel is certainly a *much* easier mod and can be done incrementally. It also provides more room for the exhaust pipes. I don't care if I lose a knot's worth of speed... is there any otehr reason not to cut this exhaust tunnel on the lower cowl a bit shorter (so it terminates forward of the firewall)?
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