Thinking about all the air leaks that typically show up in the IO550 Legacy cowl. A full size plenum has been accomplished by some folks.  What about a plenum that went from the inlet and simply exited onto the three cylinder heads on that side?  It would be smaller, maybe easier to build, lighter.   You could use a silicone seal where it would fit on the barrel to keep a tight fit and wires could be kept away I believe.

How much better would the cooling be and would the lack of air to the rest of the crankcase or cylinder bases cause problems?   Still need to route some bleed to the accessories and oil cooler which we do already but I'm talking about ducting the inlet straight to the head and avoiding most of the leakage points and perhaps achieving better overall cooling.

Second:  Why does the alternator duct exit below the engine?  The exit air may be warm but certainly less than CHT so why not duct the alternator exit back into the upper deck and regain the pressure loss that goes straight through the alternator and bypasses the cylinder fins?

Thoughts?

Paul
Legacy