kentb said:
But the layup of the baffle seal along the left side inlet doesn't seem right. I can under stand all the other seal as air pressure increases the seals will be pushed against the cowl sides and make a good seal, but the one next to the flywheel seems like it will just let the air out.
Anyone have a comment on this?
Kent
My expectation of this area is that there is not much leakage. The area immediately surrounding the inlet is at a low pressure due to the flowing air.
In fact, I've seen RV's with no baffle seal around the bottom and sides of the inlets. I can't claim that this is the right thing to do, but it indicates that the seal in this area may not be critical.
I spent some time early in my career optimizing air flow and cooling in electronic systems. I had the advantage of an expensive thermal imaging system that used LN2 coolant. What I discovered was that 'rules of thumb' can only take you so far. Individual systems needed detailed optimization.
Since we can't optimize the same way in our aircraft, we need to do the best job we can with installation, and then adjust using CHTs and flight testing. I added air dams on cylinders 1&3 with screws and nutplates, and I've experimented with blocking the heater duct and oil cooler with aluminum tape.
By far the biggest effect on CHTs that I found (after rejetting carb, tweaking baffle seals, optimizing air dams) was cleaning the flashings out between the spark plugs to allow better airflow in this area.
This one change dropped CHTs about 35F in cruise. Reflecting on this, it may due to actual CHT reduction, plus more cooling in the area adjacent to the CHT probes which gives an apparent CHT reduction.
So, Vern's rules of thumb:
Do the best job on baffle seals (the ramp area is especially tricky)
If CHTs are high in takeoff/climb, rejet the carb to enrichen the full throttle fuel mixture
If CHTs are high in cruise, check the cylinder flashings
If CHTs are uneven, adjust the air dams in small steps.
There are many more things that can be done and tweaked, but these are the ones that worked for me. I only wished I had cleaned the flashings first, because everything else is minor in comparison.
Vern