hlangebro
Well Known Member
I have had some cooling issues with the Sam James plenum. I do have a cowl flap, but still it was running high initially. I tried all the tricks in the book, sealed and everything. The inlet is big enough, the exit should be big enough...
The conclusion I came up with was that the plenum volume is too small. I modified the plenum by making it bigger and test flew it over the weekend. I was very gusty and I could only do a partial climb test. It seemed like cyl 1 and 2 were the same as before, but 3 dropped 7 degrees and 4 dropped 17 dregrees. I usually climb out at 115kias but this time I flew at 100kias, the highest temp, compensated for a 100F day was 403F on #2. This is ok, but it could be better. The lowest during the climb was 374 on #4. I still have some fixes to do, but it proved the concept that it needs more volume to slow down the air and to create a higher pressure differential across over the cylinders.
some initial pics of the mods...
https://scontent-b-lax.xx.fbcdn.net...0_10152397449741469_5650946820497656692_o.jpg
https://scontent-a-lax.xx.fbcdn.net...0_10152398595446469_6161538432748461015_o.jpg
The conclusion I came up with was that the plenum volume is too small. I modified the plenum by making it bigger and test flew it over the weekend. I was very gusty and I could only do a partial climb test. It seemed like cyl 1 and 2 were the same as before, but 3 dropped 7 degrees and 4 dropped 17 dregrees. I usually climb out at 115kias but this time I flew at 100kias, the highest temp, compensated for a 100F day was 403F on #2. This is ok, but it could be better. The lowest during the climb was 374 on #4. I still have some fixes to do, but it proved the concept that it needs more volume to slow down the air and to create a higher pressure differential across over the cylinders.
some initial pics of the mods...
https://scontent-b-lax.xx.fbcdn.net...0_10152397449741469_5650946820497656692_o.jpg
https://scontent-a-lax.xx.fbcdn.net...0_10152398595446469_6161538432748461015_o.jpg
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