A month or so ago I installed a CGR30P in my cub and during my inaugural flight with an OAT of 50 degrees, I was a little dismayed that my #4 CHT was 400 degrees in cruise at 2400 rpm, 8.6gpm (50 ROP), at around 700 msl. This engine has around 1150 smoh and all compressions a few weeks prior at annual were all 77 and better.
I ran down the rabbit hole on this and wanted to share what I found and what I ended up doing. After talking to my A&P and a few others, I decided to do the following in chronological order with the supervision and assistance of an A&P.
1. I tightened up my baffling, installed new baffle material where needed, silicone caulked everything, and made all baffling as tight as possible. I also changed out my intake gaskets and hoses to make sure I didn’t have any minor intake leaks. Both gaskets and hoses were old anyway. By doing this, I reduced my #4 cht by 10 to 12 degrees.
2. I then began down the ramp path and built multiple iterations (about 10 altogether) from what I found on here and from talking to others. I found the best ramp design was at an angle that met the midway point of the cylinder of #1 and #2. #1 ramp is only half the cylinder and #2 is the entire length of the cylinder with a “fence” on the inside. I drilled holes for front cylinder cooling. After adding ramps, I gained an additional 10 to 15 degrees of cooling on #4. So I’m now down to about 25 degrees cooler.
3. I then decided to add a lower cowl lip. I bought one from Charlie Center and installed. I found zero decrease in CHTs by adding a lower cowl lip.
4. Charlie Center suggested that I tape off around the front oil cooler to remove air flow from lower cowl. I did some prelim testing by just taping off around the oil cooler with metal tape. I found this gave me another 5 degrees of cooling. I will be fabricating up a permanent baffle for around the oil cooler in the future.
As a whole, I reduced my #4 CHT from 400 down to 367 to 372 degrees at cruise running at 2400 rpm at 8.3 to 8.6gpm (ROP).
I will post some pics here shortly. Hopefully this helps others, as the previous threads on this site really helped me visualize the ramps.
I ran down the rabbit hole on this and wanted to share what I found and what I ended up doing. After talking to my A&P and a few others, I decided to do the following in chronological order with the supervision and assistance of an A&P.
1. I tightened up my baffling, installed new baffle material where needed, silicone caulked everything, and made all baffling as tight as possible. I also changed out my intake gaskets and hoses to make sure I didn’t have any minor intake leaks. Both gaskets and hoses were old anyway. By doing this, I reduced my #4 cht by 10 to 12 degrees.
2. I then began down the ramp path and built multiple iterations (about 10 altogether) from what I found on here and from talking to others. I found the best ramp design was at an angle that met the midway point of the cylinder of #1 and #2. #1 ramp is only half the cylinder and #2 is the entire length of the cylinder with a “fence” on the inside. I drilled holes for front cylinder cooling. After adding ramps, I gained an additional 10 to 15 degrees of cooling on #4. So I’m now down to about 25 degrees cooler.
3. I then decided to add a lower cowl lip. I bought one from Charlie Center and installed. I found zero decrease in CHTs by adding a lower cowl lip.
4. Charlie Center suggested that I tape off around the front oil cooler to remove air flow from lower cowl. I did some prelim testing by just taping off around the oil cooler with metal tape. I found this gave me another 5 degrees of cooling. I will be fabricating up a permanent baffle for around the oil cooler in the future.
As a whole, I reduced my #4 CHT from 400 down to 367 to 372 degrees at cruise running at 2400 rpm at 8.3 to 8.6gpm (ROP).
I will post some pics here shortly. Hopefully this helps others, as the previous threads on this site really helped me visualize the ramps.
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