Paul 5r4
Well Known Member
Hi Friends...
History. I've been flying the RV 7A for two years. On climb out the number two CHT would always hit 400 before I reached 1000 feet! I had learned to live with it doing a kind of step climb thing.... level off/thottle back/ cool/then climb some more or enter a shallow cruise climb. I had tried the usual suggestions tight baffles etc. without success. Here's what worked and worked GREAT with several pics.
You MUST/HAVE TO/WITHOUT FAIL.... get airflow beneath the forward part of the number two cylinder. I cut a hole then built a channel for air to get beneath that cylinder. Success! Now I can climb to around 4000 feet before I hit the upper 390? range. Around 4000 feet, the temperature levels off then starts dropping because of the cooler OAT's. Having such great success with the number two cylinder I decided to attack the number three CHT the same way. It didn't get quite as hot as number two but it was pretty close. Yesterday just for fun I took off and climbed at 120 kts all the way to 10,500. Incidentally, I was heading into the wind during by climb to 10,500 and my groundspeed had dropped to 99 mph! When I turned around to head home I was doing 240 mph across the ground! Wish I could do that every time I fly!
Straight up... If a rather sloppy RTV application offends you, better bail here.
Otherwise, here are the pis of the CHT fix. (I had reached the point that I was getting ready to start cutting the cowl to increase exit airflow. Happy now I had not done that yet!!!)
You can visualize the airflow to the fins
Number two cylinder from the bottom of the baffle
Behind number three cylinder. Note minimal clearance for airflow
Hole cut. I almost cut the wrong section of the baffle
From the back
Front/inside of baffle
Looking down through newly created airflow channel
From the back behind number three cylinder
History. I've been flying the RV 7A for two years. On climb out the number two CHT would always hit 400 before I reached 1000 feet! I had learned to live with it doing a kind of step climb thing.... level off/thottle back/ cool/then climb some more or enter a shallow cruise climb. I had tried the usual suggestions tight baffles etc. without success. Here's what worked and worked GREAT with several pics.
You MUST/HAVE TO/WITHOUT FAIL.... get airflow beneath the forward part of the number two cylinder. I cut a hole then built a channel for air to get beneath that cylinder. Success! Now I can climb to around 4000 feet before I hit the upper 390? range. Around 4000 feet, the temperature levels off then starts dropping because of the cooler OAT's. Having such great success with the number two cylinder I decided to attack the number three CHT the same way. It didn't get quite as hot as number two but it was pretty close. Yesterday just for fun I took off and climbed at 120 kts all the way to 10,500. Incidentally, I was heading into the wind during by climb to 10,500 and my groundspeed had dropped to 99 mph! When I turned around to head home I was doing 240 mph across the ground! Wish I could do that every time I fly!
Straight up... If a rather sloppy RTV application offends you, better bail here.
Otherwise, here are the pis of the CHT fix. (I had reached the point that I was getting ready to start cutting the cowl to increase exit airflow. Happy now I had not done that yet!!!)
You can visualize the airflow to the fins
Number two cylinder from the bottom of the baffle
Behind number three cylinder. Note minimal clearance for airflow
Hole cut. I almost cut the wrong section of the baffle
From the back
Front/inside of baffle
Looking down through newly created airflow channel
From the back behind number three cylinder
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