ackselle
Member
I know it's been discussed at length, and I followed most of the posts, so I thought it was worth the time to post my results and resolution.
I have the following configuration:
- RV-7A
- Lycoming O-360A1A
- 74" blended airfoil Hartzell CS Propeller
- Standard Van's cowl
- RV Bits Plenum
Problem: during climb out, or long climbs, CHTs climbed too quickly. I wanted more effective cylinder head cooling. Oil temperatures were good, and it was mostly cylinders 2 and 3 causing concern.
Solution(s):
1) my first "solution" was to completely seal off any spaces/holes under the plenum to ensure maximum pressure on the top side of the cylinders - no noticeable effect on CHTs vs my original installation
2) my next attempt was to increase the space behind #3 cylinder with a washer as recommended by many on this forum - this was quite effective in keeping CHTs below 420F during climbs, but there was still much room for improvement
3) my 3rd attempt was to smooth the plenum airflow by smoothing the transition from the Vans cowl opening...I used duct tape to create a smooth flow into the plenum - no noticeable difference in CHT cooling or airspeed...not effective in my configuration (although duct tape on the front of your airplane is obvious enough to cause good conversation at the fuel pump!!!)
4) installed 1 x AntiSplat cowl flap (bottom left side of cowl) - better (CHTs now below 410F on climb)....but still much room for improvement
5) installed 2nd AntiSplat cowl flap (bottom right side of cowl) - CHT cooling issue is resolved for now. On climb out or long climbs, with OAT @ 85F, CHTs do not rise above 390F.
I installed both cowl flaps on one switch which works very well. I replaced the very small switch provided by AntiSplat with a full size double pole-center off momentary switch so I can partially open the cowl flap as needed.
The AntiSplat switch worked just fine, I just wanted a momentary switch AND something a little bigger (you'll understand if you tried to solder the switch provided with the cowl flap kit). I used one indicator light (provided in the kit) for both flaps, so the light blinks "on" when both cowl flaps are completely open.
With both cowl flaps installed, I am penalized about 3 mph cruise speed IF I leave the flaps open....but I don't need them open during cruise as CHTs are not an issue with full airflow. With the flaps closed...cruise speeds are back to normal.
So...thanks to all for your advice and discussion. This forum continues to help me enjoy what is already a phenomenal little airplane.
Cheers,
Ackselle
I have the following configuration:
- RV-7A
- Lycoming O-360A1A
- 74" blended airfoil Hartzell CS Propeller
- Standard Van's cowl
- RV Bits Plenum
Problem: during climb out, or long climbs, CHTs climbed too quickly. I wanted more effective cylinder head cooling. Oil temperatures were good, and it was mostly cylinders 2 and 3 causing concern.
Solution(s):
1) my first "solution" was to completely seal off any spaces/holes under the plenum to ensure maximum pressure on the top side of the cylinders - no noticeable effect on CHTs vs my original installation
2) my next attempt was to increase the space behind #3 cylinder with a washer as recommended by many on this forum - this was quite effective in keeping CHTs below 420F during climbs, but there was still much room for improvement
3) my 3rd attempt was to smooth the plenum airflow by smoothing the transition from the Vans cowl opening...I used duct tape to create a smooth flow into the plenum - no noticeable difference in CHT cooling or airspeed...not effective in my configuration (although duct tape on the front of your airplane is obvious enough to cause good conversation at the fuel pump!!!)
4) installed 1 x AntiSplat cowl flap (bottom left side of cowl) - better (CHTs now below 410F on climb)....but still much room for improvement
5) installed 2nd AntiSplat cowl flap (bottom right side of cowl) - CHT cooling issue is resolved for now. On climb out or long climbs, with OAT @ 85F, CHTs do not rise above 390F.
I installed both cowl flaps on one switch which works very well. I replaced the very small switch provided by AntiSplat with a full size double pole-center off momentary switch so I can partially open the cowl flap as needed.
The AntiSplat switch worked just fine, I just wanted a momentary switch AND something a little bigger (you'll understand if you tried to solder the switch provided with the cowl flap kit). I used one indicator light (provided in the kit) for both flaps, so the light blinks "on" when both cowl flaps are completely open.
With both cowl flaps installed, I am penalized about 3 mph cruise speed IF I leave the flaps open....but I don't need them open during cruise as CHTs are not an issue with full airflow. With the flaps closed...cruise speeds are back to normal.
So...thanks to all for your advice and discussion. This forum continues to help me enjoy what is already a phenomenal little airplane.
Cheers,
Ackselle
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