Looking for some guidance from the experts in this area.
I recently built a cowl exit fairing for my RV-6A (IO-320). I followed the general design of Larry's sub-cowl with some of my ideas. I also did some attempts at cleaning up the lip at the exit, but need more smoothing there. This is tough with the A model. By design, I shrunk the size of the exit. I would estimate that I reduced the exit area by about 15-20%
My baffling is in pretty good shape, with the exception of the inter-cylinder baffles, which could benefit from a bit more sealing. There is a lot of RTV sealing openings.
Prior to this cowling, I would see about 380 -390 in later stages of climb. This is mostly due to me not willing to run more than 100 ROP and that my EI is ramping up the advance as the MAP goes down. Initial climb CHT's are lower (more ROP and only 25*) and it ratchets up until I level off. Cruise temps were around 360-370 (10-20* LOP @10-12K DA).
The new exit fairing picked up around 4+ knots (still testing), which is great. However, my climb temps are getting to the 410-415 range and cruise temps are 380-390. Oil temps also higher now, but not significant (max 210) and only in the climbs. I tried a climb at a straight 25* and that reduced temps some, but not a lot.
My initial thinking was to add a cowl flap to get the flow back during climbs. However, I am not sure how I feel about cruise CHT's at 380-390.
I also notice an imbalance in temps. 1-3 used to be pretty close, with #4 10* or so higher. Now, 1&3 are 20 cooler in cruise than #3 and #4 is another 15* on top of that. I am wondering if this is related to the oil cooler stealing the air pressure or flow from that side.
My question is how to best look for a solution. I really want to make this work, as I like the free speed. I don't want to address the cruise heat with retarded timing, as that would give back the entire gain and then some. I am working on a new solution that would let me switch between two ignitions tables PLUS a 25* fixed setting to help with climb temps. Can someone point me to some good suggestions on how to better address baffling pressure loss? I have read quite a bit here on the subject and am convinced that it can be done. I just don't know what is sub-optimal on my setup.
The only openings in the baffle are a 1.25" feed for cabin heat and the baffle mounted oil cooler.
Thanks in advance for any guidance you can provide.
Larry
I recently built a cowl exit fairing for my RV-6A (IO-320). I followed the general design of Larry's sub-cowl with some of my ideas. I also did some attempts at cleaning up the lip at the exit, but need more smoothing there. This is tough with the A model. By design, I shrunk the size of the exit. I would estimate that I reduced the exit area by about 15-20%
My baffling is in pretty good shape, with the exception of the inter-cylinder baffles, which could benefit from a bit more sealing. There is a lot of RTV sealing openings.
Prior to this cowling, I would see about 380 -390 in later stages of climb. This is mostly due to me not willing to run more than 100 ROP and that my EI is ramping up the advance as the MAP goes down. Initial climb CHT's are lower (more ROP and only 25*) and it ratchets up until I level off. Cruise temps were around 360-370 (10-20* LOP @10-12K DA).
The new exit fairing picked up around 4+ knots (still testing), which is great. However, my climb temps are getting to the 410-415 range and cruise temps are 380-390. Oil temps also higher now, but not significant (max 210) and only in the climbs. I tried a climb at a straight 25* and that reduced temps some, but not a lot.
My initial thinking was to add a cowl flap to get the flow back during climbs. However, I am not sure how I feel about cruise CHT's at 380-390.
I also notice an imbalance in temps. 1-3 used to be pretty close, with #4 10* or so higher. Now, 1&3 are 20 cooler in cruise than #3 and #4 is another 15* on top of that. I am wondering if this is related to the oil cooler stealing the air pressure or flow from that side.
My question is how to best look for a solution. I really want to make this work, as I like the free speed. I don't want to address the cruise heat with retarded timing, as that would give back the entire gain and then some. I am working on a new solution that would let me switch between two ignitions tables PLUS a 25* fixed setting to help with climb temps. Can someone point me to some good suggestions on how to better address baffling pressure loss? I have read quite a bit here on the subject and am convinced that it can be done. I just don't know what is sub-optimal on my setup.
The only openings in the baffle are a 1.25" feed for cabin heat and the baffle mounted oil cooler.
Thanks in advance for any guidance you can provide.
Larry
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