"Most engines benefit from breathing easier"
I would agree with that, and the 90's 24° cam would also benefit from that as well. As would the 35° cam of the O-200. Continental did not dyno these engines with the J3 or PA11 exhausts installed. My personal preference is for the sharper lobed O-200 cam, but that's because I never have to launch at density altitudes above 10,000 feet. The 90 cams will outperform the O-200 cam when the manifold pressure drops below 21 inches.
I typically prop the O-200 to give a 55 mph climbout between 2500 and 2800 rpm and an 79-81 mph cruise at 2250-2350 rpm. In a J3, I'm leary of a 55 mph climb at more than 2800 rpm with much less than 3 gallons in the nose tank for fear of unporting the tank outlet during the climb. At 2800 rpm and 55 mph, the J3 deck angle is very steep.
I've designed an offset J3 'muffler' that fits within the stock heat shrouds (so looks externally stock with shrouds mounted) but doesn't muffle and flows somewhat better than stock while also clearing the -12 oil screen housing. I haven't built or flown it yet, but am looking forward to doing so. I haven't given any attention yet to the 11 exhaust.
I would agree with that, and the 90's 24° cam would also benefit from that as well. As would the 35° cam of the O-200. Continental did not dyno these engines with the J3 or PA11 exhausts installed. My personal preference is for the sharper lobed O-200 cam, but that's because I never have to launch at density altitudes above 10,000 feet. The 90 cams will outperform the O-200 cam when the manifold pressure drops below 21 inches.
I typically prop the O-200 to give a 55 mph climbout between 2500 and 2800 rpm and an 79-81 mph cruise at 2250-2350 rpm. In a J3, I'm leary of a 55 mph climb at more than 2800 rpm with much less than 3 gallons in the nose tank for fear of unporting the tank outlet during the climb. At 2800 rpm and 55 mph, the J3 deck angle is very steep.
I've designed an offset J3 'muffler' that fits within the stock heat shrouds (so looks externally stock with shrouds mounted) but doesn't muffle and flows somewhat better than stock while also clearing the -12 oil screen housing. I haven't built or flown it yet, but am looking forward to doing so. I haven't given any attention yet to the 11 exhaust.
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