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Cowl Vent

Techteach

Registered User
Just wanted to share the cowl vent I built for the lower cowling on our experimental J5. It's running a O-320/Catto and #3 cylinder was running hotter than I liked (405-410). After spending a few days researching the forum, I installed ramps at the nosebowl entrance. That helped even out the temps, but overall temps came up a to 370-375 and that pesky #3 was unchanged. So, I just had a feeling we weren't getting enough draw out the bottom cowl opening. I didn't want to redo the lower opening. Checking out what others have done on the forum and what's currently being used (ie. Carbon Cub), I designed up a simple vent that I could cut out on the plasma table. Ran it through a slip former, then bent the fins out. Locate/Cut/Drill/Bolt in to the lower cowling on both sides. Latest test flight - 70 degree OAT, 2400 RPM, leaned it, #3 stabilized at 380, the rest were 352-355, oil temp was 168 (oil cooler located back of #4 and was wide open, I had the winter baffle installed but the goofy weather in Wisconsin went to the mid 70's so I pulled it). I still have a few areas under the cowling I could work on to seal up (behind the prop), but so far I'm happy. Thanks to all the have posted on the forum dealing with high CHT's. That search function is dang useful and thank you for sharing what you've done.
P.S. And before someone asks, there was no change in cruise speed. 106 MPH at 2500, 100 at 2350.
Cowl Vent.jpg
 

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