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Sam James Cowling

stneki

Well Known Member
Patron
I have a Sam James Cowling on my RV7A. With this Michigan winter my cylinders are way too cold. I am looking for some type of air flow restrictor that I can insert into the inlet rings. Any help with this would be appreciated.
 
Although it may seem non-intuitive, restrict the exit.

Easy to fabricate too.
 
Look up a thread called "The Shrinking Exit" it will have lots of references to explain what Dan is suggesting. I can't find it otherwise I would post a link for you.

The problem with reducing your round inlets is described in this article:

http://www.n91cz.net/Interesting_Technical_Reports/106-111_BuildingBasics.pdf
http://www.n91cz.net/Interesting_Technical_Reports/106-111_BuildingBasics.pdf

More precisely you will get turbulent flow right behind the reducer ring and that will add drag and perhaps cause un balanced cooling that is OK with the SAME James inlets and diffuser ramps as it is now.

Like Dan suggests, it is quite easy to be effective in restricting the cowl bottom exit. A hinged AL plate is quick and easy to experiment with.
 
Yep if air can't exit it can't enter... thus why there are COWL FLAPS. With that said you are experimenting. I assume you have 4-channel CHT, EGT. Of course oil Temp is required by 14CFR 91.205.

Blocking oil cooler will increase temps. Suggest you go incremental in restrictions.
 
I fabricated an "anti - cowl flap on a servo, closes up the scoop at the exit, noise is less, speed increases, and temps are where they should be.

It is 5 inches at the forward end with the hinge, 9" at the exit end, and 11 inches in length.

Regards,

DAR Gary
 
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