I think you are on the right track - increase the outlet ! There are
also some folks who have had results from enlarging & smoothing
the inlets ....
I'm with Wayne - probably not too helpful with heat ....My questions are:
1) Does anyone know where to get ready made "shark" gills? It
would make increasing the exhaust flow a lot easier without making a big
exhaust plenum hanging down underneath the cowling as I have seen in some
pictures.
2) Did Howard's configuration provide sufficient cooling for his flying?
Yes ! My oil was up to 240+, and CHT's were way up too - with the3) Has anyone had any over temp problems with about 100 sq in of exhaust
area?
original cut out hole at the bottom ! I would definitely NOT recommend
that !!!! If you can make stand-offs to lower the whole bottom rear of
the cowling by at least a couple of inches, that will look & work better.
The key is to be sure that the rear of the cowling is AT LEAST an inch or 2
or more BEHIND the firewall - otherwise, the air flows UP & INTO the cowl,
greatly increasing temps ! Putting aluminum over the bottom firewall
lip to round it and smooth exit air flow will also help greatly ... just
fasten to belly & wrap up to 4 or 6" above the bottom of the firewall.
(Aluminum body repair tape will do, if it's too late for alum. sheet.)
That would be the vertical tube that extends downward from the4) Is it necessary to have an external carb heat dump pipe or am I
misreading the quote?
carb air box on most engines .... (approx. 1 1/2" diameter)
--
......bobp
http://www.prosumers.ca
http://bpatterson.qhealthbeauty.com
http://apatterson2.qhealthzone.com
-------------------------------orig.-------------------------
On Tuesday 16 January 2007 22:23, Gary Gustafson wrote:
I am currently working on my speed cowl and modifying it to increase
the amount of exhaust air. I have an O320 (160 HP) and it will be on wheels,
but would like to plan for eventual floats. In that regard, back in July
2002, Wayne O'Shea wrote the following in an email:
"Rule of thumb!? Cut 'till the temps are right! But yes I have read in many
places one and a half times the inlet. Didn't do any calcs when we did
Howard's. We just slit the MAM scoop down the sides and kept putting in
larger pieces of aluminum until the temps dropped to an acceptable limit. It
was then glassed in at this size and the aluminum removed."
"Howard's main outlet is 4 1/4 x 14 1/2 = ~62 sq inches and then there is
about 12 square inches around each exhaust pipe, plus he added the two 1
1/2" x 5" shark gills for another 15 sq inches for a total of ~ 101 square
inches. Don't have a speed cowling here to measure the inlet size, but I'll
guess at about 5" x 7" each side for a total of 70 sq inches. 101/70 = 1.44
ratio. If you have the measurements, what is the actual inlet square inch
number and the out/in ratio." (I measured and it is about 68 sq in.)
"On Bob's I just cut it out from one exhaust pipe to the other and forward
to about an inch behind the carb heat dump pipe. This is most likely a good
200 square inches of outlet and seems to do the trick overly well.."
My questions are:
1) Does anyone know where to get ready made "shark" gills? It
would make increasing the exhaust flow a lot easier without making a big
exhaust plenum hanging down underneath the cowling as I have seen in some
pictures.
2) Did Howard's configuration provide sufficient cooling for his flying?
3) Has anyone had any over temp problems with about 100 sq in of exhaust
area?
4) Is it necessary to have an external carb heat dump pipe or am I
misreading the quote?
Thanking any and all for your assistance.
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