Today's Message Index:
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1. 10:55 AM - Re: RV-8 Cowl Vents (Matt Dralle)
2. 12:44 PM - Re: Re: RV-8 Cowl Vents (thomas sargent)
Message 1
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| Subject: | Re: RV-8 Cowl Vents |
At 07:04 AM 8/8/2011 Monday, you wrote:
>Dear Fellow RV-8 Builders, I now have 13 hours on my 0360 Lyc. Still having #
1 CHT get too hot before TOC. So I have to throttle back and stairstep up to altitude.
Temps should be stable by now with 13 hours. So I bought from Avery the
bottom cowl louvers to improve airflow. Talked to a couple RV-8 drivers both
said the vents lowered CHTs about 20 degrees. Question is how is best to mount?
What shape and size hole(s)? The bottom of the vent plate is flat while the
cowl bottoms have compound curve surfaces. What is best for looks and effectiveness
and strength? Hope to hear from someone, Bill of Georgia N288WP
Hi Bill,
I have an IO-390 210hp on my RV-8 with the standard cowling. I don't have any
trouble with CHT's (generally well under 400f) and my oil temps are generally
in the low 180'sf. If I take off on a hot day at sea level and climb hard, I
can get the CHT on the hot cylinder to go over 400 but by that time I'm at 8000
ft and simply decreasing my angle slightly will bring it back down. The only
"non-stock" aspect of my installation is the giant oil cooler I added to the
back of the baffle. Its about twice the size of the stock one.
Before you start cutting holes in your cowling, you might want to do some more
investigation into the cause of the overheating. Might be indicative of something
else. Plugged oil line to that cylinder, maybe a blocked fuel injector on
that cylinder? Try swapping the injectors between the hottest and coolest cylinder
and see what impact this has on the CHT.
Here's some info on the oil cooler installation that has worked well for me:
http://www.mattsrv8.com/users/display_log.php?user=MattsRV8&project=638&category=2972&log=90253&row=84
Matt
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Matt Dralle
RV-8 #82880 N998RV "Ruby Vixen"
http://www.mattsrv8.com - Matt's Complete RV-8 Construction Log
http://www.mattsrv8.com/Mishap - Landing Mishap Rebuild Log
http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel
Status: 170+ Hours TTSN - Rebuilding Fuselage After Landing Mishap...
Message 2
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| Subject: | Re: RV-8 Cowl Vents |
Matt:
I just made a simple mod that you should try before doing anything drastic
like cutting holes in the cowl. On my 6A I duct taped on 2 wedges cut out
of wooden 2x2 that were about 1.5" wide from the narrow edge back to the
3/8" wide trailing edge. They are about 5" long. They were nearly
identical with the plastic rudder trim wedges that Avery sells. I put these
on the bottom of the cowl where the exhaust pipes come out with the wide
edge flush with the aft edge of the cowl. I saw an immediate drop in oil
temps of at least 10 deg. F and probably 20 F.
Last week I replaced them with 2 of the Avery rudder trim tabs, painted to
match the plane and curved a bit to match the shape of the cowl. I think
these work the same way the louvers work: The air going past the trailing
edge causes a slight decrease in pressure that helps draw more air through
the cowl. I only had to drill 4 screw holes in the cowl to mount them
"permanently". I can remove them any time I want just by taking the screws
out.. The cowl is otherwise a stock Van's cowl.
I need to do some more flying (I'm in Tucson where there's plenty of hi
temps this time of year) to test this, but the few flights I have done are
very encouraging. I'll send pictures if you like.
--
Tom Sargent, RV-6A
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