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Old 04-25-2018, 08:56 AM
Rick_A's Avatar
Rick_A Rick_A is offline
Join Date: Oct 2005
Location: Jacksonville, FL
Posts: 1,637
Default High Oil temps - Louvers vs Cowl Flap

Now that summer is approaching, I'm thinking again about what I need to do to lower the oil temps in my 7A.

I have "real" S&W oil cooler mounted on the left rear baffle. I've worked hard making sure my baffle seals are good and that I've sealed all the gaps between the engine and the baffles. Despite all that I've done, when it gets really hot outside, my oil temps run consistenly at 210 F or above. It not unusually for me to see 220 - 230+. I even sent my oil cooler to Pacific Oil coolers to have it serviced.

I just bought a pair of aluminum louvers from Cleaveland tools and started searching the forums for installation hints. In the course of my research I came across some old threads on the Anti-splat EZ Cool Flap.

So my question is: For those of you that have installed either the EZ Cool Flap or the Cleaveland louvers, what impact did they have on your Oil Temps?

I'm particularly interested in reviews of EZ Cool Flap.

FYI. I don't have a problem with my CHT's - just oil temps.
Rick Aronow,
Flying 7A Slider;
Jacksonville, FL
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Old 04-25-2018, 09:08 AM
Paul 5r4 Paul 5r4 is offline
Join Date: Oct 2006
Location: Foley, Al
Posts: 707

I have the opposite problem. Vans stock oil cooler is mounted per vans instructions on the aft baffle. My oil temps will average at best in the upper 160's in the winters here in south Alabama. Summertime temps average in the upper 170's. I even have a restrictor plate installed to reduce the airflow. I even checked the temp sender with boiling water and it's accurate to within a few degrees. I do have louvers installed but I put them in for CHT'S. They did help there. I didn't notice any oil temp changes.
Paul Gray
Foley, Alabama
N729PG..... 500+ hrs
RV 7A, Lycoming 0 320 D1A, Sensenich FP propeller
VAF supporter $$$
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Old 04-25-2018, 09:22 AM
dweyant dweyant is offline
Join Date: Sep 2012
Location: 07TS
Posts: 528

I put an oversized (8 row) oil cooler on my RV-9A. Logic being I live in Texas and it gets really hot in the summer.

It works great, and keeps my temps very reasonable in the summer. The down side is I frequently have a tough time getting them high enough, especially in the winter months.

So I saw this at Ohskosh last summer and installed it. I love it, and it makes a huge difference in the oil temp between open and closed.

Dan Weyant
Done and Flying 4/30/2015
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Old 04-25-2018, 09:38 AM
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RV7 To Go RV7 To Go is offline
Join Date: May 2011
Location: Ontario, Canada
Posts: 350
Default Vernatherm

Rick, I installed an EZ Cool Flap due to the high CHT's on my newly rebuilt engine in my 7. It did bring CHT's down about 10 degrees on climb. I am no expert but I think the louvers and flaps are mainly for better CHT cooling. I would check the Vernatherm (I am assuming a Lycoming since you didn't say the engine). It sounds like it may not be sealing the bypass when warm thereby not cooling the oil properly. ACS sells finned coolers which clamp on the oil filter which I am told will bring the oil temp down a bit.

Paul, I had a similar issue on my O320 powered 4 which ran cold oil temps when I first got it. After talking to our engine guru he suggested changing the Vernatherm. After doing that the oil temps were 180 all summer and dropped to about 160-170 in our Canadian winter (I didn't fly when below -10 C on the ground).

It was explained to me that the Vernatherm is open when cold allowing the oil to mostly bypass the cooler and then closes the bypass as the temp rises which then forces oil through the cooler.
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Old 04-25-2018, 09:55 AM
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Carl Froehlich Carl Froehlich is offline
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 4,028

If your CHTs are good, I recommend you not add additional drag with louvers - and louvers would be marginal for your problem. Get a better oil cooler.

For four cylinder engine the Air Flow Systems 2004X 10 row oil cooler mounted on the firewall and fed with a 3? SCAT hose will meet your needs. Add the 3? butterfly valve as it will be too much cooling in the winter.

For six cylinder engine I mount the 13 row 2006X cooler on the firewall and feed it with a 4? SCAT hose. I put the RV-10 through a lot of long climbs on hot days and highest oil temp every seen was 215. Most summer days the butterfly valve is partially closed in cruise to keep oil temps above 180.

I never liked mounting the oil cooler on the baffle. The weigh of the oil cooler flexing the baffle did not appeal to my engineering eye.

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Old 04-25-2018, 09:56 AM
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Rick_A Rick_A is offline
Join Date: Oct 2005
Location: Jacksonville, FL
Posts: 1,637
Default Not a vernatherm problem

Checking the vernatherm is a good idea but I checked it last year when I had the oil cooler serviced.

I also replaced my oil cooler hoses when I re-installed the oil cooler.
Rick Aronow,
Flying 7A Slider;
Jacksonville, FL

Last edited by Rick_A : 04-25-2018 at 12:14 PM.
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Old 04-25-2018, 10:11 AM
vic syracuse vic syracuse is offline
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Join Date: May 2005
Location: Locust Grove, GA
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Focus on the oil system. Louvers won't help here. Make sure you have good clean -8 size hoses going to the cooler. It is all about flow, both for the oil and for the air across the cooler.

Vic Syracuse

Built RV-4, RV-6, 2-RV-10's, RV-7A, RV-8, Prescott Pusher, Kitfox Model II, Kitfox Speedster, Kitfox 7 Super Sport, Just Superstol, DAR, A&P/IA, EAA Tech Counselor/Flight Advisor, CFII-ASMEL/ASES/RW
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Old 04-25-2018, 10:53 AM
alpinelakespilot2000 alpinelakespilot2000 is offline
Join Date: Jan 2005
Posts: 3,786

Hi Rick-
Contrary to some of the above posts, I've had good luck with one ez cool cowl flap on lower left side helping with oil temps since I installed it last summer. I would guess about 10-15F cooling drop with it open with negligible impact on airspeed. I too regularly could push 220F on a hot day in climb. I'm still likely going to investigate a more efficient oil cooler than my stock Niagara but I can now travel cross country and feel confident that I can reasonably control my OT. As others note above, it also helps, maybe even more, with CHTs.
Hope this helps.
Steve M.
Ellensburg WA
RV-9 Flying, 0-320, Catto

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Old 04-25-2018, 11:24 AM
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larrynew larrynew is offline
Join Date: Oct 2007
Location: In New Braunfels, ist das Leben schön!
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Originally Posted by vic syracuse View Post
Focus on the oil system.
How high is your oil cooler mounted on the rear baffles? There was a thread on VAF years ago about the importance of mounting the cooler as high as possible. I did just that and either got lucky or it worked. Too well as I had to install a shutter to keep the temps up during the Texas "winter". The shutter brings the temps up almost 30 degrees so I know the air flow has a huge effect.
Larry New
RV-7A - Built, flew 1000 hrs including 48 States in 7 Days, sold
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Old 04-25-2018, 11:46 AM
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DanH DanH is online now
Join Date: Oct 2005
Location: 08A
Posts: 11,238

Originally Posted by Rick_A View Post
FYI. I don't have a problem with my CHT's - just oil temps.
Which says you need a larger cooler.

The question you're asking (louvers or flap) is merely "Do I want additional fixed exit area or additional variable exit area?" Either will result in more mass flow; exit area is the throttle. More mass flow will lower both CHT and OT.

If you only want to lower OT, start by changing the division of mass flow between cylinders and oil cooler by installing a cooler with more face area. If the new cooler is constructed like the old one, only larger (same family, like a larger SW/Meggit), the rate of heat transfer for any given baffle pressure drop will also rise.

A personal a group, we tend to install coolers that are too small, just because we've always installed that size.

BTW Rick, what engine?
Dan Horton
Barrett IO-390
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