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High Oil temps - Louvers vs Cowl Flap

Rick_A

Well Known Member
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.
 
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.
 
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.

http://www.tcwtech.com/control_valve_servo_kit.html

-Dan
 
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.
Al
 
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.

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

BTW Rick, what engine?
 
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. Al

Exactly right.
 
Using SW 8406R

I'm using a Stewart Warner 8406R oil cooler and it is mounted as high as possible on the rear baffle.

This is about as big an oil cooler that I know of that can be mounted on the rear baffle. Off hand, I don't know how many rows are in this cooler.

What's the next size up from this one?

I have a TMX O-360 (ECI engine built my Mattituck). Standard 8.5 compression.
 
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I'm using a Stewart Warner 8406R oil cooler and it is mounted as high as possible on the rear baffle.

Yep, that would be the smallest oil cooler in the SW/Meggit line. Given 5" H2O deltaP, air flow is only about 22 lbs per minute.

An 8432 is an inch taller, flows 27 lbs p/min, and has 25% more heat rejection. The catch is the high oil pressure deltaP; the 8432 is a dual pass unit. It means the vernatherm must seal against higher pressure at its port.

A 10599 is the same physical size as the 8432, but is single pass. Same air flow, much less oil deltaP, roughly 20% more heat rejection than the 8406.

And of course you can go up from there, but you'll probably need to duct all the larger coolers.
 
First, I'm away from my reference material.

I've seen many installations where the mass flow to the cooler is choked off by a long SCAT hose, or other things that defeat flow.

Have you checked the cooler's specs to see what is the design "Delta P" across the core? Have you matched the cooling capacity with the Lyc lubrication heat rejection data? Have you checked the "Delta P" across your cooler installation?

Better than "flipping a coin"!

:^)
 
Some data would be very helpful.

Rick, would suggest you install some piccolo tubes to get the upper and lower cowl/plenum pressures. That would tell a lot about the cooling system.


By example, I have the SJ cowl, it classically had reports of poor cooling. Mine cools fine, I restricted the flow across the engine, (parallel valve, mags stock M1B). I have quite high pressure on top of the engine, and almost none (<1" H2O) under the engine. Not bragging, just an example of poor balance on the other side.

So if you could measure some pressures, then some clear options will be available. Lets say the lower cowl pressure is high, the oil cooling is poor. This might indicate (assuming proper timing) that the mass flow is too high and could be managed better across the engine, yielding lower total mass flow, higher upper pressure, and lower pressure below. That would push more air (higher delta-p) across the cooler and lower the oil temps. It is possible the CHT would not change, or very little.

I found huge gaps in the inter cylinder baffles under my new engine, the same on my 10-friends too.

Edit: To the original question - if the lower pressure is high, then louvers or a door would be one option to get better balance, but certainly not the only one
 
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Good idea on trying to get some air pressure measurements, but to be honest I don't have a clue regarding how to actually rig the test apparatus to do this.

To Dan's idea on the 10599 type cooler. It is a good idea but I vaguely recall getting a 10599 originally while I was building.

I think I returned the 10599 and got the 8406 because the 10599 was too tall to fit on the baffle.
 
I had the same issue and first installed the anti-splat cowl flap resulting in a very modest improvement in oil temperatures. More recently, i bit the bullet and changed the oil cooler, going with a somewhat larger and more efficient cooler over the stock Vans product that was installed. See my post here:

http://www.vansairforce.com/community/showthread.php?t=155188&highlight=erich

Changing to a larger oil cooler is a lot of work because it will almost certainly no longer fit on the back of the baffle, and mounting a new one is not trivial and reduces access to the back of your engine. Good results were achieved achieved in my case however and Im glad I did it. Bill at Airflow Systems can help you with a mounting system, which could be either something like what I show in my other post, or on the firewall.

good luck

erich
 
Good idea on trying to get some air pressure measurements, but to be honest I don't have a clue regarding how to actually rig the test apparatus to do this.

Rick, if you want to do the work, send an email and I'll return a white paper detailing the method, equipment, etc.
 
I have the same problem with my 7. It is 195 hp with oil squirters and a SJ plenum. I have to really watch my oil temp on climb or it will easily hit 235 on a hot day. I installed an 8 row cooler and checked everything for proper operation. Mine is remote mounted so I increased the scat tube to 4 inch which helped a lot. I think the issue with heat is that the SJ plenum does not have a lot of exit area and a lot of it comes through the cylinder fins. I may install a second cooler this summer as some have done as I think thats the only way to cool mine. It's also 10 to 1 compression with dual P mags
 
10599 fits

I have piston squirter engine and the 10599 oil cooler not only fits the rv-7/9 baffle, it does a fantastic job keeping the oil temp in check. Extruded alum angle across the top of baffle and on one side and so far no cracks.
 
Convinced I need a 10599

I'm glad I started this discussion before I started surgery on my lower cowl. I'm convinced that the real solution is changing to the 10599 cooler.

I'm glad to hear from grubatt on the last post that he was able to fit a 10599 in the standard location on the left rear baffle.

I think maybe that I was trying to stick as close a possible to the Vans baffle / oil cooler plans when I installed the 8604R.

Time to start getting into the specifics of fitting and installing 10599.
 
Yep, that would be the smallest oil cooler in the SW/Meggit line. Given 5" H2O deltaP, air flow is only about 22 lbs per minute.

An 8432 is an inch taller, flows 27 lbs p/min, and has 25% more heat rejection. The catch is the high oil pressure deltaP; the 8432 is a dual pass unit. It means the vernatherm must seal against higher pressure at its port.

A 10599 is the same physical size as the 8432, but is single pass. Same air flow, much less oil deltaP, roughly 20% more heat rejection than the 8406.

And of course you can go up from there, but you'll probably need to duct all the larger coolers.

Is the 10599 the same as the 10599R-T? I saw a picture of one and if the pictures is correct it shows the inlet and outlet on the same side of the cooler and not built into the end tanks. Would this be the correct one to get for the -7?
 
I note that the response from grubbat in post#21 refers to the cooler fitting in an -7/9; it does not say -7A. Im not saying it wont work, just saying that the engine mount in the -7 is not the same as a -7A, so fair warning. Might be worth another check and clarification.

erich
 
I have an RV7A and successfully retrofited a Steward Warner10599 onto the rear baffle where the standard Vans oil cooler had been installed. I had climb limiting oil temp issues right from the first flight and all the way through phase one. The only thing that fixed it, after a call to Pacific Oil Coolers, was installing the 10599 and it fixed it beautifully. I had to carve away some material from the flange closest to the engine mount, to give enough clearance to allow for engine start/stop shake and made sure that the corner of the baffles by the oil cooler was appropriately reinforced to withstand the higher weight. Oil temps are great now, even on days over 100 degrees F.

Once I had solved the oil temp problems, my limiting factor was cylinder head temps and after chasing those for many hours with many different solutions, each of which had minimal effect, the anti splat cowl flaps solved them.
 
Is the 10599 the same as the 10599R-T? I saw a picture of one and if the pictures is correct it shows the inlet and outlet on the same side of the cooler and not built into the end tanks. Would this be the correct one to get for the -7?

Mark, sorry, not familiar with a 10599 "R-T". The spec catalog I use only lists the 10599R: http://www.oilcoolers.com/LCHX_Specifications.pdf

As for "correct for a 7", I don't know. The issue is not airframe specific. The required heat exchanger capacity varies with HP, RPM, ignition advance, mixture, squirters or no squirters, upper plenum pressure, lower plenum pressure.....
 
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Mark, sorry, not familiar with a 10599 "R-T". The spec catalog I use only lists the 10599R: http://www.oilcoolers.com/LCHX_Specifications.pdf

As for "correct for a 7", I don't know. The issue is not airframe specific. The required heat exchanger capacity varies with HP, RPM, ignition advance, mixture, squirters or no squirters, upper plenum pressure, lower plenum pressure.....

Thanks Dan, I?ll see what I can find out regarding the ?T?. The -7 I?m building will be equipped with a parallel valve 360, roller cam, forged 8.5:1 pistons, no squirters, EFII, cold air induction, and a S.J. cowling with a Bill Lane plenum. I don?t even want to mess around with oil temperatures this time around...been there, done that...and I just want to get to best cooler possible for my application. I would like to remotely mount the cooler though with a short run of SCAT. I?m hoping that I can get by with a 3? SCAT and not have to go up to a 4?. I?d also like to be able to control the airflow over the cooler with some kind of a flapper valve mount inline with the SCAT tubing.
 
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