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How important is oil cooler vertical placement?

alpinelakespilot2000

Well Known Member
I've always had oil temps that have been about 10F higher than I'd like, especially on 90+F days where I can see high 210s in cruise. I've long anticipated swapping out my original Niagara 20002A with a HE-series from Pacific Oil Coolers that has a good reputation for significantly reducing oil temps but that also retains the same size footprint as the Niagara.

That said, I'm also wondering how much the vertical placement of the oil cooler matters. For instance, as you'll see in the pictures attached where I've installed 3 screws for a wintertime oil cooler cover plate, I could probably have gotten away with raising the oil cooler about 1", but think I didn't originally just because Vans FWF instructions were pretty cryptic and I didn't know what I didn't know. It does seem to make sense that having 1 less inch of cooler tucked behind the #4 cylinder where it does not get direct ram air would help.

Do you think raising the cooler 1" would have improved my oil cooler's performance significantly? Worth it? Are we talking no effect, 1-2 degree F impact, or maybe something more meanginful?

(As an aside, unfortunately, I can't simply raise my existing cooler to find out because I had to cut part of the cooler mounting flange to clear the engine mount but if I do swap it out with a new cooler want to know what I might expect if I go through the effort of locating the new one up a bit.)
 

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It will make 0 difference.

Biggest gains (temp reduction) will be made switching to tighter fin spacing that's found in the HE or "Real" SW/Meggitt/Troy/SouthWind units.

B
 
Worth a try.

Steve, My cooler is higher by about that much, but not sure I could quantify but can provide a wild guess might of 10F benefit. I have a plenum with little leakage.

If the cooler is so low (and it is) that air may be going through head fins before it gets to the oil face, then you might just test the theory by laying some HVAC tape over some head fins. I don't think it will make a big CHT difference as there is still a large area for flow downward thorough the head. It would divide the flow and is definitely a radiation block. It would also not block a large amount of cooler flow either.
 
I have had success on a -7A (200 hp angle valve) and a -4 (IO320) by spacing the oil cooler aft, off the baffle. I also angled it downward a few degrees. This creates a dedicated mini plenum in front of the cooler. It only needs to stand an inch or so off.
It’s been 20 years but I believe I got the idea from a suggestion in the RVAviator.
 
Cooler

Non RV, 320 with 10-1 pistons, mags and carb. Cooler is angled back about 15 degrees, no stand off at the bottom. Small inlets and outlets, cowl flap.
No problems in hot weather, runs a bit too cool in cooler weather.(40-50 ambient) Cooler is behind #3 which is where I believe it should be.
I have aspirations of a flow control valve, pilot controlled and get rid of the vernatherm.
 
Cooler

Forgot to mention I have a plenum that I designed and built which probably contributes to low oil temperatures.
 
Oil cooler placement

I made a frame at the rear of the baffle of 1-inch square tube and attached the cooler to that.

It allows air to reach the hidden part of the cooler. It made just the difference and did not require big mods.
 
High is good, as much of the air flow is blocked by the cylinder. You are looking for optimal flow of air to the cooler. If you mount the cooler too high you will interfere with the upper cowl. If you mount the cooler too low the air flow will be blocked even more by #4 cylinder. Look for the position that works for you and reinforce as required.
 
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