7-row or 9-row oil cooler? Parallel valve O-360

Going to be making a Spruce run this week and figured I should go ahead and pick up my oil cooler as part of the order. I?m trying to decide between a 7-row and 9-row cooler as they?re the same price, though I suspect the 9-row will be more challenging to fit.

My engine is a parallel-valve O-360. My dad has basically the same engine on his -6 and uses a 7-row, and has occasionally run into some oil temp issues (e.g., the OSH arrival and subsequent taxi). However, his cooler is firewall-mounted with a fairly long 3-inch duct and I suspect there?s an efficiency hit on the cooling airflow from that.

Much as I?d prefer to mount it remote (with a bigger duct), I?m probably going to have to go with a reinforced baffle mount as I?m tight on firewall space (2 batteries) and the taildraggert engine mount looks like it might cause some trouble with duct routing.

My inclination, especially considering the negligible price difference, is to go with a 9-row as I?m in the deep south (hot summers, mild winters) and I can always throttle it back. But that makes installation even more challenging.

Any suggestions? I posted here instead of engines due to the taildragger engine mount considerations...

Bare in mind.. Not all cooler cool that same. You can do a little research on the forum and see which ones perform better. I have seen the difference between coolers. And the price range is wide.

My 7 row is behind the #4 cylinder and I have to cover about 1/4 during the summer to keep temps up above 180. I don't recall the brand but it came with the engine from a Piper Archer.

FasGlas said:

Bare in mind.. Not all cooler cool that same. You can do a little research on the forum and see which ones perform better. I have seen the difference between coolers. And the price range is wide.

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Also, if you have piston squirters, you will have more waste heat to get rid of.

I have a Stewart-Warner 10599R eight row cooler on my O-360 and have never had cooking problems.

If you can, do firewall mounted. Here is my setup on the RV-8. Standard 3? hose to the Airflow 2006X. The butterfly valve is normally shut some to keep the oil temp up (so far this spring at least).

This is the second build using this cooler - I recommend it.
Carl

No squirters on this engine, or on Dad?s.

I really do like the idea of a firewall mount?but I also have two batteries to squeeze onto the firewall, and the mountings that so many use for a remote oil cooler on -8s and -As doesn?t work as well on the -6 and -7. The landing gear mount and extra bracing tubes in that area really cut down on access and ability to run ducting (and also really limit options for battery mounting), and I also don?t want to blow hot air right onto a battery. That?s what?s driving me to the baffle mount; it?s tight but it should be effective and I know it?ll fit. I?ll definitely have to reinforce everything surrounding it though. And I guess I probably have to wait till the cowl is fit and the baffles are trimmed before locating it...

Dad pulled off a firewall mount like Carl?s, but his battery is aft of the firewall and as noted, I?ve seen some oil temp issues under certain conditions.

I won?t completely rule out a firewall mount yet, but based on my attempts so far using dummy batteries and a 3D printed oil cooler mockup, I just can?t find a way to fit it that doesn?t blow hot air directly on a battery.

Carl Froehlich said:

If you can, do firewall mounted. Here is my setup on the RV-8. Standard 3? hose to the Airflow 2006X. The butterfly valve is normally shut some to keep the oil temp up (so far this spring at least).

This is the second build using this cooler - I recommend it.
Carl

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I only count 10 rows, the airflow 2006x is listed as a 13 row cooler. I'm considering the same question as OP and am debating between the 10 and 13 row cooler.

agent4573 said:

I only count 10 rows, the airflow 2006x is listed as a 13 row cooler. I'm considering the same question as OP and am debating between the 10 and 13 row cooler.

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Sorry, his is the 2004X cooler - I used the 2006X cooler on the RV-10 with a 4? SCAT hose. The RV-8 uses a 3? hose. The cooler on the RV-10 worked so well I decided to stick with the Airflow brand.

But - recommend using a butterfly valve to control cooling air. Every day is not 90+ degrees OAT.

Bob - I don?t like firewall mounted batteries for a variety of reasons. Is there just no other option?

I do know an RV-14A can have two firewall mounted PC-680 batteries as well as a firewall mounted oil cooler. Perhaps you can as well.

Carl

As a reference, my RV7A with IO360-M1B had the standard 7 row oil cooler mounted on the FW (#4 Cyl) and in hot summer of N. CA, I would see 185, maybe 190 but cruise temp would come down to 180. I had a oil cooler shutter installed that it was about half way closed most of winter time.

I went with the aero classics 9 row baffle mounted on my O360. It would be hard to go any bigger but it fit pretty easily. I mounted it as high as I could to keep it away from the cylinder. I had to notch the one flange for the motor mount tube but I am comfortable with clearance. I am not flying yet but so far I am happy with my choice. I can send pictures if you want.

Purchased an oil cooler this past week. Now the question is mounting everything.

Carl Froehlich said:

Bob - I don?t like firewall-mounted batteries for a variety of reasons. Is there just no other option?

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Not really. I could theoretically put them aft of the baggage compartment but that's less than desirable from a CG standpoint. I don't have room on the cabin side of the firewall because of the housing for the EFI plumbing.

I do know an RV-14A can have two firewall mounted PC-680 batteries as well as a firewall mounted oil cooler. Perhaps you can as well.

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The -14A has a bigger firewall and it's a nosewheel (that seems to provide more access on the sides). Now, after some additional fiddling and firewall Tetris I think I might have found a workable solution. Both batteries stacked on the right side, cooler on the left.

Ignore the outlines above the firewall recess; those were a concept I had for batteries on each side. Current thinking is the main and crossfeed relays to the right/outboard of the batteries, starter relay below.

Pictures don't work.....

agent4573 said:

Pictures don't work.....

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#*$&^*#$^*

I?ll try and fix that. No idea why it works sometimes and not others.

Pictures work now.

I never thought about 3d printing components for placement. I'll have to do that when I hit that stage.

agent4573 said:

Pictures work now.

I never thought about 3d printing components for placement. I'll have to do that when I hit that stage.

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Yeah, the oil cooler was a pain (I made it in three parts and it got a bit distorted, but it?s close enough for rough planning). I?ve started doing it with avionics boxes too, so I can start placement and running wires ahead of time and without damaging expensive boxes.

[RANT] The oil cooler description should be a manufacturer and part number, not some semi-arbitrary number of rows; what about passes? structure of end tanks and bars? What the **** is a row anyway? [RANT OFF]

On my YIO-360-A1B6 (Angle Valve, 200HP, Squirters) I started with a firewall mounted Aero Classics Clone of the Stewart Warner 8406R, HE 8001602, fed by a 2.5" duct. Temps hit 240 so this was no bueno.

Changed to 2.75" duct, temps still above 220. Discovered some of the fins were smushed and I couldn't correct them, so I bought a Meggitt 8406R (formerly Stewart Warner). Temps dropped to 215.

Changed to a 3" duct, temps dropped to 200.

Changed to a Stewart Warner 10599R, temps dropped to 185.

The 8406R is a "7-row" and the 10599R is a "9-row" - both are single pass, unlike the 8432R & S.

Stay cool...

B

bjdecker said:

On my YIO-360-A1B6 (Angle Valve, 200HP, Squirters) I started with a firewall mounted Aero Classics Clone of the Stewart Warner 8406R, HE 8001602, fed by a 2.5" duct. Temps hit 240 so this was no bueno.

Changed to 2.75" duct, temps still above 220. Discovered some of the fins were smushed and I couldn't correct them, so I bought a Meggitt 8406R (formerly Stewart Warner). Temps dropped to 215.

Changed to a 3" duct, temps dropped to 200.

Changed to a Stewart Warner 10599R, temps dropped to 185.

The 8406R is a "7-row" and the 10599R is a "9-row" - both are single pass, unlike the 8432R & S.

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Thanks for great data. As you discovered 2.75 is too small, but in my opinion 3" is still too small. Duct area of 4" dia. is about the right area to feed the cooler.

Also / other threads show the cooler exit shrouded or diverging duct on it to allow the air to transition smoothly improves their flow. The firewall boxes where air takes a sharp turn to go through cooler are not ideal.

I've always found the 7 row stewart-warner cools better than the early 7 row Aero Classic. I don't know about the rebranded SW name . Original Stewert Warner just cool better from experience. Not sure if other brands, aero classic have upped their game...

A bigger cooler can amend for less than ideal installations. A smaller cooler with an optimum installation may cool as well. However there are always compromises. If the installation works then that is all that matters.

gmcjetpilot said:

Also / other threads show the cooler exit shrouded or diverging duct on it to allow the air to transition smoothly improves their flow.

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Steve has repeatedly explained the principle behind the short diverging exit shroud. It is not to "smooth the flow". It is to reduce pressure immediately downstream of the cooler grid.

The same is true of an exit duct running all the way to the cowl exit. It presents the cooler with freestream pressure rather than the somewhat higher pressure inside the lower cowl.

Flow is based on deltaP. Either way, reducing pressure downstream of the cooler increases mass flow.