Second Oil cooler

Scott Anselm wrote:

Here are some more pics that show it better I hope.  All I really did was add and extension with a bit of a drop to the rear of the cowl.  I stole the idea from some of the Cub guys here in Alaska.  I'm not a Cub guy but apparently for one of the mods of float installs there is a similar cowl extension required.

I am not an engineer either, but  the cowl airflow depends on both the ram air at the front and the exit flow.  If you have a cowl that does not allow good flow at the exit as I did then an extension may help. With my cowl in it's original configuration It stopped about 3 inches short of the firewall and I suspect  that was creating some back flow and relatively high pressure,  By adding the extension with the sweep down as well the air flows smoothy over the bottom cowl and and, more or less like a wing, creates a lower pressure behind it. 

Anyway, that seemed to greatly increase the flow of air through the engine compartment and over the oil cooler without much if any loss of airspeed.

Hope this helps,

Scott

Thanks, Scott! Makes more sense to me now and appreciate those extra photos. So I guess I'm wondering if you have any suggestions for me in terms of how I could modify my cowl to increase cooling and get the 25-30F temp reduction that you did. I'm attaching photos. You can see there’s a big gap in front and around the oil cooler. I was thinking of bridging that gap with weather stripping. But do you think that alone would fix the problem by forcing more air into the oil cooler by preventing the air from going around the sides of the cooler? 

The exit out the bottom of the cowling is quite large. There's a little deflector tab on the bottom where the air starts to exhaust out the bottom.

Upon looking at these photos, do you get any ideas? I'm trying to figure out what to do here since my oil and coolant temps both run too hot (coolant too hot on the ground and oil too hot in the air).

Also, I noticed that the backside of oil cooler looks like the muffler shroud is ejecting onto it and maybe melting the coils? This can’t help the oil overheating issue? Any idea why it would be designed to be spraying hot air at the backside of the oil cooler? Do you think I should try capping it so the muffler shroud is not ejecting hot air onto the backside of the oil cooler and see if that makes any difference?

That’s the front of shroud. Back of shroud connects to my cabin heat. See below photos:

I'm far from an expert but I would think a seal around the cooler would help but I would also look at extending both back and down ( I see there is a small extension)  the addition at the rear of your  oil opening in the cowl.  It looks like you have a nose gear so you will have some gap but with the large gap you have under the engine in the cowl I would guess you have a lot of turbulence from air hitting the firewall and nose gear. Partially closing that gap with a nice smooth transition and little more drop may help. Just look at it from how to create a smooth efficient airflow.  A slight "V" in the middle if the extension might let it flow better around the landing strut.

Again, just an idea but fairly easy to do and much less cost than messing with the oil system as a first attempt for a solution.

Good luck,

Scott

The muffler shroud opening is the intake air for your heater and not specifically ejecting hot air forward into the radiator.  The damage to the radiator fins looks more like contact/interference than melting.  With radiator and muffler movement they may be hitting under high vibration conditions like when starting the engine. Still, the proximity to the radiator is not ideal and there is  going to be some radiant heat transfer from the muffler to the radiator. Proper air flow should mitigate that.  

Scott Anselm wrote:

I'm far from an expert but I would think a seal around the cooler would help but I would also look at extending both back and down ( I see there is a small extension)  the addition at the rear of your  oil opening in the cowl.  It looks like you have a nose gear so you will have some gap but with the large gap you have under the engine in the cowl I would guess you have a lot of turbulence from air hitting the firewall and nose gear. Partially closing that gap with a nice smooth transition and little more drop may help. Just look at it from how to create a smooth efficient airflow.  A slight "V" in the middle if the extension might let it flow better around the landing strut.

Again, just an idea but fairly easy to do and much less cost than messing with the oil system as a first attempt for a solution.

Good luck,

Scott

Thanks, Scott!

What does that small extension even do? I'm not sure I understand its purpose and how it's doing anything being so small. So are you saying it might work to shape a piece of sheet metal like the attached and bolt that to the bottom of the cowling? And if I did that, should I remove the small extension that currently exists? 

Jeff Blakeslee wrote:

The muffler shroud opening is the intake air for your heater and not specifically ejecting hot air forward into the radiator.  The damage to the radiator fins looks more like contact/interference than melting.  With radiator and muffler movement they may be hitting under high vibration conditions like when starting the engine. Still, the proximity to the radiator is not ideal and there is  going to be some radiant heat transfer from the muffler to the radiator. Proper air flow should mitigate that.  

Ah, that makes sense regarding that muffle shroud opening. Thanks for clarifying that, Jeff. And I agree, the damage to the radiator fins is likely related to high vibration conditions. I assume those few damaged fins aren't going to have any adverse effect on the cooling?