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  #11  
Old 04-20-2021, 05:06 PM
Mtherr Mtherr is offline
 
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Location: Montréal, Canada
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I noticed a fairly large opening 1 inch wide by almost 1 inch deep at the base of the cylinder no 3. The baffle is straight, but where the cylinder has no more fins, all that area is open. Should I close this? Seems that this is useless....

Outside of this, I do have a conduit to the oil cooler behind that cylinder (a 3 inch SCAT) and a 1 inch conduit (or 3/4 inch) to cool the magneto.

I also check about increasing the clearance behind the fins (with a washer)... seems not relevant for the O-360 I have; perhaps this mod is more useful for the IO-360.

What do you think?
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RV6A "Second Wind" C-GERZ (born N242UL)
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  #12  
Old 04-21-2021, 07:15 AM
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rv8ch rv8ch is online now
 
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Quote:
Originally Posted by Mtherr View Post
I noticed a fairly large opening 1 inch wide by almost 1 inch deep at the base of the cylinder no 3. The baffle is straight, but where the cylinder has no more fins, all that area is open. Should I close this? Seems that this is useless....

...
The way you describe it, it does sound useless. Do you have a photo? This seems kind of strange. As DanH said, all air that comes into the cowl should be passing by some part of the engine where it's picking up heat and sending it out the bottom of the cowl. That's the principle. If any air passes through without picking up heat, it's wasted.
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  #13  
Old 04-21-2021, 09:28 AM
Kent Ashton Kent Ashton is offline
 
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Pics needed! For example, this is a pusher engine but see the between-cylinder baffle. All air must be forced to go through the fins. If it can take an easier (open) route from top to bottom it will. If it can go through a gap, crack or hole anywhere else, some of the flow will go there and bypass the fins. That's wasted energy, unnecessarily increases cooling drag, and allows the engine to run hotter
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  #14  
Old 04-21-2021, 10:20 AM
Mtherr Mtherr is offline
 
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Thanks Kent. I can see the area I am talking about on your picture (top right). This area is perfectly closed on your installation and totally open on mine. This gives me a good idea of what needs to be done.

Trying to attach pictures, but I have difficulties. (And i consider myself quite computer litterate)...

I also have cooling draft tubes to the magnetos... I am wondering if this is needed at all (I did not have those on my previous aircraft and all was good).
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  #15  
Old 04-21-2021, 01:44 PM
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Michel - that does look like a gap that should be filled. I recommend spending some time with the RV-14 documentation, even though you have a -6. It's available mostly on the Van's website, and you can buy a USB key with all of the files. They have a lot of great information about how to do the engine baffles.

https://www.vansaircraft.com/service...sort=undefined
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  #16  
Old 04-26-2021, 03:18 AM
Mtherr Mtherr is offline
 
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My cabin heat intake is behind the cylinder no 3, stealing a lot of air from going down the fins, I imagine. Would it be better to have this intake on the cyl. No 1 baffle? I also have my oil cooler air intake on the cyl 3 baffle.
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  #17  
Old 04-26-2021, 06:13 AM
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DanH DanH is offline
 
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Quote:
Originally Posted by Mtherr View Post
I noticed a fairly large opening 1 inch wide by almost 1 inch deep at the base of the cylinder no 3. The baffle is straight, but where the cylinder has no more fins, all that area is open. Should I close this? Seems that this is useless....
Yes, absolutely. And you'll find the same opening at the no-fin base of #4.

I seem to recall the baffle kit as having a tab there, which should be bent to close much of the gap. The rest is sealant.

Quote:
Outside of this, I do have a conduit to the oil cooler behind that cylinder (a 3 inch SCAT) and a 1 inch conduit (or 3/4 inch) to cool the magneto.
(Opinion warning) 3" is too small for an oil cooler, and blast tubes are wrong as a soup sandwich. This is 2021. Anything on the accessory case which won't operate without the very marginal cooling of a blast tube is either a bad design or way out of date.

Quote:
I also check about increasing the clearance behind the fins (with a washer)... seems not relevant for the O-360 I have; perhaps this mod is more useful for the IO-360.
It is relevant for your parallel valve cylinder, just like the angle valve cylinder.

The "washer trick" is not a great way to address it. It allows some flow to the lower fins on the intake side of the head, but it also allows a leak to an area of no fins (photo below, section on the right), which is useless. The best approach is a bypass duct, which is not a new idea. You can find them on quite a few baffles in certified GA. I've attached photos of a Grumman Tiger's bypass on #3, and two photos from my own 390.
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Last edited by DanH : 04-26-2021 at 08:00 AM.
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  #18  
Old 04-26-2021, 07:37 AM
tracy tracy is offline
 
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Michel, I haven’t read the responses so this may have already been said. I placed a washer between #3 cylinder and rear baffle. On the 8, there is a screw that secures baffle to cylinder and a washer or two goes on that screw to increase the space between cylinder and baffle. This let my #3 run cooler by around 15*f.
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  #19  
Old 04-27-2021, 04:05 PM
Mtherr Mtherr is offline
 
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I have to say a big THANK YOU to all who provided information. This really helped. I modified my baffle to integrate a bypass duct behind cylinder no 3. I also sealed all openings I could see. I flew today climbing at an aggressive angle and I was able to stay under 400F (!). Very happy with this now.
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  #20  
Old 04-27-2021, 11:39 PM
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rv8ch rv8ch is online now
 
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Quote:
Originally Posted by Mtherr View Post
I have to say a big THANK YOU to all who provided information. This really helped. I modified my baffle to integrate a bypass duct behind cylinder no 3. I also sealed all openings I could see. I flew today climbing at an aggressive angle and I was able to stay under 400F (!). Very happy with this now.
Félicitations, great to hear that it's better!
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