Citabria High Oil Temps

Interesting, well you should be creating some suction with that setup but doesn’t look ideal. The cutoff exhaust pipes are creating pressure right where the suction should be. Plus looks like the exhaust have a slight forward cut on them creating extra back pressure in the system. Should be into the slipstream angled aft. Getting correct exhaust pipes would be my first priority,(any chance they got swapped Left to Right?) also agree with Hyperbiper on the leaning, then would try just a half or inch 45 degree lip on the bottom the cowl if needed but the exhaust and leaning should help. Looks like someone was trying get that 1 extra mph at cruise.
 
Agreed with all of the above. I always thought the exhaust looked funny. There may or may not be a owner produced part in production as we speak. Said product has the ability to act as a negative pressure lip up to 2.5" but can be adjusted. Again, just rumor. Word is, it looks a lot like a cowl flap.
 
Ok current plan is to extend the tail pipes to clear the cowling and dump the exhaust properly. This will only be temporary until I finish the field approval for installation of Sutton Exhaust. So I’ll just clamp something on in the mean time. Does anyone happen to know off hand the diameter of the tail pipes? I hear there’s an FAA-PMA aisle at Napa that sells aviation grade tail pipe extensions.
 
Swing by a muffler shop they can make an extension and swell it to fit. Might even tac weld them in place for safety.
 
Bruce said:
Swing by a muffler shop they can make an extension and swell it to fit. Might even tac weld them in place for safety.
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I’d do that if I were to run this permanently. But the field approval paperwork for my Sutton exhaust is finally coming along and I expect to be able to swap exhaust entirely here very soon. It will more or less be an experiment. Going to extend the exhaust a couple inches, go fly and see if there is a notable difference.

I also have a negative pressure lip I want to try out, but I’ll test with just extended exhaust first.
 
Well big progress was made today. Negative pressure lip did almost nothing. Exhaust extensions did absolutely nothing. I did however, after no fewer than 5 sets of eyes looked at it, finally get a solution. While the red baffle seals are new and seal well against the cowl, the aluminum baffle plates themselves are just full of gaps. We sealed the easy ones with speed tape and even covered the lower 1/3 of cylinder 1 and 2 with speed tape and took it for a flight. It was 90° F outside and the CHT never got above 400° F this time. In cruise, it stabilized around 390° which is high but acceptable. I am confident that sealing the rest of the gaps and getting the airflow correct will bring things back to normal where they should be. It is to a point now that even as it is, I feel confident in taking it on trips. It will only get better from here.

Side note, my CHT probe is of the spark plug adapter type, which I’m told reads higher than a bayonet type. Perhaps something to change in the future.
 
A self dispensing can of red or black rtv will make short work of gaps up to 1/2” or so. Didn’t even think to mention it. We use it alot. Also great for chafe protection or a light oil resistant adhesive.
 
Hammersmith said:
A self dispensing can of red or black rtv will make short work of gaps up to 1/2” or so. Didn’t even think to mention it. We use it alot. Also great for chafe protection or a light oil resistant adhesive.
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Red RTV is gonna find it’s way all over that baffle system this Weekend. I’ll probably leave the speed tape on the cylinders for now before I make permanent plates. It’s definitely losing a LOT of air under 1&2 as it is now.
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Danger Will Robinson!!!
While you want to channel cooling air down thru the cylinder fins you don't want to make any "hot spots" by covering up any of the fins themselves especially the fins at the base of the cylinders (where you have the silver tape)...and don't forget to inspect the inter-cylinder baffles which are incredibly important to control cooling airflow.
A roll of 4" 3/32" black baffle seal, sharp scissors and a handful of pop rivets can make sealing the baffles-to-crankcase gaps work well and look good without excessive use of RTV...
Sounds like progress is being made...

Chris
 
Good catch! Thanks for pointing that out. I do have a roll of baffle material on the shelf. Plan is to tighten up all the gaps and seal it as good as possible. If more air control is needed I’ll put some aluminum pieces up where the tape is now although my hope is to not need that. Tape was proof of concept and won’t be on there for any more flights.
 
ehaecker said:
Good catch! Thanks for pointing that out. I do have a roll of baffle material on the shelf. Plan is to tighten up all the gaps and seal it as good as possible. If more air control is needed I’ll put some aluminum pieces up where the tape is now although my hope is to not need that. Tape was proof of concept and won’t be on there for any more flights.
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Many aircraft baffles do have an aluminum piece that goes half way up the cylinder then has a curved piece that follows the cylinder down to about the 80% point. Might be worth looking into what the current baffling from American champion looks like. Follow the proven systems.
 
Best I can tell, they don’t use any such thing. I do see it very common in many other airframes. If I have to do it, I will, but I’m hoping that a good cleanup and tightening of the factory baffles will get me there.

there’s are several gaps like this alternator bracket that could stand to be sealed to more than they are now. I’m not sure if this is how all aircraft are or if this is some kind of hack job from years ago. Regardless, there is plenty of room for improvement.

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That whole right front baffle looks a little suspect to me. But I have been wrong before… never seen anything go under the edge of a cylinder before.A59D18B2-AC44-49CE-849D-603909FC4789.webp
 
Completely agreed. Losing a lot of pressure under cylinders 1 & 2 that should be going over them.

Jusr gotta love buying old airplanes that have been rebuilt twice. It wouldn’t be fun if it was simple.
 
Have you looked at right rear baffle? On Decathlons those are known for bowing rearward at the top under pressure and dumping air. Common solution is an extra brace to the top of the cylinder.

Also, my left rear baffle does not make good contact with the cowl at the sharp corner above the oil cooler. There is definitely a gap there, but really hard to discover because it can't be inspected visually. I reach in thru the oil filler door and trace with my finger.
 
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