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Cooling makes me nuts

C

cplne

Registered User
OK so I replaced all the baffling on toe PA12 O-320 Cylinder 3 and 4 hotter than heck 420 degrees on the rise. Really nothing noticeable. All right back to my aerobatic days and the heat issues. Take a piece of hose and tape it to the bottom underneath the cowl, cause some turbulence, tape around the oil cooler in front of the cowl, voila instant relief. Not there quite yet but making progress maybe when the cylinders are broke in. Sorry assed cowl design, I’m afraid I’m going to have to keep throwing money at her and install an aft oil cooler and maybe a different air filter design.. I’m all ears opinions and facts appreciated..
 
One thing to consider with a chin cooler, the opening is about 1.5x the area of the cooling core. I used 1/2" foam pipe insulation and Gorilla tape to seal between the opening and the cooler so the only air coming through the opening is that which is going through the core. Once you've done this, an aft cooler would make no improvement. How well does your rear bulkhead fit against the ceiling of the cowl? That was where I was losing air. I put a strip of self-stick low density foam across the cowl ceiling so the felt crushes into it. Between that and the oil cooler inlet, I have really good temp numbers. PS-- if yours uses silicone flaps, inspect them very carefully. I've seen several heat issues where it was just assumed the silicone flaps were going to "inflate" in flight and seal. Unless they fit very well in a static condition, that's NOT going to happen. Good luck.
 
We did make silicone seals, spent most of the day installing, a little relief but cylinders 3 and 4 still hot. Thank you Mr. Piper for the one piece bowl. I very much love having to take the prop off and on and to remove the cowl. Tomorrow is another day
 
I would think moving the oil cooler is only going to make issues worse. Open the bottom if possible. Add the seaplane lip. What are the front cylinder temps? If they are cool I would steal some air from them with metal tape up front. Can you lean 150 degrees before you hit rich of peak? If not consider richer jet in carb. You may need bigger cheeks with the bigger motor. The good thing is you know you have a problem, think of all the guys that have no ideal how bad the CHT's are.
DENNY
 
cplne said:
I very much love having to take the prop off and on and to remove the cowl.
Click to expand...

You could make a custom two piece pool cue wait I mean ya don't tug on supermans cape.. darn it.. I mean you could make a two piece bowl so you don't have to take the purroppp off every time, its not difficult
 
Thanks Denny. Yes when I bought this poor old girl she didn’t have a CHT at all so I have no numbers to compare. I just replaced all 4 cylinders and expect some relief when the rings seet. Front Cylinders running at 330 degrees @ 80 degrees rear cylinders stable now at 410. I’m not familiar with the seaplane lip, where can I find one? This old gal is getting the love she deserves, pisses me off when I see the abuse these old planes have taken over the past 70 years. Many thanks to everyone’s good advice
 
Maybe swap cylinders, put the hot ones in front ?

Kiding aside, lots of tips and tricks offered in previous threads, search "high CHT's"
as Denny suggested, ensure you have adequate fuel, good place to start.

Doug
 
Do a search on seaplane lip you will find some posts and should be some pictures. Call Stoddards they might have one in stock, or Charlie Center/Crosswinds. Randy at Carbon Concepts may also be making them. Take some aluminized tape and cover the bottom half if the front cylinders. This will force some more air to the rear ones, mine are blocked about that high.
DENNY
 
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I spoke with Charlie this morning, great guy with lots of knowledge. Looks like I’m going to have to manufacture a Lip as nobody seems to carry them for the 12. Shouldn’t be a problem. Charlie gave me a number of things to check
 
Now I never considered that. The left side is open 2 inches, the Right side 2 3/4 crazy. It’s probably been like that for many years. Whachya thinking?
 
Taking baby steps but making progress. Today’s flight cylinders 3 and 4 ran at 400 degrees improvement but not there yet. It was a much cooler day and maybe The rings have seeted The biggest help was taping the gap around the oil cooler. As soon as the tape blows back temps go up 15 degrees only on 3 and 4. The other gap was around the air filter. What I need to find is a flame resistant foam to stuff around the oil cooler. The back of the top cowl has a small gap but the bulkhead in front of the accessories is tight. Keep the suggestions coming, I’m going to beat this thing.
 
Redo that stuff on the back. It does not take much space for a lot of air to bypass the cylinders. Notice how much air can escape through the cowl door hinges. Open them, clean well and apply the aluminized tape over the hinge when open. I asked at Stoddards today they said call Charlie Center for the seaplane lip.
DENNY
 
Thanks Denny. Spoke with Charlie and he doesn’t have one for the 12. I’ll manufacture one. I’ll tape the hinges tomorrow and let you know
 
My home made lip consisted of taking a half inch piece of flexible tubing and taping it to the underside of the cowl. It’s an eyesore but just an experiment. This is an old trick we used in my akro days, our planes ran in the Red all the time.
 
Thanks to all for your suggestions. I used most of them and have things under control. Most notably was the rear cowl lip and taping up the oil cooler entry in the cowl. Taping the front cylinders, hinges and all new baffle helped. Maybe something else is going on here. At full takeoff and climb power Cylinders 1 and 2 run 310 degrees 3&4 climb to 425. When I level off and reduce the power to 2400 RPM Cylinders 1&2 climb to 330 degrees however 3&4 drop to 390, any ideas? I’ll check the intake tubes but find it hard to believe both 3&4 would have a leak and 1&2 not. Thanks to you guys I’m making progress
 
Sounds like you need to build ramps on your front cylinders. That will raise your front chts and lower your rear chts by 20F. You are really spinning your wheels and making a lot of smoke if you don’t search this site for:”CHT”....lots and lots of hard data is awaiting you....
 
Ramps/cylinder blocks to even out temps. Start blocking 2/3 up on R side cylinder and 1/2 up on left side jug. . Tune the temps for cruise using the exact same power setting. Plan on trimming down in 1/8 or 1/4” increments until CHT temps are closer for the most used configuration. Small changes in ramp height effect temps dramatically.....now you’ll at least cook all your cylinders evenly:p This will even out temps but will not ultimately solve your cooling problem.......also, switching props may change which cylinder is the hottest
 
I missed the cheek post they sound about right for a 0320. Are you climbing at full throttle? The carb is set up to add extra fuel above 2500 rpm to add in cooling. If you try to climb hard at 2400-2500 RPM I would expect to see higher temps in the rear cylinders. Did you check to see if when running 2400 RPM you can lean 150 degrees before any cylinder hits peak EGT.
DENNY
 
Any mods to new cyls, porting, higher compression etc?
Did you confirm adequate leaning authority?
 
I’ve been running full rich while breaking in the cylinders, I’ll try to lean on the next flight. Definitely will make some ramps and a Seaplane Lip. They were on the plane when I bought her...right
 
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