Worrisome CHTs on an Overhauled Engine and New Engine Monitor

Joe Cabral

Joe Cabral

Filing Flight Plan
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joe-cabral
So, I bought a Piper PA-28-181 with an overhauled (complete) Lycoming O360-A4M back in December. The engine now has about 175 hours. I installed a JPI EDM 830 engine monitor back in June and I (and my local A&P) are perplexed by the indications. My CHTs rocket up to 360-370 just on taxi (mixture full rich, before run-up) after the engine has been running for just 5-10 minutes. My climb-outs, full power, full rich yield CHTs in the 450-480 range in minutes, I have to reduce my climb angle from 76kts to 90+kts before I get to pattern altitude, just to keep the temps around 410-440 - still unsat. When I cruise at 60% power, and about 100 degrees rich of peak, I get somewhat acceptable CHTs in the 375-390 range for #1, #3, and 385 - 405 on #2, #4... #2 and #4 are always my highest CHTs.

I'm looking for advice please... The local A&P checked baffles and made some small repairs but it had no impact. Where should I go from here? Would appreciate advice please. Thank you ~
 
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mixture ain't mixing right, or your baffling installation is wrong. I know he said he checked it... well "certified" maintenance and a buck twenty gets me a cup of coffee in this life.

Archers are cavernous engine installations, they're not anywhere near what tightly cowled setups (Lancairs, some turbo mooneys et al) do, prone to overheat sitting on the ground without headwind. These things don't do that unless the airflow inside the cowl is wrong.

My other guess would be your fancy engine monitor is throwing garbage numbers, but who knows. We're getting further and further from occam's razor (baffles be all football bat) at that point. Keep us posted and good luck.
 
Any idea of your fuel flows or at least, average consumption?
Sounds too lean although of course other possibilities exist.
 
hindsight2020 said:
or your baffling installation is wrong.
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Most likely. I have found engines missing the intercylinder/interhead baffles. They sometimes end up staying on the core, or just don't get reinstalled if the engine was removed and overhauled.

1723344779202.png
#9 is the baffle in question. It's a Lycoming part, not a Piper part, and won't show in the Piper parts manuals. If you look into the cowl's front openings with a flashlight and mirror you should be able to see part #10 on top between the two cylinders, on both sides of the engine. If it's not there, those baffles are probably missing, and the air is not being forced properly through the fins on the head and cylinders. They fill a large gap there, and big gaps destroy the pressure differential between the top and bottom of the engine, reducing cooling flow a whole bunch. The rubber baffle seals also need to be all there and in good order.

A check of mag timing is also a good idea.

I would confirm that the new temp instrumentation isn't way off by running the engine uncowled for a few minutes to bring the CHTs up, then check the heads with a laser infrared thermometer immediately after shutdown with the master on and JPI running. Aim the gun at the CHT probe boss, not the fins.
 
Joe Cabral said:
So, I bought a Piper PA-28-181 with an overhauled (complete) Lycoming O360-A4M back in December. The engine now has about 175 hours. I installed a JPI EDM 830 engine monitor back in June and I (and my local A&P) are perplexed by the indications. My CHTs rocket up to 360-370 just on taxi (mixture full rich, before run-up) after the engine has been running for just 5-10 minutes. My climb-outs, full power, full rich yield CHTs in the 450-480 range in minutes, I have to reduce my climb angle from 76kts to 90+kts before I get to pattern altitude, just to keep the temps around 410-440 - still unsat. When I cruise at 60% power, and about 100 degrees rich of peak, I get somewhat acceptable CHTs in the 375-390 range for #1, #3, and 385 - 405 on #2, #4... #2 and #4 are always my highest CHTs.

I'm looking for advice please... The local A&P checked baffles and made some small repairs but it had no impact. Where should I go from here? Would appreciate advice please. Thank you ~
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Do you have a PowerFlow exhaust? If so I can share my experience with CHTs and PowerFlow exhausts
 
Let'sgoflying! said:
Any idea of your fuel flows or at least, average consumption?
Sounds too lean although of course other possibilities exist.
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Yes, about 8.5 - 9.5 GPH when in 60% cruise. I see about 14.5 GPH on full throttle climb-out (when my CHTs hit the mid-400s). Does that (14.5) seem low for this engine? Thank you.
 
Joe Cabral said:
I do not. How is PowerFlow impacting your CHTs?
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After my overhaul and installing a JPI 830 engine monitor, noted high CHTs. First thing I thought was something wasn't right with the overhaul but after exhausting everything, I found the answer after contacting Darren Tilman, General Manager at Power Flow. After running a test he suggested. He told me that my carb was running too lean. He suggested that I needed to adjust the mixture, I was running too lean at full throttle. After a series of adjustments and retests, my high CHTs went away.
 
yabut he says he's also getting higher than normal CHTs (for ground ops) while idling. That reads like baffle trouble in an otherwise loosely cowled contraption, like pa28s are FWF.
 
It's amazing how little it takes to be messed up. There was a little three inch l-shaped piece broken from the baffling in front of my #1 cylinder that greatly increased the temps when it was missing. I didn't realize what was up until I removed the nosebowl and half of it came off.
 
All the probes are installed correctly? Since CHTs are similar, likely I gather.
With that engine temp, I’d image the oil temp would be elevated also? Correspondingly so, over 200F?
 
Joe Cabral said:
Yes, about 8.5 - 9.5 GPH when in 60% cruise. I see about 14.5 GPH on full throttle climb-out (when my CHTs hit the mid-400s). Does that (14.5) seem low for this engine? Thank you.
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Sounds a bit low.

Rule of thumb, 1 GPH per 10 HP. So should be more like 18 GPH or more.
 
Here's Lycoming's fuel flow chart for the O-360. The OP's note doesn't specify field elevation, but presuming it's near enough to sea level that the engine can make 100% power, it calls for a minimum fuel flow of about 14.9 gph. So 14.5 gph would be a little low. Don't know if it's enough low to explain such high CHT's.

Probably also worth checking magneto timing along with the other suggestions.

Fuel Flow Leaning O360.jpg
 
start with the easy stuff. check mag timing, a degree or so can make a big difference. check baffling, all in place, tight,sealed and no leaks. check the seals on the top, you should see rub marks on the top of the cowl from the seals. as for fuel flow, 14 is low for full power, full rich TO. on my 180 i run 23/2300 which gives about 70% and i lean out at about 8.5 to 9.5 for cruise. if you are getting those number at full rich, you have a lean carb problem. check the part number on the carb, they could have put the wrong carb on it at overhaul.
 
Not sure about the O-360 but for my IO-360B1E I am getting 16 GPH in the climb. That is what it should be for my plane full power.
 
Honestly this sounds like an induction leak. Your fuel flow seems reasonable. I would check for an air leak causing you to run lean even with good fuel flow.
 
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