Unusual rise in CHT on one cylinder

Fearless Tower

Fearless Tower

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Fearless Tower
I was flying to Tennessee yesterday in the Baron (IO-470s) and around mid-way on the flight out I noticed that the NR 5 cylinder CHT on the left engine was climbing....went from 370 to almost 400 in about a minute (observed on the JPI monitor). All other CHTs stayed put. Oil pressure/oil temps didn't budge.

I tried leaning it out further and after a couple minutes I was able to get the CHT to drop down below 380 again and stayed put the rest of the flight. Had no problems/anomalies with any CHTs on the return trip.

So, now I'm wondering what was going on? Obviously it wasn't an airflow blockage halfway through cruise flight at 8K. Could something (sediment?) gotten lodged in an injector and caused that particular cylinder effecting the fuel flow? Or do I have a problem brewing in that cylinder?

Thoughts?
 
Rise like that either means an air flow block or you were on the verge of detonation. Take a peek at your exhaust valve and see how much carbon you have there.
 
Fearless Tower said:
Could something (sediment?) gotten lodged in an injector and caused that particular cylinder effecting the fuel flow?
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Were you ROP or LOP? Blockage of the injector ROP would probably cause EGT/CHT to rise, blockage LOP would further cool.
 
Bill Jennings said:
Were you ROP or LOP? Blockage of the injector ROP would probably cause EGT/CHT to rise, blockage LOP would further cool.
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Honestly, I don't know for that cylinder.

Ever since my last annual when the shop adjusted fuel flows, I have had trouble running LOP. Usually gets too rough before I can achieve LOP on the NR6 cylinders (both engines) and I have to go ROP to keep NR6s below 380. So for that the few flights I have had since, the temps on NR6s have been the driving factor.

Yesterday at 8K I was slightly ROP on 6.
 
Sounds like they did a bad job of adjusting the fuel flows. I've had shops inadvertantly scramble my balanced injectors. I'd start with that and then check to see what happens (but since you'll be in the cowls anyhow, check Henning's suggestions as well).
 
flyingron said:
Sounds like they did a bad job of adjusting the fuel flows. I've had shops inadvertantly scramble my balanced injectors. I'd start with that and then check to see what happens (but since you'll be in the cowls anyhow, check Henning's suggestions as well).
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That's kind of what I was thinking.

Funny thing was, on the return trip, I was able to run LOP just fine with all temps below 380 and no anomalies.
 
Scrambled injectors is my guess. Do you have GAMI's?

If the fuel flow is unbalanced and you are running near peak, you could have one cylinder running smoothly in the "red box" while the rest are safely LOP or ROP and running at normal temperatures.

Not sure which JPI you have but you can do the GAMI lean test to see if your injectors are balanced enough. Begin leaning slowly and note the fuel flow when the first cylinder peaks. Continue leaning and note the fuel flow when the last cylinder peaks. If the difference is more than .5GPH your injectors should be re-balanced.
 
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Not sure on the 470, but on the io520 I shoot for 380F CHT on the climb and 350 cruise. 380 in cruise seems toasty to me.

I also don't run LOP.


I'd agree it sound like a valve issue, did you do a run up since?
 
The fuel flows do change with temperature so it's possible that it changes from flight to flight. My fuel flows are such that the peaks are much closer together after the engine has been running a while than it is within the first 20 minutes or so of the flight.
 
Fearless Tower said:
That's kind of what I was thinking.

Funny thing was, on the return trip, I was able to run LOP just fine with all temps below 380 and no anomalies.
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If they scrambled the injectors why would it have been temporary? As I read the posts you were cruising along and then the CHT went up. You were able to get it back down by leaning further, and then on the return flight it was normal.

I'd guess crud in the injector that got flushed out. I'm not sure what else could cause a temporary condition.

John
 
jsstevens said:
If they scrambled the injectors why would it have been temporary? As I read the posts you were cruising along and then the CHT went up. You were able to get it back down by leaning further, and then on the return flight it was normal.

I'd guess crud in the injector that got flushed out. I'm not sure what else could cause a temporary condition.

John
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The mixture can creep, also as Ron mentioned earlier it always seems you need to re-adjust 15-20 minutes into cruise flight.

Here is my thinking... you're at 8000 with the throttle wide open and you lean. The leanest cylinder is 35F LOP while the richest is running right at peak. Engine runs smooth and fuel flow is good, CHT's are good. Fast forward 15 minutes and the mixture has drifted with your richest cylinder now at 15F rich of peak, while the others are at peak or below. Would definitely cause a high CHT in that cylinder.
 
dell30rb said:
The mixture can creep, also as Ron mentioned earlier it always seems you need to re-adjust 15-20 minutes into cruise flight.

Here is my thinking... you're at 8000 with the throttle wide open and you lean. The leanest cylinder is 35F LOP while the richest is running right at peak. Engine runs smooth and fuel flow is good, CHT's are good. Fast forward 15 minutes and the mixture has drifted with your richest cylinder now at 15F rich of peak, while the others are at peak or below. Would definitely cause a high CHT in that cylinder.
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I suppose but why only this flight?
 
Fearless Tower said:
Honestly, I don't know for that cylinder.

Ever since my last annual when the shop adjusted fuel flows, I have had trouble running LOP. Usually gets too rough before I can achieve LOP on the NR6 cylinders (both engines) and I have to go ROP to keep NR6s below 380. So for that the few flights I have had since, the temps on NR6s have been the driving factor.

Yesterday at 8K I was slightly ROP on 6.
Click to expand...

You need to work that out or it's going to eat a lot of money in fuel and cylinder work. Continentals are not that difficult to get balanced.
 
Fearless Tower said:
Ever since my last annual when the shop adjusted fuel flows, I have had trouble running LOP. Usually gets too rough before I can achieve LOP on the NR6 cylinders (both engines)
Click to expand...

These symptoms can be caused by a leak or mechanical problem, but since both engines are doing it, and the shop worked on the fuel flow it sounds like an injector problem.

Do you already have GAMI injectors? If so for $150 per engine they will provide support and parts to re-balance the injectors. You should be able to operate with all cylinders well lean of peak and no roughness.

I haven't had to go through the process of balancing injectors before, but this new (to me) swift has a 6cyl IO-360 and the previous owner's son was a mechanic and dialed it in with GAMI's. They all peak around the same time and it runs very smooth lean of peak. Also very cool, no cylinder above 345CHT
 
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Assuming you have GAMIs (I seem to recall you do), make sure all the injectors are cleaned and in the right cylinders. It is pretty common for planes to not run LOP properly after a shop touches them. Usually, it seems like the shop doesn't like LOP ops. Another one is that some shops that work mostly on Lycomings might get the cylinder order backwards since Continentals and Lycomings are reversed.

Otherwise, yes, that could be a potential valve issue or alternately a potential detonation issue for a few minutes. You could have had a piece of lead that got stuck in the electrode and creating a hot spot allowing for detonation, which then got dislodged explaining why the problem went away. Are you noticing EGTs wandering? If so, might be worth a borescope and possibly a pull of #5.
 
Fearless Tower said:
I was flying to Tennessee yesterday in the Baron (IO-470s) and around mid-way on the flight out I noticed that the NR 5 cylinder CHT on the left engine was climbing....went from 370 to almost 400 in about a minute (observed on the JPI monitor). All other CHTs stayed put. Oil pressure/oil temps didn't budge.

I tried leaning it out further and after a couple minutes I was able to get the CHT to drop down below 380 again and stayed put the rest of the flight. Had no problems/anomalies with any CHTs on the return trip.

So, now I'm wondering what was going on? Obviously it wasn't an airflow blockage halfway through cruise flight at 8K. Could something (sediment?) gotten lodged in an injector and caused that particular cylinder effecting the fuel flow? Or do I have a problem brewing in that cylinder?

Thoughts?
Click to expand...

Induction leak that cylinder. Leaning all evened them out?
 
Do you have Champion spark plugs? If so, are they massive electrode or fine wire?

Champion plugs built between 2007 and 2011 have been causing problems with CHT's, up to and including pre-ignition that melts a hole through the piston.
 
Fearless Tower said:
Didn't really even them out - the NR5 and NR6 cylinders remained higher than the others, but they are the rearmost cylinders and tend to run warmer.
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Negative. 5 and 6 on Continentals are front cylinders. Continental is back to front, Lycoming is front to back.

But 5 and 6 do tend to run warmer with stock injectors because of the weird nature of the intake system.
 
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