Elevated CHT in only one cylinder on departure

[PeytonM]

I took off from a local airport for a 20 minute flight in my 201. I saw the #2 CHT start to rise rapidly within 2-3 mins after liftoff and headed for 400, so I reduced power and let temps settle down. After CHTs were back down, I brought the power to 24-24 and leaned normally. As you can see, all systems normal to landing. Today we checked compression, plugs and induction on #2. All good. I'll have fuel injector checked next, although I'm not sure how I could explain an elevated CHT without an elevated EGT.

I would appreciate other suggestions and explanations.

https://www.savvyanalysis.com/flight/785022/66dfe1ef-da5c-4183-9ddf-78aa3cb130a5

[Cruiser]

There are only two things that will cause high CHT without a fuel problem, a change in cooling (obstruction/blockage) or exhaust gas on the CHT probe.

[NotarPilot]

What about pre-ignition?

[PeytonM]

If it was exhaust gas on the CHT, wouldn't I see that throughout the entire flight, especially after I added power? I found no obstruction to cooling or changes in baffling.

I thought of preignition, but wouldn't I see a change in EGT?

I'm leaning towards a defective CHT probe. Will see what Savvy says.

Thank you for your suggestions.

[Bob - S50]

I'd vote for either an:

 

Intermittent probe problem but not likely.  I would think such a failure would cause something other than a smooth rise in indication.

 

or

 

Detonation.  I can't tell without the fuel flow, and I don't know what your normal EGT indications are, but it looks like your EGT's are a bit high during climb.  That would indicate to me insufficient fuel flow.  That can lead to detonation at high power settings.  Don't know why it would occur on just one cylinder.

 

If that is the case, I think you did a good job by pulling the power back and letting the cylinder cool.  Probably saved it from pre-ignition and a destroyed engine.

 

Let us know what Savvy says.

 

Bob

[carusoam]

Exhaust valve sticking.....?

Possible and probable cause of single CHT rise.

If it sticks closed, it will be very obvious. Partially closed, not so much.

Share this idea with your mechanic. The solution to cleaning the guide is called the rope trick...

.........

Unless the ignition timing could change on one cylinder...

Not likely and improbable...

Thinking out loud,

-a-

[Piloto]

Check the cylinders bottom side baffles. A steep take off at gross weight can cause uneven cooling airflow.

 

José

[PeytonM]

Final resolution: bad CHT probe!

[carusoam]

Thanks for the follow-up...

Best regards,

-a-

[PeytonM]

Turns out it was NOT the probe.

A few more TOs still showed high CHT on cyl #2. Upon very close examination of the baffling on the left side of the engine, we found there were a couple of areas where the two pieces of aluminum had pulled apart, creating a path of least resistance.

Makes sense: I saw the high CHT during TO, because I had a high deck angle with lowest airspeed and lowest airflow. The CHT was normal in cruise when I had high airspeed and airflow, masking the baffling issues.

A couple of you hit the nail: defective baffling. Thank you!! Problem resolved.

[aaronk25]

#2 cylinder is the only cylinder that is dramatically affected by angle of attack on climb out.

I and others have cut down the metal baffel in front of it by 1/2-3/4 inch.

If you didn't do any thing different might be cause for concern.

[jetdriven]

Don't you mean the #1 cylinder? Right front? It has front battle. I cut mine down 1/2" as well. It's about 40 degrees cooler now.

[aaronk25]

Don't you mean the #1 cylinder? Right front? It has front battle. I cut mine down 1/2" as well. It's about 40 degrees cooler now.

Well hot dog...I got it mixed up. Ok never mind my last post......back to drawing board.

[PeytonM]

Here is further update. After screwing around with baffling, cleaning plugs, checking probes, replacing a probe, I thought I had it fixed. After 10-15 hours of flying and no high CHT, I was confident.

Then guess what: another excursion to high CHT (375-400) only on #2, when in level flight on way down to Panama City at the end of September, 2015. (This was a long maintenance battle, with first sign of problem in December, 2014!)

I was about 45 mins into the 5 hour flight. Again, I reduced power to about 20" and the CHT fell back into line. I returned to FT operation with no issues for the rest of the flight to Panama City (including a fuel stop.)  At Panama City, I had an oil change and did replace both plugs on #2 with new.  (The Champions had about 250 hours on them.) The plugs looked normal; no obvious defect. I borescoped cylinder #2 and saw no evidence of any issues. 

I have not seen the transitory CHT issues on #2 since, 5 months and 50 hours later. Go figure.

The only correlation was the original problem had manifested itself after the Annual in November 2014. I don't know what could have happened at the Annual to cause this. I will let you know if the #2 CHT dragon raises its head again. (I hesitated posting this update, potentially damning myself...) Ground Hog Day anyone???

[jetdriven]

Nope, just crappy champion plugs.

[aaronk25]

Nope, just crappy champion plugs.

Speaking of crappy spark plugs I pulled the 1 year old 150hour set out of my boat and replaced with the factory recommended AC Delco plugs.

The champion were the equivalent marine ones and but 1 out of 12 plugs (twin v6s) had corrosion and slight rust around the base while the others had none. I think the plug was shorting out and the energy actually created the corrosion almost like electrolysis in the water where it eats the drives.

Previously I had a intermittent miss in that motor that I was chasing and it's gone now. I've never seen a AC Delco or NGK plug do that but sure enough the champion quality hits again.

Sent from my iPhone using Tapatalk

[PeytonM]

At my next Annual (November, 2015), I switched all the plugs to Tempest (still massives.)  Fifty (50) plus hours since Annual and I am pleased to report good, consistent CHTs across all cylinders: 325-360 (depending on OAT) according to my JPI 700.  "I'm a believer..." * and a new customer. 

*composed by Neil Diamond, recorded by The Monkees, 1966