Low EGT high CHT

[Pabloecanales]

Hey guys!

 

All my cylinders look fine except for #6 which is running cooler EGTs than the rest (1250°F) , and very high CHT (around 400°F) which is 20 degrees above the rest

 

We already checked and swapped probes, baffles, etc

 

What does low EGT and CHT mean?

 

 

Sent from my iPhone using Tapatalk

[N201MKTurbo]

How does it behave on the individual magnetos?

[M20F]

Last time you posted it was on a similar issue but #6 was cold:

c1 390°F

c2 380°F

c3 365°F

c4 350°F

c5 370°F

c6 214°F
 
So what did you change that caused it to go up almost 200 degrees?

[carusoam]

Pssst….

Can somebody tell me what engine we are discussing….

Or did I miss it somewhere in the post?

 

Mike has a great memory…

Best regards,

-a-

[carusoam]

Pablo,

By the title alone…

Questions regarding….

1) ignition timing 

2) electronic ignition 

3) improved ignition systems 

May arise…

 

Things that improve or increase timing, before top dead center…

Usually increase the percentage of fuel that is burned in the cylinder, compared to in the exhaust…

Hence the CHT increasing while the EGT goes the other way…

See if you can add some details to your avatar area… which Mooney, where are you… always helps the conversation…

PP thoughts only, not a mechanic…

Best regards,

-a-

[ArtVandelay]

Generally, it’s an ignition problem, since it is only 1 cylinder we can rule out a bad magneto or ignition timing.

Pull both spark plugs, if dirty, clean them, if not replace them.

[A64Pilot]

Too advanced timing can drop EGT and send Cyl head temp high, but on only one cylinder?

I’d still check mag timing, and baffling on that cylinder, perhaps you have both going on.

[N201MKTurbo]

7 hours ago, ArtVandelay said:

Generally, it’s an ignition problem, since it is only 1 cylinder we can rule out a bad magneto or ignition timing.

Maybe, As @A64Pilot said, the only thing that can cause this is advanced timing. How can that happen on one cylinder? It could be a carbon track on the distributer block, or preignition. That's why I would run it on the individual mags to see if it was mag related. 

[jlunseth]

There isn’t any one probable cause. There are two general causes. One is the spark, two is the fuel. If you turn off one plug in the cylinder you will see low EGT and high temps. That can be caused by any number of things in the spark chain, many of which have been listed by others, fouled plug, broken or defective plug, flaw in the harness (sometimes a wire goes around sheet metal too tightly and over time gets cut), problem in the magneto. It appears you have a TN engine. A unique issue to turbo’s engines is high altitude arcing. Air acts as an insulator that prevents arcing in the cap. Up high there is not enough air, which can allow arcing to develop, and therefore carbon tracking. Once there is a track you effectively have a wire cross-connecting one of the sockets to someplace you do not want it connected to. Magnetos in high altitude aircraft are generally pressurized to prevent this, but a leak in the pressurization system will cause arcing. Corrosion can develop in a socket, both in the wire connector coming in to the socket and in the socket itself.

The other possible cause is fuel. If for some reason the fuel flow to one cylinder is restricted, say by a partially blocked injector, then the hot cylinder may be running well lean of the other five, lean enough when you think you are running ROP to bring the EGT down but still close enough to peak to cause heat. It can also be a problem in the fuel distribution system.

You didn’t say what flight regime you are in when the problem shows up. In my engine the temperature patterns between the cylinders will be completely different between climb and cruise for example. A particular cylinder will be hot in climb but cool in cruise.

Like Anthony I am a little confused about what engine this is though. Your avatar seems to say a TN’d F but you list temps for a six cylinder. Which engine?

[Shadrach]

I too think this is ignition issue. If this were a preignition event, I would expect it to progress to much higher CHTs than what you are experiencing. 

[Shadrach]

31 minutes ago, jlunseth said:

There isn’t any one probable cause. There are two general causes. One is the spark, two is the fuel. If you turn off one plug in the cylinder you will see low EGT and high temps. That can be caused by any number of things in the spark chain, many of which have been listed by others, fouled plug, broken or defective plug, flaw in the harness (sometimes a wire goes around sheet metal too tightly and over time gets cut), problem in the magneto. It appears you have a TN engine. A unique issue to turbo’s engines is high altitude arcing. Air acts as an insulator that prevents arcing in the cap. Up high there is not enough air, which can allow arcing to develop, and therefore carbon tracking. Once there is a track you effectively have a wire cross-connecting one of the sockets to someplace you do not want it connected to. Magnetos in high altitude aircraft are generally pressurized to prevent this, but a leak in the pressurization system will cause arcing. Corrosion can develop in a socket, both in the wire connector coming in to the socket and in the socket itself.

The other possible cause is fuel. If for some reason the fuel flow to one cylinder is restricted, say by a partially blocked injector, then the hot cylinder may be running well lean of the other five, lean enough when you think you are running ROP to bring the EGT down but still close enough to peak to cause heat. It can also be a problem in the fuel distribution system.

You didn’t say what flight regime you are in when the problem shows up. In my engine the temperature patterns between the cylinders will be completely different between climb and cruise for example. A particular cylinder will be hot in climb but cool in cruise.

Like Anthony I am a little confused about what engine this is though. Your avatar seems to say a TN’d F but you list temps for a six cylinder. Which engine?

 1250° solely from mixture would likely be very rich or very lean and would be unlikely to cause an elevated CHT.

 

For those wondering which engine, previous posts indicate we’re discussing an IO550 that seems to have really odd issues with #6.

 

[Shadrach]

11 hours ago, Pabloecanales said:

 

Hey guys!

 

All my cylinders look fine except for #6 which is running cooler EGTs than the rest (1250°F) , and very high CHT (around 400°F) which is 20 degrees above the rest

 

We already checked and swapped probes, baffles, etc

 

What does low EGT and CHT mean?

 

 

Sent from my iPhone using Tapatalk

 

A 20° delta in CHT from the rest isn’t “high” but your raw EGT number is a real curiosity with that CHT.

[A64Pilot]

I’m not saying advanced timing is the ONLY thing, but it’s a likely thing and is very easy and inexpensive to eliminate as a cause. I like starting to eliminate with the easy and cheap things, another thing to try is swap injectors between this cyl and another, easy and cheap. You know maybe plugs while your at it, but do only one thing at a time.

Do a mag check at cruise too, I’ve seen plugs that won’t fire well under a load pass a ground mag check, the more I think about it, the more I lean towards a weak plug, but doesn’t EGT increase if on one Mag? So maybe not.

It could be a lean cyl if LOP or a rich one if ROP coupled with a baffling issue, 20F is nothing. In fact I’d be tempted to say what he has isn’t really abnormal, except I’m assuming it’s a change, and significant changes aren’t normal, they have a cause.