Cylinder head temps

[Clarence]

Hi all,

A question for "E" model owners with "Dog house" baffles.  What values do you get for CHT in cruise at 2500 RPM?  I can hardly break 340-350 in most conditions, 325 is more typical.  I spent a lot of time on my baffles when I installed the engine and wonder if it's too cold?

Clarence

 

 

 

[Piloto]

Your temperatures are good. CHT is a function of EGT. Max CHT is typically reached at about 50F rich of peak EGT. As you go higher in altitude CHT increases for the same EGT temp. CHT decreases for LOP EGT settings.

José 

[Ned Gravel]

Clarence:

My temp profile is very similar to yours.

[mooneygirl]

Hi Clarence, so funny. I was just on the phone with a mechanic who is going to build me some new baffling. My CHTs in cruise are in the high 300s.  Lately on climb out it is hard to keep under 400. I have resorted to getting my first 1000 feet of altitude going 105 mph and nosing over to 130 for a cruise climb, to keep my number 2 cylinder below 400.  I will watch this list for comments.

[Immelman]

Clarence,

My experience is similar unless in very high outside air temperatures, or low speed flight (such as best angle or climb or practicing MCA). In cruise flight, even at higher power settings (75%), I seldom break 350dF.

As ugly and battered as the old 'dog house' is with its multiple patches, RTV gone wild over the edges of the spark plug covers, etc, it does a good job.

[scottfromiowa]

Clarence:

I always trim for a cruise climb (120mph).  I generally see about 300-350 IF I AM FULL RICH.  I will often lean (slightly if not a hot day) when over 3,000 (while in climb).  I watch closely and DON'T let cylinders get over 350 in climb.  My number 2 is always about 25 degrees hotter than remaining cylinders (maybe cylinder with OEM probe, and GEM second probe so in a slightly different location?).  I climb at max RPM and full throttle...

I bet if you leaned a little in climb you would see increased temps...(NOT suggesting this)...cool is good.

[drpep]

I also seem to be getting consistent readings on my JPI 830 anywhere from 325 to 345. 

[DaV8or]

Quote: Piloto

As you go higher in altitude CHT increases for the same EGT temp.

[PTK]

 

CHT rises with cold air in a normally-aspirated engine.  More power is produced with cold air because cold air is denser requiring stoichiometrically more fuel flow.  And depending how dense the air (how cold) the engine is producing higher power at a leaner mixture (more air, less fuel).  More power and/or a leaner mixture equates to higher CHT. 

 

[PTK]

CHT rises with cold air in a normally-aspirated engine.  More power is produced with cold air because cold air is denser requiring stoichiometrically more fuel flow.  And depending how dense the air (how cold) the engine is producing higher power at a leaner mixture (more air, less fuel).  More power and/or a leaner mixture equates to higher CHT. 

[Clarence]

Thanks to all who replied,

I spoke with a rep at Lycoming about the cylinder temps he said Lycoming would consider below 200 dF to be cold.  After unsticking my #2 exhaust valve and reaming all of the exhaust guides, the flight test was fine with CHT's 325 to 350.

 

Clarence

[carusoam]

Clarence,

I can't think of anything more important, and less discussed than sticky/stuck valves. Especially on on a four cyllinder engine during departure....

-a-

[M016576]

Quote: allsmiles

 

CHT rises with cold air in a normally-aspirated engine.  More power is produced with cold air because cold air is denser requiring stoichiometrically more fuel flow.  And depending how dense the air (how cold) the engine is producing higher power at a leaner mixture (more air, less fuel).  More power and/or a leaner mixture equates to higher CHT. 

 

[M016576]

I do have a question regarding a single high CHT.. I have heard this multiple times before, too, not just here...

I've heard people say that "well, I have one CHT in the 380's, the others are in the 340's... maybe it's just the probe location" or "it's the factory probe."  I know that EGT probes are placed in a somewhat arbetrary location in the exhaust stack and that their exact value is somewhat trivial (it's the comparison to where it peaks that we care about, not the number it peaks at).  But with CHT, we're looking at an actual number that determines the current strength of our cylinder head and how the wear cycle will effect it in the future.  Wouldn't a probe located anywhere that shows a higher number be one to heed?  or is there a specific location that is known to read higher than the actual cylinder head temp for some reason?  Thanks in advance! -Job

[GXPD]

Most times my CHTs run between 330-350F.  See last few flights data.  CHT1 is about 30deg cooler than the others.    I can see why CHT3&4 would be higher but you would think CHT 1&2 would be similar.  Anyone else see the same trends?

[Ned Gravel]

Steve:

If that cylinder is getting more gas than the others, it will register cooler.  That is why full rich is the coolest you can get on the rich side of peak. 

Just a thought.

 

[Clarence]

Hi Steve,

I have fashioned extentions on my front baffles in an attempt to even out all of my CHT's.  I continue to tweek them to get them as close as possible. They now run within 25 dF of each other.  I noticed that on a new Acclaim in the shop even the front cylinder fins are covered with a baffle almost to the top of the barrel.

Clarence

[Cruiser]

Quote: GXPD

Most times my CHTs run between 330-350F.  See last few flights data.  CHT1 is about 30deg cooler than the others.    I can see why CHT3&4 would be higher but you would think CHT 1&2 would be similar.  Anyone else see the same trends?

[docket]

This is slightly off topic but make sure that your temp gauge is right.  My Moritz OEM gauge was off by almost 80 degrees.  I didn't realize it until I put in an engine monitor.

[GXPD]

Cruiser

I think you're probably right.  CHT 1 has consistently been lower and that's why I have not really worried about it.  Will check type and location of the CHT probe on #1. THNKS

Quote: Cruiser

 Was there a point at which the previous flight showed all cylinders the same temp? The graph you show has #1 cylinder consistently below the others. Without you comments above I would say that #1 has the OEM CHT sensor with a piggyback sensor for the engine monitor. Don't know why but they always show 20 - 50 dF different than the standard probes on the other three cylinders.