EGT/CHT Temps

[Glidergeek]

What temps are acceptable without melting cylinders and pistons, burning valves and causing expensive noises? After using my JPI 700 for 150 hours transitioning from an Alcor gauge I try to keep my EGT's below 1400* is about 50-75 ROP. This usually keeps my CHT's around 350*-360* in cruse. Anybody have any good knowledge of this? Application is O-470-50 Pponk, temps are easily manageable.

[DBI]

I have a PPonk 0-470-50 in my airplane as well. Like you, I run ROP and keep my EGT below 1400 and keep my CHT's around 375 in cruise. I do get a bit nervous during my cruise/climb when CHT's can creep up above 400. I watch that pretty carefully and do not allow it to stay above 400 for very long. If you are keeping your CHT's at or below 365 that seems pretty good to me.

[SixTwoLeemer]

Ive always heard that 380* and 1380* were pretty good targets...just add a 1

[DBI]

Ive always heard that 380* and 1380* were pretty good targets...just add a 1

Hmmm... very good "rule of thumb". Never thought of that Thanks!

[dirtstrip]

I was taught peak EGT in degrees is a reference point not an actual hard number target that is transferable from one engine to another. Placement of the probe changes the temp reading but the value of the gauge remains in finding the peak EGT not a particular degree and from there you lean by degrees to your target on either side of peak, whatever peak reading is.

CHT at 400 supposedly cuts the hardness of the aluminum by 50% according to my Superior O 360 engine manual. That is considered max and is also to be avoided. I would like the 360 number if I could hold it.

[flynengr]

dirstrip wrote:

I was taught peak EGT in degrees is a reference point not an actual hard number target that is transferable from one engine to another. Placement of the probe changes the temp reading but the value of the gauge remains in finding the peak EGT.....

I was a little shocked to see peak EGT's at 1580F after the JPI install in my 180; I used the same holes in the exhaust manifold that the old Mixture Mizer came out of, and they admittedly are on the tight side of the recommended distance from the head. That said, if you believe the contemporary recommendations for engine operation, the relative movement is all that matters with EGT, absolute scale doesn't mean anything. For CHT on Continentals, I have heard the same number as 62L, 380 max cruise. I usually set the cowl flaps to give me 360 to 370 on the hottest cylinder, seems to be one notch when its warm out and 2 notches when cool, cruising at 23 squared.

Flynengr

[shortfielder]

Hey Russ
Pm sent
Gary

[260Driver]

Some good reading on the subject: http://www.avweb.com/news/savvyaviator/savvy_aviator_59_egt_cht_and_leaning_198162-1.html

BL, EGT's are relative.

When running LOP on my IO-540 I'll see EGTs in the high 14's/low 15's...I keep my CHTs below 400

[Glidergeek]

Hey Russ
Pm sent
Gary

Got it Gary I scoured all the info I could this morning and never saw any numbers until the link from 260driver. 380 and high 14's to 1500* I'll try that.
Thanks all

[172heavy]

Some good reading on the subject: http://www.avweb.com/news/savvyaviator/savvy_aviator_59_egt_cht_and_leaning_198162-1.html

BL, EGT's are relative.

When running LOP on my IO-540 I'll see EGTs in the high 14's/low 15's...I keep my CHTs below 400

EGT is only a reference number; the CHT is the critical number. Damage is done when there is sufficient heat developed in the cylinder to damage parts, generally damage occurs when pre ignition and detonation occur, this is where the engine analyzers can save your engines, set your CHT alarm @ at a lower temp than critical, something like 380F, (gives you time to react) there is a specific signature for a pre ignition condition, the EGT will decrease rapidly and the CHT will increase rapidly, the burn is happening so fast or all at once, and the cylinder absorbs more of it and less heat is flowing out the exhaust. The highest CHT temps are developed around 50 to 100F rich of peek EGT, this is also your highest power setting. Personally on my engine I run rich of peek on climb out and lean of peek on most cylinders in cruse, on climb out I will adjust my speed and mixture to keep my hottest cylinder under 370F, once at cruse altitude I go lean of peek, with the JPI I can find the sweet spot by monitoring my speed, fuel flow and MPG. For my engine I found that the sweet spot is balancing EGT on #4 and #6 cylinders, #4 is lean of peek and #6 is rich of peek.

[Grassstrippilot]

EGT is a reference number. As a follow up to the posted article, here is an EAA webinar that Mike Busch just did in June that covers combustion theory and addresses CHT and EGT temps. Excellent presentation and worth watching. You don't need to be a member to watch them and there are a lot of good ones on there. Like others have said, 380 is what he recommends for a limit.

http://www.eaavideo.org/video.aspx?v=1678859198001

[z3skybolt]

This subject....


...is getting to be like religion and politics.

Bob

[172heavy]

EGT is a reference number. As a follow up to the posted article, here is an EAA webinar that Mike Busch just did in June that covers combustion theory and addresses CHT and EGT temps. Excellent presentation and worth watching. You don't need to be a member to watch them and there are a lot of good ones on there. Like others have said, 380 is what he recommends for a limit.

http://www.eaavideo.org/video.aspx?v=1678859198001

This is pretty much how I manage my engine; Mike’s Webinars have taught me allot.
I agree with about 99% of what he has to say, the red box concept is a very important one to understand, there several points that I would like to ask him about and clarifications that I would like him to make, I think that there more variables in this equation that effect engine performance and reliability. I certainly can’t argue with his success in engine longevity.

[Backcountry Tundra]

This subject....


...is getting to be like religion and politics.

Bob

Yes although everyone seems to be agreeing that god is LOP! would be nice to get more imput on this from bush lads here...guys like me tha constantly go up and down, change power settings, fly t/o-t/d at different alts, etc... Wonder if following the 380CHT is the way to go rather than trying to keep my EGT at 1370 (LYC IO-390 220hp).

Lets hear from you mountain folks!

Cheers, BCT

[blackrock]

There is a lot of good information on engine operation on the http://groups.yahoo.com/group/lycoming/
Yahoo Group.

This is a post from one of the most respected contributors on that site (in reference to an O-320):

Re: CHTs

Lycoming says to keep it above 150F and below 435F in cruise and below
redline 500F in climb. If it were mine I would be fine with 275-400 in
continuous cruise and below 450 or so in climb.
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts
are hopefully helpful to you. Please use the information provided
responsibly and at you own risk."

[172heavy]

This subject....


...is getting to be like religion and politics.

Bob

Yes although everyone seems to be agreeing that god is LOP! would be nice to get more imput on this from bush lads here...guys like me tha constantly go up and down, change power settings, fly t/o-t/d at different alts, etc... Wonder if following the 380CHT is the way to go rather than trying to keep my EGT at 1370 (LYC IO-390 220hp).

Lets hear from you mountain folks!

Cheers, BCT

CHTs are for engine protection, EGTs are for tuning, High CHTs will ruin your engine, and high EGTs will have no effect on engine longevity.
The hotter you get a set of cylinders the weaker they get, the more times they heat up and cool them down, the faster the change, the greater the delta, the weaker they get. I live in the mountains; when leaving the valley I take off from 2600 and climb to a minim altitude of 7500 or 8500, I rarely allow any CHT to reach 380F, I adjust my speed, climb rate and fuel mixture to keep my temps low, I only run LOP in cruse or decent, generally @ or above FL8500. But that is on a Franklin 220.

[hotrod150]

.... I run rich of peek on climb out and lean of peek on most cylinders in cruse, on climb out I will adjust my speed and mixture to keep my hottest cylinder under 370F, once at cruse altitude I go lean of peek, with the JPI I can find the sweet spot by monitoring my speed, fuel flow and MPG. For my engine I found that the sweet spot is balancing EGT on #4 and #6 cylinders, #4 is lean of peek and #6 is rich of peek.

Do you have time to look out the window once in a while while you're doing all this? Holy smoke, glad I just have a little 320 Lycoming- I take off with full throttle, pull it back to 2500 for cruise-climb or cruise, and pull the red knob out "a little". Up higher, pull it out "a little more". I like to keep things simple.

[172heavy]

.... I run rich of peek on climb out and lean of peek on most cylinders in cruse, on climb out I will adjust my speed and mixture to keep my hottest cylinder under 370F, once at cruse altitude I go lean of peek, with the JPI I can find the sweet spot by monitoring my speed, fuel flow and MPG. For my engine I found that the sweet spot is balancing EGT on #4 and #6 cylinders, #4 is lean of peek and #6 is rich of peek.

Do you have time to look out the window once in a while while you're doing all this? Holy smoke, glad I just have a little 320 Lycoming- I take off with full throttle, pull it back to 2500 for cruise-climb or cruise, and pull the red knob out "a little". Up higher, pull it out "a little more". I like to keep things simple.

Most of my flights are in the two hour range per leg and a total of four to six hours, It’s a game I play getting the most that I can out of what I have. Once you find the sweet spot its easy to find it again, you know where it is. 8.7 GPH @ 145-148MPH that’s a point to point average. With the wife, me and our stuff. Most Franklin powered 172s get 10 to 12 GPH around 152 MPH. We put around 130 hours a year on our 172, 130x$5.00=$650.00 to $1950 per year savings, not to mention the engine will last longer running it like this. People say fuel is cheap, but in ten maybe fifteen years what will I save? But then as you know pilots are all rich.