Low CHTs during engine break-in

[moon_dog]

Just got a top done in my 1970 F. Picked her up for the first test flight and orbited the airport for just over an hour. CHTs were somewhat hot on climb but when I leveled off, the CHTs were surprisingly low (lowest was 305, highest 333). Power settings were correct for break-in. My A&P suggested leaning to bring the temps up, which worked a bit, but the highest I could get them was 388 highest/346 lowest.

I did keep the power up the whole time until letdown. But based on everything I’ve heard, I was expecting to need to work to keep the CHTs down, not up? Anyone else have a similar experience?

I plan to just keep flying it low and fast and try to keep those CHTs in the high 300s… obviously very worried about glazing. 

Thanks all.

Edit: engine indicator is JPI EDM-830

Edited October 26, 2022 by moon_dog
Added engine monitor

[Jsno]

I would expect above 400 on initial break in.  Are the cylinders plated?  Nickel take about 1/2 hour for the temps to fall, steel an hour or two and chime take the longest.  Also did yo run much on the ground or keep it to a minima?  They could have glazed with a lot of low power running.  Keep flying and your oil usage will tell the story of glazing or you could borescope and see.  Don't know the indicator you are using, it could be defective.  You could test by dropping one probe in boiling water and see what it reads. What year and model are yo flying?

 

[mooneyflyer]

Bad Probe?

[Ragsf15e]

8 hours ago, moon_dog said:

Just got a top done in my 1970 F. Picked her up for the first test flight and orbited the airport for just over an hour. CHTs were somewhat hot on climb but when I leveled off, the CHTs were surprisingly low (lowest was 305, highest 333). Power settings were correct for break-in. My A&P suggested leaning to bring the temps up, which worked a bit, but the highest I could get them was 388 highest/346 lowest.

I did keep the power up the whole time until letdown. But based on everything I’ve heard, I was expecting to need to work to keep the CHTs down, not up? Anyone else have a similar experience?

I plan to just keep flying it low and fast and try to keep those CHTs in the high 300s… obviously very worried about glazing. 

Thanks all.

Edit: engine indicator is JPI EDM-830

I’ve broken in new (OHd) cylinders on mine and not had high temps.  Where are you? What’s the OAT?  Keep up the high power, you probably be just fine.

[moon_dog]

55 minutes ago, Ragsf15e said:

I’ve broken in new (OHd) cylinders on mine and not had high temps.  Where are you? What’s the OAT?  Keep up the high power, you probably be just fine.

That is comforting. I’m in the Bay Area, CA. OAT was ~15 C, so not cold!

Going to find some warmer temperatures this weekend and see how she does. 

[PT20J]

A large part of the break in happens in the first couple of hours. Lycoming ran my rebuilt engine in a test cell for about 2 hours, and I never saw elevated CHTs.

[Ragsf15e]

33 minutes ago, moon_dog said:

That is comforting. I’m in the Bay Area, CA. OAT was ~15 C, so not cold!

Going to find some warmer temperatures this weekend and see how she does. 

To be honest, I didn’t see increased oil use either.  I’m pretty anal and I have a jpi-930, so I have good data, but it was pretty hard to tell when break in was “complete”.  I flew her hard for 10 hours following the lycoming guidance, then used ROP around 65% or higher for some trips (which is pretty much the lycoming guidance anyway), and then I flew her as desired (sometimes LOP lower power).  I did definitely use Mineral oil and changed oil at 10 hours and 25 hours.  Mike Busch has some stuff on breaking in with xc20w-50 if you like, but definitely no additives for a while.  After the 25 hours I switched to my normal oil.  After ~50 I started putting cam guard in again.  
 

If you follow the lyc guidance and the engine is running fine, I would probably just be happy.

[Shadrach]

On 10/26/2022 at 11:17 AM, moon_dog said:

That is comforting. I’m in the Bay Area, CA. OAT was ~15 C, so not cold!

Going to find some warmer temperatures this weekend and see how she does. 

Heat does not break in cylinders, pressure does... Heat is a proxy for peak pressure. Friction also contributes to CHT during initial break in.  There is no need to "get the heat up" in and of itself nor is there a need to hammer the cylinders to break them in. You want high mean pressure with good temp control.  

Where is the timing set on your engine?  It takes a fair amount to heat up an IO360 in an F model when timed to 25°, if it's timed to 20°, it will run even cooler. 

I broke the cylinders in on my F model (timed to 25°) back in 2010.  I ran it full rich for the climb and flew racetrack patterns above the airport at 2000msl.  I am a heretic so I did most of the break in wide open throttle, LOP (not advocating). My CHTs never exceeded 350° in level flight.  I landed after about 2 hrs and changed the oil. I did two similar flights the same week. Oil control was well established in under 10 hours but I can't say exactly when. Cylinders have performed flawlessly since.

Stick to Lycoming's break in procedure and don't overthink the temps. You should be fine.

[A64Pilot]

On 10/26/2022 at 1:16 PM, Shadrach said:

 

Stick to Lycoming's break in procedure and don't overthink the temps. You should be fine.

This.

Heat, bad Cool, good  

I’ve broken in a few and honestly never had any issue with temps, but I climb at a much higher speed than most too. I think the ones seeing high temps may be climbing at Vy or lower.

[moon_dog]

Thanks all. I have been continuing the break-in at high power settings, alternating RPMs. Leaning with the a "big pull+" and getting the lowest CHT to ~340 degrees. Not consuming much oil either. The mechanic says the lower temp cylinders may just take a bit longer to break in but shouldn't be cause for concern, just not what he usually sees.

The baffling is very tight, so I think it's just cooling well. I'll take it.

[Shadrach]

44 minutes ago, moon_dog said:

Thanks all. I have been continuing the break-in at high power settings, alternating RPMs. Leaning with the a "big pull+" and getting the lowest CHT to ~340 degrees. Not consuming much oil either. The mechanic says the lower temp cylinders may just take a bit longer to break in but shouldn't be cause for concern, just not what he usually sees.

The baffling is very tight, so I think it's just cooling well. I'll take it.

Doing the “big pull” reads  like you’re operating LOP. You can break cylinders in quickly and at healthy temperatures while LOP but it should be done at max MP at DA’s under 3000’.  One needs to know what they’re doing and be comfortable running at max power levels on the lean side of peak. It’s not something to try unless you have a really good understanding of what you’re doing.

[Ragsf15e]

 

1 hour ago, moon_dog said:

Thanks all. I have been continuing the break-in at high power settings, alternating RPMs. Leaning with the a "big pull+" and getting the lowest CHT to ~340 degrees. Not consuming much oil either. The mechanic says the lower temp cylinders may just take a bit longer to break in but shouldn't be cause for concern, just not what he usually sees.

The baffling is very tight, so I think it's just cooling well. I'll take it.

He’s in the Bay area, so maybe he’s that low?  Usually people use ROP for break in just to achieve high enough power and cooling.  Doing it lop is a little bit more specific because it could be harder to achieve high power while being lean enough to stay cool depending on your altitude.

[Shadrach]

1 hour ago, Ragsf15e said:

 

He’s in the Bay area, so maybe he’s that low?  Usually people use ROP for break in just to achieve high enough power and cooling.  Doing it lop is a little bit more specific because it could be harder to achieve high power while being lean enough to stay cool depending on your altitude.

It’s not for everyone by any means but it can be optimal under the right conditions. Worked beautifully for me. At 11 years and 600hrs we continue to have excellent oil control and compression.  Cold compression test taken last week. I’m not saying compression numbers say a lot, but it’s nice when the numbers are near perfect.