hais Posted April 5 Report Posted April 5 IO550N, engine break-in. Looking at this photo, do #2 and #5 cylinders still need break-in or is this CHT difference negligible and break-in can be considered completed?
Brandt Posted April 5 Report Posted April 5 My view is 20 degrees high is still breaking in. But it usually only takes about 2 hours for the temps to drop.
Fritz1 Posted April 5 Report Posted April 5 make sure CHT thermocouples read the same when cold, when in doubt swap around, clean thermocouple connectors, difference can be caused by a lot of factors including respective cylinders still breaking in 1
dkkim73 Posted April 5 Report Posted April 5 Tend to have the same initial reaction as @Brandt. Plus that is over the Mike Busch 380F rule-of-thumb, so high post-breakin. How many hours since swap?
M20F Posted April 6 Report Posted April 6 More information is required. How many hours and what break instructions did you receive?
hais Posted April 6 Author Report Posted April 6 1 hour ago, dkkim73 said: Tend to have the same initial reaction as @Brandt. Plus that is over the Mike Busch 380F rule-of-thumb, so high post-breakin. How many hours since swap? 1 hour ago, M20F said: More information is required. How many hours and what break instructions did you receive? 50 minutes. Intention was to run for 2 hours until they drop below 380F. The break-in was cut short because of an alternator problem. That left the question: do we repeat the break-in when the alternator is fixed, or is this good?
Brandt Posted April 6 Report Posted April 6 21 minutes ago, hais said: 50 minutes. Intention was to run for 2 hours until they drop below 380F. The break-in was cut short because of an alternator problem. That left the question: do we repeat the break-in when the alternator is fixed, or is this good? Not so much repeat as finish it. I have always been told if you don’t finish it you can glaze the cylinders, which you don’t want.
GeeBee Posted April 6 Report Posted April 6 Don't know your altitude but it looks like you're running hard there (28.1/2700) Continental says to run it had 75% power at best power (100 ROP) for the first hour. Then run between 65 and 75 best power there after until oil consumption stabilizes. Finally break in should be complete by 25 hours. So get your airplane to a Density altitude where you are at 75% WOT. Lean to best power and cruise it for a while and see where your CHTs settle. You'll know when it breaks in when the CHTs settle down and often, this happens quite rapidly. I've ferried factory new aircraft and at on glance in cruise CHT is near 400 then the next glance they are 350. https://continental.aero/service-bulletins/pma/e-sb003.pdf In the case of your picture, I would not be concerned with a new engine at that high of a power setting. What are your numbers at cruise at 75% 100 ROP? Once they settle within 30 degrees of each other, you're good. That can take up to 25 hours.
dkkim73 Posted April 6 Report Posted April 6 With only 50 min and those numbers, agree still has to break in. My two recent episodes of breaking in new cylinders were each an initial careful 2 hr flight with the QA mechanic taking down numbers. It was faster the second time for unclear reasons. We also modulated the power every 15 min between two higher power settings. I also ran higher power settings than 75% for this, in part due to a misunderstanding of what 75% was by the mechanic. After temps drop, then cruise ROP at least at 65-75% until oil consumption stabilizes. FWIW I dragged this out the first time by adding oil too readily (consumption is higher at higher fill levels). Right now things seem pretty stable around 15hrs. HTH David
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