Break in done?

[Mconner7]

I have 8 hours on my newly overhauled O-540 carb engine. The oil consumption is practically non existent the last 4 hours.

I am sure the rings have seated but the CHT’s go to 410-415 on takeoff and drop as soon as I get the speed up and the power set for climb. At full rich (20+ gph) the CHT’s are all in low to mid 300’s.

Cylinders 4 and 6 are the hotter, if I try and lean below 15 gph at 65%, they are both close to 400. #4 heats very slowly but #6 will shoot from 350 to 400+ with just a 1 gph leaning.

Suggestions welcome.

 

[rocketman1988]

Break in

My chts didn’t really come down and stabilize til I had about 25 hours on the engine.

 

[BobTurner]

Is this a 260 HP variety? If so, you should see close to 25 gal/hr of fuel flow on a full power sea level takeoff. What do you see, full power?
You’re flowing a lot of gas for 65% power. Is this down low? e.g., are cylinders closer to each other when leaning at 9,000’ with full throttle? If yes, you’re looking for an air leak into the #6 induction tube.

 

[lr172]

Cylinders 4 and 6 are the hotter, if I try and lean below 15 gph at 65%, they are both close to 400. #4 heats very slowly but #6 will shoot from 350 to 400+ with just a 1 gph leaning.

Suggestions welcome.

a 50* jump in CHT with 1 GPH difference is quite irregular and points to a sensor issue or some other cylinder or fuel injector issue. That is not normal break in behavior. It is possible that the rings are taking a while to fully break in and that could cause the 400 CHT, but still think that is high for 15 GPH @ 65% power if you were anywhere near cruise speed and lower altitudes. But it is not unheard of for a set of rings to take 15-20 hours to seat properly. Usually the major metal smoothing (i.e. the high friction, heat producing part of ring seating) is done in a couple hours and the next 20 hours are just light polishing (minimal, but not non existent, heat production). Minimal oil consumption typically means that the ridges have effectively been worn down in the cross hatch, but if one cylinder didn't break in when the other 5 did, you may not notice it, so low oil consumption may not be definitive that complete ring seating has been achieved on all cylinders. May want to do a compression test on #6 to see if a compression ring was cracked during installation. It happens. Also do a borescope inspection to view the cross hatch and look for unusual scratches.

I would be confirming the integrity of the CHT sensors and wiring for 4 and 6 as well as any issues you may have introduced on baffle reassembly that could be affecting cooling air flow.

Larry

 

[Mconner7]

Is this a 260 HP variety? If so, you should see close to 25 gal/hr of fuel flow on a full power sea level takeoff. What do you see, full power?
You’re flowing a lot of gas for 65% power. Is this down low? e.g., are cylinders closer to each other when leaning at 9,000’ with full throttle? If yes, you’re looking for an air leak into the #6 induction tube.

Bob,
250 hp and the fuel flow on takeoff is at least 22-23 gph. I agree that the intake tube is suspect, I will pull it and check for leaks.

 

[Mconner7]

a 50* jump in CHT with 1 GPH difference is quite irregular and points to a sensor issue or some other cylinder or fuel injector issue. That is not normal break in behavior. It is possible that the rings are taking a while to fully break in and that could cause the 400 CHT, but still think that is high for 15 GPH @ 65% power if you were anywhere near cruise speed and lower altitudes. But it is not unheard of for a set of rings to take 15-20 hours to seat properly. Usually the major metal smoothing (i.e. the high friction, heat producing part of ring seating) is done in a couple hours and the next 20 hours are just light polishing (minimal, but not non existent, heat production). Minimal oil consumption typically means that the ridges have effectively been worn down in the cross hatch, but if one cylinder didn't break in when the other 5 did, you may not notice it, so low oil consumption may not be definitive that complete ring seating has been achieved on all cylinders. May want to do a compression test on #6 to see if a compression ring was cracked during installation. It happens. Also do a borescope inspection to view the cross hatch and look for unusual scratches.

I would be confirming the integrity of the CHT sensors and wiring for 4 and 6 as well as any issues you may have introduced on baffle reassembly that could be affecting cooling air flow.

Larry

Thanks Larry,
I agree that the break in friction heating is still noticeable. I have looked over the baffles carefully and am sure they are in good shape and still see 400-415 on all CHT’s on takeoff, dropping nicely with a small power reduction and extra airspeed. I will troubleshoot #6 for its odd behavior and let ya know.

 

[Avanza]

Break in will take at least 25 hr and can be up to 50 hr.
Oil consumption is one thing. CHT must come down also.
It´s important to run the engine on at least 75 % power, preferably more
and change in rpm after 30 min at a time.
This means staying below 6.000 ft if possible. RICH mixture at all times.
Do not exceed CHT of 430 F at any time. Shallow climb, keep speed up.
The baffling around the cylinders should have sealant to prevent air leaking
past the outside of the cylinders. A smal amount of sealant between the cylinder heads is preferd. Look carefully for any air leaks and fix it.
This is important.
CHT will drop with more hours on the engine.

Good luck

 

[lr172]

Thanks Larry,
I agree that the break in friction heating is still noticeable. I have looked over the baffles carefully and am sure they are in good shape and still see 400-415 on all CHT’s on takeoff, dropping nicely with a small power reduction and extra airspeed. I will troubleshoot #6 for its odd behavior and let ya know.

I don't believe that a 50* CHT rise with 1 GPH of leaning is break in friction heat. Something else is causing that IMHO and unlikely to be an intake leak (major problems at idle and mostly benign at WOT with tapering between them - EGT will fall off at idle with an intake leak). the 4-415 CHT on take off likely means that rings are still seating with a good possibility of getting better once thy do. However, you do have a limited window for ring seating, so suggest you keep the power above 75% if you can keep temps below around 420-430. At 8 hours and winter wx, you should be below 400 at cruise speeds and sounds like you are.

 

[Dad's RV-10]

a 50* jump in CHT with 1 GPH difference is quite irregular and points to a sensor issue or some other cylinder or fuel injector issue. That is not normal break in behavior. ...

Fuel injector issue can be ruled out. It's a carb'd engine.

 

[Mconner7]

I don't believe that a 50* CHT rise with 1 GPH of leaning is break in friction heat. Something else is causing that IMHO and unlikely to be an intake leak (major problems at idle and mostly benign at WOT with tapering between them - EGT will fall off at idle with an intake leak). the 4-415 CHT on take off likely means that rings are still seating with a good possibility of getting better once thy do. However, you do have a limited window for ring seating, so suggest you keep the power above 75% if you can keep temps below around 420-430. At 8 hours and winter wx, you should be below 400 at cruise speeds and sounds like you are.

Larry,
Here is a pic of the temps at 70%, 17 gph. If I lean to 15.5, #6 goes above 400.

 

[lr172]

Larry,
Here is a pic of the temps at 70%, 17 gph. If I lean to 15.5, #6 goes above 400.

#5 tends to run on the high side and yours is quite a bit lower than the others. I would investigate this also. At 24", that could be due to a leanness due to an intake leak that wouldn't make much of an impact at WOT. 17 down to 15.5 is NOT a significant amount of leaning when that far ROP; Best power/peak CHT (80-100 ROP) should be around 13.5 at 70%. I remain convinced that something else is responsible for the rise, if the temp is even rising (i.e. sensor issue). Am guessing that going from 17->15.5 makes a minimal difference in CHT for 1-4, kind of proving my point. Elevated temps due to break in only change the absolutes, not the relative. During the reduction from 17->15.5, what is the avg CHT increase for 1-4?

For best break in, you want to be as close to best power as possible once down to 75% power, as long as you can keep the CHTs in check, as this puts more outward pressure on the rings. For the first couple of hours, full rich is advantageous, but later on best power is where you wnat to be.

Larry

 

[Mconner7]

Here is another data point, #4 will stay at 395 but #6 will continue to climb if any leaner.

 

[Mconner7]

#5 tends to run on the high side and yours is quite a bit lower than the others. I would investigate this also. At 24", that could be due to a leanness due to an intake leak that wouldn't make much of an impact at WOT. 17 down to 15.5 is NOT a significant amount of leaning when that far ROP; Best power (80-100 ROP) should be around 13-13.5 at 70%. I remain convinced that something else is responsible for the rise, if the temp is even rising (i.e. sensor issue). Am guessing that going from 17->15.5 makes very little difference in CHT for 1-4, kind of proving my point. Elevated temps due to break in only change the absolutes, not the relative.

Larry

I have done some mods to the rear baffle on #5 to try and keep it cooler.

And remember, it’s Florida winter, 85*….

 

[Avanza]

Have you checked the timing of the mags? 25 deg ?

Good luck

 

[Draker]

Break in will take at least 25 hr and can be up to 50 hr.
Oil consumption is one thing. CHT must come down also.
It´s important to run the engine on at least 75 % power, preferably more
and change in rpm after 30 min at a time.
This means staying below 6.000 ft if possible. RICH mixture at all times.
Do not exceed CHT of 430 F at any time.

Here's something I don't understand: We're really expected to blast away at >75% power for 25 hours of Phase I testing?? Half of my test plan involves important low-power operations: slow flight, stalls, flap operation, moderate power climbs and descents, airspeed accuracy at lower speeds AOA calibration, and anything that requires being below maneuvering speed, like calibrating the autopilot, stability checks, accelerated stalls, G limit testing, and on and on.

I want to properly flight test this thing, not just haul *** around and around in circles for 25 hours. What do people with new engines really do?

 

[Mconner7]

Have you checked the timing of the mags? 25 deg ?

Good luck

I set them both when I hung the motor…

 

[rocketman1988]

Here's something I don't understand: We're really expected to blast away at >75% power for 25 hours of Phase I testing?? Half of my test plan involves important low-power operations: slow flight, stalls, flap operation, moderate power climbs and descents, airspeed accuracy at lower speeds AOA calibration, and anything that requires being below maneuvering speed, like calibrating the autopilot, stability checks, accelerated stalls, G limit testing, and on and on.

I want to properly flight test this thing, not just haul *** around and around in circles for 25 hours. What do people with new engines really do?

Break the engine in per the manufacturer's instructions; if you choose not to, you may end up with glazed cylinders and the subsequent removal of said cylinders for honing.

Personally, I would alter your test plan. If that means flying around at 75% power for a time, so be it.

 

[lr172]

Here's something I don't understand: We're really expected to blast away at >75% power for 25 hours of Phase I testing?? Half of my test plan involves important low-power operations: slow flight, stalls, flap operation, moderate power climbs and descents, airspeed accuracy at lower speeds AOA calibration, and anything that requires being below maneuvering speed, like calibrating the autopilot, stability checks, accelerated stalls, G limit testing, and on and on.

I want to properly flight test this thing, not just haul *** around and around in circles for 25 hours. What do people with new engines really do?

I am not a believer in the need to fly at 75% for 25 hours, though do strive to use 75% power for 25 hours. For me, I flew 10 hours at 75% excluding take off and landing. On my second flight I did some stalls and brief slow flight to be sure that plane was handling as expected. Other than that, I flew 1-2 hour sessions at 75% for 10 hours. For me that was enough and began to insert the various testing stuff into those break in flights.

We all have to do what we think is right, but I do not believe that 25 hours purely at 75% is required to break in an engine. Though I agree fully that high pressure is good for seating rings and therefore keeping power up high is a good thing, just don't believe it must be for 100% of the engines 25 hours. If that were the case, taxiing and warm up would be prohibited. Pretty much every auto engine rolls off the line and immediately goes to typical driving patterns with VERY LITTLE full power application and the engines last for 250K miles. Yea, I know, someone is going to tell me that airplane engines are different. Sorry, but it is all pretty much cast iron rings riding up and down a steel cylinder wall or steel rings on a cast iron wall.

All that said, ring flutter during break in is a very real thing and strongly suggest folks follow the guidelines regarding avoiding low MAP descents during a minimun of the first 10 hours, with 25 preferred. In this area, planes are very different than cars due to engine loading via the prop.

Larry

 

[Draker]

Break the engine in per the manufacturer's instructions; if you choose not to, you may end up with glazed cylinders and the subsequent removal of said cylinders for honing.

Personally, I would alter your test plan. If that means flying around at 75% power for a time, so be it.

I am not a believer in the need to fly at 75% for 25 hours, though do strive to use 75% power for 25 hours. For me, I flew 10 hours at 75% excluding take off and landing. On my second flight I did some stalls and brief slow flight to be sure that plane was handling as expected. Other than that, I flew 1-2 hour sessions at 75% for 10 hours. For me that was enough and began to insert the various testing stuff into those break in flights.

Thanks for the confirmation. Spent Saturday at 85% power doing some airspeed and climb testing and also just enjoying this incredible machine. My oil consumption has been basically zero for the last three hours or so, so I'm thinking the engine may already be getting close to broken in.

 

[FireMedic_2009]

Break in will take at least 25 hr and can be up to 50 hr.
Oil consumption is one thing. CHT must come down also.
It´s important to run the engine on at least 75 % power, preferably more
and change in rpm after 30 min at a time.
This means staying below 6.000 ft if possible. RICH mixture at all times.
Do not exceed CHT of 430 F at any time. Shallow climb, keep speed up.
The baffling around the cylinders should have sealant to prevent air leaking
past the outside of the cylinders. A smal amount of sealant between the cylinder heads is preferd. Look carefully for any air leaks and fix it.
This is important.
CHT will drop with more hours on the engine.

Good luck

25-50 hrs for break-in would be for chrome cylinders, which take the longest, but not for steel. Steel cylinders break-in the quickest and usually take less than 10-15 hrs. Less than 10 hrs in not unheard of. The fact that the oil consumption is has pretty much stabilized in the last four hours indicates the rings have seated. However maybe #6 has not.

 

[Mconner7]

Ok it’s done!

Have you checked the timing of the mags? 25 deg ?

Good luck

Today I checked my slick, it was at 23*….I retimed the SureFly Sim and then flew it back from NC to Tampa Bay. Everything is dead on, even EGT’s and small variations in CHT’s. Leaning was normal, I am obviously making more power now.

What a relief! Thanks to all!