Engine break-in.

[Lood]

I fetched my F last Saturday after all the cylinders had been re-honed and new pistons rings were fitted. We did two 15 min circuit flights to check for and sort out a minor oil leak here and there. I then hit the road home. Unfortunately, I couldn't get as low as I needed to due to the available daylight that was left and on average, I probably flew at about 5500 ft - give or take a little. I did get 23" of MAP and kept the RPM at 2600 for the first hour. After that, I switched between 65% and 75% power at 15 min intervals and during the last 30 min of the 2.5 hour flight, I flew at 70% - all as per Lycming's recommendations. All power settings were taken from the tables in my POH. However, I'm a little worried that I might not have made 75% power.

The engine shop filled the engine right up to 8 on the dipstick though. After the 2.5 hours flight home plus the initial two 15 min circuit flights as well as a couple of quick ground runs, the oil level is now at 7 on the dipstick. Like all 360's, mine aslo doesn't like to be filled all the way. It normally loses the oil untill around 6 on the dipstick before it's happy.

The engine shop asked me to keep flying it at at least 75% power for another 10 - 15 hours or so and this coming Saturday is going to be quite cold here, according to the forecast. Here at home, I can also fly lower, so my intention is to do another 2 hour flight at a minimum of 75%. I'll keep monitoring the oil level as Lycoming suggests that it should stabilize at some point, provided that the rings seated correctly and that the cylinders weren't glazed. All other temps and pressures were good during the flight and the engine ran nice and smooth - all the way.

I'd like to hear some opinions and advice, please as I've never done this and my good friend that has lots of experience had to leave the country for business and couldn't join me on the first flight.

[Parker_Woodruff]

You have a Mooney M20F, so you've got an engine that should run well lean of peak.

This is as good a reason as any to fly Low and Fast.

I'd take it any altitude where you can run LOP at high power.  I'd go hang out down low at 10 GPH LOP.  That's 75% power when LOP (regardless of altitude) and you should have cool cyls to go along with it.

[carusoam]

Lood,

What is your OAT in this wintery SA?  Has your airspeed gone back up where you were expecting it to be?

 

Best regards,

-a-

 

[Lood]

Regarding LOP, I've read quite a lot about it and it all makes a lot of sense to me. I've even done the Gami spread test and that was very good. However, I'm rather cautious to try LOP on my own. I would prefer to have someone with adequate experience in LOP operations with when I do it for the first time.

Regarding the speed, I didn't really bother to check it. I had to fly low level for 2.5 hours to get the required power from the engine. Low level flying ain't part of my normal day to day flying, so it took up a bit more concentration than normal - even more so with an engine that had just been worked on. I didn't really pay much attention to the speed, but instead, I kept my eyes outside most of the time and when inside, I was mostly monitoring temperatures. I did a calculation on what I remember and got to a TAS figure to the better side of 140kt. Power setting was WOT (23" MP), 2600 rpm and about 100 deg ROP. Alt was about 5500 ft and OAT 10 deg C.

I'll do a proper speed test again on Saturday.

[Shadrach]

Lood,

Your engine should be well broken in by 5 hours. If oil consumption has not stabilized in 10hrs, it likely never will... LOP is typically easy with an IO360. However, IIRC your home airport is significantly above SL and has DAs well above those necessary for high power LOP...so high power ROP is your only option. I would urge you to fly early morning when it's as cool as possible...other than that - stay low and stay rich.  Also, be mindful in descent and approach to not let the prop drive the engine, keep alt changes shallow and power high.

Why did you alternate between 65% and 75%? If it were me I would be running ~200ROP and as high power as possible. The goal is keep a high mean internal pressure which pushes the rings evenly (relatively speaking) against the cylinder wall through out the power stroke. 

I do not feel that Lycoming's break-in CHT redline of 420df is optimal . CHTs in that range suggest high peak pressure... that is not best way to make power for break-in...<400df is better.

 

I'd not worry about the speed until consumption has stabilized and temps are in line.  I doubt seriously that the new cylinders are going to make a huge difference in speed. Glazed cylinders are not going to stop an otherwise healthy engine from making rated power...It's going to use a lot of oil, run hotter CHTs and deposit lots of combustion byproducts in the engine oil......

[Lood]

Ross, my thoughts as well. Max temp forecasted here for Saturday is 9 deg C which means that the DA will be just under 5000 ft. I can easily get 75% in those conditions. I downloaded a Lycoming Service Instruction in which they point out step by step how the engine break-in procedure should be done. It calls for a 2 hour flight with 75% during the first hour and the alternating between 65% and 75% during the second hour. There after, they recommend cruise power settings of 65 - 75% untill oil consumption stabilizes. The document warns that DA's of higher than 8000 ft will be unacceptable for break-in procedures and recommend 5000 ft.

After the initial 2 hour flightand provided all temps and pressures are fine, they prescribe a full power flight of 30 min. I sort of tried to follow their advice as closely as possible.

[Shadrach]

Good deal, I did not recall 65% being part of their recomendation, but it's been 10 years since I needed to think about it. Glad you got your bird back.... Good luck!