Engine Break-In Tips
Engine break-in is a very important phase in the life of your engine. Successful break-in will help to provide you with an engine which uses minimal oil and achieves optimal performance. While it may seem counter-intuitive, engine break-in is actually a period of controlled wear between mating parts.
Engine manufacturers typically provide instructions for engine break-in. Aero Recip provides copies of OEM break-in instructions with Lycoming and Continental engines. For Pratt and Whitney engines, Aero Recip provides enhanced break-in instructions based on our years of experience along with the OEM guidance.
Let’s look at some highlights of these various instructions:
LYCOMING – SERVICE INSTRUCTION 1427C
“The purpose for this engine break-in procedure is for the correct piston ring seating and stable oil consumption on a top overhauled engine or a newly overhauled engine that is installed in the aircraft.”
“At cruise altitude, decrease power to approximately 75% and continue flight for 2 hours. For the second hour, do power settings alternating between 65% and 75% power as per the applicable POH.”
“For correct piston ring seating, in a top overhauled or a newly overhauled engine, operate the aircraft at 65% to 75% cruise power until oil consumption is stable.”
“For a normally aspirated (non-turbocharged) engine, it will be necessary to operate at cruise power at lower altitudes. Density altitude in excess of 8,000 feet (2438 m) will prevent the engine from reaching sufficient cruise power for an acceptable break-in; 5000 feet (1524 m) is recommended.”
“DO NOT DO CLOSED THROTTLE DESCENTS. CLOSED THROTTLE OPERATION DURING DESCENTS WILL CAUSE RING FLUTTER WHICH CAN CAUSE DAMAGE TO THE CYLINDERS AND RINGS.”
CONTINENTAL – MAINTENANCE MANUAL M-0
“The recommended break-in period for Continental Motors engines is 25 hours.”
“At Cruise Altitude: Maintain level flight cruise at 75% power with best power or richer mixture for the first hour of operation.”
“Best power mixture is 100º – 150ºF (38º-66ºC) rich of peak exhaust gas temperature.”
“For the second and subsequent hours of flight, alternate cruise power settings between 65% and 75% power with appropriate best power mixture settings.”
“Avoid long descents at high engine RPM to prevent undesirable engine cooling. If power must be reduced for long periods, adjust the propeller to minimum governing RPM to obtain desired performance levels. If outside temperature is extremely cold, it may be desirable to increase drag to maintain engine power without gaining excess airspeed. Do not permit cylinder head temperature to drop below 300ºF (149ºC).”
“Avoid long descents at cruise power RPM with manifold pressure below 18 in. Hg.”
PRATT & WHITNEY ENGINES – AERO RECIP PROVIDES ENHANCED BREAK-IN INSTRUCTIONS.
Pratt & Whitney does not have extensive instructions relating to engine break-in, they state:
“lean mixture cruising (high manifold pressure) and over-speeding should be avoided in this period, except in cases of emergency.”
“Higher than normal cylinder temperatures may be evident for the first several hours of operation until rings are properly seated, and particular care should be taken to ensure that specified temperature and manifold pressure limits are not exceeded.”
“Service experience indicates that straight mineral oils are preferred for engine test, and the first 25 – 50 hours of operation, to provide quicker piston ring break-in plus internal sealing or coating on oil wetted surfaces.”
- WHILE AERO RECIP RECOMMENDS FOLLOWING MANUFACTURER’S, INSTRUCTIONS REGARDING OILS APPROVED FOR ENGINE BREAK-IN, WE DO NOT RECOMMEND THE USE OF SEMI-SYNTHETIC OILS, AS THE SYNTHETIC COMPONENT OF THE OIL CAN HAMPER THE BREAK-IN PROCESS.
- IT IS IMPORTANT TO REMEMBER THAT MOST ASHLESS DISPERSANT OILS ARE IN FACT MINERAL BASED OILS AND ARE SATISFACTORY FOR ENGINE BREAK-IN.
- TYPICALLY, TURBOCHARGED ENGINES REQUIRE ASHLESS DISPERSANT OIL FOR BREAK-IN AND THROUGHOUT THEIR LIFE.
- IT IS VERY IMPORTANT TO REMEMBER TO PRE-OIL YOUR ENGINE THOROUGHLY PRIOR TO INITIAL GROUND RUNS AND FLIGHT TESTING.
- WHILE AERO RECIP DOES NOT WANT YOU TO ABUSE YOUR NEWLY OVERHAULED ENGINE, WE JOKINGLY TELL CUSTOMERS TO “FLY IT LIKE THEY STOLE IT” AND DON’T BABY THEIR ENGINES.