… a practical guide to getting the most from your new engine
The following steps are ways to ultimately increase engine longevity, performance, and minimize maintenance costs. These are all great reasons to carefully plan your engine’s break-in and maximize the time you spend in the air.
- Take-Off: Conduct a normal take-off with full power full rich conditions. Monitor the engine RPM, oil pressure, cylinder head temperatures and oil temperatures for overheating or irregular oil pressure. Make sure all gauges are in the green.
- Ascent: Reduce to climb power in accordance with the flight manual and maintain a shallow climb attitude to gain optimum air speed and cooling. This will ensure you do not ‘force’ the engine and will prevent overheating.
- Hour 1: Level flight cruise should be at 75% power with best power or richer mixture for the first hour of operation which will continue the ring seating process.
- Hour 2: The second hour power settings should alternate between 65% and 75% power with the appropriate best power mixture settings. Vary the power setting every 15 to 30 minutes utilizing best power settings. Best power mixture settings are necessary to maintain high cylinder combustion pressures.
- Cruising: Engine controls or aircraft attitude should be adjusted, as required, to maintain engine instrumentation within specifications.
- Descent: The descent should be made at low cruise power settings with careful monitoring of engine pressures and temperatures. Avoid long descents more than 15 minutes with cruise RPM and manifold pressure below 18 In. Hg. You do not want to be powering back the engine for an extended period of time. If necessary, decrease the RPM sufficiently to maintain manifold pressure.
Best power mixtures occur between 75 and 125°F rich of peak exhaust gas temperatures. Mixtures richer than best power actually reduce cylinder pressures and cylinder temperatures and can increase the time required to properly seat the piston rings.
Best economy mixture settings reduce cylinder pressures and should be avoided. Reduced cylinder pressures with increased cylinder temperatures can result in “glazed cylinder walls,” which can only be corrected by removing the cylinders to re-hone the barrels and replace the piston rings.