What is the speed grading for cold running-in after an engine overhaul?
2 Answers
Cold running-in typically starts at 400-600 r/min and ends at 1000-1200 r/min. Here is additional information about running-in a newly overhauled vehicle: 1. Determining the running-in load: The initial load is usually (10-20)Pe (where Pe is the rated power), and the final running-in load is generally (0.8-1.0)Pe, with gasoline engines typically recommended at 0.80Pe. 2. Running-in duration: Adding an appropriate amount of active additives to the lubricating oil can significantly improve the running-in process. The cold running-in duration for each speed level is approximately 15 minutes, totaling 60 minutes.
As an experienced auto repair veteran, I've handled countless overhauled engines, and the cold run-in phase is absolutely not to be taken lightly. The so-called speed staging simply means dividing the engine speed into several stages for gradual increase during cold run-in. Typically, we follow a three-stage process: First, maintain between 1,000 to 1,500 RPM for 20 to 30 minutes to allow thorough oil lubrication of all components and warm up the engine block. Second, increase to 1,500 to 2,000 RPM for 30 to 40 minutes to promote initial break-in of cylinder liners and piston rings. Third, push to 2,000 to 2,500 RPM for 15 to 20 minutes to simulate road conditions and test stability. The purpose of staging is mainly to distribute frictional heat and avoid localized overheating that could cause cylinder scoring or bearing damage, which significantly extends engine life and reduces post-break-in noise. Many people take shortcuts and skip steps, resulting in reduced overall engine durability. I recommend monitoring coolant temperature not exceeding 90°C during operation, and checking the oil pan for metal shavings afterward to ensure quality. The entire process requires calm patience - rushing it may ruin new components and require rework.
