Why can't the engine exceed 4000 RPM when revving in neutral?
2 Answers
The reason why the engine can't exceed 4000 RPM when revving in neutral is: The engine's program has a self-protection function. When the engine reaches the rated RPM, the speed control system will automatically regulate the fuel supply to prevent the RPM from increasing further, so the fuel supply will be automatically cut off after reaching a certain level. Consequences: Long-term revving will obviously increase oil consumption because high temperatures can easily vaporize the engine oil, which then enters the combustion chamber, causing oil burning. Once the oil level becomes insufficient, the engine can't be properly lubricated, which will damage the engine. Principle: When the throttle is floored, the throttle opening becomes too large, and the engine control unit will correspondingly increase the fuel injection volume. This can easily lead to incomplete combustion, resulting in carbon deposits. Therefore, long-term revving not only increases fuel consumption but also reduces engine power.
I've been driving my family's old car and noticed that revving the engine in neutral only goes up to 4,000 RPM. After pondering for a while, I finally understood why. It turns out the engine can't rev too high when stationary—this is to protect engine components from wear or overheating. When the car isn't moving, the power has nowhere to go, and high RPMs can easily damage internal parts like the crankshaft or valves. The ECU (the car's control computer) intelligently limits the RPM to prevent accidents. Additionally, noise and emissions are considered, as high-speed idling is both noisy and polluting. I asked a mechanic during a repair, and they mentioned that doing this frequently could damage the transmission and exhaust system. So, it's best not to try this often—normal driving allows the RPM to rise safely. Safety first! Regular vehicle check-ups can also prevent such issues, and maintaining good driving habits is essential.
