What indicates a successful engine speed check during testing?

A successful engine speed check during testing is indicated by the speed matching the manufacturer's specifications. This specification ensures that the engine is operating optimally within the performance parameters established by the manufacturer. When the engine speed aligns with these specifications, it suggests that the engine is efficiently functioning as designed, which is crucial for both performance and longevity.

If the engine were to operate outside of these specifications, it could indicate potential issues such as improper calibration or mechanical problems, which could lead to inefficient operation or potential damage. Therefore, confirming that the speed is as per the manufacturer's guidelines is a direct measure of engine performance and reliability.

Other options, while they may suggest various states of engine operation, do not directly confirm successful performance according to defined standards. For instance, an engine running quieter or producing more heat might suggest changes that are not necessarily positive, while increased fuel consumption is typically a sign of inefficiency rather than success. Only aligning with the specified engine speed provides the clear insight needed into the engine's operational effectiveness.