No, it is not possible to increase RPM (revolutions per minute) of an engine without increasing fuel or changing the air-fuel mixture. RPM is directly proportional to the amount of fuel being burned in the engine. The more fuel is being burned, the faster the engine will rotate, and the higher the RPM will be.
However, it is possible to increase the RPM of an engine without necessarily increasing the amount of fuel being burned. This can be done by adjusting other factors that affect the engine's performance, such as the timing, air intake, and exhaust systems. For example, increasing the air intake can help to improve the engine's performance by allowing more air to enter the combustion chamber, which can improve fuel combustion efficiency and help to increase RPM.
It's important to note that any modifications to the engine's performance should be done with care, and it's recommended to consult with a qualified mechanic or engineer to ensure that the modifications are safe and effective. Additionally, modifying the engine's performance may impact its emissions and fuel efficiency, which may be regulated by local laws and regulations.