Does a vehicle engine have a constant speed?
No, that is why there is a gearbox
How the speed of a vehicle is related to engine speed and how tha vehicle speed is affected by the engine torque and gear ratio?
A smaller number as a gear ratio means more speed. Higher ratios have higher torque and less speed. The size of the engine just determines hp and tq for that engine unless it is upgraded. The gear ratio and engine determine the vehicles top speed and acceleration. More torque means more power therefore more acceleration.
The speed of an engine connected to an alternator is generally maintained as constant & the variation of load is taken care of by the engine governor which accordingly increases` the fuel rack or decreases the fuel rack & thus the fuel input to the engine. All of this happens at a constant engine speed maintained by the governor. If without any change in the load on the engine, the fuel supply is increased…
The tachometer measures the number of revolutions the engine makes in a minute. This indirectly equates to the speed of the vehicle. Depending on the gear that the vehicle is in, you could determine speed with a tachometer. To determine your speed, you would need to know the gearing of the rear end as well as the circumference of the wheels.
CVT generally refers to a Constant Velocity Transmission. This means that the engine will spin a a more constant speed while a vehicle accelerates. A CVT is similar to a snowmobile clutch system where the gear ratio is changed by two clutches that open and close to change the "gear ratio" of the belt that runs between them. this tecnology has been adapted to some automobiles and it is called CVT.