Driving at 45-55 kmph, in correct gear & fuel savings

An IC engine performance is optimum at certain torque RPM conditions. This data has been known for long. I have seen this in early sixties (speed about 30 mph). At high gear and this speed the engine RPM and torque are the best thermodynamically. I am surprised that with all the advancement in IC engines, this does not seem to have changed. Well, thermodynamics also has not changed I guess.

I am driving bike since 15 years now and car since 2 years.
Driving in correct gear , I know most of the people know it. But the speed at which you are going and the gear you are using.

This also includes many things, if you are just starting the vehicle then put it in gear1, then slowly go to the top gear.

When you are slowing down your vehicle you need to go to a lower gear and drive.

Let me give you an example, if you are driving your bike in gear 3, and you had to slow down because of some bad road condition (most common in India).

Then you have two options, one is to shift to second gear or else, you can hold the clutch and accelerate more so that the vehicle doesnt get turned off and drive on.

So in the above scenario shifting to gear 2 is optimal and the other case is not.

This happens and we do it many times.

I remember reading that in 4-wheelers, if you maintain the RPM at about 1440; then you can have the max efficiency. How do we know that the RPM of 1440 corresponds to speeds of about 45-55 kmph? I think in car it's about 60-62 kmph (will have to check).

Kaustubh KatdareI remember reading that in 4-wheelers, if you maintain the RPM at about 1440; then you can have the max efficiency. How do we know that the RPM of 1440 corresponds to speeds of about 45-55 kmph? I think in car it's about 60-62 kmph (will have to check).

You can easily find the best efficient speed in the speedometer and do check the green range which represents the speed to obtain optimum efficiency.

It's little bit tricky to explain but I would try my best to answer it.RPM does not mean the revolution per minute of the wheel and it denotes the rpm of the engine.Higher the rpm denotes harder working of the engine.You would have also noted that in all specifications of cars and bikes while explaining about the power and torque, they would have quoted that "x" hp in "y"rpm or "u"Nm torque in "w' rpm.It all denotes the engines rpm.

The engines power is transmitted through clutch then followed by gearbox, propellor shaft,differential and to wheels.
following link helps to calculate the speed from rpm :<a href="https://wahiduddin.net/calc/calc_speed_rpm.htm" target="_blank" rel="nofollow noopener noreferrer">Speed versus RPM calculator</a>

Also do remember that gradual up shifting and down shifting helps in improving the efficiency and life time of the gearbox.Over throttling in a short period can increase fatigue of the engine.

Observations:

A.V.RamaniAn IC engine performance is optimum at certain torque RPM conditions.

+1
RPM meter (Revolution per *minute) which denotes Engine Piston RPM is the main key factor whether you are getting optimal fuel efficiency (not the mileage) or not.

ianoopObservations:

+1
RPM meter (Revolution per meter)

IS IT revolution per minute or revolution per meter?

SarathKumar ChandrasekaranIS IT revolution per minute or revolution per meter?

Typo😖