Whats the difference between 'speedometer' and 'tachometer'?

Question

Why should there be a tachometer in a vehicle? How important is it to the driver?

Answer 1

HELLO

SPEEDO SHOWS HOW FAST YOU ARE GOING DOWN THE ROAD (MILES PER HOUR)

TACHO SHOWS HOW FAST THE ENGINE IS TURNING

(REVOLUTIONS PER MINUTE)

CARS WILL NORMALLY IDLE ABOUT 900 TO 1,000 RPM

MY CAR IS AN AUTOMATIC SO I PRESS DOWN ON ACCELERATOR AND EVERY TIME IT REACHES 2.500 TO 2, 600 RPM IT CHANGES UP A GEAR THIS IS BECAUSE I AM CRUISING. IF I WANT TO GET SOMEWHERE QUICKER I CAN PUSH A SPORT BUTTON AND IT WILL CHANGE GEAR AT 4,000 RPM

WITH A MANUAL GEARBOX IT TELLS THE DRIVER WHEN TO CHANGE SO AS NOT TO OVER REV THE CAR AS THIS DAMAGES THE ENGINE

Answer 2

A speedometer measures your speed across the ground.  A tachometer (greek?:  fast, swift)  measures your engines speed in revolutions per minute (RPM).

Before the advent of automatic transmissions, one had to manually shift gears and it was important to make the shift from 1st to 2nd, for instance, before the engine reached its "redline"  the point at which one could cause catastrophic damage to the engine.  Most modern transmissions protect the engine even when in the manual shift mode.

So, tachometers aren't quite as important as they used to be and are more eye candy in most autos.  Any thing with a standard gearbox requires one.  There is obviously a correlation between engine speed and auto speed.  Normally, you can go up to about 35-40 in 1st  without over revving an engine.  To go faster the transmission (either automatically or manually) must go to higher gears to get the top speed out of a car.

Answer 3

Seepdometer = how fast you drive

Tachometer = meassures flywheel RPMs

Answer 4

the speedometer measures "ground speed" ex: how fast you're moveing Tachometer measures the revolutions of the engines crank shaft,,as to thier usefullness it varies,,on automatic transmission cars not much u can do there except during close menuvers to help in fine movements and control of speeds(rock climbing) also one could "keep an eye on thier transmission" the engine would rev higher if transmission is slipping,,on my old stick truck when i was really winding out the gears i could tell wen i was close to "over revving" the engine on slick surfaces i could tell earlier wen i was "slipping a tire"

Hope this Helps!

Answer 5

a tach is used to measure the engines revolutions per minute or rpm. you dont really need one unless you have a manual transmission and a clutch. a speedo just tells how fast your going

Answer 6

speedometer tell you how fast the vehicle is moveing and tachometer tells you how fast the engine is spinning.  tachometers are more important for cars that have manual transmissions so you know when to shift.

Answer 7

A tachometer is a guage on how fast the engine is spinning as noted by RPM(Rotation Per Minute).  It is important in manual transmissions but I do not see why they are in automatic transmissions as the shifting is done for you.  Although, you can tell if your car is not idling right or shifting properly by looking at the tachometer.  Speedometer is just referring to how fast the car is traveling.  Tachometer and speedometer measures two different variables.  There are current motorcycles that do not have a tachometer but I have not seen a car without it.