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Most cars have an RPM indicator next to their speedometers. What do you use it for?
What do most people use it for, in general?
The tachometer - rpm indicator - tells you how fast your engine is spinning. Usually, if it says "3" it means the engine is turning at 3,000 revolutions per minute.
For most drivers, especially those who have automatic transmissions in their cars, the tachometer is of no practical use. For people who drive hard, and/or race, it indicates when you should shift.
If you have an automatic transmission the tachometer (that's what most people call it) is just an information gauge. It tells you how fast the engine is turning the crankshaft. It is interesting to know that because you get some idea of how hard the engine is working. The higher the RPM, the more fuel is being burned. You'll also learn something about how the automatic transmission behaves. When does it shift? When does it let the RPMs climb?
With a manual transmission you can use the tachometer to help you decide when to shift. Most engines produce the most power in the upper 1/3 of the RPM range. Some get a bit ragged near the redline.
Please explain a mechanics term of REDLINE for the novice people.
Redline is that red line on tachometers that indicate an engine is running faster than it should. It CAN spin that fast for short periods of time, but it SHOULDN'T.
Not so, You can also manually shift a automatic transmission
and run the rpm's into the red.
For example when using 4lo on a 4wd and with a automatic transmission like a manual you need to watch the rpm's/.
When down shifting, so you don't over speed the engine.
Quote:
Originally Posted by Big George
The tachometer - rpm indicator - tells you how fast your engine is spinning. Usually, if it says "3" it means the engine is turning at 3,000 revolutions per minute.
For most drivers, especially those who have automatic transmissions in their cars, the tachometer is of no practical use. For people who drive hard, and/or race, it indicates when you should shift.
RPM, Revolutions Per Minute How many times the crank shaft is rotating in a minute.
Some turn a blind eye to it while others use it to manage there speed, power/ torque and when to shift the transmission.
Please explain a mechanics term of REDLINE for the novice people.
It's a line that's red. Didn't you go to kindergarten?
Okay, seriously, "redline" in gearhead terms is the RPM range where you begin to run the risk of damaging your engine. Historically this point has been indicated on the tachometer by a literal red line, hence the origin of the name.
At the risk of beating that issue to death, the "redline" is the maximum RPM the engine manufacturer deems safe for the engine. The tachometer shows a red area (probably more common than a red "line"). For most engines there is no value in running the engine above redline anyways because the power is falling off.
Some engines have rev limiters, or a circuit that cuts off the fuel supply to the engine when redline is exceeded.
Redline is a design issue. The faster an engine spins, the more oil it needs. The parts are moving faster. Valves may not open/close correctly at very high engine speeds. Vibration grows because parts that aren't perfectly balanced are noticed more at high RPMs.
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