An automatic transmission refers to the mechanism that can shift the gear of a vehicle with the increase or decrease of speed, without requiring the driver to change them manually.
It adjusts to the rotational speed of the internal combustion engine so that the gear can handle the speed range and torque outputs. A 4 speed automatic transmission refers to the number of gears that the transmission can shift in to.
Each gear in a gearbox denotes a certain speed range. A 4-speed gear means the car can move between four different ranges of speed and RPM. A transmission is a complex component that allows the engine to run at various speed ranges. For example, it allows the car to run at 10, 20, 45, and 60 kilometers per hour at 1, RPM. As it is a 4-speed transmission, it lets the car to run at that RPM for four different speeds. The car can be driven at 6 different speeds at that RPM range if it were a 6-speed transmission.
To submit your questions or ideas, or to simply learn more, see our about us page: link below. Efficiency In recent 6-speeds, the extra speed from a 5-speed allows the engine to run at a lower RPM and save fuel, comparatively.
Shifting Differences Whereas in a 5-speed, drivers are advised to accelerate above 25mph in fourth gear, in a 6-speed car, drivers are advised to accelerate above 35mph in fifth gear.
Getting the Feel As manual shifting is a fairly intuitive skill set, there is no easy advice for a driver who is changing from a 5-speed car to a 6-speed. References City Data. In each gear you have a range where power is at it's highest. Below this gear speed your power is low have you ever tried to accelerate in 5th from stationary? And above it you hit the speed limitations of the engine.
So having more gears means you can spend more time in the power band - so acceleration efficiency is improved, however this may be offset by the time it takes to change between gears. As an example, large trucks may have 12 gears - they need the power to accelerate heavy loads.
But as the gear ratios are so close it takes a long time to get up to the top speed. The top speed itself has nothing to do with the number of gears. All that is important for the top speed is the power and max speed of the engine and the gear ratio of your top gear. I'd suggest removing that one you should only ask one question at a time. There are two main reasons auto manufacturers have started putting more gears into their cars: acceleration and gas mileage.
The main purpose of it is to keep the engine in its torque band. This is the area where the engine is working at its most efficient improved gas mileage and since it doesn't have to build back up to its torque band after a shift it's already there , it accelerates faster.
Within reason, the top gearing for most automatic overdrive transmissions are going to be pretty much the same within reason. This means the top speed is going to be about the same. The top end power is what is going to limit you, all other things being equal Time and time again when improvements are introduced, even minor changes to a vehicles spec, the ultimate end today is fuel consumption.
Lower fuel consumption means lower emmissions. This slower engine speed allows the engine controls to fully optimise power, fuel consumption and the all important emmissions. The slower engine speed gives the designer of the engine more time per revolution to implement a greater degree of control. They are counting in milli-seconds today. A vehicles performance, ie acceleration, is increasingly becoming irrelevant in todays cities. In London UK a ten mile journey by car during a working day will take at least an hour.
A car for primarily city use today would be better gauged by cost of ownership, annual tax band, insurance band and projected maintenance costs. Given that, let's consider the three options for transmission: four, five and seven gears. Almost certainly. We haven't assumed that any of the individual gears match between the various sets. However, this is easy to check: look up the gear ratios for the gearsets. If all other properties are identical, an identical top gear ratio will give you an identical top speed.
A smaller number of gears will almost certainly produce slower acceleration than a higher number of gears.
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