Our mechanical engineer is here to help the average motorist in Singapore with his series of thematic Q&A articles.
THIS issue’s question-and-answer article is, again, about automatic transmissions, which equip the vast majority of cars in Singapore.
Like going from first gear to second gear, it’s a continuation from our previous issue’s Tech feature, which answered a few good questions about shifting from “D” to “N” while the car is moving, leaving a car’s automatic transmission in “P” without engaging the parking brakes, and switching to an automatic’s Sport or Power mode.
The questions this time are mainly about automatic transmissions with an “M” mode (manual), or its equivalent, for do-it-yourself gearchanging on the go, by using the gearlever (with requisite side gate) or paddle-shifters for “+/–” actuation up/down through the available gears.
Most automatic-transmission cars come with a manual mode these days. Would more wear take place if a driver were to change gears manually on a regular basis?
The simple answer is no. Modern automatic transmissions which allow manual gear selection have sophisticated controls to maintain efficiency and reliability of both engine and transmission.
You cannot, for instance, select 6th gear when you start from rest, nor can you select reverse when travelling at 100km/h. In fact, the control system basically takes charge in the event of any transmission abuse.
Using the manual mode gives the driver a limited but useful level of control in various circumstances. A good example is when driving down a spiralling multi-storey carpark – the manual mode can maintain the gear in 1st to provide maximum engine braking and hence a constant slow speed.
My car has paddle-shifters and seven gears. I have the habit of skipping through the gears rapidly, like from 6th to 3rd.
When I was driving a manual car, I used to shift directly from 4th to 2nd gear. There was no damage to my manual car’s gearbox then. But if I do it with my current car’s paddle-shifters, will I damage or wear out the transmission prematurely?
Unlike manual transmissions, it is not possible to shift directly from 6th to 3rd in an automatic car. You need to run down the sequence, through 5th and 4th, before arriving at 3rd gear.
In a manual gearbox, the driver does all the clutch work. In an automated manual gearbox such as a dual-clutch transmission, the computer makes all the decisions and commands the actuator to do the “clutch” work. As the system is computer-controlled, there is no danger of shifting to a lower gear if the speed is too high for the gear ratio.
No matter how many times you flick the paddle, it will never switch from 6th to 1st, for example, at a speed of 80km/h. It works for upshifts, too – the transmission will not allow you to select a higher gear if the speed is too low.
So there is no risk of damaging your vehicle’s transmission if you paddle down (or up) rapidly.
When I went to view the new 1-litre Opel Astra, the salesman told me it has an Easytronic transmission that is actually a manual gearbox without a clutch pedal. How does it work?
Opel’s Easytronic is a manual gearbox that changes gears automatically. It is called a robotised manual transmission because the clutch operation is fully controlled by the on-board computer.
There are two operating modes available to the driver – fully automatic in D (drive), whereby the system changes gears with no input from the driver, and semi-automatic in M (manual), whereby the driver controls the gearchanges by flicking the gearlever forward (to upshift) or backward (to downshift). In either operating mode, the clutch is operated by the car’s gearbox controller.
The robotised system can perform smoothly if you bear in mind that there is a clutch controlled by a “robot” and ease off the accelerator pedal during every gearchange.
Another key difference between a robotised manual gearbox and a conventional automatic gearbox is the lack of a P (park) position for the gearshifter. You need to put the robotised manual gearbox into N (neutral) and engage the parking brake.