Most of the cars these days function with a manual or an automatic transmission, or an advanced version of either of these two. There is a third variation too, which is called semi automatic transmission. What does semi automatic mean? Well, it features functions from both transmission types; hence, the name has been given. How does this transmission work? How is it different from manual and auto transmissions?
What Is Semi Automatic Transmission?
Semi auto cars are rare to find in the car these days – thanks to the popularity of the dual-clutch system. However, many models these days come with a dual-clutch/automatic gearbox that the driver can operate in a semi-automatic fashion.
What does semi-automatic mean? It’s not what you guess by the name! It is not automatic in any sense but resembles a manual gearbox without the clutch pedal. If you consider semi automatic vs manual, the only difference between them is that the semi-automatic version uses actuators and computers instead of cables and pipes for shifting the gears.
The main advantages of a semi-auto gearbox are that it facilitates better fuel efficiency (just like a manual transmission) and also as easy to use as an auto gearbox.
How Does A Semi Automatic Transmission Work?
A semi-auto unit follows the working principle of all other transmission types – using engine’s kinetic energy to turn the wheels through the rotation of an input shaft and various gears. There is a clutch in between the engine and the gearbox that allows the latter to engage (when the engine controls it), disengage (when it can spin or not without the engine interference), and partially engage.
A manual transmission uses a pedal to engage and disengage the clutch and a lever for the shifting of gears. Things are slightly different for a semi automatic gearbox that makes use of a set of actuators and a hydraulic motor in the places of a gear lever and clutch pedal, respectively. There is also a control unit (aka computer) that is in the charge of various actions including engine torque, the speed of the car, accelerator pedal position, and some others. It mainly works to determine the time and direction of the gear shifting.
When the control unit detects a situation where gear-changing is required, it engages the clutch to disengage the semi-auto transmission from the engine. Then, the shift actuators will activate a gear shifting and disengages the clutch to reestablish the connection between the engine and the transmission.
The Differences Between Automatic And Semi-Automatic Transmissions
Although their names sound almost similar, these two transmission types are different from each other in a few ways.
The Gear Lever Layout – If an automatic has a gear lever, it will be the typical “PRND” layout (denoting Park, Reverse, Neutral, and Drive). A semi-automatic could have either push-button or lever controls. The gear lever will not have a “Park” mode and there will be an “Automatic” option instead of the “Drive” mode. Most modern cars are likely to have +/- buttons for manual handling of the gear shifting. So, the layout is likely to be Neutral, Reverse, Automatic, and +/- buttons.
Functions – An auto transmission changes gear without any input from the driver. All you have to do is to put it in the drive mode and it will then change the gears according to the speed of the car. A semi automatic transmission, on the other hand, will not shift the gears by itself but will help the driver to navigate through gears. The driver has to give inputs for the car to move up or down a gear.
Which Cars Have The Semi Automatic Gearbox?
The semi automatic transmission has been around from the early 1930s. So, it needless to say that you will find this mechanism in the cars of almost all the automakers. Now a days it’s common to see semi automatic transmission cars in Ethiopia such as Suzuki Dzire and Swift. This is the reason Suzuki Dzire doesn’t have a park gear level.
Source https://carfromjapan.com/
