Many modern drivers have not even heard of such a concept as "double squeezing the clutch" when changing gears in manual transmissions. However, it will be useful for all drivers to be aware of this method. You need to start considering this issue with the history of the automotive industry. On old cars in the checkpoint, there were no synchronizers at all.
Synchronizers are devices that equalize the peripheral speed and prevent the gear from locking until the speeds of the gear of the input shaft and the secondary shaft are equal. To avoid breakdowns of the gearbox and extend its service life, the so-called double squeezing of the clutch (when shifting upward) and re-gasing when shifting down were used. In other words, without such tweaks, it was almost impossible to change gears of the gearbox without synchronizers (there would be a rattle).
Let's take a closer look at these switching methods. So, double squeeze is used when shifting gears from low to high. For example, let's take a shift from first gear to second.
Double Clutch Method:
We accelerate in first gear (up to 3000 rpm);
Press the clutch pedal and release the gas pedal;
Turn on "neutral";
Release the clutch completely;
We make a short pause, during which synchronization occurs (the engine speed will drop to about 2000) i.e. if we went in second gear;
Depress the clutch pedal again;
We turn on the transfer (in this example - the second);
We increase the engine speed by pressing the gas pedal.
Using the same algorithm, they switch from the second speed to the third, etc.
Re-gasification:
Now about the gas supply. It is used when switching from upper gears to lower ones. For example, consider shifting from second gear to first.
Let go of the gas pedal, and brake the engine in second gear. If necessary, slow down by pressing the brake pedal;
Squeeze the clutch pedal and completely release the gas pedal;
Turn on "neutral";
Release the clutch pedal completely;
We add a little engine speed by pressing the gas pedal, at this moment synchronization occurs (engine speed rises if you were driving in first gear);
Fully depress the clutch pedal;
We turn on the first gear;
Release the clutch pedal;
We are moving in first gear.
The main points here are the observance of a pause or rebase, with a neutral gear engaged. The main difficulty lies in the correct choice of the pause duration and the correct rebase, but with experience everything turns out to be much easier than it seems at the beginning. With the advent of the skill, everything will happen, as they say, "automatically."
Of course, modern gearboxes equipped with synchronizers (which are precisely designed to save drivers from all these "double squeezes") do not require the use of the above methods of gear shifting, nevertheless, if you master them, you can significantly extend the life of the gearbox. In any case, such a skill will not be superfluous, especially when shifted from upper gears down. I would like to note that the downward rotation will help to extend the life of the synchronizers (the load on them will decrease), and also if the machine does not pull up the hill, it will help to switch without loss of traction, increasing the torque down.
A generation trained in Soviet driving schools or chauffeurs who worked in the old domestic auto industry will not be puzzled by such a question. They know perfectly well what double squeezing is, what is overrunning and how to brake with the engine. These are the main questions that the driver had to master in the first stages of training.
In the modern world, these issues are not relevant, since there are fewer and fewer machines operating on such principles. Until now, they function with village farmers, in our general education schools as a clear example in labor lessons, colleges, technical schools and, of course, in the army.
However, these questions need to be known to any driver, since it was the basis of the basics and in the event, God forbid, cataclysms of a universal scale and if the earth turns into a deserted desert, ala "Mad Max", then they will be relevant. Why? Because the only equipment that will function is old lawn grass, lorries, army armored cars and other monsters of the Cold War era.State-of-the-art cars with tiptronic gearboxes, CVTs and a robotic transmission will sink into oblivion like a sweet dream that will not come true and comrades who are used to driving in the "D" position will either retrain or run on foot.Let's get closer to the point.
What is double squeezing and rebasing?
Double squeezing and rebasing is a mandatory procedure for ballet with pedals for cars whose gearbox is devoid of synchronizers. It should be noted that earlier they were not installed on the boxes, but later, when the engineering thought reached the point that the car should not only be useful, but also convenient to operate, synchronizers appeared.What are synchronizers?
Synchronizers are mechanisms that synchronize the rotational number of the shaft and gears. This makes shifting easier, makes shifting smooth and quick, and reduces wear and damage. Yes, and it eliminates the characteristic rattle that everyone has heard, especially when traveling on old buses.A double release is required not only when there are no synchronizers, but also when they are faulty or the box is frankly dead.
The very process of double squeezing is shifting up a gear by double pressing the clutch pedal. Why is this needed? Let me explain. This is necessary so that the engine speed would be level with the shafts and gears, otherwise the latter will fly apart or jam, whoever is lucky. How does this happen? You drive at the first speed, spin the engine up to 3000 rpm and plan to switch to the second, you need to drop the gas, press the clutch and move the lever to neutral, lower the clutch and wait until the engine speed drops to 2000 and press the clutch again, which will switch to the second. Thus, you equalize the speed of the input and output shaft. The box is in order and you can move on.
Relaunching is the reverse process in which you try to downshift without killing the gearbox. It happens as follows. You are approaching a bend where you cannot get through in fourth gear. You slow down and if you do not lower the gear, then you risk stalling, since there is not enough revolutions to spin the box with the engine. You smoothly throw the throttle and squeeze out the clutch, release from speed and put into neutral. Next, the following happens, you need to gain speed, since the gear of the low gear has a higher gear ratio. You need to work the gas pedal or, as they say, to re-gas, in order to raise the engine speed. The revs have risen, they are synchronized with the shaft and you can press the clutch and switch to a lower gear and continue driving on it.
The main thing in the process is to observe the pause of the gas rotation, with a neutral gear. It's like a beginner who gets behind the wheel of a car for the first time and does not understand how to catch the right moment of clutch when starting off, so that the car does not bite and stall. There are no special secrets here, the skill appears with experience.
Why is this necessary if modern cars with manual transmissions are equipped with synchronizers? There is a simple answer to this. Imagine that you have a pickup truck or a small truck, such as Gazelle and Valdai, and you are transporting some kind of cargo. After all, the road is not always flat and straight, there are descents and ascents or sections of rough terrain with a gravel road, and there are bumps, ravines through which it passes. Well, so that these same synchronizers did not order to live long after the first ascent, you need to use a rebase. You go uphill and understand that in this gear the car will not pull out, there will not be enough revolutions, you do a rebase, switching to a lower one and the car will not be difficult to switch under a slope without losing the necessary inertia.
There is one more thing that every driver should know - engine braking. Why is he married if I have four gallant wheels that will do everything. It is necessary, especially when the brakes have failed, ice or steep descent in mountainous areas. In these cases, the ability to brake the engine is essential. How does this happen? If you suspect that your brakes are failing, downshift, the engine rpm will rise and the transmission speed will drop as you downshift. The car will start to slow down. Then switch in the same way until the danger is over and you can either continue driving or use the braking system to stop. But this is on a manual transmission, but how to brake with a machine? It is necessary to transfer the box to overdrive and gradually reduce the speed, when the speed drops to 90 km / h, transfer to the second and wait for the code, the speed drops to 50 km / h and then switches to L. It's simple. However, most modern machines do not require such movements and adapt themselves to your style, if at a certain moment you threw the gas, then due to a lack of speed, it will reduce the gear itself, slowing down the entire structure.
There are many types of rebase. Its initial use was due to the absence of synchronizers in the variable gearbox, which excluded their smooth engagement. Today, re-gasification is used for smoother changes in engine speed when downshifting at high speed. In the event of a downgrade, the engine and gearbox are heavily stressed, which can adversely affect performance.
How to properly re-gas?
- With a standard rebounding on the rise, before overtaking, in a turn, we reset the fuel supply and squeeze the clutch. Without stopping in neutral, we lower it.
- Press and release the accelerator pedal and briefly increase the fuel supply. We bring the engine speed to the value of the maximum torque. Let go of the clutch and open the throttle.
- When lowering through the gear, turn off the fuel supply to the engine, squeeze the clutch. We turn on the neutral gear and bring the engine speed to the value of the maximum torque with a margin for engaging a low gear.
- Shift down and release the clutch pedal. We increase the fuel supply.
- In the event of an extreme situation, we use high-speed rebreathing. Slowly engage the clutch before the engine starts to lose rpm by holding the throttle open.
- At the time of a sharp rise in revolutions, we include a lower gear and clutch. Delaying the release will cause the clutch to slip, which will raise the engine speed to the level you want.
- Applying re-gasification to compensate for the loss of revolutions when increasing the gear, disengage the clutch, move the gear knob to the neutral position. Sharply, but in doses, we increase and decrease the fuel supply. Engage an overdrive, remove your foot from the clutch pedal and open the fuel supply.
Everyone who drives a car is quite rightly confident that he can do it. But how rationally do we drive our car? Today's Driving Schools lesson will discuss when to change gears.
Why did you come up with a checkpoint? The answer to this question can be obtained by listening to the motor while driving at the same speed, but in different gears. The lower the stage, the higher the rpm at which the given tempo is maintained. That is, at the same speed, each of the gears has its own motor speed. And vice versa - at the same engine speed, the car gets the opportunity to develop different speeds. The gearbox allows the engine to be used in the rpm range that is most beneficial in terms of its maximum efficiency or economy.
Move on schedule
The "golden mean" of switching must be sought in the rpm range corresponding to the maximum torque and the greatest power (see graph). It is the first parameter that determines the intensity of the acceleration of the car.
Experiments and calculations of designers show that for a passenger car with an eight-valve gasoline engine with a volume of 1.0 - 2.5 liters, acceleration with shifting to top gear at speeds close to the maximum torque - about 3000 - 4000 per minute is optimal. In this case, the accelerator should be pressed about half of its stroke - opening the throttle to a greater angle increases fuel consumption, but saves a minimum of time.
A little more energetic
Those who like more energetic "drive" (within reason, of course) can shift the point of engagement of the next gear three or four hundred revolutions higher, and the pedal can be sunk up to two-thirds of the stroke.
In a simple and understandable form for each driver, these graphics and calculations can be expressed through the speed of the car, therefore, the instructions for the car usually stipulate the maximum speed of movement in each gear. For example, in cars with engines of 1.2 - 2.0 liters and a five-speed gearbox, during normal driving in the first gear, it is not recommended to exceed the speed of 30 - 35 km / h, in the second - 45 - 60 km / h, in the third - 90 - 95 km / h, on the fourth - 110 - 130 km / h. Manufacturers allow for a short-term excess of these indicators by 10 - 15 km / h when overtaking or on ascents. This means that the tachometer needle (if it is in the car) can be driven into the red zone of the scale for 10 - 15 seconds.
Uniform movement
Maintaining the optimum engine speed when driving without acceleration and deceleration is determined by the same principles as during acceleration. Excessively low or high revs are undesirable and even harmful.
Driving at low revs requires more frequent gear changes, since at the slightest increase in load, you need to move to a lower gear. At the same time, by maintaining higher revs in lower gear, the driver "saves" one shift and also has a reserve of power for acceleration.
However, the positive aspects of driving in lower gears at high speed - the ability to shift less often or slightly better dynamics - are offset by excessive fuel consumption and a reduction in the resource of the power unit.
"A special case"
Accelerating on a steep incline, switching should be done a little later than usual, since during the movement with the transmission disengaged (with the clutch depressed), the car will have time to lose more speed than on flat terrain or a gentle slope.
Deceleration
When decelerating, competent motorists switch from top gear to lowest gear in the same rpms range (see graph) when the engine is most powerful. The main thing is to turn on the lower stage on time, without allowing the crankshaft speed to fall below the limit, beyond which the motor no longer has a torque reserve for the subsequent increase in speed.
Tachometer to help
For a rational drive, it is useful to learn and remember two technical characteristics from the operating instructions for your car. Firstly, the engine speed at which the maximum torque is achieved, and secondly, the speed at which the motor develops the highest power.
Acceleration will be most energetic if, with the right gear and accelerator, the revs are kept close to maximum torque and maximum power.
The fastest possible speed is achieved with the highest engine power.
Naturally, you should not drive with your eyes fixed on the tachometer in order to keep the arrow near the memorized numbers. It is enough to get used to the sound of the engine corresponding to the given rpm and learn how to automatically change gears exactly at the right moment, recorded by the memory.
On cars without a tachometer and with good noise insulation, experienced drivers, by the reaction of the car to pressing the gas pedal, by the rise and fall of acceleration, feel when to change gear.
Misconception # 1: "economic"
Some drivers abuse short accelerations - without letting the engine spin, they immediately go up to the next gear. Someone explains this by the desire to save the engine and gasoline, someone wants silence in the cabin and thus avoids the rumble that the engine emits.
Meanwhile, shifting up too early during acceleration, when the engine speed has not yet reached the maximum torque, has only a negative effect. The engine wears out more intensively due to low oil pressure and increased loads on the parts of the cylinder-piston group. In addition, during such driving, fuel consumption increases, since in order to continue acceleration from low revs in each next highest gear, it is necessary to press the gas pedal harder and open the throttle to a larger angle.
It is also unprofitable to delay the acceleration process with a small throttle opening - by a third of the pedal travel or less. Any acceleration requires the supply of an increased portion of fuel, so its prolongation inevitably leads to an increase in fuel consumption. Time, of course, is not saved either.
Less noise
-Limited "agility" of the machine (for low-power small class models)
-Increased engine wear
-Excessive fuel consumption
-More frequent switching
Misconception # 2: "athletic"
Many drivers suffer from another "ailment" - the habit of "twisting" the motor during acceleration. They say that we drive in a sporty way, while athletes know how dynamics and speed are achieved.
But in urban conditions, it would be more correct to call this manner nervous. The fuel of such drivers intensively flies into the pipe, but the main thing is that the goal - driving in a sporty way - is still not achieved. Modern motors are very high-speed and are distinguished by the maximum torque shifted to the high-speed region. But there is no sense in "turning" the engine above the highest power rpm - the dynamics gain in comparison with the optimal mode will be, but small. In addition, "extra" crankshaft speed leads to a reduction in the resource of engine parts and an increase in fuel consumption.
