Such a tricky and hard-to-pronounce word for a simple Russian person, like sequential, is derived from the English sequence, which in translation means: sequence. AND English name sequential manual gearbox in Russian sounds like sequential box gears. This is a device on cars of a certain class, allowing only sequential gear shifts from first to high and vice versa, without jumping.
traditional box
On traditional gearboxes installed on most domestic cars, the neutral position of the gearshift lever is set in the middle. In order to move off, we depress the clutch and shift into first gear. In the future, with a set of speeds, their sequential switching is recommended.
However, nothing prevents us from starting immediately at the second speed, if the road condition is normal and the engine is designed for such an action. Trying to start the engine with a dead battery, we, pushing the car, can immediately turn on the third, and even the fourth, to make it easier. Nothing prevents this. Decreasing the speed to perform a maneuver, we, having slowed down, from the fourth gear go immediately to the second or to the first. Having mixed up, you can turn on the wrong speed on the go, which is far from harmless for a car.
Automatic transmission
To simplify driving, an automatic transmission was invented, which freed the driver from the need to select a driving mode on a particular section of the road. The machine itself switches, while the driver, working with one foot, either increases speed or slows down. Driving a car with automatic transmission requires less skill, and it is not in vain that permission to operate such vehicle now placed in a separate category. 
But work on improvement mechanical transmission did not stop. As a result, a sequential transmission appeared, which also does not provide for the presence of a clutch pedal, but works on different principles. And its main feature is strictly sequential switching of speeds.
Sequential principle
Sequential gear changes can be noted, for example, on motorcycles, where they are switched on by foot. The neutral position there is most often located between first and second gear. The same mechanics are used on tractors, on big trucks. Sequential switching has received the greatest distribution in the boxes of sports cars, where every millisecond is precious and speed reduction when switching is unacceptable. The use of hydraulics allows you to further accelerate this process and reduce it to a minimum.
The sequential mechanism is based on a conventional manual gearbox, somewhat complicated in the process of modernization. The main feature is that it can be used to switch from low to overdrive without reducing the speed of the car, which invariably occurs with the operation of a traditional gearbox. 
Cam or sequential
It must be said that a cam gearbox is installed on a number of racing cars. Although if the cam transmission is also made sequential, it is already very high speed switching modes will be even higher. And this is already applied on Formula 1 cars.
Unlike the helical gears on a traditional car gearbox, the cam gears are spur gears and long. This makes it related to the transmission of a sequential box. And it is this feature that allows both systems to switch without slowing down. At the same time, the device of the box itself is simpler - there are no synchronizers, but instead of many small teeth on the gear and clutch, there are end projections. Those same cams that directly engage with the gap. 
Peculiarities
On cars with a sequential gearbox, the shift lever is located on the steering wheel. Alternatively, buttons can be installed on the steering wheel. Desired button marked with the letter "S". Provides both automatic and manual switching. In this case, the box can operate in three modes:
- Standard mechanical.
- Mechanical sports.
- WITH automatic switching without the participation of the driver.
The advantages of this car of the future are the following points:
- A car with a sequential gearbox, like with an automatic transmission, does not have a clutch pedal - this is good for novice drivers.
- This box provides a choice between automatic and manual switching.
- High gearshift speed, which is reflected in the efficiency of the engine.
The disadvantage so far is the low wear resistance of the box mechanism.
Usually when it comes to gearbox racing car they say the following phrase: if in a paired acceleration race against each other an ordinary car and a racing car with engines of the same power come out, the last one will undoubtedly become the winner.
The key to victory is the cam gearbox.
The main advantage of the cam box is the speed of gear shifting. If you accelerate to ordinary car, shifting gears up as quickly as possible, almost with a blow, then changing each gear will take about 0.6 s. Approximately how much it takes for high-speed clutch disengagement / engagement. Pilot racing car can change gear three times faster - and do it without depressing the clutch, and at each shift it will win more than 0.4 s! This will happen due to the fact that with each switch in a conventional car, the engine speed drops and, accordingly, the intensity of acceleration decreases. To find out how a high-speed racing gearbox works, we went to Udelnoye, the base of the Red Wings team near Moscow, which competes in rally and circuit racing.
Features of racing mechanics
Denis Komarov, technical director of the racing team, prepares the cam gearbox for photography. He carefully wipes with a rag one of the gears of the unit - a huge spur wheel. If such a gear lay in the workshop by itself, one would think that it came from the box of a big old truck. Meanwhile, it belongs to the compact hatchback Citroen C2.
The large diameter of the wheel is due to two factors. First, the box of a rally car transfers a solid torque from the engine to the wheels. And secondly, the wheel is spur. The advantage of the usual helical gears, which are used in the boxes of “civilian” cars, is that due to the longer tooth and, accordingly, the larger load distribution surface, they can transmit the same torque with smaller dimensions. In addition, they are noticeably quieter. But spur gears are used in race cars not by chance: they do not create axial loads on the shafts and increase the efficiency of the box.
Surprisingly, a racing gearbox is no more difficult, and even simpler than a regular civilian one. There are no synchronizers here, but instead a large number small teeth that engage when the gear is engaged on a conventional box, large cams are used - end protrusions on the gear and clutch (usually there are 5-7 of them per wheel). In order for the gears to engage as soon as possible, the cams engage with a large gap across the width. Therefore, when switching gears to rally car you can hear the characteristic metallic clatter - these are the cams of the gear and the clutch collided with each other.
cam box it is arranged in the same way as a regular serial one, only instead of helical gears, spur gears, instead of gear couplings cam and no synchronizers
The cam box requires great dexterity from the pilot - especially when shifting down: in order to synchronize the engine and transmission speeds, it is necessary to delicately work the accelerator pedal and perfectly feel the car. With careful driving, the pilot uses the clutch when going down, during the race - especially on cars with a sequential cam box - he practically does not need the clutch pedal. This is also why rally drivers press the pedals differently than civilian drivers. Their right foot usually rests on the gas pedal, and the left is in charge of the clutch and brakes. It is very important to work accurately with the accelerator, because without a properly executed regassing, the downshift will either not happen at all, or will be accompanied by a hard blow.
That's why rally car drivers smile mischievously when I ask how popular the cam box is among tuning enthusiasts. Of course, there are street racing fans who replace stock boxes with cam boxes. Such a replacement improves acceleration dynamics, but requires constant concentration of attention from the driver when switching down, and also fills the cabin with noise from the operation of spur gears. The cam box howls about as loud as a civilian helical when there is no oil in its crankcase. Add here the high cost of cam boxes (up to € 20,000 per unit) and low service life - and we come to the conclusion that installing a cam box on an ordinary car is completely unjustified. Of course, the life of the car depends on subjective factors. In harsh racing conditions, synchronizers do not last long. So if you're driving civil car turns out to be a maniac, the cam box, quite possibly, will serve him longer than usual. However, over time, the racing unit will begin to make a characteristic knock, indicating that the rounded cams do not provide reliable engagement. Such a box needs to be replaced by worn-out pairs. Denis says that the cam box is dismantled after each race for testing, and some pairs in the box have to be changed every 2-3 stages of the race. And that's okay!
Back and forth: good and bad
There is another reason why cam boxes are not suitable for ordinary roads. Although these units are often equipped with a conventional seeker shifting mechanism, the fastest and most popular gearboxes among riders are sequential ones. In rally cars, the pilot shakes a lot, so moving the shift lever back and forth is much more convenient than shifting gears, as in a conventional car. In addition, this kinematics of the lever allows you to save a few milliseconds on each switch.
On standard cars a synchronized search-type gearbox is used. The choice of gear shifting is carried out in an H-shape with clutch release. Synchronizers are small gear rings that carry the entire load from the engine and transfer it to the wheels.
When using the engine high power standard synchronisers can't handle the increased power, and the gears start to "fly out" or simply stop turning on. In motorsport, cam gears are replacing synchronized gearboxes.
Cam gearbox.
The difference between cam gearboxes and conventional ones lies primarily in a small number of large teeth (5-7) of the gear shift clutch and gears, instead of small teeth on synchronized gearboxes. The teeth are straight, instead of helical, in order to remove the axial movement of the shafts. Gear shifting is clear and smooth, which is very important in auto racing, especially drag racing. The gear shift mechanism is search and sequential.
Search it works like a standard gearbox, only more clearly, without depressing the clutch, you just need to loosen the gas pedal, and you can shift gears. The clutch is only needed when pulling away in first gear.
Sequential mechanism(pictured) allows you to shift gears one step up or down, like on a motorcycle. The shift lever moves only back and forth, the number of the selected gear is displayed on the display.
The shift forks are controlled by a special shaft, which has wave-shaped grooves. With each push of the lever, it rotates by a certain degree, and the shape of the grooves helps to move the fork to a neutral position, or to engage a gear.
To change gear in sequential checkpoints you can use the pneumatic or electric drive of the lever, placing the drive button for convenience - on the steering wheel, or use the steering column switch.
Why are such gearboxes not used in ordinary cars?
The sharpness of the gear shift saves time but creates a large shock load on the gears of the gearbox, which leads them to premature wear. For example, a gear shift on a conventional car takes 0.6 s. while on cam boxes, switching takes 0.2 s. When switching 5 gears, the gain is 2 s. and even more, since the engine speed does not have time to fall, and are in the zone maximum power. Two seconds is a very big gain in drag racing, where hundredths of a second determine the outcome.
Gearbox ratios.
In tuned cars, various gear ratios(rows) checkpoint. The main disadvantage of the standard gearbox is that the first gear is too short. It is designed for ultra-slow driving in traffic jams, slipping in the mud, but no matter how dynamic acceleration car on the race track.
If you try to quickly accelerate in first gear to maximum speed in a standard car, the speed will hardly exceed 40 km / h and then with a crunch it shifts into a long second gear, in which acceleration is almost twice as much.
For more efficient acceleration, closer gear ratios of the gearbox and a longer first gear are used, in which the speed is not much less than in the second.
Optimization of engine working resources during control has occupied the minds of designers since the release of the first car. This was achieved different ways, but one of the basic ones was the increase in efficiency when interacting with the gearbox (gearbox). The very mechanics of pairing two nodes requires a certain amount of dynamic effort, but it is impossible to do without this function. One of the most energy-efficient systems for changing the torque frequency is cam gearbox, which, however, has significant limitations in its application.
Features of the device mechanism
Although cam "boxes" are superior to standard transmissions in a number of characteristics, their design can be considered as simplified with respect to conventional mechanics. main feature from point of view technical device is to get rid of synchronizers. Together with them, the device of a whole group of elements was optimized, which were supposed to make the transmission control easier, but they also lengthened the period for issuing a command through several nodes. As a result, the whole infrastructure with fine teeth was replaced by a set of cam rows. At a gearbox of this type, one clutch can contain up to 7 cams, which increases the margin of the hitch area in width. At the same time, the size of the gear in this system is larger than in standard gearboxes, not to mention the replacement of the beveled shape of the teeth with a straight one. The latter was due to the need to reduce friction losses and minimize axial load on the shaft.
Operating principle
The technique of work can be sequential or search. In the first case, sequential gear shifting is implemented, and in the second - the usual one, as in a standard gearbox. In practice, it is the sequential principle that is more often used, since it allows to reflect the capabilities of the cam design to a greater extent. Switching can be carried out up and down, as well as on the sides. Control from the driver is made through a lever connected to the shaft. For example, switching a cam gearbox on a VAZ-2108 is characterized by rigidity, reliability and simplicity. The lever moves the wave-shaped grooved shaft, turning it by a certain degree. As a result, either the “neutral” or the transmission is activated. By the way, in order to further save time, the gearshift knob itself is made large and high so that the driver spends less time manipulating mechanical control. In technical terms, the semi-automatic cam systems occupy the highest stage of development, in which the driver only needs to wait required switching electronics.
Operating Capabilities
The operating torque when handling the cam shifting system is significantly reduced, which saves time. Regardless of the characteristics of the engine, the rate of change of torque in a cam gearbox is faster than in conventional transmission. The time to complete the operation is 0.4-0.6 s, which is noticeable when compared with disengaging / engaging the clutch on a car with a standard "box". More importantly, the design of sequential mechanisms expands the possibilities for tuning. This applies to cases of complete re-equipment of the car in a racing modification with foot shifting. IN this case it is necessary to install together with the gearbox pairs and the main differential pair, which can correct the dynamic qualities of the machine. Again, an ordinary driver is unlikely to need such an update, but for a connoisseur of sports tuning, it will provide a new driving quality.
The use of cam gearbox models
On cars designed for roads common use, such mechanisms are rarely used. For such provision, there must be certain grounds associated with an increase in dynamics or a simplification of the structural base of the transmission unit. Often, cam gearboxes are used in single tuning events to demonstrate certain capabilities of conceptual models. In the case of the Japanese sports car Mitsubishi Lancer evolution the combination of a sequential “box” and a 420 hp engine, in particular, made it possible to accelerate to 100 km / h in 3.5 s.
Gearbox cam mechanism on VAZ
In Russia, the production of components for transmission cam units is carried out by the Lada Special Transmission plant. This group produces sequential mechanisms suitable for VAZ cars. According to users, domestic products demonstrate high stability, clarity of operation and reliability. But you can also turn to solutions from Eastern European manufacturers like TST and Dogbox. In the lines of these companies, you can find the closest sequential gearboxes on the VAZ. Cam mechanisms foreign production usually shipped loose. For example, kits without mounting hardware are often offered, which makes it necessary to additionally look for accessories for fixing the unit to the carrier base. Sometimes automatic transmissions are taken as donor kits.
Cam gearboxes for the "classic"
Of course domestic cars the needs for equipping with cam "boxes" are not limited. Classic sedans and hatchbacks that are used on public roads, can be converted to the sequential principle of gear shifting. For this use special modifications cam gearboxes for VAZ and "classics" in one configuration or another. As a rule, these are mechanisms with a cam clutch and gear units with 5-7 elements on the surface. The more cams, the higher the resource of the unit in a pair of clutch-gear. On the other hand, the complexity of the design increases the price and complicates the integration process of the device. And even if the basis of the product fits into the mounting base in terms of parameters, then additional difficulties can be caused by the refinement of the gear shift fork. Often, for these purposes, regular fixtures, which are finalized by welding or milling. Ready-made "boxes" assemblies may well be used, but this mainly applies to obsolete 5-cam mechanisms.
Cam "boxes" and racing mechanics
Yet the target niche for the use of cam gears are sports cars. An example of a sports car from Mitsubishi has already been given, and the use of this unit in cars is not limited to this. This practice continues Subaru Impreza, provided with a sequential "box". And with regard to this model, it is worth noting the differences in approaches to completing the cam unit. IN civilian versions The sports car applies precisely the consistent principle of changing torque. But in the rally modification, this decision is prohibited, so the basic search switching mechanism is left. A striking example of the use of this design is the cam row of the Toyota MR2 gearbox. This is a two-seater sports car, the latest modifications of which received a five-speed sequential “box” SMT. The features of this node include the fact that it is able to withstand loads from engines with a power of about 800 hp.
Restrictions on the use of sequential checkpoints
Even if we discard the fact that only drivers with the appropriate experience in the physical control of the transmission can handle the cam "boxes", there are several fundamentally important kinematic nuances in the operation of such devices. Sequential shifting reduces the vehicle's maneuverability when performing complex lane changes on public roads. In other words, even clever racing pilot will have a big loss when switching the fork due to the need for regassing with sharp transitions from lower to upper stages. On a straight track, where you need to constantly and confidently maintain a high speed limit, the cam gearbox manifests itself with best sides, however, in civil car its advantages turn into disadvantages.
Conclusion
The concept of sequential gear shifting, with all its features, retains the prospects for technological development. This is confirmed by the active merging of such transmission mechanisms with electronics. For example, today there are cam units operating on the commands of the Motec programming computer. One of the main functions electronic block in a car with such a filling, as the developers say, there will be automatic control the operation of the ignition system and the performance of regassing.
Transmissions that are used in the rally, I would divide into several types.
1. Full stock.
Factory synchronized manual transmission. Without any changes. In motorsport and in rally, it is almost never used because the standard gearbox is designed for city-highway operation, and is too long for a rally and the car with it is slower than it could be.
2. Tuning stock.
principle of operation of the synchronizer
When the main pair and gear ratios are changed, most often a limited slip differential (worm or disc) is installed, which greatly improves the dynamic capabilities of the car on slippery surfaces.
worm gear limited slip differential
Limited slip disc differential
The gearbox is still based on synchronizers and helical. Often used for tuning city cars. T.K. Compared to stock, it greatly improves the dynamics of the car. This is how rally driving looks like a checkpoint. This is my onboard from the Russian Rally Cup - Golden Dome Rally 2013
3. Cam gearbox.
It takes its name from the cam clutches, which replace the synchronizers and allow you to turn on quickly and without depressing the clutch to produce shocks, both up and down, the gear will turn on reliably.
The gears in this gearbox are spur gears. It is used together with a disc differincial of increased friction. This checkpoint is no longer used for urban tuning. has a reduced resource and high cost. This is what driving with a cam gearbox looks like, shifts are fast and without a clutch.
4. Sequential gearbox.
The difference from a simple cam gearbox is that instead of the usual switching scheme, this gearbox has a lever travel only forward (gear down) and backward (gear up). In fact, the difference is in the mechanism and principle of switching, and the clutches and spur gears are the same as in a conventional cam gearbox. On this moment in a rally this is the pinnacle everything else is prohibited. Such gearboxes are used on all modern and fast rally cars, including cars of the World Championship WRC rally. Here is an example of how driving with a sequential gearbox looks like
But back to my car.
When I bought Logan there was a JH3 box in its case there was a shortened symbiosis Main Couple and short row. This allowed the machine weak motor be much faster than standard logan. After finishing driving in a Renault monocup, where changes to the checkpoint were prohibited technical requirements, I decided to further improve the dynamics of the car by installing a short final drive.
Transmission 4.9 (my former 4.5, factory 4.3) was found in Europe,
the table shows how the speed changes in gear, but unfortunately it is quite difficult to show how the dynamics of the car improves
though, unfortunately, it turned out to be not cheap, at the same time they strengthened the gearbox housing so that the increased torque from the internal combustion engine could be transmitted.
This eventually played a cruel joke. Due to poor-quality work performed by third-party specialists, the gearbox broke down 2 times, and then completely fell apart.
The reason was in the reinforcement plate, which was designed to hold seats shafts from displacement. After that I decided to switch to next level. A new cam gearbox was purchased from the Baltic company samsonas.
With this transition, I simultaneously improved the dynamics of the car, increased reliability, improved handling. The fact is that in my previous gearbox there was no limited slip differential of the so-called "blocking". And in this gearbox, it is on-disk, which allows you not to lose on acceleration and improves cornering.
