Staged turbocharging
A sequential turbo can also be of use to a system where the output pressure must be greater than can be provided by a single turbo, commonly called a staged twin-turbo system. In this case, multiple similarly sized turbochargers are used in sequence, but both operate constantly. The first turbo boosts pressure as much as possible (for example to three times the intake pressure). Subsequent turbos take the charge from the previous stage and compress it further (for example to an additional three times intake pressure, for a total boost of nine times atmospheric pressure). This configuration is commonly found on piston engine aircraft which usually do not need to rapidly raise and lower engine speed (and thus where is not a primary design consideration), and where the intake pressure is quite low due to low atmospheric pressure at altitude, requiring a very high pressure ratio. High-performance diesel engines also sometimes use this configuration, since diesel engines do not suffer from pre-ignition issues and can use significantly higher boost pressure than engines.
Basics
Honda Civic Hatchback EE9 Logbook Map sensor
If you literally translate twin turbo in English, you will get either “double turbo” or “double turbo”. In principle, both options are correct. That is, from the name you can understand that there are not one, but two turbines. There are several varieties of ways to use two superchargers at the same time:
- Stepped.
- Parallel.
- Consistent.
Any of the systems, one way or another, is controlled by an electronic control unit; without it, it will be impossible to create efficient operation of the twin turbo. The ECU controls the input sensors of the turbochargers, the electrical drive systems of the air control valves, due to which the operation of the twin turbo is very finely tuned.
Parallel operating principle
A parallel twin turbo is the simultaneous operation of two turbochargers that operate in parallel to each other. The identical operation of two turbines is achieved due to the fact that each turbine captures the same portion of exhaust gases. Each compressor also leaves the same amount of air at the same pressure. Compressed air enters the common intake manifold, where it is then distributed among the cylinders. Parallel twin turbo is typical for V-shaped engines, especially diesel engines, where the degree of inertia is very important. Two small turbines provide less inertia than one large one.
Consistent operation
The meaning of the sequential twin turbo is that the turbochargers do not operate simultaneously, but sequentially replace each other. That is, when the engine starts, one compressor starts, and as the number of crankshaft revolutions increases, the second one turns on. This solution allows you to save fuel and not constantly use one of the turbines. By the way, such a twin turbo system includes two compressors with identical characteristics. The transition between turbines is also ensured by an electronic control unit. In such a system, its main task is to regulate and distribute the flow of burnt gases between turbines. The gas flow to the second compressor is controlled by a special solenoid valve. Also, such characteristics for turbines are often entered into the ECU in order to minimize the side effect of turbo lag. The use of twin turbo has been seen on both petrol and diesel engines.
Twin turbine
Staged operation of turbines
When considering the twin-turbo stage system, it is important to note that it is the most technically competent and advanced system, which determines the greatest increase in efficiency. In such a system there is electronic control of both the burned gases and the outgoing compressed air flow
Here, unlike previous options, it is possible to use two turbochargers of different sizes. When the engine speed is low, the burnt gas bypass valve is closed. Gases follow the twin turbo system, first visiting a small compressor, where they receive maximum pressure output with minimal inertia. Next, they enter a large turbine. When the speed increases, the turbines begin to work together. The bypass valve gradually opens and begins to gradually spin up the second turbine, letting gases flow directly through it. When the speed rises to maximum, the valve opens completely, and the large turbine begins to operate at its full power and air flows from it into the engine.
Maserati biturbo engine diagram
The meaning of a biturbo or twin-turbo scheme is that two turbochargers have less inertia and their turbines spin faster, which leads to an increase in engine output. There are also sequential biturbo circuits, where one turbine operates at low engine speeds, and the second is connected later. The most striking examples of modern use of biturbo include Pagani Huayra, Koenigsegg Agera, McLaren MP4-12C.
Conventional turbocharged cars, as a rule, are content with one turbocharger, and the biturbo circuit is a more complex mechanism, and therefore is used only on the most powerful versions of civilian models. In addition, recently the use of a cheaper twin-scroll scheme, even on powerful modifications, seems to be economically profitable. In turn, to increase the efficiency of diesel engines, they often prefer to use one turbocharger instead of a biturbo, but with variable turbine geometry.
The most technically sophisticated schemes for increasing the efficiency of supercharged engines include a layout with three turbochargers (BMW X5 M50d) or four (Bugatti Veyron), as well as a combined Twincharger scheme, where a mechanical supercharger works in tandem with a turbocharger (models from the Volkswagen and Volvo concerns). Well, the most common way to increase the efficiency of supercharged engines remains the intercooler, which is used on almost all modern turbocharged engines.
Sequential turbocharging
Fuel supply system in diesel engines - types and differences
BMW 3 Series Diesel turbo setup (Sequential turbo)
Sequential turbos refer to a set-up in which the engine uses one turbocharger for lower engine speeds, and a second or both turbochargers at higher engine speeds. Typically, larger high-flow turbochargers are not as efficient at low RPM, resulting in lower intake manifold pressures under these conditions. On the other hand, smaller turbos spool up quickly at low RPM but cannot supply enough air at higher engine speed. During low to mid engine speeds, when available spent exhaust energy is minimal, only one relatively small turbocharger (called the primary turbocharger) is active. During this period, all of the engine's exhausted energy is directed to the primary turbocharger only, providing the small turbo's benefits of a lower boost threshold, minimal turbo lag, and increased power output at low engine speeds. As RPM increases, the secondary turbocharger is partially activated in order to pre-spool prior to its full utilization. Once a preset engine speed or boost pressure is achieved, valves controlling compressor and turbine flow through the secondary turbocharger are opened completely. (The primary turbocharger is deactivated at this point in some applications.) In this way a full twin-turbocharger setup provides the benefits associated with a large turbo, including maximum power output, without the disadvantage of increased turbo lag.
Sequential turbocharger systems provide a way to decrease without compromising ultimate boost output and engine power. Perhaps the most noteworthy application of this system is the fourth-generation (1993-1998), which is generally regarded as having the most reliable sequential turbo system yet fitted to a production automobile, with a reported failure rate of less than 1% as of 2011. Other examples of cars with a sequential twin-turbo setup include the 1986-1988, the 1990-1995 JC, 1992-2002 (engine), the 1994-2005 (engine), and the 2.2 HDi. GM has filed a patent for a sequential twin-turbo system that uses a new bypass valve design said to optimize exhaust flow to the turbines of both turbochargers. According to the 2020 patent description, the exhaust manifold features two outlets with one directing to the turbine of the high-pressure turbocharger, while the second exhaust manifold outlet directs exhaust gases to the turbine of the low-pressure turbocharger via a connecting channel. Additionally, exhaust gas exiting the high-pressure turbine is directed to the inlet of the low-pressure turbine. The new bypass system features two throttle valves located on the same spindle mounted perpendicular to each other. With the throttle valves mounted on the same plane, one valve opens to direct exhaust gas flow to one of the turbochargers while the other valves simultaneously blocks exhaust gas flow to the other turbocharger. The vehicle ECU (electronic control unit) sends a signal to the spindle's actuator to rotate the throttle valves based on rpm and load. GM says the new design allows engineers to optimize exhaust gas flow to both turbines without the compromises of traditional sequential turbocharger systems. Additionally, the system could utilize a variable-geometry turbine or a fixed-geometry turbine on the high-pressure turbo.
Operating principle edit edit code
Turbo Studio
The operating principle is based on the use of exhaust gas energy. The flow of exhaust gases hits the turbine impeller (fixed to the shaft), thereby spinning it and the compressor blades located on the same shaft, pumping air into the engine cylinders. Since when using supercharging, air is forced into the cylinders (under pressure), and not only due to the vacuum created by the piston (this vacuum can only take a certain amount of the air-fuel mixture), then a larger amount of the air-fuel mixture enters the engine. As a result, during combustion the volume of fuel burned with air increases, the resulting gas is under greater pressure and, accordingly, a greater force is generated pressing on the piston. [ style
]
As a rule, turbo engines have lower specific effective fuel consumption (grams per kilowatt-hour, g/(kWh)) and higher liter power (power removed from a unit of engine volume - kW/l), which makes it possible to increase the power of a small engine without increasing engine speed.
Due to the increase in the mass of air compressed in the cylinders, the temperature at the end of the compression stroke increases noticeably and the likelihood of detonation arises. Therefore, the design of turbo engines provides for a reduced compression ratio, high-octane fuel grades are used, and an intermediate charge air cooler (intercooler) is provided, which is a radiator for cooling the air. A decrease in air temperature is also required to ensure that its density does not decrease due to heating from compression after the turbine, otherwise the efficiency of the entire system will drop significantly. [ style
] Turbocharging is especially effective in diesel engines in heavy-duty trucks.
It increases power and torque with a slight increase in fuel consumption. [ source not specified 238 days
] Turbocharging with variable geometry of turbine blades is used depending on the operating mode of the engine.
The most powerful (relative to engine power) turbochargers are used on diesel locomotive engines. For example, on a D49 diesel engine with a power of 4000 hp. a turbocharger with a capacity of 1100 hp is installed. [ source not specified 238 days
]
Turbocompressors of marine engines have the greatest (in absolute value) power, which reaches several tens of thousands of kilowatts (MAN B&W engines). [ source not specified 238 days
]
Straight-6 TwinPower Turbo: N55
When TwinPower Turbo technology is installed on a 6-cylinder engine, its benefits become clear. The N55 twin-turbo engine replaced the more expensive N54 unit in 2009. But both modifications are very similar to each other. Comparable output to BMW's own 4.0-litre V8, with a lighter block and lower torque, is even more tan, which can be found in the E92 M3 with the powerful S65 V8.
The N55 produces 302 hp and 300 Nm (400 Nm) of torque. It is installed in the 335i, 135i and all SUV versions. There is an even more powerful version under the symbol N55HP, with a power of 315 hp and a torque of 450 Nm. This version is available on top models such as the 640i, 740i, and even the sporty M140i super-heavy hatchback.
The debut of the engine took place in 2009, it began to be installed on the fifth GT series. Equipped with an advanced version of the 6-cylinder engine, the BMW 535i Gran Turismo can accelerate from 0 to 100 km/h in just 6.3 seconds. The maximum speed of this beast is limited to 250 km/h. In terms of fuel consumption, the BMW 535i GT consumes 8.9 liters per 100 kilometers. CO2 emissions are 209 g/km.
Author: Sergey Vasilenkov
Information publication: Traffic police news, accidents, traffic fines, traffic police, Online traffic rules exam. Technical inspection
Essence of the question
Many modern cars use such engine technologies to increase fuel use. Due to the larger amount of injected fuel, the overall speed increases. This technology was known back in the twentieth century - the arrangement of two pipes was called Double Turbo, Twin-turbo, and so on. Today they are presented as twin-turbo and biturbo technologies.
What does it mean
Biturbo is a turbocharger design that looks like two turbines. The first of them is large in size, and the second is smaller. While the former adds powerful airflow to the engine, the smaller turbo serves as the main element for mid-range performance. This system is aimed at smoother operation of accelerated motion.
The twin-turbo design is more focused on increasing power than on stable operation of the car. For this reason, it uses two identical turbines that directly affect the speed of movement.
Assembly Features
Most often, the twin-turbo system allows the use of a single intake manifold, which reduces maintenance costs somewhat, although the engine power is reduced. To compensate for this, separate manifolds and intake tracts were used. This made it possible to use the system for small engines, on which turbochargers were always placed in series.
BMW has its own vision for twin-turbo technology - the location of the turbines was in the camber of the V8, and not on the sides, as usual. The main feature was that the compressors were powered by cylinders that were located on both sides. Thanks to this solution, “turbo lag” was reduced by 40% without significant power losses. In addition, this reduced vibrations from equipment operation.
Operating principle and features
Parallel system
A relatively simple system involving a symmetrical pair of compressors operating simultaneously to distribute incoming air evenly. Most often, this scheme is used on V-shaped diesel engines, where each compressor supplies air to the intake manifold of its own group of cylinders.
Reducing inertia is achieved by reducing the mass of the turbine rotor; as is known, two small compressors provide a little more pressure and spin up faster than one, but larger in size and performance. Thus, the width of the turbo lag is significantly reduced, and the engine provides slightly better performance throughout the entire speed range.
Serial system
With this arrangement, two comparable compressors (not necessarily identical in characteristics) operate in complementary mode.
Sequential Twin Turbo diagram: 1 - boost bypass valve (bypass); 2 — air supply control valve; 3 — pressure difference sensor; 4 — exhaust gas supply control valve; 5 - secondary turbocharger; 6 — intercooler; 7 - primary turbocharger; 8 — exhaust gas bypass valve (wastegate).
One, usually lighter and faster, supercharger works constantly, eliminating the deep and wide turbo lag, the second, based on a signal from the electronics that monitors engine speed, is switched on to work at more severe conditions, providing maximum power and fuel efficiency. This series-parallel scheme (in peak modes both turbines operate simultaneously) is used on engines of any fuel cycle.
In 2011, the German BMW introduced an improved Triple Turbo sequential charging system.
Step system
The most complex and advanced system providing the widest power range.
Scheme of adjustable two-stage turbocharging: 1 - charge air cooler; 2 — boost valve (bypass); 3 — high-pressure stage turbocharger; 4 — low-pressure stage turbocharger; 5 - exhaust gas bypass valve (wastegate).
To create such a boost, two compressors of different sizes are installed, connected to each other by a system of pipes and bypass valves.
This type of turbocharging is called staged because in minimum modes the exhaust gases spin up a small turbine, and the engine spins up easily. As the speed increases, the valve opens and the large turbine begins to spin, but the pressure it creates needs to be increased, which is what the small turbine located behind it does.
When reaching maximum speed, the large turbine produces such high pressure that the small supercharger becomes aerodynamic drag. At this moment, the automation opens the bypass valve, and compressed air flows into the engine, bypassing the smaller turbine.
Fig - operation of the adjustable two-stage turbocharging system
The complexity of such a system is more than compensated by the flexibility of operation and the highest performance of the engine.
Modern Twin Turbo charging systems use other technical tricks to provide less sluggishness and more power. Electronic regulation of the volume of exhaust gases on the turbine wheel, variable geometry of the blades, a bleed valve, the unforgettable whistle of which indicates the safe removal of excess air in the intake manifold when releasing gas. The bypass valve is capable of not only turning on and off a turbine that is not currently in use, but also ensuring that pressure is maintained during short-term closing of the throttle, returning the reserve to the intake manifold instantly, during the time the valve is closed.
Video:
https://youtube.com/watch?v=avzbP2FYtSM
Twin Turbo can use such an important system as the intercooler in different ways. This can be one radiator with a common manifold, or separate coolers for each supercharger. The stepped system, for obvious reasons, always makes do with one radiator.
Turbocharger delay [edit | edit code ]
Turbocharger lag is the time it takes for power output to change after a change in throttle state, manifesting itself as a slower throttle response compared to the behavior of a naturally aspirated engine. This is due to the fact that the exhaust system and turbocharger require time to spool up to provide the required charge air flow. Inertia, friction and compressor load are the main causes of turbocharger lag.
- Types of Twin Turbo systems and their differences
- What is Twin-Turbo (Twin turbo)
- Types of turbocharging systems and their operating principles
- Parallel
- Consistent
- Stepped
- What are the advantages of using Twin-Turbo and are there any disadvantages?
Literally translated from English, the phrase twin-turbo means “double turbo” or “double turbo”. Both translations are correct. Now let's leave the linguistic aspect and study in detail the technical side of this type of turbocharging.
What is Twin-Turbo (Twin turbo)
In order to achieve a noticeable increase in engine power, a turbine is installed in its design. Twin-Turbo is one of the types of car turbo systems and it is on this that we will focus our attention. Twin turbo involves installing two identical turbines at once , which greatly increase the performance of the entire turbocharging system. This arrangement is much more efficient than a turbo system, which uses only one turbine.
Initially, the biturbo was designed to solve the main problem of all inflatable engines - eliminating the so-called “turbo lag”. This phenomenon manifests itself in a decrease in elasticity and a sharp drop in engine power at low speeds.
All this happens at a time when the engine turbine, under exhaust gas pressure, does not have time to spin up to optimal speed.
System composition edit edit code
In addition to the turbocharger and intercooler, the system includes: a control valve (wastegate) (to maintain a given pressure in the system and relieve pressure into the exhaust pipe), a bypass valve (to divert charge air back into the intake pipes to the turbine in the event of closing the throttle valve) and/or a “bleed off” valve (blow-off valve - to release charge air into the atmosphere with a characteristic sound when the throttle valve is closed, provided there is no mass air flow sensor), an exhaust manifold compatible with a turbocharger, as well as sealed pipes: air for supplying air to the intake, oil for cooling and lubrication of the turbocharger.
History of invention edit edit code
The turbocharging principle was patented by Alfred Büchi in 1911 in the United States Patent Office.
The history of the development of turbochargers began approximately at the same time as the construction of the first models of internal combustion engines. In 1885-1896, Gottlieb Daimler and Rudolf Diesel conducted research into increasing power output and reducing fuel consumption by compressing air pumped into the combustion chamber. In 1905, the Swiss engineer Alfred Büchi first successfully carried out injection using exhaust gases, achieving an increase in power of up to 120%. This event marked the beginning of the gradual development and implementation of turbo technologies.
The scope of use of the first turbochargers was limited to extremely large engines, in particular ship engines. In aviation, turbochargers were used with some success on Renault-powered fighters as early as the First World War. By the second half of the 1930s, the development of technology made it possible to create truly successful aircraft turbochargers, which were used mainly for increasing altitude in significantly boosted engines. The Americans achieved the greatest success in this by installing turbochargers on P-38 fighters and B-17 bombers in 1938. In 1941, the United States created the P-47 fighter with a turbocharger, which provided it with outstanding flight characteristics at high altitudes.
In the automotive industry, truck manufacturers were the first to use turbochargers. In 1938, the first turbo engine for a truck was built. The first mass-produced passenger cars equipped with turbines were the Chevrolet Corvair Monza and Oldsmobile Jetfire, which entered the American market in 1962-1963. Despite the obvious technical advantages, the low level of reliability led to the rapid disappearance of these models.
The introduction of turbo engines to sports cars, particularly Formula 1, in the 70s led to a significant increase in the popularity of turbochargers. The prefix “turbo” began to come into fashion. At the time, almost all car manufacturers offered at least one model with a gasoline turbo engine. However, after several years, the fashion for turbo engines began to fade, as it turned out that a turbocharger, although it allows you to increase the power of a gasoline engine, greatly increases fuel consumption. At first, the delay in the response of the turbocharger was quite large, which was also a serious argument against installing a turbine on a gasoline engine.
A fundamental change in the development of turbochargers occurred with the installation of a turbocharger in the Saab 99 Turbo production car in 1977 and then in 1978 with the release of the Mercedes-Benz 300 SD, the first passenger car equipped with a diesel turbo engine. In 1981, the Mercedes-Benz 300 SD was followed by the VW Turbodiesel, while maintaining significantly lower fuel consumption levels. In general, diesel engines have a higher compression ratio and, due to adiabatic expansion during the power stroke, their exhaust gases have a lower temperature. This reduces the heat resistance requirements of the turbine and allows for cheaper or more sophisticated designs. That is why turbines on diesel engines are much more common than on gasoline engines, and most new products (for example, turbines with variable geometry) first appear on diesel engines.
Features of Twin Turbo operation
TwinTurbo supercharging system
Systems with two compressors are used on both diesel and gasoline engines. However, the latter require the use of higher quality fuel with a high octane number, which reduces the likelihood of detonation (a negative phenomenon that occurs in the engine cylinders, destroying the cylinder-piston group).
In addition to the main function of reducing turbo lag time, the Twin Turbo design allows you to get higher power, reduces fuel consumption and maintains maximum torque over a wide speed range. This is achieved by using different compressor connection schemes.
Parallel twin-turbo
3.5 (Twin Turbo)
Paralleled twin-turbo refers to the turbocharger configuration in which two identical turbochargers function simultaneously, splitting the turbocharging duties equally. Each turbocharger is driven by half of the engine's spent exhaust energy. In most applications, the compressed air from both turbos is combined in a common and sent to the individual. Usually, each turbocharger is mounted to its own individual exhaust/turbo manifold, but on inline-type engines both turbochargers can be mounted to a single turbo manifold. Parallel twin turbos applied to V-shaped engines are usually mounted with one turbo assigned to each cylinder bank, providing packaging symmetry and simplifying plumbing over a single turbo setup. When used on inline engines, parallel twin turbos are commonly applied with two smaller turbos, which can provide similar performance with less than a single larger turbo. Some examples of parallel twin-turbo inline engines are 's, BMW's and 's B6284T and.
The , introduced in 1981 and featuring an aluminum 90-degree V6, was the one with a twin-turbo charged engine. Other examples of V formation engines with parallel twin-turbos include Mitsubishi's, and; Nissan's and ; and 's, 1997-2005, and.
While a parallel twin-turbo set-up theoretically has less than a single turbocharger set up, this is not always the case due to many factors. Marginally reduced combined inertial resistance, simplified exhaust plumbing, and the simultaneous spooling of both turbos means that there can still be a noticeable bit of lag, especially in high-flow turbo/high boost applications. Some ways to counter this are to use a light pressure set up with smaller turbos, where the turbos are designed to output less boost but spool earlier. While this setup sacrifices some top end power, it still has less lag than a similar engine with a single turbo set up making the same power. Another system would be the use of . This system changes the angle of the guide vanes depending on the exhaust pressure, giving the system excellent power throughout the rev range. Once used mainly in turbocharged, Chrysler was the first to use it in mass-production gasoline-powered vehicles with the, debuted in 1989.
It is possible to use parallel operation with more than two turbochargers. Two such examples are the and , both of which run four turbochargers in parallel. The EB110 runs 4 turbos on a 3.5 liter V12 engine, producing 542 hp (404 kW) at 8000 rpm, while the Veyron uses an 8.0 liter 16 cylinder engine to generate 1,001 (736 ; 987 ). The uses the quad-turbo 8.0 W16 engine that produces 1216 (894 ; 1,200 ).
Layout differences
According to manufacturers, there is a big difference between these systems. In fact, there are no significant differences in technology. This is a successful marketing ploy that has a positive effect on product sales. Biturbo and twin-turbo are capable of using different technological variations in the form of different turbine sizes, therefore they are universal systems.
For example, turbocharging in many cars is called Twin-turbo (Mitsubishi 3000 VR-4). At the same time, the car is equipped with a V6 engine, which has two turbines for three cylinders that use the exhaust gas flow. German production also has similar systems, but they are called Biturbo.
As practice shows, the Japanese use twin-turbo to a greater extent, while biturbo is more popular in Europe. In our country, you can purchase both variations with different technological features.
Classic version
Twin turbo technology means that two compressors are used. It is quite difficult to install two exhaust pipes on one line, since there must be space between them. A common problem is unequal energy distribution between two compressors. This drawback was solved by the original shape of the twin-turbo turbine in the form of an impeller, which synchronized the operation of the entire device.
The layout of the twin-turbo system has some disadvantages:
- the presence of a so-called “turbo lag”, in which the turbines do not operate;
- the nearest turbine suffers accelerated wear;
- gas supply occurs at a slower rate;
- complex installation for V-type motors.
Toyota offered its own solution to these problems - it made its own version for biturbo turbochargers. At low speeds, the valves of the product are closed, so the exhaust gases exit through the first turbine. It, in turn, spins up quickly and allows you to bypass the “turbo lag” at an early stage. When the engine reaches 3500 rpm, the engine opens special valves for excess gas, causing all the hot air to be redirected to the turbocharger, significantly increasing engine power.
Results
Summarizing the above, we can conclude that the differences between Twinturbo and Biturbo are only in the name. If you are really interested in different supercharging systems, you should pay attention to parallel and sequential layouts. In addition, it would be useful to become more familiar with the differences between a turbocharger and mechanical supercharging and the advantages of their combined use.
In recent years, automobile companies are increasingly beginning to use turbocharging systems in their engines. In this way they compensate for the tendency towards a decrease in displacement and, as a consequence, a drop in power. But if previously only one turbine was used in engines, now there can be several of them. Let's figure out what is hidden behind the mysterious terms “bi-turbo” and “twin-turbo”?
If you dig deeper, it turns out that there is practically no difference, and the differences in “bi-turbo” and “twin-turbo” lie in different approaches of engineers and marketing tricks of companies. Some car enthusiasts believe that the difference in biturbo and twin-turbo systems reflects the operating pattern of the turbocharging system as a whole, for example, sequential or parallel. And they will be partly right. But to fully understand the issue, let's understand the very essence of the turbocharging system.
