Boost controller
Encyclopedia
A boost controller is a device to control the boost level produced in the intake manifold of a turbocharged
or supercharged
engine by affecting the air pressure delivered to the pneumatic and mechanical wastegate
actuator. A boost controller can be a simple manual control which can be easily fabricated, or it may be included as part of the engine management computer in a factory turbocharged car, or an aftermarket electronic boost controller such as those made by GReddy
.
located in the wastegate actuator to allow the wastegate to open and re-direct exhaust gas so that it does not reach the turbine wheel. In this simple configuration, the spring's springrate and preload determine how much boost pressure the system will achieve. Springs are classified by the boost pressure they typically achieve, such as a "7 psi spring" that will allow the turbocharger to reach equilibrium
at approximately 7 psi (0.48263301051 bar).
One primary problem of this system is the wastegate will start to open well before the actual desired boost pressure is achieved. This negatively affects the threshold of boost onset and also increases turbocharger lag. For instance, a spring rated at 7 psi may allow the wastegate to begin to (but not fully) open at as little as 3.5 psi (0.241316505255 bar).
Achieving moderate boost levels consistently is also troublesome with this configuration. At partial throttle
, full boost may still be reached, making the vehicle difficult to control with precision. Electronic systems can allow the throttle to control the level of boost, so that only at full throttle will maximum boost levels be achieved and intermediate levels of boost can be held consistently at partial throttle levels.
Also to be noted is the way in which boost control is achieved, depending on the type of wastegate used. Typically manual "bleed type" boost controlers are only used on swing type (single port) wastegate actuators. To increase boost, pressure is taken away from the actuator control line, therefore increasing boost. Dual port swing type wastegate actuators and external wastegates generally require electronic boost control although adjustable boost control can also be achieved on both of these with an air pressure regulator, this is not the same as a bleed type boost controller. To increase boost with an external or dual port wastegate, pressure is added to the top control port to increase boost. When boost control is not fitted, this control port is open to the atmosphere.
A manual boost controller is a simple mechanical and pneumatic
control to allow some pressure from the wastegate actuator to escape or bleed out to the atmosphere
or back into the intake
system. This can be as simple as a T-fitting on the boost control line near the actuator with a small bleeder screw. The screw can be turned out to varying degrees to allow air to bleed out of the system, relieving pressure on the wastegate actuator, thus increasing boost levels. These devices are popular due to their negligible cost compared to other devices that may offer the same power increase.
Additionally, another type of manual boost controllers use a ball and spring to control the amount of boost. This is installed with one vacuum line coming from the intake somewhere after the turbocharger, and one vacuum line going to the wastegate. A knob changes the force on the spring which in turn dictates how much pressure is on the ball. The tighter the spring, the more boost that is needed to unseat the ball, and allow the boost pressure to reach the wastegate actuator. There is a bleed hole on the boost controller after the ball, to allow the pressurized air that would be trapped between the wastegate actuator and the ball after it is seated again. These type of Manual boost controllers are becoming vastly popular since they do not provide a boost leak, allowing faster spool times and better control than a "bleed type" boost controller.
Generally a manual boost controller will not be accessible from inside the car, though some are designed to be. An installation that allows access from inside the car (as opposed from inside the engine compartment) is more complex, as the tubing must be longer and a hole must be drilled. It is possible and beneficial to use two manual boost controllers at different settings with a solenoid to switch between them for two different boost pressure settings. Some factory turbocharged cars have a switch to regulate boost pressure, such as a setting designed for fuel economy
and a setting for performance.
Manual boost controllers do not solve partial throttle/full boost, drivability, and response or lag issues. They can be used in conjunction with some electronic systems.
Electronic boost control adds an air control solenoid
and/or a stepper motor
controlled by an electronic control unit
. The same general principle of a manual controller is present, which is to control the air pressure presented to the wastegate actuator. Further control and intelligent algorithms can be introduced, refining and increasing control over actual boost pressure delivered to the engine.
At the component level, boost pressure can either be bled out of the control lines or blocked outright. Either can achieve the goal of reducing pressure pushing against the wastegate. In a bleed-type system air is allowed to pass out of the control lines, reducing the load on the wastegate actuator. On a blocking configuration, air traveling from the charge air supply to the wastegate actuator is blocked while simultaneously bleeding any pressure that has previously built up at the wastegate actuator.
Control for the solenoids and stepper motors can be either closed loop
or open loop
. Closed loop systems rely on feedback from a manifold pressure sensor to meet a predetermined boost pressure. Open loop systems have a predetermined control output where control output is merely based on other inputs such as throttle angle and/or engine RPM
. Open loop specifically leaves out a desired boost level, while closed loop attempts to target a specific level of boost pressure. Since open loop systems do not modify control levels based on MAP sensor, differing boost pressure levels may be reached based on outside variables such as weather conditions or engine coolant temperature. For this reason, systems that do not feature closed loop operation are not as widespread.
Boost controllers often use pulse width modulation (PWM) techniques to bleed off boost pressure on its way to the reference port on the wastegate actuator diaphragm in order to (on occasion ) under report boost pressure in such a way that the wastegate permits a turbocharger to build more boost pressure in the intake than it normally could. In effect, a boost-control solenoid valve lies to the wastegate under ECU (engine control unit) control. The boost control solenoid contains a needle valve that can open and close very fast. By varying the digital control frequency to the solenoid, the solenoid valve can be commanded to be open a certain percentage of the time. This effectively alters the flow rate of air pressure through the valve, changing the rate at which air bleeds out of the T in the manifold pressure reference line to the wastegate. This effectively changes the air pressure as seen by the wastegate actuator diaphragm. Solenoids may require small diameter restrictors be installed in the air control lines to limit airflow and even out the on/off nature of their operation.
The wastegate control solenoid can be commanded to run in a variety of frequencies in various gears, engine speeds, or according to various other factors in a deterministic open-loop mode. Or by monitoring manifold pressure in a feedback loop- the engine management system can monitor the efficacy of PWM changes in the boost control solenoid bleed rate at altering boost pressure in the intake manifold, increasing or decreasing the bleed rate to target a particular maximum boost.
The basic algorithm sometimes involves the EMS (engine management system) "learning" how fast the turbocharger can spool and how fast the boost pressure increases. Armed with this knowledge, as long as boost pressure is below a predetermined allowable ceiling, the EMS will open the boost control solenoid to allow the turbocharger to create overboost beyond what the wastegate would normally allow. As overboost reaches the programmable maximum, the EMS begins to decrease the bleed rate through the control solenoid to raise boost pressure as seen at the wastegate actuator diaphragm so the wastegate opens enough to limit boost to the maximum configured level of over-boost.
Stepper motors allow fine control of airflow based on position and speed of the motor, but may have low total airflow capability. Some systems use a solenoid in conjunction with a stepper motor, with the stepper motor allowing fine control and the solenoid coarse control.
Many configurations are possible with 2-, 3-, and 4-port solenoids and stepper motors in series or parallel. Two port solenoid bleed systems with a PID controller
tend to be common on factory turbocharged cars.
This also allows the use of a much softer spring in the actuator. For instance, a 7 psi (0.48263301051 bar) spring together with a boost controller may still be able to achieve a maximum boost level of well over 15 psi (1 bar). The electronic control unit
can be programmed to control 7 psi (0.48263301051 bar) psi at half throttle, 12 psi (0.82737087516 bar) at 3/4 throttle, and 15 psi (1 bar) at full throttle, or whatever levels the programmer or designer of the control unit intends. This partial throttle control greatly increases driver control over the engine and vehicle.
The solenoid and stepper motors also need to be installed in such a way to maximize the advantages of failure mode
s. For instance, if a solenoid is installed to control boost electronically, it should be installed such that if the solenoid fails in the most common failure mode (probably non-energized position) the boost control falls back to simple wastegate actuator boost levels. It is possible a solenoid or stepper motor could get stuck in a position that lets no boost pressure reach the wastegate, causing boost to quickly rise out of control.
The electronic systems, extra hoses, solenoids and soforth add complexity to the turbocharger system. This runs counter to the "keep it simple" principle
as there are more things that can go wrong. It is worth noting that virtually all modern factory turbocharged cars, the same cars with long warranty periods, implement electronic boost control. Manufacturers such as Subaru
, Mitsubishi
and Saab
integrate electronic boost control in all turbo model cars.
and often as built-in features in full aftermarket stand-alone engine management systems such as the Hydra Nemesis, AEM EMS and MegaSquirt
.
(such as a factory turbocharged car) may allow higher boost pressure than tolerable by the engine or turbocharger reducing life and reliability. Care should be taken to avoid exceeding the limits of any the engine systems components such as the engine block, fuel injectors, or engine management system. This is as true with boost control as it is with fuel and timing controls or any number of other engine system modifications.
In particular, users may find the extremely low cost and ease of adding a manual boost controller a particular draw for extra power at low cost compared to more comprehensive modifications. Users should carefully consider how installing any boost controller may affect and interact with existing complex engine management systems. Additional boost levels may not be tolerated by the existing turbocharger, causing faster wear. Fuel injectors or the fuel pump may not be able to deliver additional fuel needed for higher air flow and power of higher boost pressure. Or the engine management system may not be able to properly compensate for fuel or ignition timing, causing knock and/or engine failure.
in the intake to restrict airflow as desired boost is approached. It is also possible to actually release large amounts of already compressed air similar to a blowoff valve
but on a constant basis to maintain desired boost at the intake manifold. The currently popular exhaust gas bypass via wastegate is superior to creating intake restriction or wasting energy by releasing air that has already been compressed. These methods are rarely used in modern system due to the large sacrifices in efficiency, heat, and reliability.
Other methods may come into widespread use in the future, such as variable geometry turbocharger
s. With a sufficiently large turbine, no wastegate is necessary. Low speed response and faster spool up are then obtained using variable turbine technologies rather than a smaller turbine. These systems may replace or supplement typical wastegates as they develop. Control methods for the variable mechanical controls, such as the principles of closed loop will still apply even if they no longer involve pneumatics
.
Turbocharger
A turbocharger, or turbo , from the Greek "τύρβη" is a centrifugal compressor powered by a turbine that is driven by an engine's exhaust gases. Its benefit lies with the compressor increasing the mass of air entering the engine , thereby resulting in greater performance...
or supercharged
Supercharger
A supercharger is an air compressor used for forced induction of an internal combustion engine.The greater mass flow-rate provides more oxygen to support combustion than would be available in a naturally aspirated engine, which allows more fuel to be burned and more work to be done per cycle,...
engine by affecting the air pressure delivered to the pneumatic and mechanical wastegate
Wastegate
A wastegate is a valve that diverts exhaust gases away from the turbine wheel in a turbocharged engine system. Diversion of exhaust gases regulates the turbine speed, which in turn regulates the rotating speed of the compressor. The primary function of the wastegate is to regulate the maximum boost...
actuator. A boost controller can be a simple manual control which can be easily fabricated, or it may be included as part of the engine management computer in a factory turbocharged car, or an aftermarket electronic boost controller such as those made by GReddy
GReddy
is a Japanese automotive aftermarket company specialising in performance tuning parts for cars. The company is widely known for its subbrand of tuning parts GReddy and the turbochargers under this brand.-The Trust Company:...
.
Principles of operation
Without a boost controller, air pressure is fed from the charge air (compressed side) of the turbocharger directly to the wastegate actuator via a vacuum hose. This air pressure can come from anywhere on the intake after the turbo, including after the throttle body, though that is less common. This air pressure pushes against the force of a springSpring (device)
A spring is an elastic object used to store mechanical energy. Springs are usually made out of spring steel. Small springs can be wound from pre-hardened stock, while larger ones are made from annealed steel and hardened after fabrication...
located in the wastegate actuator to allow the wastegate to open and re-direct exhaust gas so that it does not reach the turbine wheel. In this simple configuration, the spring's springrate and preload determine how much boost pressure the system will achieve. Springs are classified by the boost pressure they typically achieve, such as a "7 psi spring" that will allow the turbocharger to reach equilibrium
Mechanical equilibrium
A standard definition of static equilibrium is:This is a strict definition, and often the term "static equilibrium" is used in a more relaxed manner interchangeably with "mechanical equilibrium", as defined next....
at approximately 7 psi (0.48263301051 bar).
One primary problem of this system is the wastegate will start to open well before the actual desired boost pressure is achieved. This negatively affects the threshold of boost onset and also increases turbocharger lag. For instance, a spring rated at 7 psi may allow the wastegate to begin to (but not fully) open at as little as 3.5 psi (0.241316505255 bar).
Achieving moderate boost levels consistently is also troublesome with this configuration. At partial throttle
Throttle
A throttle is the mechanism by which the flow of a fluid is managed by constriction or obstruction. An engine's power can be increased or decreased by the restriction of inlet gases , but usually decreased. The term throttle has come to refer, informally and incorrectly, to any mechanism by which...
, full boost may still be reached, making the vehicle difficult to control with precision. Electronic systems can allow the throttle to control the level of boost, so that only at full throttle will maximum boost levels be achieved and intermediate levels of boost can be held consistently at partial throttle levels.
Also to be noted is the way in which boost control is achieved, depending on the type of wastegate used. Typically manual "bleed type" boost controlers are only used on swing type (single port) wastegate actuators. To increase boost, pressure is taken away from the actuator control line, therefore increasing boost. Dual port swing type wastegate actuators and external wastegates generally require electronic boost control although adjustable boost control can also be achieved on both of these with an air pressure regulator, this is not the same as a bleed type boost controller. To increase boost with an external or dual port wastegate, pressure is added to the top control port to increase boost. When boost control is not fitted, this control port is open to the atmosphere.
Manual boost control
Pneumatics
Pneumatics is a branch of technology, which deals with the study and application of use of pressurized gas to effect mechanical motion.Pneumatic systems are extensively used in industry, where factories are commonly plumbed with compressed air or compressed inert gases...
control to allow some pressure from the wastegate actuator to escape or bleed out to the atmosphere
Atmosphere
An atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...
or back into the intake
Intake
An intake , or especially for aircraft inlet, is an air intake for an engine. Because the modern internal combustion engine is in essence a powerful air pump, like the exhaust system on an engine, the intake must be carefully engineered and tuned to provide the greatest efficiency and power...
system. This can be as simple as a T-fitting on the boost control line near the actuator with a small bleeder screw. The screw can be turned out to varying degrees to allow air to bleed out of the system, relieving pressure on the wastegate actuator, thus increasing boost levels. These devices are popular due to their negligible cost compared to other devices that may offer the same power increase.
Additionally, another type of manual boost controllers use a ball and spring to control the amount of boost. This is installed with one vacuum line coming from the intake somewhere after the turbocharger, and one vacuum line going to the wastegate. A knob changes the force on the spring which in turn dictates how much pressure is on the ball. The tighter the spring, the more boost that is needed to unseat the ball, and allow the boost pressure to reach the wastegate actuator. There is a bleed hole on the boost controller after the ball, to allow the pressurized air that would be trapped between the wastegate actuator and the ball after it is seated again. These type of Manual boost controllers are becoming vastly popular since they do not provide a boost leak, allowing faster spool times and better control than a "bleed type" boost controller.
Generally a manual boost controller will not be accessible from inside the car, though some are designed to be. An installation that allows access from inside the car (as opposed from inside the engine compartment) is more complex, as the tubing must be longer and a hole must be drilled. It is possible and beneficial to use two manual boost controllers at different settings with a solenoid to switch between them for two different boost pressure settings. Some factory turbocharged cars have a switch to regulate boost pressure, such as a setting designed for fuel economy
Fuel economy in automobiles
Fuel usage in automobiles refers to the fuel efficiency relationship between distance traveled by an automobile and the amount of fuel consumed....
and a setting for performance.
Manual boost controllers do not solve partial throttle/full boost, drivability, and response or lag issues. They can be used in conjunction with some electronic systems.
Electronic boost control
Solenoid
A solenoid is a coil wound into a tightly packed helix. In physics, the term solenoid refers to a long, thin loop of wire, often wrapped around a metallic core, which produces a magnetic field when an electric current is passed through it. Solenoids are important because they can create...
and/or a stepper motor
Stepper motor
A stepper motor is a brushless, electric motor that can divide a full rotation into a large number of steps. The motor's position can be controlled precisely without any feedback mechanism , as long as the motor is carefully sized to the application...
controlled by an electronic control unit
Electronic control unit
In automotive electronics, electronic control unit is a generic term for any embedded system that controls one or more of the electrical systems or subsystems in a motor vehicle....
. The same general principle of a manual controller is present, which is to control the air pressure presented to the wastegate actuator. Further control and intelligent algorithms can be introduced, refining and increasing control over actual boost pressure delivered to the engine.
At the component level, boost pressure can either be bled out of the control lines or blocked outright. Either can achieve the goal of reducing pressure pushing against the wastegate. In a bleed-type system air is allowed to pass out of the control lines, reducing the load on the wastegate actuator. On a blocking configuration, air traveling from the charge air supply to the wastegate actuator is blocked while simultaneously bleeding any pressure that has previously built up at the wastegate actuator.
Control details
Closed loop
Closed loop may refer to:* A feedback loop, often found in:** Control theory#Closed-loop transfer function, where a closed-loop controller may be used** Electronic feedback loops in electronic circuits** PID controller, a commonly used closed-loop controller...
or open loop
Open loop
An open loop is a rhetorical device to instill curiosity by creating anticipation for what will come next. The device is sometimes also called a tension loop for the tension and anticipation it creates.- Short Example :...
. Closed loop systems rely on feedback from a manifold pressure sensor to meet a predetermined boost pressure. Open loop systems have a predetermined control output where control output is merely based on other inputs such as throttle angle and/or engine RPM
Revolutions per minute
Revolutions per minute is a measure of the frequency of a rotation. It annotates the number of full rotations completed in one minute around a fixed axis...
. Open loop specifically leaves out a desired boost level, while closed loop attempts to target a specific level of boost pressure. Since open loop systems do not modify control levels based on MAP sensor, differing boost pressure levels may be reached based on outside variables such as weather conditions or engine coolant temperature. For this reason, systems that do not feature closed loop operation are not as widespread.
Boost controllers often use pulse width modulation (PWM) techniques to bleed off boost pressure on its way to the reference port on the wastegate actuator diaphragm in order to (on occasion ) under report boost pressure in such a way that the wastegate permits a turbocharger to build more boost pressure in the intake than it normally could. In effect, a boost-control solenoid valve lies to the wastegate under ECU (engine control unit) control. The boost control solenoid contains a needle valve that can open and close very fast. By varying the digital control frequency to the solenoid, the solenoid valve can be commanded to be open a certain percentage of the time. This effectively alters the flow rate of air pressure through the valve, changing the rate at which air bleeds out of the T in the manifold pressure reference line to the wastegate. This effectively changes the air pressure as seen by the wastegate actuator diaphragm. Solenoids may require small diameter restrictors be installed in the air control lines to limit airflow and even out the on/off nature of their operation.
The wastegate control solenoid can be commanded to run in a variety of frequencies in various gears, engine speeds, or according to various other factors in a deterministic open-loop mode. Or by monitoring manifold pressure in a feedback loop- the engine management system can monitor the efficacy of PWM changes in the boost control solenoid bleed rate at altering boost pressure in the intake manifold, increasing or decreasing the bleed rate to target a particular maximum boost.
The basic algorithm sometimes involves the EMS (engine management system) "learning" how fast the turbocharger can spool and how fast the boost pressure increases. Armed with this knowledge, as long as boost pressure is below a predetermined allowable ceiling, the EMS will open the boost control solenoid to allow the turbocharger to create overboost beyond what the wastegate would normally allow. As overboost reaches the programmable maximum, the EMS begins to decrease the bleed rate through the control solenoid to raise boost pressure as seen at the wastegate actuator diaphragm so the wastegate opens enough to limit boost to the maximum configured level of over-boost.
Stepper motors allow fine control of airflow based on position and speed of the motor, but may have low total airflow capability. Some systems use a solenoid in conjunction with a stepper motor, with the stepper motor allowing fine control and the solenoid coarse control.
Many configurations are possible with 2-, 3-, and 4-port solenoids and stepper motors in series or parallel. Two port solenoid bleed systems with a PID controller
PID controller
A proportional–integral–derivative controller is a generic control loop feedback mechanism widely used in industrial control systems – a PID is the most commonly used feedback controller. A PID controller calculates an "error" value as the difference between a measured process variable and a...
tend to be common on factory turbocharged cars.
Advantages
Since less positive pressure can be present at the wastegate actuator as desired boost is approached the wastegate remains closer to a completely closed state. This keeps exhaust gas routed through the turbine and increases energy transferred to the wheels of the turbocharger. Once desired boost is reached, closed loop based systems react by allowing more air pressure to reach the wastegate actuator to stop the further increase in air pressure so desired boost levels are maintained. This reduces turbocharger lag and lowers boost threshold. Boost pressure builds faster when the throttle is depressed quickly and allows boost pressure to build at lower engine RPM than without such a system.This also allows the use of a much softer spring in the actuator. For instance, a 7 psi (0.48263301051 bar) spring together with a boost controller may still be able to achieve a maximum boost level of well over 15 psi (1 bar). The electronic control unit
Electronic control unit
In automotive electronics, electronic control unit is a generic term for any embedded system that controls one or more of the electrical systems or subsystems in a motor vehicle....
can be programmed to control 7 psi (0.48263301051 bar) psi at half throttle, 12 psi (0.82737087516 bar) at 3/4 throttle, and 15 psi (1 bar) at full throttle, or whatever levels the programmer or designer of the control unit intends. This partial throttle control greatly increases driver control over the engine and vehicle.
Limitations and disadvantages
Even with an electronic controller, actuator springs that are too soft can cause the wastegate to open before desired. Exhaust gas backpressure is still pushing against the wastegate valve itself. This backpressure can overcome the spring pressure without the aid of the actuator at all. Electronic control may still enable control of boost to over double gauge pressure of the spring's rated pressure.The solenoid and stepper motors also need to be installed in such a way to maximize the advantages of failure mode
Failure mode
Failure causes are defects in design, process, quality, or part application, which are the underlying cause of a failure or which initiate a process which leads to failure. Where failure depends on the user of the product or process, then human error must be considered.-Component failure:A part...
s. For instance, if a solenoid is installed to control boost electronically, it should be installed such that if the solenoid fails in the most common failure mode (probably non-energized position) the boost control falls back to simple wastegate actuator boost levels. It is possible a solenoid or stepper motor could get stuck in a position that lets no boost pressure reach the wastegate, causing boost to quickly rise out of control.
The electronic systems, extra hoses, solenoids and soforth add complexity to the turbocharger system. This runs counter to the "keep it simple" principle
KISS principle
KISS is an acronym for the design principle Keep it simple, Stupid!. Other variations include "keep it simple and stupid", "keep it short and simple", "keep it simple sir", "keep it simple or be stupid" or "keep it simple and straightforward"...
as there are more things that can go wrong. It is worth noting that virtually all modern factory turbocharged cars, the same cars with long warranty periods, implement electronic boost control. Manufacturers such as Subaru
Subaru
; is the automobile manufacturing division of Japanese transportation conglomerate Fuji Heavy Industries .Subaru is internationally known for their use of the boxer engine layout popularized in cars by the Volkswagen Beetle and Porsche 911, in most of their vehicles above 1500 cc as well as...
, Mitsubishi
Mitsubishi Motors
is a multinational automaker headquartered in Minato, Tokyo. In 2009 it was the fifth-largest Japan-based automaker and the 17th-largest in the world measured by production...
and Saab
Saab Automobile
Saab Automobile AB, better known as Saab , is a Swedish car manufacturer owned by Dutch automobile manufacturer Swedish Automobile NV, formerly Spyker Cars NV. It is the exclusive automobile Royal Warrant holder as appointed by the King of Sweden...
integrate electronic boost control in all turbo model cars.
Availability and applications
Electronic boost control systems are available as aftermarket stand-alone systems such as the HKS EVC and VBC, Apex-i AVC-R, or Gizzmo IBC / MS-IBC as a built-in feature of modern factory turbocharged vehicles such as the Subaru Impreza WRX STiSubaru Impreza WRX STI
The Subaru Impreza WRX STI, has the highest trim in the Subaru Impreza compact car line, produced by Japanese automaker Subaru.In the late 1980s, Subaru created the Subaru Tecnica International division to coordinate development for the FIA World Rally Championship and other motorsports activities...
and often as built-in features in full aftermarket stand-alone engine management systems such as the Hydra Nemesis, AEM EMS and MegaSquirt
MegaSquirt
MegaSquirt is the registered trademark of an aftermarket electronic fuel injection controller designed to be used with a wide range of spark-ignition internal combustion engines It is a complete standalone fuel injection controller with software and hardware, developed by Bruce Bowling and Al...
.
Dangers in use
Installing a boost controller in a vehicle that is already well tunedEngine tuning
Engine tuning is the adjustment, modification or design of internal combustion engines to yield optimal performance, to increase an engine's power output, economy, or durability....
(such as a factory turbocharged car) may allow higher boost pressure than tolerable by the engine or turbocharger reducing life and reliability. Care should be taken to avoid exceeding the limits of any the engine systems components such as the engine block, fuel injectors, or engine management system. This is as true with boost control as it is with fuel and timing controls or any number of other engine system modifications.
In particular, users may find the extremely low cost and ease of adding a manual boost controller a particular draw for extra power at low cost compared to more comprehensive modifications. Users should carefully consider how installing any boost controller may affect and interact with existing complex engine management systems. Additional boost levels may not be tolerated by the existing turbocharger, causing faster wear. Fuel injectors or the fuel pump may not be able to deliver additional fuel needed for higher air flow and power of higher boost pressure. Or the engine management system may not be able to properly compensate for fuel or ignition timing, causing knock and/or engine failure.
Past and future
There are other outdated methods of boost control, such as intake restriction or bleed off. For instance, it is possible to install a large butterfly valveButterfly valve
A butterfly valve is a valve which can be used for isolating or regulating flow. The closing mechanism takes the form of a disk. Operation is similar to that of a ball valve, which allows for quick shut off. Butterfly valves are generally favored because they are lower in cost to other valve...
in the intake to restrict airflow as desired boost is approached. It is also possible to actually release large amounts of already compressed air similar to a blowoff valve
Blowoff valve
A blowoff valve or dump valve is a pressure release system present in most turbocharged engines.Its purpose is to prevent compressor surge, and reduce wear on the turbocharger and engine...
but on a constant basis to maintain desired boost at the intake manifold. The currently popular exhaust gas bypass via wastegate is superior to creating intake restriction or wasting energy by releasing air that has already been compressed. These methods are rarely used in modern system due to the large sacrifices in efficiency, heat, and reliability.
Other methods may come into widespread use in the future, such as variable geometry turbocharger
Variable geometry turbocharger
Variable-geometry turbochargers are a family of turbochargers, usually designed to allow the effective aspect ratio of the turbo to be altered as conditions change. This is done because optimum aspect ratio at low engine speeds is very different from that at high engine speeds...
s. With a sufficiently large turbine, no wastegate is necessary. Low speed response and faster spool up are then obtained using variable turbine technologies rather than a smaller turbine. These systems may replace or supplement typical wastegates as they develop. Control methods for the variable mechanical controls, such as the principles of closed loop will still apply even if they no longer involve pneumatics
Pneumatics
Pneumatics is a branch of technology, which deals with the study and application of use of pressurized gas to effect mechanical motion.Pneumatic systems are extensively used in industry, where factories are commonly plumbed with compressed air or compressed inert gases...
.
External links
- MBC Concept Overview, Installation, and Setup
- How To Guide - Manual Boost Controller Installation from addictiveperformance.com