Automatic Performance Control

Last updated

Automatic Performance Control (APC) was the first engine knock and boost control system. The APC was invented by Per Gillbrand at the Swedish car maker SAAB. U.S. Patent 4,372,119

Contents

SAAB introduced it on the turbo charged Saab H engines in 1982, [1] and the APC was fitted to all subsequent 900 Turbos through 1993 (and 1994 convertibles), as well as 9000 Turbos through 1989. The APC was sold to Maserati to equip the carbureted Maserati Biturbo, with different settings for the Biturbo, and was known as the Maserati Automatic Boost Controller (MABC).

knock sensor
pressure transducer
control unit
solenoid valve Saab-apc.svg
  1. knock sensor
  2. pressure transducer
  3. control unit
  4. solenoid valve

The APC allowed a higher compression ratio (initially, 8.5:1 as opposed to 7.2:1, and, on 16-valve variants introduced in 1985, 9.0:1). This improved fuel economy and allowed the use of low-octane petrol without causing engine damage caused by knock.

The APC controls boost pressure and the overall performance, specifically the rate of rise and maximum boost level - and it detects and manages harmful knock events.

To control the turbocharger, the APC monitors the engine's RPM and inlet manifold pressure via a pressure transducer, and uses these inputs to control a solenoid valve that trims the rate of rise of pressure as well as the maximum pressure by directing boost pressure to the turbocharger's pneumatic wastegate actuator.

To detect knock, a piezoelectric knock sensor (basically a microphone) bolted to the engine block responds to unique frequencies caused by engine knock. The sensor generates a small voltage that is sent to the electronic control unit, which processes the signal to determine if, in fact, knock is occurring. If it is, then the control unit activates a solenoid valve that directs boost pressure to the turbocharger's pneumatically controlled wastegate, that opens to bypass exhaust gases from the turbocharger directly to the exhaust pipe, lowering turbo boost pressure until the knock subsides. Knock events that are managed by the APC can be "seen" when the in-dash boost needle "twitches" slightly. The APC unit has a 'knock' output where an LED may be connected. This LED will then light up if knock is detected. Because the knock sensor becomes less accurate at high revolutions, the APC tapers maximum boost pressure after approximately 4,500 RPM.

APC boost gauge

turbo/APC boost gauge in a Saab 900 Saabturboapc.jpg
turbo/APC boost gauge in a Saab 900

Saab Full Pressure Turbo (FPT) models with this unit include the APC name displayed on a non-numeric boost pressure gauge in the instrument panel. Although knock sensors are common even on non-turbocharged and turbocharged engines today, Saab has continued to use the APC name prominently as a differentiating feature.

The white area on the left side of the scale shows manifold vacuum under normal driving conditions, the short white dash is atmospheric pressure (engine off), the orange scale is where there is safe turbo boost, the red scale is boost above 0.5 - 0.7 bar where the wastegate may be opened or a fuel cut due to overboost may occur.

Saab integrated the APC's boost control functionality with ignition control in 1990 with the introduction of the DI/APC system, available in 9000 models only. The DI/APC system managed knock not only by decreasing boost via a solenoid but by retarding ignition timing as well; DI/APC also managed the engine's basic ignition timing.

See also

Related Research Articles

Turbocharger Forced induction device for internal combustion engines

A turbocharger, colloquially known as turbo, is a turbine-driven, forced induction device that increases an internal combustion engine's power output by forcing extra compressed air into the combustion chamber. This improvement over a naturally aspirated engine's power output is because the compressor can force more air—and proportionately more fuel—into the combustion chamber than atmospheric pressure alone.

Saab 9000 Motor vehicle

The Saab 9000 is an automobile produced by the Swedish company Saab from 1984 to 1998. Representing the company's foray into the executive car scene, it was developed as a result of the successes of the turbocharged 99 and 900 models. The 9000 remained in production until May 1998 and it was replaced by the Saab 9-5 in late 1997, although some final cars were produced into 1998. The Saab 9000 was only available with petrol engines and never as a convertible.

The GM Ecotec engine, also known by its codename L850, is a family of all-aluminium inline-four engines, displacing between 1.4 and 2.5 litres. While these engines were based on the GM Family II engine, the architecture was substantially re-engineered for the new Ecotec application produced since 2000. This engine family replaced the GM Family II engine, the GM 122 engine, the Saab H engine, and the Quad 4 engine. It is manufactured in multiple locations, to include Spring Hill Manufacturing, in Spring Hill, Tennessee while the engine block and cylinder heads are cast at Saginaw Metal Casting Operations in Saginaw, Michigan.

Chrysler 2.2 & 2.5 engine Motor vehicle engine

The 2.2 and 2.5 are a family of inline-4 engines developed by Chrysler Corporation originally for the Chrysler K- and L-platforms cars and subsequently used in many other Chrysler vehicles. After its launch in 1981, it became the basis for all Chrysler-developed 4-cylinder engines until the Chrysler 1.8, 2.0 & 2.4 engine family was released in 1994. It was the first Chrysler engineered four cylinder engine since the Chrysler flathead four cylinder was discontinued in 1933.

A blow-off valve (BOV), dump valve or compressor bypass valve (CBV) is a pressure release system present in most turbocharged engines. Its main purpose is to take the load off the turbocharger when the throttle is suddenly closed.

General Motors 54° V6 engine Motor vehicle engine

General Motors' Opel subsidiary in Europe designed a compact V6 engine with an unusual 54° vee angle. It was an iron block/aluminum head DOHC design with 4 valves per cylinder. All 54° engines were assembled at Ellesmere Port in England.

The Trionic 8 is an advanced engine management system in the Trionic series, created by Saab Automobile. It is used in both Saab 9-3 and Opel Vectra vehicles, and is available with 150, 175 and 210 horsepower (160 kW) engines. It will also be used for a flexifuel version starting production spring 2007. Saab Trionic T8 has been developed by Saab and is a very advanced engine management system. The Engine Control Module (ECM) is used principally to regulated the air mass, fuel and ignition timing.

Saab B engine Motor vehicle engine

The Saab B engine is an inline four-cylinder car petrol engine developed by Saab Automobile. A redesign of the Triumph slant-four engine, the B engine displaced 2.0 L and first appeared in 1972. The B engine was used in the Saab 99 and 900 models. Saab began to phase the engine out in 1981.

Saab H engine Automobile engine; redesign of the Saab B

The Saab H engine is a redesign of the Saab B engine, which in turn was based on the Triumph Slant-4 engine.

A wastegate is a valve that controls the flow of exhaust gases to the turbine wheel in a turbocharged engine system.

MAP sensor

The manifold absolute pressure sensor is one of the sensors used in an internal combustion engine's electronic control system.

The anti-lag system (ALS) is a method of reducing turbo lag or effective compression used on turbocharged engines to minimize turbo lag on racing or performance cars. It works by delaying the ignition timing very slightly to balance an inherent loss in combustion efficiency with increased pressure at the charging side of the turbo. This is achieved as a small amount of fuel/air mixture escapes through the exhaust valves and combusts in the hot exhaust manifold spooling the turbocharger creating higher usable pressure.

Variable-geometry turbocharger

Variable-geometry turbochargers (VGTs), occasionally known as variable-nozzle turbines (VNTs), are a type of turbochargers, usually designed to allow the effective aspect ratio of the turbocharger to be altered as conditions change. This is done because the optimum aspect ratio at low engine speeds is very different from that at high engine speeds.

Twincharger refers to a compound forced induction system used on some piston-type internal combustion engines. It is a combination of an exhaust-driven turbocharger and a mechanically driven supercharger, each mitigating the weaknesses of the other. A mechanically driven supercharger offers exceptional response and low-rpm performance as it does not rely on pressurization of the exhaust manifold. A turbocharger sized to move a large volume of air tends to respond slowly to throttle input while a smaller, faster-responding turbo may fail to deliver sufficient volume through an engine's upper RPM range. The unacceptable lag time endemic to a large turbocharger is effectively neutralized when combined with a supercharger which tends to generate substantial boost pressure much faster in response to throttle input. The end result being a zero-lag powerband with high torque at lower engine speeds and increased power at the upper end. Twincharging is therefore desirable for small-displacement motors, especially those with a large operating rpm, since they can take advantage of an artificially broad torque band over a large speed range.

Twin-turbo, also known as biturbo, refers to an engine in which two turbochargers compress the intake fuel/air mixture. The most common layout features two identical turbochargers in parallel. The two turbochargers can either be identical or different sizes. Twincharger is a combination of supercharger and turbocharger.

A transmission control unit (TCU), also known as a transmission control module (TCM), or a gearbox control unit (GCU), is a type of automotive ECU that is used to control electronic automatic transmissions. Similar systems are used in conjunction with various semi-automatic transmissions, purely for clutch automation and actuation. A TCU in a modern automatic transmission generally uses sensors from the vehicle, as well as data provided by the engine control unit (ECU), to calculate how and when to change gears in the vehicle for optimum performance, fuel economy and shift quality.

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.

Trionic T5.5 is an engine management system in the Saab Trionic range. It controls ignition, fuel injection and turbo boost pressure. The system was introduced in the 1993 Saab 9000 2.3 Turbo with B234L and B234R engine.

Trionic is an engine management system developed by Saab Automobile, consisting of an engine control unit (ECU) that controls 3 engine aspects:

  1. Ignition timing,
  2. Fuel injection
  3. Acts as a boost controller.

References

  1. Jack, Keebler (July 1982). "Turbocharger with a brain". Popular Science. July 1982: 85.