Automatic Performance Control
- Automatic Performance Control
Automatic Performance Control (APC) was the first engine knock and boost control system that was introduced on turbo charged Saab H engines in 1982 and was fitted to all subsequent 900 Turbos through 1993 (and 1994 convertibles), as well as 9000 Turbos through 1989.
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 serves two purposes: it controls boost pressure - 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 actuator, which opens the wastegate to bypass exhaust gases from the turbocharger, 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.) Because the knock sensor becomes less accurate at high revolutions, the APC tapers maximum boost pressure after approximately 4,500 RPM.
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 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 knocking 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.
Wikimedia Foundation.
2010.
Look at other dictionaries:
Automatic Train Control — Japanese style ATC indicator. Automatic Train Control (ATC) is a train protection system for railways, ensuring the safe and smooth operation of trains on ATC enabled lines. Its main advantages include making possible the use of cab signalling… … Wikipedia
Control system — For other uses, see Control system (disambiguation). A control system is a device, or set of devices to manage, command, direct or regulate the behavior of other devices or system. There are two common classes of control systems, with many… … Wikipedia
Control engineering — Control systems play a critical role in space flight Control engineering or Control systems engineering is the engineering discipline that applies control theory to design systems with predictable behaviors. The practice uses sensors to measure… … Wikipedia
Automatic dependent surveillance-broadcast — (ADS B) is a cooperative surveillance technique for air traffic control and related applications. An ADS B out equipped aircraft determines its own position using a global navigation satellite system and periodically broadcasts this position and… … Wikipedia
Automatic summarization — is the creation of a shortened version of a text by a computer program. The product of this procedure still contains the most important points of the original text. The phenomenon of information overload has meant that access to coherent and… … Wikipedia
Automatic milking — is the milking of dairy animals without human labour.The milking processThe milking process is the collection of tasks specifically devoted to extracting milk from an animal (rather than the broader field of dairy animal husbandry). This process… … Wikipedia
Automatic link establishment — Automatic Link Establishment, commonly known as ALE, is the worldwide de facto standard for digitally initiating and sustaining HF (High Frequency) radio communications.cite web|title=Frequency Agile Systems in the MF/HF Bands |author=Telecom… … Wikipedia
Automatic Pilot — was a San Francisco, California band. Created in 1980 by members of the San Francisco Gay Men s Chorus, they were described by The Advocate as a non official offshoot of SFGMC along with three official subgroups. [Guthman, Edward: Merry… … Wikipedia
Automatic Terminal Information Service — Automatic Terminal Information Service, or ATIS, is a continuous broadcast of recorded noncontrol information in busier terminal (i.e. airport) areas. ATIS broadcasts contain essential information, such as weather information, which runways are… … Wikipedia
Control reconfiguration — is an active approach in control theory to achieve fault tolerant control for dynamic systems [1]. It is used when severe faults, such as actuator or sensor outages, cause a break up of the control loop, which must be restructured to prevent… … Wikipedia
