Boost controller: Difference between revisions

Revision as of 03:41, 13 May 2021

Revision as of 03:42, 13 May 2021

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{{Refimprove|date=January 2017}}

A '''boost controller''' is a device to control the [[Turbocharger#Pressure increase / boost|boost]] level produced in the [[intake manifold]] of a [[Turbocharger|turbocharged]] or [[supercharger|supercharged]] engine by affecting the air pressure delivered to the pneumatic and mechanical [[wastegate]] actuator.

A '''boost controller''' is a device that regulates intake manifold air pressure of supercharged engines. Pressure is the result of flow and restriction and positive manifold pressure above ambient atmospheric pressure resulting from the supercharger(s) supplying the engine with excess intake air flow is referred to as "boost".

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.

Mechanical spring-loaded bypass or relief valves which begin "leaking" excess intake air or exhaust gas "drive pressure" powering a turbocharger to limit "boost" are boost-limiting devices which must be manually adjusted to increase or decrease maximum boost and are typically safety devices for engine and powertrain protection against excessive boost and/or insufficient fuel delivery and resulting catastrophic engine failure do to excessive cylinder pressures and/or temperatures. Commonly referred to as blow-off valves and wastegates,these devices cannot be "tuned" while the engine is in operation and have no ability to control boost pressure within the "safe" operating range.

A boost controller regulates boost within the safe operating range by electromechanically or electronically regulating boost production and depending on the system and components involved may or may not "leak" intake air or exhaust gas at all.

In a turbocharged engine "drive pressure" powering the turbocharger(s) is a function of exhaust gas volume and density powering the exhaust turbine(s) connected to the intake impeller(s) which "pump" atmospheric air into the engine intake manifold.

Exhaust gas volume, density and "power" vary with engine load; throttle position; ignition timing; fuel delivery; fuel type; engine speed; compression ratio; intake and exhaust valve lift, duration and overlap; atmospheric air temperature, humidity and barometric pressure; vehicle weight; transmission type and gearing; final drive gear ratio; traction and intake manifold pressure itself and only fuel delivery and ignition timing are truly "tuneable" in real time with the engine in operation and independently of engine and vehicle speed and load.

"Boost controllers" typically regulate "boost" pressure by manipulating fuel delivery and ignition timing with no ability to directly regulate boost unless used in conjunction with blow-off valves and/or wastegates or electromechanical pressure-relief valves which are variable-flow "leaks" in the overall intake air system and external to the actual intake manifold which is the intake air system "downstream" of the throttle butterfly valve(s) which are the intake air restriction that produce intake manifold "vacuum" in spark-ignition internal combustion engines.

Which unlike compression-ignition diesel engines are "air-throttled" instead of "fuel-throttled" and which rely on intake manifold "vacuum" for proper fuel atomization and air-fuel mixing as well as a constant engine load at "idle" for consistent engine operation regardless of varying fuel and air "energy density" as fuel and air temperature, humidity, barometric pressure, relative humidity vary constantly during "extended" vehicle operation.

Ultimately "boost controllers" are used only in aftermarket high-performance "race" vehicles and require extensive use of other "upgrades" in highly modified "street cars" loosely based on "stock" vehicles used in/for "street racing" and/or other non-sanctioned, unregulated and unlimited "drag racing" and are not found in/on true "professional" drag racing classes and vehicles because at the top levels of drag racing the vehicles are too "fast" or more accurately "quick" for even modern electronics and "high technology" to "control" any aspect of engine and vehicle performance in "real-time" without the means of "boost control" - which is basically always "pulling" - or "retarding" - ignition timing and/or reducing fuel delivery and/or "retarding" injection timing without the engine and vehicle "bogging" at the "starting line".

The "high technology" also adds orders of magnitude more complexity, cost, weight, parasitic electrical load, failure potential and opportunity for human error in "tuning" with a net reduction in "power" and "speed" and ultimately any "data" acquired and logged during a "run" is not applicable to the next "run" when atmospheric conditions will have definitely changed and the boost "map" will not be valid.

== Principles of operation ==