Exhaust back pressure control system

An exhaust back pressure control system for an internal combustion engine having an engine exhaust port and an engine control microcomputer including:

• a valve for selectively restricting said engine exhaust port;
• an engine speed sensor mounted on the engine and operatively connected to said microcomputer and said microcomputer generates a fuel delivery output signal, said microcomputer being responsive to said engine speed sensor and fuel delivery output signal to generate a desired back pressure output signal from a table of desired exhaust back pressure relative to engine speed and fuel consumption stored in a memory of said microcomputer;
• a coolant temperature sensor mounted within the cooling system of the engine, said microcomputer being operatively connected thereto and responsive to proportionally reduce said desired back pressure output signal in response to coolant temperature excursions beyond a predetermined range;
• and,
• means for operating said valve in response to said output signal from said microcomputer.

A system for controlling exhaust back pressure under direction of an engine microcomputer, said system including:

• a valve within an exhaust port from a turbocharger operable to close off a portion of said exhaust port, thereby increasing exhaust back pressure;
• means for operating said valve including a piston within a hydraulic cylinder housing formed as an integral part of said turbocharger, said piston being mechanically engaged to said valve to cause closing thereof;
• a lube oil pressure supply line to said cylinder housing from a engine crankcase;
• an electrically operated oil flow control valve for regulating the oil pressure within said cylinder;
• and
• an electronic engine control microcomputer connected to said control valve, said microcomputer generating a pulse width modulated output signal to operate said control valve according to a duty cycle providing a regulated oil pressure within said cylinder, said pulse width modulated output signal corresponding to a desired exhaust back pressure calculated by said engine microcomputer as a function of engine speed, engine load, and coolant temperature.

A method for controlling exhaust back pressure in an internal combustion engine under cold ambient conditions, said engine having an electrically controlled valve disposed to restrict the exhaust from said engine and a microcomputer for controlling said valve, said method being performed by said microcomputer and including the steps of:

• monitoring the engine speed and the fuel consumption of said engine and generating a desired back pressure signal from a lookup table stored in the memory of said microcomputer;
• monitoring the engine coolant temperature and generating a multiplier signal of between and including zero and one dependent on said coolant temperature according to a preselected relationship of said multiplier and said coolant temperature stored within the memory of the microcomputer;
• applying said multiplier to the desired back pressure signal derived from said lookup table and, if the multiplier produces a value greater than zero, generating a multiplied desired back pressure signal;
• monitoring the ambient air temperature and, upon said temperature being below a preselected ambient temperature, generating an enablement signal permitting transmission of said multiplied desired back pressure signal to said valve;
• monitoring the actual back pressure in an exhaust manifold of said engine, comparing the actual back pressure signal to the multiplied desired back pressure signal generated above, and, upon a deviation of said actual back pressure signal from said multiplied desired back pressure signal being detected, sending an output signal to said valve to move said valve to produce an actual back pressure equal to the multiplied desired back pressure.

Microcomputer apparatus for controlling exhaust back pressure in an internal combustion engine under cold ambient conditions, said engine having an electrically controlled valve disposed to restrict the exhaust from said engine in response to an output signal from said microcomputer, said apparatus comprising:

• a plurality of engine parameter sensors connected respectively to said microcomputer, including sensors for engine speed, coolant temperature, ambient air temperature, and exhaust back pressure;
• means within said microcomputer for generating a fuel delivery output signal to said engine;
• means within said microcomputer responsive to said engine speed sensor and said fuel delivery output signal for generating a desired back pressure signal from a lookup table stored in the memory of said microcomputer comprising a matrix of desired back pressures determined for various ranges of engine speed and fuel consumption;
• means within said microcomputer responsive to said coolant temperature sensor for generating a multiplier signal of between and including zero and one dependent on said coolant temperature according to a preselected relationship of said multiplier and said coolant temperature stored within the memory of the microcomputer, said microcomputer applying said multiplier to the desired back pressure signal derived from said lookup table and, if the multiplier produces a value greater than zero, generating a multiplied desired back pressure signal;
• means within said microcomputer responsive to said ambient air temperature sensor and, upon said ambient air temperature being below a preselected ambient air temperature, generating an enablement signal permitting transmission of said multiplied desired back pressure signal to said valve;
• means within said microcomputer responsive to said exhaust back pressure sensor for comparing the actual back pressure signal to the multiplied desired back pressure signal generated above, and, upon a deviation of said actual back pressure signal from said multiplied desired back pressure signal being detected, producing said output signal to said valve.