Engine operation to estimate and control exhaust catalytic converter temperature

A method of inferring engine exhaust gas temperature including:

• providing inputs indicating air/fuel ratio, exhaust gas recirculation rate, spark timing, air charge intake, engine speed rpm;
• providing stored look-up tables indicating air/fuel ratio versus a first constant, air/fuel ratio versus a second constant, exhaust gas recirculation (EGR) versus a third constant, engine aircharge versus a fourth constant, engine rpm and engine aircharge versus MBT, engine rpm and engine discharge versus nominal exhaust temperature;
• multiplying an output from the EGR rate sensor and an output of the engine aircharge versus the fourth constant table to produce a first product;
• adding the output from the table of air/fuel ratio versus the second constant, the product, and an output of the rpm versus MBT table to produce a first sum;
• finding a difference between the spark timing input and the first sum;
• applying the difference to a table for spark delay versus constant;
• multiplying an output of the spark delay table by the output of the EGR versus constant table and the rpm versus nominal exhaust temperature table to produce a second product;
• multiplying the second product by an output of the air/fuel ratio versus constant to produce a third product of the exhaust temperature;
• providing stored tables and memory for adjusting exhaust temperature as a function of air/fuel ratio, exhaust gas recirculation, spark delay and engine speed;
• coupling an input indicating air/fuel ratio to information stored as a function of air/fuel ratio;
• coupling an input indicating EGR rate to information stored as a function of EGR;
• coupling an input indicating air charge to information stored as a function of air charge and engine speed;
• coupling engine speed to information stored as a function of engine speed;
• multiplying the output of information stored as a function of air charge and an input indicating exhaust gas recirculation and applying the output to a first adder;
• applying the output of information stored as a function of air/fuel ratio and information stored as a function of engine speed to the first adder;
• applying an input indicating spark timing to the negative input of a difference module and applying output of the first adder to the positive input of the difference module;
• applying the output of the difference module to an exhaust temperature adjustment table stored as a function of spark retard;
• applying the output of the exhaust temperature adjustment table to a second multiplier along with information stored as a function of exhaust gas recirculation, engine speed stored as a function of spark retard to provide an output indicative of exhaust temperature.

A method of inferring engine exhaust gas temperature including:

• providing inputs indicating engine speed and engine aircharge;
• providing look-up tables stored in memory including a first look-up table indicating an exhaust gas recirculation constant versus aircharge, a second look-up table indicating MBT spark versus engine speed, a third look-up table indicating nominal exhaust temperature (EXT) versus engine speed, and a fourth look-up table indicating a constant versus spark delay;
• applying an input indicating aircharge to said first, second, and third tables;
• applying an input indicating engine speed to said second and third tables;
• applying outputs from said first and second tables to a first summer;
• applying an output of said first summer as an input to said fourth table;
• applying an output of said fourth table to a first multiplier;
• applying an output of said third table to said first multiplier;
• and
• using an output of said first multiplier as an indication of exhaust gas temperature.

A method of operating an internal combustion engine wherein the method of operating the engine includes:

• using a predicted exhaust gas temperature in conjunction with determining an exhaust gas recirculation mass flow rate;
• determining exhaust gas recirculation mass flow rate (EM) using:
• EM=EGR-MASS-STP*SQRT[BP % PEXH)-29.92]*SQRT [1460/(EGT-EGRORIF % 460)]
• wherein:
• p2 EGR-MASS-STP--exhaust gas recirculation mass flow at a predetermined or standard temperature and pressure
• BP--barometric pressure
• PEXH--exhaust gas pressure
• SQRT--square root function
• EGT--exhaust gas temperature
• EGRORIF--exhaust gas temperature at the metering orifice of the exhaust gas recirculation valve
• 29.92--barometric pressure
• 1460 DEG.Rankin--temperature of the exhaust gas at the metering orifice
• 1000 DEG.Fahrenheit--temperature of exhaust gas at the metering orifice
• providing inputs indicating air/fuel ratio, exhaust gas recirculation rate, spark timing, air charge intake, engine speed rpm;
• providing stored look-up tables indicating air/fuel ratio versus a first constant, air/fuel ratio versus a second constant, exhaust gas recirculation (EGR) versus a third constant, engine aircharge versus a fourth constant, engine rpm and engine aircharge versus MBT, engine rpm and engine discharge versus nominal exhaust temperature;
• multiplying an output from the EGR rate sensor and an output of the engine aircharge versus the fourth constant table to produce a first product;
• adding the output from the table of air/fuel ratio versus the second constant, the product, and an output of the rpm versus MBT table to produce a first sum;
• finding a difference between the spark timing input and the first sum;
• applying the difference to a table for spark delay versus constant;
• multiplying an output of the spark delay table by the output of the EGR versus constant table and the rpm versus nominal exhaust temperature table to produce a second product;
• multiplying the second product by an output of the air/fuel ratio versus constant to produce a third product of the exhaust temperature;
• providing stored tables and memory for adjusting exhaust temperature as a function of air/fuel ratio, exhaust gas recirculation, spark delay and engine speed;
• coupling an input indicating air/fuel ratio to information stored as a function of air/fuel ratio;
• coupling an input indicating from EGR rate to information stored as a function of EGR;
• coupling an input indicating air charge to information stored as a function of air charge and engine speed;
• coupling engine speed to information stored as a function of engine speed;
• multiplying the output of information stored as a function of air charge and an input indicating exhaust gas recirculation and applying the output to a first adder;
• applying the output of information stored as a function of air/fuel and information stored as a function of engine speed to the first adder;
• applying an input indicating spark timing to the negative input of a difference module and applying output of the first adder to the positive input of the difference module;
• applying the output of the difference module to an exhaust temperature adjustment table stored as a function of spark retard;
• applying the output of the exhaust temperature adjustment table to a second multiplier along with information stored as a function of exhaust gas recirculation, engine speed stored as a function of spark retard to provide an output indicative of exhaust temperature.