Method for diagnosing an engine using computer based models

A method for diagnosing an engine having an exhaust manifold and a turbocharger, including the steps of:

• sensing an exhaust temperature of said exhaust manifold and responsively delivering an exhaust temperature signal;
• sensing at least one parameter of said engine and responsively producing at least one parameter signal;
• receiving said at least one parameter signal and responsively determining a modeled exhaust temperature value;
• receiving said exhaust temperature signal, comparing said exhaust temperature signal and said modeled exhaust temperature value and responsively producing a first difference signal;
• sensing a boost pressure of said turbocharger and responsively delivering a boost pressure signal;
• sensing at least one other parameter of said engine and responsively producing at least one other parameter signal;
• receiving said at least one other parameter signal and responsively determining a modeled boost pressure value;
• receiving said boost pressure signal, comparing said boost pressure signal and said modeled boost pressure value and responsively producing a second difference signal;
• and
• receiving said first and second difference signals, comparing said first and second difference signals, and responsively diagnosing said engine.

A method for diagnosing an engine having a turbocharger and a plurality of cylinders, each cylinder having an associated piston, including the steps of:

• determining the volumetric efficiency of said engine and responsively producing a volumetric efficiency signal indicative of the mass flow efficiency of said engine;
• determining the fuel to air ratio and responsively producing a fuel to air ratio signal;
• receiving said fuel to air ration signal and said volumetric efficiency signal, responsively determining the power delivered to the pistons, and producing a brake power signal indicative of said determined power;
• determining the heat lost through said cylinders and responsively producing a cylinder heat loss signal;
• receiving said cylinder heat loss signal, responsively determining the temperature of the exhaust gas and producing a modeled exhaust temperature signal indicative of said determined temperature;
• sensing the actual exhaust temperature and responsively producing an actual exhaust temperature signal;
• receiving said modeled exhaust temperature signal and said actual exhaust temperature signal, comparing said modeled and actual exhaust temperature signals and responsively producing a first difference signal;
• initializing a turbine speed to a predetermined value;
• determining an intake manifold air temperature and responsively producing an intake manifold air temperature signal, respectively;
• receiving said intake manifold air temperature signal and responsively determining the mass flow rate into the engine and responsively producing a mass flow signal;
• determining a filtered air pressure and temperature and responsively producing filtered air pressure and temperature signals, respectively;
• receiving said mass flow signal, turbine speed, said filtered air pressure and temperature signals, and said intake manifold air temperature signal and responsively producing a modeled boost pressure signal;
• sensing an actual boost pressure and responsively producing an actual boost pressure signal;
• receiving said modeled and actual boost pressure signals and responsively producing a second difference signal;
• receiving said first and second difference signals, comparing said first and second difference signals, and responsively diagnosing said engine.