Method and system to operate diesel engine using real time six dimensional empirical diesel exhaust pressure model

1. A method to estimate real time exhaust pressure in an internal combustion engine with an exhaust gas recirculation system (EGR), an ECM with memory and a variable Geometry turbocharger (VGT) with an inlet, to control EGR flow rate and combustion emissions, comprising:

determining VGT turbocharger vane position;

determining engine RPM;

determining engine load;

determining EGR valve position;

determining intake manifold temperature;

determining turbocharger RPM; and

using the above six variables as inputs to three two-dimensional tables that are summed to estimate a final turbocharger inlet pressure and to control exhaust emissions.

2. The method of claim 1 , wherein turbocharger RPM, engine RPM, VGT vane position, engine load, EGR valve position and intake manifold temperature are in at least one table within memory of the ECM; said table generated according to the formula:

z

=

c

1

⁢

x

2

+

c

2

⁢

x

+

c

3

⁢

y

2

+

c

4

⁢

y

+

c

5

⁢

x

2

⁢

y

2

+

c

6

⁢

xy

+

c

7

⁢

x

2

⁢

y

+

c

8

⁢

xy

2

+

c

9

wherein:

z is the table output,

x is the first input to the table,

y is the second input to the table, and

c 1 ; c 2 ; c 3 ; c 4 ; c 5 ; c 6 ; c 7 ; c 8 ; c 9 are coefficients of the polynomial used underlying turbine inlet pressure model.

3. The method of claim 2 , further including the steps of:

assuming a fixed model z=a*c

wherein a is the vector a=[x 2 , xy 2 , y, x 2 y 2 , xy, x 2 y, xy 2 , 1]; and

solving for the coefficients of the vector c

wherein c=[a′*a] −1 *a′*z−.

4. The method of claim 1 , wherein the exhaust emissions are NOx.

5. The method of claim 1 , wherein EGR valve position is measured as a function of percent the EGR valve is open.