How to correct my Matlab Simulink model to let it be conform to the reality ?

Hello !

I would like to know, how could I know which parameters should I change in my model to let it conform to the reality. I tried many times to do the math for the parameters but I still can not get a conform project. We want to get a maximal speed of 3.28m/s and a traction of 2.0601N but we get a maximal speed of 3.25(Good) and a traction of just 0.6N(Bad). Do you know which parameters could be bad modelized ?

I would like to modelize an RC Car. I put the matlab project and the measured infos in attachments. Sorry if I did not give enough infos.

Thank you for reading !

Measured infos:

For the motor:

Armature resistance: 1 Ohm

Armatue inductance: 2.21e-4 H

Back-emf constant: 0.00030805

Rotor inertia: 9.47625 g*cm²

No-load current: 0.27A

DC Supply voltage when mesure no-load current: 6.6V

For the battery:

Nominal voltage: 6.5-7V

Internal resistance: 8 Ohm

Car:

Car weight: 0.570kg

Wheel radius: 3.45cm

Car speed: 3.28m/s

Car traction: 2.0601N