IC-engine specific intake/exhaust gas constants?

[70AARCUDA]

...I'm aware the specific gas constant for 'pure' air without water vapor is 287.0 J/(kg*K), but what is it for todays' typical (a) intake air+fuel mixture at max HP and max FE; and (b) exhaust gas with typical EGR? Are they the same, similar or vastly different values (only need integer values)?

...I ask because I've found three different values, going in different directions, in the old IC-engine books.

...looking for somebody to "break-the-tie" and steer me in the correct direction.

 

[SomptingGuy]

Lean and stoichiometric combustion products have a mean molecular weight very close to pure air, so they have a gas constant of 287 J/kg/K. Intake air, with fuel will have a slightly higher molecular weight and therefore slightly lower gas constant. Air + gasoline at 14.7 A/F has a gas constant of about 271 J/kg/K.

- Steve

 

[70AARCUDA]

Thanks! I appreciate both the information and the explanation.