How to completely disable cylinder deactivation?

[cz5gt]

I have both. My observation is steady highway at up to 65mph the Turbo mpg is 30+ which is similar to the NA.
Above 70 ..well mazda has tuned the turbo model to be running very rich at high speeds and mpg drops to around 24-25.
City driving is low mpg but thats expected in stop and go. For city the Turbo is not the engine one wants for more highway driving its perfect

 

[N7turbo]

I have both. My observation is steady highway at up to 65mph the Turbo mpg is 30+ which is similar to the NA.
Above 70 ..well mazda has tuned the turbo model to be running very rich at high speeds and mpg drops to around 24-25.

I haven't done any data logging to look at AFRs, but at 75mph the engine is turning at 2500 rpm, which is right in the range where the turbo is making good boost. Fuel economy suffers but the passing torque is really nice.

 

[RedBaron]

Above 70 ..well mazda has tuned the turbo model to be running very rich at high speeds and mpg drops to around 24-25.

I would attribute this more to wind resistance (and friction losses) rather than running rich. The ECM will (should) always strive for perfect stoichiometric ratio for emissions reasons.

 

[sinistriel@]

The 2.5t has multiple base fueling maps that it can choose from and then apply all sorts of corrections to, like intake air temp, calculated EGT, ignition multipliers, etc.
Here is a screenshot of one of the base fuel tables. Then a screenshot from when I had my car of what AFR looks like cruising at freeway speed. It does a good job of hitting targets.