2001 V70XC - sharp mpg drop... 14.8 last night

[xHeart]

No sure if it is a hopeful sign.
A 50+ miles highway drive yielded 15.6 mpg.

[xHeart]

Numbers are much better today. Weather temp is in 50s.

Filled up 11.87 gallons after a 222 miles -- 150 miles on urban streets.
It is now 18.81 mpg. But the DIM shows average 15.4 mpg.

The instantaneous read is as high as 77mpg with 35mph @1500rpm.

[xHeart]

Does MAP supersedes MAF for fuel and air mixture since MAP is mounted over the fresh air hose to ETM, not the MAF? MAF is on the air hose to turbo.

[draser]

I'm seeing mine going up as well, 20.4 today. On your question MAF vs MAP: MAF drives the air volume fuel management strategy, i.e. injector pulse duration: MAP drives the speed density strategy where injector pulse is calculatwd based on air pressure, engine temp, intaks air temp. Not sure how they coexist with each other.

[xHeart]

I'm seeing mine going up as well, 20.4 today. On your question MAF vs MAP: MAF drives the air volume fuel management strategy, i.e. injector pulse duration: MAP drives the speed density strategy where injector pulse is calculatwd based on air pressure, engine temp, intaks air temp. Not sure how they coexist with each other.

Thank you dr.

Is there a specific code that would point to MAP failure?
Meanwhile, another fill of 14.6 gallons after a 269.9 miles.
The instantaneous data over DIM is revealing -- 65mph @ close to 2000rpm yields almost 58mpg.
Now curious if we drivers are missing the good science in speed limit of 55, 65, and now 75 mph.

[jimmy57]

On Bosch systems that is not really a MAP. It is used for boost pressure monitoring. The earlier extrapolation algorithm where MAF vs engine speed was used for boost level calculation was not as accurate. Primarily it is a feedback sensor used for turbo control valve operation.
On Denso systems where the MAP is manifold mounted it is used for lower throttle load sensing when airflow is low the MAF sensitivity error is larger. Once engine air consumption picks up then manifold pressure sensitivity diminishes and MAF is a better gauge of engine load.
MAP was the only load sensor on strict speed-density fuel systems. Volvo only used that on the Regina/Rex system on the 89-94 740/940 non turbo 230F engines.
The boost pressure sensor on the 99 and later turbo cars with Bosch system usually are noted by boost control codes. The MAF value vs boost pressure indication fall out of mapped value range. It is rarely the pressure sensor is is more likely the MAF sensor.