Hacking air pressure sensor for fe?

[Piwoslaw]

My diesel has an air pressure sensor just after the turbo. I'm wondering what the effect of changing its signal could be. Would tricking the ECU into thinking the pressure is greater (more air) or smaller (less air) result in using slightly less fuel for the same amount of work? On the other hand, the ECU's map could already be fine-tuned to the lowest possible fuel consumption and fooling around with the signals would reduce fe, increase emissions, or both?

I'll add that my turbine is supposed to have variable geometry, so hacking the pressure sensor may put more or less air into the cylinder. Or maybe manually changing the turbo's geometry would be a better idea? Then the ECU could compensate for more/less air in the most efficient manner?

[Piwoslaw]

In two new threads (1.9L VW/Audi/Skoda/SEAT Diesel Mod alert! and Diesel mods and testing) there is quite a bit of discussion about how to put more air into the cylinders of a turbodiesel (better intake ducting) and whether or not this causes more fuel to be used.

Tampering with airflow meters, air pressure sensors, and variable turbine geometry is another way to "fool" the ECU into packing more air. So is this a good route to go down? Also, if I fool the ECU into thinking the (post-turbine) air pressure is lower than in reality, then will it change the turbine's geometry to compensate? Will the (pre-turbine) air flow meter's readings be used to confirm the air pressure sensors signal, so should that be tampered with, too?

[Angmaar]

Maybe there's a way to hack the "variable" part of the turbo so that it doesn't compress the air as much (heating up the air). If the air is cooler you "should" get better FE.

[Joenavy85]

i suspect this would cause problems with running lean. if the computer thinks there is less air going into the engine than there really is(or warmer air) it will inject less fuel. yeah this could effect fe in a positive way since you are injecting less fuel, but i suspect that running lean for extended isn't any better for a Diesel than it is for a gasoline engine.

NOTE: I am not, nor have i ever been an expert in regards to diesel engines, this is only my thought as to what would happen