gen3, 5.3 liter GMT800 Suburban with VSR78/75 will go positive pressure as low as 2200 rpm, 13 PSI at 3000 rpm
PE is delay 'til 118kPa
Part throttle cruise, highway on flat ground runs around 80kPa, light accel, or climbing a grade makes 1 or 2 PSI , still holding AFR= 14.6
Turbo is obviously ADDING to airflow equation, can I expect to get BETTER economy than stock NA engine while running with "slight boost" at 14.6 AFR ?

Turbo V8 should be "capable" of higher efficiency than NA, right?

 

Not really. Turbo motors are capable of better economy than the larger NA motor that would be required to make the same amount of horsepower, but at light cruise you are just dragging around an extra weight that just happens to also block the intake and exhaust to some minor degree.

 

So, we have ZERO chance of an increase in volumetric efficiency at part throttle light load cruise?
Fairly small ish engine for the Turbine size, I wonder if anyone has ( Gauged) pre turbine exhaust pressure? Can't see that it would be very restrictive at 55-60 kPa intake pressure.
The little FORD 3.5 gets decent fuel economy- pushing through TWO tiny Turbines.

 

yes, it can be more efficient than NA—but not automatically, and not in the way most people expect. You’re right to question what’s happening at 1–2 psi while still commanding 14.6.

 

My '61 Chevy pickup has an LQ4/4L80/9" and a 7875. The Express 3500 the engine and trans came out of was rated at 11mpg, I'm getting 14 if I never accelerate at all.

Sure, the van is heavier, but the truck is a parachute.

I think you could probably get better mileage since the exhaust isn't leaving the cylinder as easy since the turbo is in the way; you're potentially not fully filling the cylinder.