Turbo FE?

[lca13]

Why is a turbo car any different?

1st off, I don't necessarily buy the "lots of throttle during acceleration phase". One theory is to get to cruising speed quickly with as little time spent in the fuel rich acceleration RPM range. For one, it is indeed in the fuel rich range.... the harder you accelerate the richer the fuel mixture (typically). Second it is counter to standard advice. Lastly I think one can make a simple physics argument that harder acceleration will burn more fuel than slow smooth acceleration (think small increments of acceleration on top of constant speed, with little additional stress on the engine and no fuel richening, versus WOT with hard torque on the parts, thus more friction).

10 lbs of boost does not mean double the air displacement. In fact, the throttle pretty much guarantees you will never fill the cylinders, and the throttle argument suggests to me that if you slowly accelerate, the behavior and FE between turbo and normally aspirated engines would basically be the same. For hard acceleration, there may be a difference, but firstly it is balanced out by the fact that it takes the same amount of energy to get the car to cruising speed in both cases.... any differences in expenditures is due to losses.... I can see the hard turbo acceleration case yielding more losses, though.

I try to accelerate nice and slowly in my VX. But it is because I can do this in lean burn mode, versus rich with hard acceleration. I monitor my injector pulses with a DMM and smooth slow acceleration yields injector utilizations in the 3-8% range with cruising in the 6-8% range depending on speed. Dropping out of lean burn into even a moderate acceleration bumps the fuel utilization up into the teens, and WOT practically dumps fuel into the cylinders with a utlization as high as 40%. In my car, slow acceleration doesn't even show up as acceleration in the way fuel is consumed, and I think that is the best case.