With all this dicussion of "minimizing pumping losses"

[theholycow]

Originally Posted by *************

Well I was just thinking that a turbo with no boost, basically heating up the intake air would mean that less fuel is burned because less air is available but at the same time would mean more throttle in order to accelerate.

That's the description of a Warm Air Intake, a common DIY mod discussed here.

However what a turbo does is force so much more air and fuel into the cylinder that the temp of the air is negated since more overall air/fuel is in the cylinder than under atmospheric pressure with lower intake temps.

Turbos are not at all about the temperature of the intake air, they're solely about the volume of air. A turbo also does not force more fuel into the cylinder. Instead, it merely forces air in and the fuel system puts in as much fuel as is necessary for the desired air/fuel ratio. People using them for performance generally try to use the coldest air they can, so that its density results in additional air mass in the cylinders.

Wouldn't a low boost turbo act as an assistance to the air intake without increasing the amount of fuel being burned?

Yes, but it would be a net loss, or if it was a perfect machine with no friction, it would be a net draw. The pumping energy that is saved on intake by having the turbo push it in would be lost again by having to push it out to operate the turbo. You are effectively using an air pump to drive a fan.

Now, if a low-boost blower could be powered by scavenged energy, such as steam pressure from exhaust heat or regenerative braking, I suppose it could reduce pumping losses.

Also I'm just wondering how it would be possible to increase the fuel economy of cruising speed over pulse and glide as it isn't practical nor a good idea for some vehicles.

Such vehicles would need to be driven slower, or would need major mechanical or design changes. My VW is a bit impractical for P&G at highway speeds because of its low gearing and sometimes unpredictable drive-by-wire system, combined with my crappy rev-matching skills. P&G on the highway destroyed the benefit I had from P&G on slower roads. It does seem to work with a modified P&G strategy where I don't use neutral, just letting the engine braking happen (which at least uses DFCO); I gained 1.5mpg over the previous attempt I described above with the highway difficulty.