Pumping Losses: Gasser/Oil burner

[TandW]

I see a lot of finger pointing at gassers because they pull vacuum against the throttle plate. Is their someone knowledgeable among us who can explain how this compares to the pumping losses in a diesl as they compress air to a very high pressure in a single stage, and rely on a back pressure producing turbocharger. Has there been a fair comparison made?

[TandW]

I see a lot of finger pointing at gassers because they pull vacuum against the throttle plate. Is their someone knowledgeable among us who can explain how this compares to the pumping losses in a diesl as they compress air to a very high pressure in a single stage, and rely on a back pressure producing turbocharger. Has there been a fair comparison made?

[Mutha]

I have not seen this "finger pointing". Can you reference a article or link to an article detailing the pros and cons of your premise?

Thanks - Glenn

[Reno Curmudgeon]

As I understand it, diesels do not have pumping losses because they do not have throttle bodies. Any work done to compress the charge is paid back by the burn.

[TandW]

December's Motorhome magazine has yet another damning reference to this in the Powertrain Q&A section on page 96. As built, diesels have massive engine blocks and also all internals or running gear. They have an inherently larger natural flywheel effect. They require massive cooling systems and lubrication systems. They are best suited to stationary applications where they are optimized to run at one speed. That said, from an engineering standpoint, what are the pumping losses from a diesel and a gas engine of like displacement? Or should it be looked at as how much work each powerplant can produce per input of equal fuel btu's? What are the friction losses of each type when compared doing the same work? Is the manufacturing and maintenance carbon footprint of one type greater than the other? If you are at all familiar with combustion principles, then you know that it is most desirable to have the "fuel" follow the air. Not so with a diesel and so we have particulate visible in the exhaust. I predict the eventual demise of the diesel because of this and also due to fuel vendors now selling fuels for there btu value. Your thoughts?

[RustyJC]

There are valid reasons that applications such as heavy (Class 8) trucks, locomotives, etc. (neither of which are constant speed applications) run diesel engines. The Diesel cycle is inherently more efficient in terms of BTUs consumed per brake horsepower hour produced due to (among other factors) lower pumping losses and higher expansion ratio. Another is durability and engine life that are a function of the beefier construction of the diesel as required by its higher compression and peak firing pressures as well as its lower RPM and, generally, piston speeds.

If Otto cycle (spark-fired) engines were more cost-effective in these financially sensitive applications, you could be sure that the trucking and railroad industries would be using them.

The work done during the exhaust stroke to produce drive pressure for the turbocharger is largely recovered by the pressurized air that pushes the piston down on the intake stroke. Well-matched turbochargers will have locations in their operating maps where boost pressure exceeds drive pressure.

Rusty