Page 4 - Winter 2018 Travelore Issue 44
P. 4

Page 4 - DRVC Travelore
How They Work
Diesel Engines and Turbochargers
ONE OF THE ESSENTIAL components of a modern diesel engine is the turbocharger. As many of you know, Cummins engines have been installed in more RVs in the last ten years than any other brand of diesel. In developing this article, attention was placed on how Cummins implements the use of the tur- bocharging systems. Though the technology is essentially similar, there are differences in turbochargers and the application to which they are best applied just as there are difference in diesel engines and their implementations. The basic technology in both, however, remains constant.
This article is intended to take some of the mystery away and provide an understanding of how and why diesel engines with turbochargers are used in today’s over-the- road engines. The first in a series, other subjects to be cov- ered in subsequent
issues of “Travelore” will deal with the following topics:
- The charge air cooler (CAC)
- Operational issues of a turbo- charger (includ- ing the impor- tance of filtration and drying)
- Best practices (starting, driv- ing and shutting down)
- Differences between the genset engine and the chassis engine
- Diesel technology and the EPA (Environmental Protec- tion Agency)
Diesel Engine Design
The diesel engine (a compression-ignition engine) was named after Rudolf Diesel. Diesel engines have much higher thermal efficiency (engine efficiency) than typical gas engines. This means that by contrast, a diesel engine has greater pulling power than a typical gas one making it an ideal engine for moving heavy equipment, such as a Class A motorhome or a heavy-duty pickup towing a long fifth wheel trailer.
As mentioned, a diesel engine is an internal combustion engine in which the ignition of fuel, injected into the combustion chamber, spontaneously combusts from the
increased temperature in the cylinder.
The high tempera- ture is the result of a higher level of compression The compression ratio in a gas engine
is approximately one-half that of the typical diesel (gas engines are in the 10:1 range while most large diesels are around 18:1 range or greater). To stop a running diesel, it is critical to cut the flow of fuel which, essen- tially, starves the engine.
Combustion Chamber
Connecting Rod
Bracing Web
Crank Shaft
Bearing Cap
In cold weather situations, additional sources of heat may be used to aid
in starting a diesel. But, once up and running, the engine continues to operate unassisted by other heat sources. Modern diesel engines may use intake manifold heaters to aid in starting when cold. Additionally, most diesel-pow- ered RV’s have 120 volt AC-powered or Aqua-Hot block heaters that can be used to pre-warm the engine in very cold temperatures.
The Turbocharger
While an engine can breathe in and operate on surround- ing air collected through intake valves, it’s not ideal.
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