Page 390 - Understanding Automotive Electronics

2735 | CH 11 Page 377 Tuesday, March 10, 1998 1:30 PM

FUTURE AUTOMOTIVE ELECTRONIC SYSTEMS 11

In the past, the 2-stroke/cycle engine was virtually eliminated as a
passenger car power plant due to the emission regulations of the Clean Air Act.
Poor emission performance results, in part, from less efficient combustion
than the 4-stroke/cycle engine. In addition, the traditional 2-stroke/cycle
engine requires mixing lubricating oil with gasoline, resulting in poor
emissions.
The potential for this engine in cars may be returning due to recent
developments in technology, including electronic fuel control. Figure 11.8 is a
schematic cross-sectional drawing of a 2-stroke/cycle engine. Some of the new
technology on this engine that is missing from the traditional 2-stroke/cycle
engine includes the intake and exhaust valves, supercharger, direct fuel
injection, and oil injector jet for lubrication. In at least one engine
configuration under development, there are four valves per cylinder that assist
in scavenging (i.e., removing exhaust and charging the cylinder with intake air).
In addition, a Roots-type supercharger helps in scavenging and mixture
distribution.
The direct fuel injection provides highly atomized fuel droplets. The
control of fuel droplet size to very small droplets improves the surface/
volume ratio of fuel, resulting in reduced emissions and improved fuel
economy.

Figure 11.8
2-Stroke/Cycle
Engine
Configuration

FPO

UNDERSTANDING AUTOMOTIVE ELECTRONICS 377