Performance and Fuel Economy Trends

•In the late 60’s and early 70’s, car manufacture’s main goal was to increase power by increasing engine displacement.  This large engine displacement resulted in an increase in power and torque but ultimately resulted in a decrease in fuel efficiency.
•With larger bore engines, these vehicles burned more fuel per mile driven because of the there is a larger amount of combustion that is occurring within the engine.
•As you can see in the figure above, fuel economy has greatly increased over time along with horsepower.  This increase in fuel economy and horsepower is due to adjustments in such factors like the air to fuel ratios and overall better engine designs.
•To further show the changes in horsepower and fuel economy, refer to the graph shown above.  It is shown that in the early 80’s there was a dramatic decrease in the performance of vehicles because of the safety concerns associated with the very common big bore engines of the early 70’s and late 60’s.  In the late 80’s, vehicle started becoming much more safe and car manufactures started to increase engine horsepower once again.  As car manufactures started to increase horsepower again, fuel economy started to decrease in the early 80’s until about 2005.  More research and development regarding fuel economy and engine design in the early 2000’s resulted in increases in both fuel economy and engine power from 2005 until now.Capture699
•This graph shows specific relationships between different performance aspects of vehicle over time.  It can be seen from the HP/Displacement curve that engines have increase the amount of power created per volumetric unit of displacement.  This has been made possible through the improvements of engine design and adjustments in air to fuel ratios.  The Fuel Consumption/Displacement curve shows that there has generally been a decrease in the amount of fuel consumed per volumetric unit of displacement.  This again can be attributed to the improvements in engine design over the past 40 years.  The third curve, Fuel Consumption/HP, shows that the amount of fuel consumed by an engine has decreased per horsepower produced by the engine.  In other words in the past 40 years cars has become more fuel efficient without a relative lose in power produced by the engine.  Engineers have designed engines to be more fuel efficient without sacrificing engine power.
Author: Matt Smith