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Old 11-20-2019, 11:03 AM   #11 (permalink)
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Originally Posted by Taylor95 View Post

Despite some inaccuracies and bad comparisons I noticed in the article, it explains well that engine efficiency plays just an important part in fuel economy as coefficient of drag does. So some cars that are shaped like bricks (my Jeep) can still get good FE without making too many concessions to aerodynamics. Not something too many ecomodders consider as most cars here have small engines and have a fairly low cd already.
I've never heard of a comparison with a wall,only a brick,which would be Cd 0.85.
Members mentioned a flat plate,that would be Cd 1.11.
All ICE engines, whether gas or diesel will have an engine map,on which there will exist an island of lowest BSFC.Engineers might shoot for gearing which would hold the engine load,at cruise velocity,near the optimum BSFC on level road.
The CVT(Van Dorne) transmission is designed to maximize BSFC,keeping the engine in its 'sweet-spot' under all transient conditions.One reason why hybrids with the Atkinson-cycle engine do so well.Their gutless as far as torque goes,but they've got the motor to compensate.
Since,on the open road,at constant speed,aerodynamic drag is 80-90% of load,it remains the greatest impediment to efficiency.And why all Tesla cars,Prius,Insight,and Hyundai Ioniq,etc.,can clean the best ICE car's clock in efficiency (119-130 mpge).
A early 1970s JEEP CJ would get 33.5% better fuel economy with the body of a Prius ( all other factors held constant). With air-suspension it could probably 'go' where a CJ goes.I've no idea what a person could get with a GDI-turbo ICE engine or TDI diesel in a standard JEEP body.

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