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Old 11-20-2019, 12:03 PM   #11 (permalink)
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wall

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Originally Posted by Taylor95 View Post
https://jalopnik.com/what-kind-of-fu...1839901794/amp

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.
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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).
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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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Old 11-20-2019, 12:14 PM   #12 (permalink)
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The author of the article calculated that a brick wall with a Prius engine would still get 29 mpg at 50 mph.
I came up with,around 22.5 mpg at 62-mph.It would be a little better at 50.
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Old 11-20-2019, 12:21 PM   #13 (permalink)
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My favorite what-if would be a Prius with a Dasher 5-speed, 36hp VW and Porsche cooling fan. The donor vehicle got 40mpg with a 0.41 Cd. The Prius would loose hundreds of pounds of weight. I estimate equal economy and less acceleration.
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Old 11-20-2019, 02:00 PM   #14 (permalink)
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air-cooled,5-speed,Prius-Dasher

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My favorite what-if would be a Prius with a Dasher 5-speed, 36hp VW and Porsche cooling fan. The donor vehicle got 40mpg with a 0.41 Cd. The Prius would loose hundreds of pounds of weight. I estimate equal economy and less acceleration.
A Dasher with a Prius body,and tires,if the same frontal area and weight would be 47.8-mph HWY.The air-cooled engine though,would knock the BSFC into the dirt.Without liquid-cooling,there's no way to operate it at temperatures high enough to achieve the thermal efficiency of the Dasher engine.You could lose 15%,ending up at around 41.5 mpg,not a great incentive for all the work.
Also,at 36-bhp,you'd have to get a run at every hill,entering the grade at top speed,just to have a chance to crest at any speed at all and not impeding other traffic.It's the only way I could operate my '64 Ghia,with the 40-horse,1,200 cc.Even rowing down through the extra gear,she'd still find it hard to climb.
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Old 11-20-2019, 04:29 PM   #15 (permalink)
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The Dasher gets 45mpg with [approx. 0.32 Cd?] so not much gain there. You're prolly right about the BSFC.

My panel van had a 1600 with dual Solexes and weighed (empty) about as much as a Beetle (worse Cd). It topped out at 80 on I-5 and topped the Coast Range at 75.

The Type II is sort of a pebble-ized brick end-on, so it's back to ontopic.
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Without liquid-cooling,there's no way to operate it at temperatures high enough to achieve the thermal efficiency of the Dasher engine.
I baked a few air-cooled engines trying.
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Old 11-23-2019, 12:23 PM   #16 (permalink)
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Put the wall on its side
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Old 11-26-2019, 12:50 AM   #17 (permalink)
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A person riding a commuter bicycle might have a Cd of 0.6 and there is hope of fairing it to get a Cd of 0.3 as usable daily rider.
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Old 12-09-2019, 05:57 PM   #18 (permalink)
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Quote:
Originally Posted by Taylor95 View Post
The author of the article calculated that a brick wall with a Prius engine would still get 29 mpg at 50 mph.
the Best i have ever done with a 40 cell Prius battery and 6.0L engine was 28.7 MPG combined 31City/26.4hwy
4x the power of a prius
but only get 25.5MPG on average not too bad for a 6.0l 364Ci engine



not too bad for a 6 foot 6 foot brick wall?

what would you rather drive a v8 6.0l SUV or a 2.7l V6 Chrysler 300? which both get 25mpg?

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