JK Drag Coefficient?
10-16-2009, 03:00 AM
#31
JK Jedi
Join Date: Oct 2007
Location: Colorado
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10-16-2009, 12:43 PM
#33
JK Junkie
This is all fine and dandy, but the aerodynamic problem are thethings that make a JK a
Jeep: flat grill, near vertical winshield, height, bir tires
and mirrors, fenders, etc not to mention frontal area. And then we add mods to make it even less streamline.
I love my JK but like Harleys and bulldozers whic I also admire, aerodynamic effiency is not one of its
virtues.
Jeep: flat grill, near vertical winshield, height, bir tires
and mirrors, fenders, etc not to mention frontal area. And then we add mods to make it even less streamline.
I love my JK but like Harleys and bulldozers whic I also admire, aerodynamic effiency is not one of its
virtues.
It appears they did a lot of little things to improve the C/D of the JK, would love to know the official number though, haven't been able to find it. Some things they did:
More rake to grill and windshield, curve to windshield, integrated fog lights, rear of tub actually narrows inward toward the tailgate, added the (dreaded) airdam, cleaned up the surfaces of the frontal area (compared to the TJ), most of the lines are rounded and curved, again compared to the TJ. I think all of these things help the JK get pretty damn respectable fuel economy compared to the TJ despite being heavier with more frontal area. Obviously the 3.8L is an efficiency factor as well.
More rake to grill and windshield, curve to windshield, integrated fog lights, rear of tub actually narrows inward toward the tailgate, added the (dreaded) airdam, cleaned up the surfaces of the frontal area (compared to the TJ), most of the lines are rounded and curved, again compared to the TJ. I think all of these things help the JK get pretty damn respectable fuel economy compared to the TJ despite being heavier with more frontal area. Obviously the 3.8L is an efficiency factor as well.
10-16-2009, 12:53 PM
#34
JK Super Freak
This is all fine and dandy, but the aerodynamic problem are thethings that make a JK a
Jeep: flat grill, near vertical winshield, height, bir tires
and mirrors, fenders, etc not to mention frontal area. And then we add mods to make it even less streamline.
I love my JK but like Harleys and bulldozers whic I also admire, aerodynamic effiency is not one of its
virtues.
Jeep: flat grill, near vertical winshield, height, bir tires
and mirrors, fenders, etc not to mention frontal area. And then we add mods to make it even less streamline.
I love my JK but like Harleys and bulldozers whic I also admire, aerodynamic effiency is not one of its
virtues.
10-16-2009, 01:30 PM
#35
JK Junkie
It's all good!
10-17-2009, 01:32 PM
#37
JK Junkie
I can't really say I miss the 4.0L, I just have fond memories. It was also easier to change the plugs on the 4.0L.
10-18-2009, 06:34 AM
#38
JK Newbie
Join Date: Aug 2006
Location: Chandler, AZ
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No one seemed to have the info posted. I finally found it on a South African car site called CARtoday. Be patient its a PDF and takes a minute to load. It is a review of the 4 Door CRD.
Back to the Cd, they list it as being better than the TJ at - - - .495 which, if my math is correct, (never is) comes out to just slightly WORSE than a barn door.
OK, for fun here are some things to compare it to.
Type of Object Drag Coefficient - cd -
Old Car like a T-ford 0.7 - 0.9
Common Car like Open Vectra (class C) 0.29
Passenger Train 1.8
Bike Upright Commuter 1.1
Bike racing 0.88
Tractor Trailed Truck 0.96
Dolphin 0.0036 wetted area
Bird 0.4
Solid Hemisphere 0.42
Solid Hemisphere flow normal to flat side 1.17
Thin Disk 1.1
Cube 0.8
Streamline body 0.04
Squared flat plate at 90 deg 1.17
Long flat plate at 90 deg 1.98
Hollow semi-sphere opposite stream 1.42
Hollow semi-sphere facing stream 0.38
Hollow semi-cylinder opposite stream 1.20
Wires and cables 1.0 - 1.3
Laminar flat plate 0.001
Turbulent flat plate 0.005
Subsonic Transport Aircraft 0.012
Supersonic Fighter 0.016
Person (upright position) 1.0 - 1.3
Ski jumper 1.2 - 1.3
chart copied from http://www.engineeringtoolbox.com/dr...ent-d_627.html
Last edited by 3Lug; 10-18-2009 at 07:03 AM. Reason: added chart
10-18-2009, 08:59 AM
#39
JK Enthusiast
Join Date: Aug 2008
Location: Doha, Qatar
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All right, broke out the full sized wind tunnel and did the math.
It's 9
. . . or 90
. . . carry the 1 . . . where'd that decimal go?
Yep 9.
Who am I kidding? I have a biology degree. And my jeep is 9000 miles away.
It's 9
. . . or 90
. . . carry the 1 . . . where'd that decimal go?
Yep 9.
Who am I kidding? I have a biology degree. And my jeep is 9000 miles away.
10-18-2009, 12:59 PM
#40
JK Super Freak
The only thing that really sucked on the 4.0l was accessing anything on the front of the engine like the water pump.