Quote:
Originally Posted by COcyclist
I have been pondering this for a while since observing that many posts about work done on the front of a vehicle get shot down in flames. (Picture Snoopy with smoke pouring out of his doghouse) Also, what I personally consider to be a couple of our leading authorities on this site (Aerocivic and Aerohead) have reshaped the fronts of their vehicles, as well as streamlining the back. Then I am reading a post from MetroMPG about the 2012 Chevy Malibu ECO aerodynamic tweaks and came across this:
10 counts: Underbody panels - two in the mid-body area under the floor pan on either side of the center tunnel, and two in the rear area covering the fuel tank and rear area on either side of the exhaust
10 counts: Rounded front corners - from the bottom of the fascia up through the headlamps - help air flow smoothly along the Malibu's body sides
10 counts: Tire deflectors positioned forward of the front tires act as "mini-air dams" to minimize wind disruptions
7 counts: The closed upper grille on select models pushes wind to the sides of the Malibu
7 counts: Outside rearview mirrors are specifically designed to deflect wind without "upsetting" the airflow
7 counts: Shutters in the lower grill opening on select models open and close automatically to maximize aerodynamic efficiency. This increases cooling airflow to the engine under certain conditions, such as under high-engine loads at low speeds, and reduces aerodynamic drag when extra cooling is not needed
5 counts: The front air dam redirects airflow to minimize aerodynamic disruptions
5 counts: The notch angle of the vehicle - the angle from the top of the rear glass to the trailing edge of the decklid - was optimized to reduce wind drag
2 counts: An integrated decklid spoiler incorporates a crisp, trailing edge that helps separate air from the rear of the Malibu.
The "rounded front corners" is 10 counts and the "decklid spoiler" is only 2 counts. Hmmm. I don't dispute the science that a full teardrop shape is essential for lowest drag in optimized vehicles. I just feel there may be some gains to be had at the front too. For many of us, a full boattail presents visibility, added length and parking problems. Should we as Ecomodders, do more work on the front before concluding that it is boattail or nothing?
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If you have a body-on-frame vehicle,like a Chevy Colorado/Hummer H3,you can take some liberties with the upper structure,as it is basically superfluous to 'strength.'You could yank off the top,discard,and fabricate a Ford Probe-IV body to bolt back on.And with active suspension,PRESTO!, you've got Cd 0.15.And no boat-tail!
With unit construction as in all passenger cars, you're dealing with a structure which has undergone finite element analysis for strength,crashworthiness,mass production,etc.,and they're a completely different animal if you take a plasma cutter,Sawsall,or what have you to attempt major alterations.
The thing about boat-tailing as Hucho tells us:
*The front of your car is already okay as far as attached flow and any additional streamlining will pay diminishing returns.
*If you go after the rear,you maintain all the multi-billion dollar engineering which went into the car,you're taking nothing away,only adding drag reduction which wasn't available from the car lot.
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When Chevy boat-tails the Malibu they get Cd 0.12.When they fair in all the tires and wheels the Cd goes below 0.10.
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There is only so much which can be done with the front.And yes,I have cleaned up the front of my vehicles,but no more than what Korff recommended in 1963,or R.G.S.White in 1968,with his recipe for Cd 0.24.
I'm going for sub-Cd 0.10 and that will require the best onset flow I can get to the rear if I'm to crack 40-mpg with the truck.I've seen 47.9 mpg pulling the trailer under 'favorable' conditions,so there's still fruit on the tree.But these gains,other than the enclosed front wheels,will be coming from aft-body mods.
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If you really want to idealize the front you're going to need the $3,000 windshield and all the mods to make that fit.That's a hard one for most folks to swallow.
