Ford Fusion aero mods: Cd from 0.34 to 0.21

[ankit]

Originally Posted by .Cd

When they say that the LS430 was tested at .25, do you think that they cheated a little ?
What about those big pimpin' open spoke wheels , huge side mirrors , and overall boxy shape ?

Do you think it actually has a .25 out the showroom door ?

They could say it had a .10 drag coefficient and no one would know the difference.

It's hard to believe that the difference between the Lexus and the Fusion is only .05 cd. I mean compare the two pictures, maybe the cd for the fusion is lower?

[Silveredwings]

If the same volume of air passes through a smaller cross-section or channel, the speed of that air will increase while passing through. It may be counter intuitive but the pressure at that same point will decrease (the Bernoulli Effect). Think of it as a venturi.

In the case of lowering an air dam and the ground, I don't think the volume will be the same as before lowering, since the gap is more of an orifice than a venturi. If the front of the car channels air under the car (unlike an air dam), however, the airspeed probably does increase and Darin has a good point Doesn't he always? .

[hondaworkshop]

2000 Honda Civic Hatchback = .38

[aerohead]

Originally Posted by MetroMPG

OK, so it's a Bonneville car. But it's instructive about the basics what to do to improve aero:



- grille blocking
- smooth wheel covers
- narrower tires
- deleted mirrors
- deleted wipers
- lowering, in conjunction with...
- full undertray
- rear decklid extension (improved roof to trailing edge angle)

Sorry! I'm late to the party on this one,but I'll throw my two cents in.How fast did the car go? If its over 200-mph,compressibility issues would be looming up on the crew.As mentioned already,since this is a pure racing environment,safety may play as big a role as drag reduction and speed.The Fusion's roofline approximates an airfoil form,and the bellypan may be there to minimize static pressure under the car in an effort to forestall takeoff.

References state that air velocity under a car is always a fraction of road speed,therefore Bernoulli's theorem would come into play,dictating that pressure would have to be higher than the surrounding flow field.Not good! The smooth underbelly,acting like a traveling duct, would better allow low pressure from the wake,to be communicated under the car to help spoil the lift created by the more stagnant flow.

With respect to the airspeed under the car,as a function of ride height,my thought is that because of the plan radius of the front airdam,that air is being channeled around the car as much as the rulebook will allow,and while the air volume under the car will be an arithmaic function of the gap between salt and dam,the actual velocity remains a fixed fraction of groundspeed,as the dam doesn't aggressively funnel air under,but rather around.

The lowering also improves the fineness ratio,as well as the rear deck foil,both of which reduce drag,and the rear foils horizontal projection moves separation and lift completely behind and under the foil,a great boon to lift reduction and directional stability,creating a pressure weather-vane,if you will.

And I agree that the fences are also only for safety,should the car loose traction ( not an unusual event at Bonneville ),and yaw into a more wing-section attitude,sideways,as NASCAR vehicles which we may have all seen literally fly off the track.

Being a fuel-cell car,the nose can be sealed,and while not a great drag reducer for race cars ( they can be idealized for low drag ),again,it cuts off airflow "through" the car,for added stability and safety at high speed.

The 0.08 Cd reduction is really impressive and tailshadows Ford's active suspension contribution to their PROBE-IVand V concept car low drag numbers.Since the PROBE-V achieved Cd 0.137 in the 1980s,the Fusion's 0.21 doesn't carry the same wow-factor,buts its still instructive,and of great value to anyone who lives between the lines.Liked the article,thanks!

[SuperTrooper]

I had a '91 Subaru XT that had an adjustable air suspension. The car would drop about 1" at 50 MPH. Hmmmmm... The car was very aero for it's time: 0.29 Cd. Flush door handles.

I wonder how difficult it would be to add an air lift system. There are plenty out there for the low-rider crowd.

Anybody have any experience with air lift suspensions?

[gascort]

air ride can be pretty tough; you need to be good at customization and welding.

[donee]

Originally Posted by ankit

It's hard to believe that the difference between the Lexus and the Fusion is only .05 cd. I mean compare the two pictures, maybe the cd for the fusion is lower?

Hi All,

The picture on the first page is not the .25 Cd LS-430. There is one of the newer ones in my work parking lot most days. Its much more aero-looking, and even similar looking to the Fusion Aero. First off the grill work is allot smaller. And there are wheel dams, like on the Prius et al. Which tends to obviate the effect of the wheel spokes. At least a little bit. One of the more obvious aero features on the LS-430 is the rear trunk lid shape, which is scooped out and blends perfectly in with the surounding body work.

[mcrews]

Originally Posted by cfg83

MetroMPG -



Hrmmmmmm, I want to say "now I am glad I never did a belly pan". But, I think the Belly Pan benefit is being effected by the lowering. Would the belly-pan benefit have been more if they had never lowered it? Do you know what I mean? Did they test/simulate each mod independently?

CarloSW2

That exact same thought crossed my mind.
A sreet car (mass-produced) can only be SOOOO low.
Look at the work that just Audi put into the underbody panels.

I would think that there is an invers relation betweeen the amount of space and how smooth the bottom of the car needs to be. IMHO

[aspera]

Originally Posted by Cd

Metro, after looking at the gallery, I assumed wrongly that they ran at Bonneville with those stock door handles.
The door handles were flush at Bonneville.

I just reviewed my old Speedweek pics of the 999 from Bonneville. Mine show stock looking door handles covered in green/white/black vinyl.

One of the aero tricks that I really liked was how they jacked the 999 up. It was sort of like the jacking holes that rally cars use, except much larger and you had to open the rear doors for access. Once a rear door was opened, a foot-long pipe with an upside-down trailer ball was pinned in place with an aircraft pip pin. Then a floor jack would lift the upside-down trailer ball. They went to a lot of effort to hide the jacking points.

The whole rear of the car was one big science project. It looked like NASA. The fiber tanks were protected by a roll cage that even extended to the trunk. (Trunk cage?) It was all pretty slick, except the snorkel exhaust pipe that stuck out beyond the rear of the car. That was goofy.

Thanks for letting me know about other good stuff !