Show me your airdams or bellypan + results!?
 

Im still not sure which mod would be best! Anyone out there that has done some tests? the mods are for a 2004 ford fiesta hatch. there is various pros and cons for both. the hatch is quite compact so underneath it is rather smooth only really needing a belly pan in the front. im planning a 800 mile round roadtrip and petrol prices here are through the roof!

Im trying to make a data base for everyone to see what sort of airdam or belly pan design would suit their car best.

What was your results with either mainly a front belly pan or airdam?

interesting read https://hanchagroup.wordpress.com/20...esign-is-best/

That link was surprising! I think I get how #6 worked so well though. By reducing the airflow beneath the car sooo drastically not only is underbody drag reduced but so is drag at the rear of the car because there's less to exhibit drag. Very illuminating!

best
 

so far,for a 'practical' road-going car,the streamline half-body is 'best' for low drag.
It's sloped-back 'BUG' nose,with its generous plan curvature naturally forms a splitter and with the flat belly gets all the air moving around the body at similar velocity and pressure netting low lift and drag.
http://i1271.photobucket.com/albums/...ntitled7_7.jpg
The modern splitter nose dates to the mid-1930s,with the research of Fachsenfeld.It prevents any air to be directed under the vehicle,gets the forward stagnation point very low (very good for low drag),directs air to the cooling system inlet,kicks the remainder around or over with full attachment.
Since mass-produced cars are different from the 'ideal' form,we attempt to capture as much benefit we can from the splittered BUG nose,while permitting 'real' day to day driving on real roads and driveways without tearing anything off the car.
Low-drag concept cars ate combining active suspension and active aerodynamics to reach a more 'ideal' nose which can survive the rigors of real driving.
SAE recommends a clear 16-degree line of sight 'RAMP' angle from the front tire/road interface,looking forward and up in order to not destroy body parts.

it was quite surprising. but note how the airdam is moved to the very front of the bumper in 6. this is to prevent any overhang in the front so air can cleanly be deflected over the car. it all depends in what shape car you have. pics below are of my car and my plans.

Attachment 17550 this should work as my car has a minimal overhang in the front. the second pic shows the ideal shape but that would be difficult to do nicely.

Attachment 17551
only question here is what to make that front splitter of so it wont break off. the car doesn't have too much of a nose overhang but it will still get scraped if I plan on lowering it as much as I want to

If you plan on driving over any bumps, you may want to be realistic/practical about the depth of your air dam.
However, that being said, if you have diagonal support rods attached to the lower part of the air dam on one end and attached to the car on the upper end, it should be strong enough to withstand scraping.

pics are not too scale! looking at about a 15 to 20 cm gap

15cm
 

In his Masters Thesis on Dodge Ram aerodynamics,Feysal Ahmed discovered that between 'flush' with the vehicle belly,and 76mm ground clearance to the bottom of the airdam,that there was a drag increase.
This has been reported by two other investigators,and discovered by one of our members,who had to raise his airdam back up to rid himself of the drag penalty.
If you can get instant mpg numbers in the car,you might want to experiment with cardboard and duct tape to optimize the gap.

FWIW on the new Porsche 981, they have a half inch airdam sitting right under the bumper with what seems like radiator exhaust vents a few inches behind it. The radiators may or may not primarily exhaust to the fenders, I have not checked. All I know is that there is really beautiful ductwork going to the radiators :)

Why would you not do both? Most cars need both, you surely don't want the undertray angling up from the "axle" to the front bumper, that would generate lift, which is both drag and instability.