which to do for under air diversion

[talldudenumber5]

i was thinking about adding something to the under side of my car like an air dam and here are the ideas i have i just do not know which one to go with.

in the picture:
this is a very very rough drawing of my car underneath.
you may have to click on the thumbnail picture to get a better look

The grey - my car came stock with an under belly tray that covers cleanly from the front bumper to just under the driver/passenger (i.e. the engine bay

The 3 ideas:

1. yellow half wing thing - since there is a partial belly pan i thought i could just divert the air just around the wheel like you see on those solar cars

2 yellow ovular line since the bumper is not a ovular shape, (i.e. the best aero shape) i thought make an airdam under the car that is

3. just follow the line of the bumper all the way around like everyone else

[COcyclist]

I assume this is for the Maxima? Will you extend the belly pan in the future? If so, you may only need the part of the airdam that is in front of the front tires. If the underbody is smooth you don't need to add all the frontal area of a complete airdam. Mock it up with tape and cardboard and test it with your ScanGauge to see which works best for you.

[euromodder]

The yellow half-wing-thing scoops about half its width more air under the car.
If you want to do fairings in front of the wheels, have a look at the second incarnation of the LoReMo :

The fairings also act as splitters and divide the air going underneath the car and guide the rest sideways.

[Otto]

1. See Hucho pp. 142 and 183, and note that front-to-back airflow under the car is much more oblique than you may have thought. Actually, not that much of the flow is front-to-back, but rather obliquely to the side. Tuft tests and under-car pictures or video with a lipstick camera will tell what direction the air under your car is really flowing.

2. Arrange the wheel fairings accordingly for highway cruise speed. In other words, the oblique flow at 35 mph may not necessarily be the same as at 75 mph, so unless you plan a variable geometry pair of wheel fairings, set their toe-in angle to minimize drag at your normal cruise speed.

3. A semi-circular or elliptical planform as shown by your yellow line is good, in fact better than the vast majority of cars on the road today, which were apparently designed by goofy stylists rather than competent aerodynamicists. Ideally, wheel fairings would be confluent with the nose of the car (bumper cover). Presumably, the LoReMo shown in the post above has this, but comparing it to Hucho's Calibra on page 183 has me wondering if LoReMo nose may actually trap more under-nose air and so create more drag than optimum.

Thoughts?

[euromodder]

Originally Posted by Otto

Presumably, the LoReMo shown in the post above has this, but comparing it to Hucho's Calibra on page 183 has me wondering if LoReMo nose may actually trap more under-nose air and so create more drag than optimum.
Thoughts?

Indeed the front lip seems to be rather high up on the LoReMo, far higher than the sides, and scooping up more air.
I wanted to illustrate the front wheel fairings guiding the air outboard, rather than under the car. And as you say, they are in line with the rest of the nose.
On talldude#5's car they wouldn't come up as high being mounted underneath the bumper.


There seems to be more going on underneath the Loremo than meets the eye anyway.
Front:


Rear:


I only wonder if we're ever going to see anything of it.

[Otto]

Originally Posted by euromodder

Indeed the front lip seems to be rather high up on the LoReMo, far higher than the sides, and scooping up more air.
I wanted to illustrate the front wheel fairings guiding the air outboard, rather than under the car. And as you say, they are in line with the rest of the nose.
On talldude#5's car they wouldn't come up as high being mounted underneath the bumper.


There seems to be more going on underneath the Loremo than meets the eye anyway.
Front:


Rear:


I only wonder if we're ever going to see anything of it.

I suppose the best way to explore this is to start by installing a flat undertray, then do tuft testing with a lipstick camera under the car to see what is really going on with the airflow. Then, add wheel fairings aligned with the relative wind, then fine tune with ABA testing.

Flow fences are a possibility, as are vortex generators on the undertray.

And, on a related note, last week on Bloomberg cable TV channel was video footage of a recent GT car race at Nurburgring in Germany. Showed some of the nose and tail refinements on cars like Lotus, Maseratti, etc.. Interesting stuff. One of the under-tail diffusers had flow fences splayed out somewhat, rather than straight back. I'd like to find good undertray pictures of those cars.

[AeroModder]

Looks like they're doing a reverse airfoil treatment to the underside.

EDIT: Caught the bug and built those deflectors in front of my tires. XD

[aerohead]

If you'll search the 'Full-Boat-Tail trailer with Gap-Fillers for T-100' thread you can see what I've done on the trailer.It's in the direction of what you're up to.

[talldudenumber5]

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