Belly pan + air dam
 

Recently I was considering - is there any point to installing both an air dam and a belly pan? The pan reduces turbulence, whereas the dam reduces the amount of air moving through the turbulent area. If the underside is already relatively clean, would a dam just add frontal area, or might there still be benefits?

Frontal area is up to you, but smoothing out the nose can't hurt.

I'm almost certainly going to go with an air dam on the HCH, but my Insight is already pretty clean underneath:

http://i1072.photobucket.com/albums/...psrlojv6hy.jpg

http://i1072.photobucket.com/albums/...psjfeclddx.jpg


So, to air dam or not? Will I likely see gains, or will the extra frontal area just hurt me?

I'm purely guesstimating here; but if the air dam is no lower than 95% of the pan, then no harm done. It there is a diverter to manage the stagnation point and/or ducting for front wheelwell air curtains, bonus points.

You may find that Aerocivic-style sidewall air dams and spats might be more beneficial.

I always planned on using an air dam as an attachment point for the belly pan, but it looks like you have that covered.

This looks like it might be a case of "can't tell without A-B-A-B testing" since the underside is already so smooth.

I don't have numbers to back it up, but I've always been under the impression that having an airdam with the bottom edge level with the lowest point on your undertray (i.e., no lower than any point on the non-suspension parts of the car) is best, and to keep the tray level from there back to at least the rear wheels. Seems to me like having it level in front would be better than wedging more air under the car. And I think I recall hearing that it's better to have the stagnation point on the front of the car lower than higher, and the airdam would lower the stagnation point.

But I don't know. I too am not eager to duplicate work just to test. :D

From looking at what you have already done with the belly pan I doubt you will see a reduction of cD*A from adding an air dam, however you could experience other benefits such as reduced lift in either the front or back, depending on where you positioned the air dam.

I would also consider doing an air dam style flexible tire spat in front of your front tires at about a thirty degree angle towards the inside. You have probably more to gain keeping the wind off your high cD tire than your relatively smooth underbelly.

From the factory, the car already has small deflectors on the front. One of mine was missing, so I made something out of coroplast, but it's missing again after the accident. Any pictures showing what the optimal solution would be?

http://i.imgur.com/HIde2SX.jpg

http://i.imgur.com/4cRoXZz.jpg

http://ecomodder.com/forum/member-fr...42-mudflap.jpg

Yours looks right to me; just make it out of angle stock and conveyor belt material. I suggest the two U-shaped pieces fastened along their longer edges but with the forward edge open so the whole can flex more on impacts.

I agree with freebeard, the optimal solution is the one that survives road use. There are some good pictures and discussion on an older thread I made on this topic that I will link below.

http://ecomodder.com/forum/showthrea...ngs-32068.html

no lower
 

The 1983 Ford Probe-IV concept is one example of intentionally placing the lower edge of the airdam below that of the belly.At Cd 0.152,it worked out pretty well for Ford.
http://i1271.photobucket.com/albums/...ead2/scan2.jpg

optimal
 

Honda probably dialed in,in the wind tunnel,what was optimum for the production car; and everything it would experience in the real world.
That would not be confused with 'ideal',which they took a completely different tack on their solar racers.
Cd 0.25 vs Cd 0.10 is a reflection of what tightening up wheel drag can mean.
http://i1271.photobucket.com/albums/...d2/Solar-1.jpg
http://i1271.photobucket.com/albums/...Untitled17.jpg

Got my dam installed on my HCH1 today.


Factory "air dam":
http://i.imgur.com/ZqMNFYF.jpg


Underbody aerodynamic mess:
http://i.imgur.com/zPtKCFT.jpg


Dam installed:
http://i.imgur.com/dpXRrDy.jpg