Air Dam vs. Front Undertray- One negates the other?

[aerohead]

Ford's concept car,Probe-IV had a completely smooth belly and yet,had a moveable front airdam which lowered into position above 40-mph for even greater drag reduction.So it looks like the two can easily complement one another.
Their dam had its own belly which lowered with the dam,eliminating pressure drag which is otherwise created behind an airdam.

[AeroModder]

Alright, I'll probably try that. I've already got a better idea for my air dam, since I ended up having somewhat sharp edges on it. When I fold a lip back to bolt it onto the bumper, I'll clip off a bit to be able to bend the coroplast easier and have it all in one piece. I'll have to start cutting up the last 4x8' sheet I've managed to not touch yet, though.

On the freeway, I definitely noticed that my air dam/canards setup was producing downforce. Normally, the front end felt floaty, indacative of lift, but it was much more responsive and even a little touchy. After removing the canards, it feels more neutral. Looks like I've just about achieved my goal of eliminating lift. That sloping front undertray was producing quite a bit...

I'm also looking into some stock car tricks for producing downforce without the drag penalties by having the air from the engine compartment exit through the wheelwells. That way I can get zero front lift and smooth out the front end more for less drag.

[AeroModder]

Update: This tank recorded an average of 24 MPG with the canards removed. Around 1 MPG better than my second best tank, which had the canards in.

This week I'll be replacing my modified intake plenum with the stock one, which I found from a donor Tempo in a junkyard. The difference is a half inch in tube diameter. The throttle body and current plenum have 2" wide diameters, and the stock has a 1 1/2" diameter tube. I'll be testing whether or not my plenum modification has any effect on power as well as economy.