Today I'm installing a lower air dam on my Fiesta w/ABA & ScanGauge testing

[2000mc]

How wide does the air dam go? So long as it reaches out to at least as wide as the inner edges of the front tires, I think it would be good.
Is the bumper cover open on the bottom side, or can you see the radiator/condenser from just infront of the airdam? I'm wondering if you may have inadvertently made an airdam that is great for cooling purposes, creating higher pressure infront of the radiator / air dam, while causing lower pressure behind the radiator / air dam, causing more air to go through the radiator, not around the car. I would close / cover up the bottom side of the bumper cover (assuming it's open) to help make sure the air your blocking is going around, not through. That by itself could potentially reduce air flow through the cooling system to less than stock( I kinda doubt it though) but monitor how each step affects your coolant temps. If the air dam is creating a lower pressure behind the radiator, it would help draw more air through the radiator, so you could exploit that by blocking part of the grill opening

[H-Man]

I remember the crisis fighter pinto needed a partial grill block with the air dam because otherwise it would just go through the engine bay.

[FordFiestaS]

Slightly cooler air today then the original A, B, B (yep 2 B's) tests runs thus far..... but time now permits me to do it.

So off I go. Report to follow.

[tyronasauras]

Ditto on adding some grill block to make the air dam effective. Also you can extend the corners a bit lower, like another inch, Dynamat folded to attach on the front and back side works good and will stiffen it and keep it quiet. It deforms easy with any impact without causing damage to anything else or your main air dam. You can't really move the air from the middle of the car to the sides. The crown of the road is high in the center and limits how low you can go there.. Happy to have the air to the Radiator come from air that would have gone under the car anyhow and block the top of the grill to have that air easily go over the top of the hood

[tyronasauras]

Originally Posted by FordFiestaS

Photos of ScanGauge II readings here :

Test run #2 (B) of ABA results. | My802.com

Summary of Guage readings :

A gain of only .5 MPG. Assuming there is actually a gain and not some other variable rearing it's head.

Trip time : = @ 1.1 hrs

Distance : = @ 55.3 miles

Max speed run (B) gained 3 mph (essentially equal)

Average speed : = @ 49 mph

MPG (A) @ 50.5 MPG - (B) @ 51 MPG

So all in all not a biggie. One more run to go tomorrow.

Your test speed was 49 MPH which was nice for MPG, but I think a test at 60 and 70 MPH would show a much bigger improvement or difference, My guess is 1.5 MPG with a modest upper grill block on the top side, like 6" of blu tape for a test

[FordFiestaS]

Sadly some construction altered my route. About 2 miles short w/some end results varied slightly but....

Nonetheless an OK run.

Photos of results posted here :

Final run of ABA front spoiler Fiesta S | My802.com

Slightly "better" MPG 's w/o air dam even though temps were about 15° cooler.

I need to work more on this as not all is lost.

I read the previous posts and agree with all points given.

I live in Vermont and our state speed limit is 50mph with a few exceptions. I used a route that was 55mph RT 7 from Bennington to Manchester VT. Great ride BTW this time of year with the leaves.

I will modify the grill block I used to have and make a better air dam.

For now any input is greatly appreciated.

[2000mc]

i dont think i'd read into it too much with a different route. different days already throws in more of a variable than you would want, although id expect the opposite affect from the temperture. testing at 65mph months apart on different routes, but with a car that should be delivering virtually the same results, ive had results of 37.5 one day and 43.5mpg another. the roads were asphalt vs concrete, virtually flat vs shallow rolling hills, different temperatures, wind.

[aerohead]

Originally Posted by FordFiestaS

Sadly some construction altered my route. About 2 miles short w/some end results varied slightly but....

Nonetheless an OK run.

Photos of results posted here :

Final run of ABA front spoiler Fiesta S | My802.com

Slightly "better" MPG 's w/o air dam even though temps were about 15° cooler.

I need to work more on this as not all is lost.

I read the previous posts and agree with all points given.

I live in Vermont and our state speed limit is 50mph with a few exceptions. I used a route that was 55mph RT 7 from Bennington to Manchester VT. Great ride BTW this time of year with the leaves.

I will modify the grill block I used to have and make a better air dam.

For now any input is greatly appreciated.

Your average speed is going to have to be as close to 55-mph as possible in order to pull out any meaningful results.And you need to be fully warmed up:engine/transaxle/differential before you ever begin.A 15-degree temp difference can hit you hard by itself.
The shape of the car can be the only variable on the test.