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Recumpence 05-26-2013 05:21 PM

Chin spoiler question/air dam question
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Hey Guys,

OK, I have finally begun the aero mods of my C-Max. So far I have made Lexan wheel covers. Next I want to look at a few items that are "Low hanging fruit". The main couple would be to complete the belly pan as it is non-existant from the rear doors back to the bumper as well as the chin spoiler/air dam. Before I do anything I want input from you guys as I am somewhat new at aero modding (bear in mind, I can fabricate anything, I can TIG weld, machine, etc).....

I have already asked this question, but I believe I did not phrase it well. So, I want to ask it again before I embark on a bunch of labor building stuff....

Here is the deal, my car already has a belly pan under the nose. However, the chin is 9 inches off the ground and the lowest part of the pan (roughly just behind the front axles) is only 6 inches off the ground. I know the smooth pan under that area smooths the airflow. However, I cannot get around the thought that the air is being compressed there as it goes from the 9 inch high nose to the 6 inch high pan rear section. So, my thought is to lower the nose to the 6 inch height that the rear of the pan sits. I have had at least one person tell me I would be increasing the frontal area and that would negate any additional benefit the reduced under side turbulence would give. However, my thought is, the frontal area already is composed of that lower pan area, so if I lower the nose to match, the car still has the same frontal area.

Anyway, what are your thoughts about this? I assume it is better to divert the air around and over the car rather than accellerate and compress it under the car......

What do you guys think?


Oh, here is the wheel cover picture. It is hard to see anything because the cover is clear. :)

Frank Lee 05-26-2013 06:43 PM

Cover looks nice... when clean. Let us know how long it stays nice n clean.

You are right about the frontal area.

I think the aero would be better with the low splitter; of course it will be more vulnerable to getting damaged too. I think it would be better because a higher nose is going to want to squish the flow out to the sides... right about where the front wheels are. The splitter should do a better job of directing flow around the outside of the wheels, where we want it anyway.

I'm wrestling with the very same issue right now with the T-Racer. For now I have opted to keep the stock air dam and I've made a CAD (Cardboard Aided Engineering) prototype fill panel between the formerly wide open front bumper and front bulkhead. It also compliments the adjustable lower grille block and the brake vent block-off plates.

Sven7 05-26-2013 07:18 PM

Go as low as you please. Lawn edging will give a bit when you scrape. I'm not going to try to find it right now but we have had those who maintain air dams are never too deep. I believe one of "those" is Hot Rod Magazine...

Xist 05-26-2013 09:40 PM;d=1369599756

Very nice! Keep us updated on those!

Xist 05-27-2013 06:58 PM

I remember a Prius owner on here covering his wheels because he used his conventional brakes so infrequently that they started rusting. Hopefully, Recumpence is not creating much brake dust.

Smurf 05-27-2013 07:21 PM

How about some details on those wheel covers? What thickness of Lexan? You just drilled and tapped into the thick part of the wheel spokes in five spots, cut the hole for the air hose?

Recumpence 05-27-2013 07:36 PM

The Lexan is 1/4 inch thick. This was used for a couple reasons. First because it was readily available. Second because this thickness makes the surface of the covers nearly perfectly flush with the tire sidewalls.

There is a 2 inch hole drilled with a hole saw for the valve stem.

I drilled and tapped five 1/4-20 holes for each cover. They are drilled and tapped 3/4 inch deep into the very thick aluminum spokes. This was the best method I could come up with to mount them.

I am a bit concerned about dirt on the inside. If they get dirty and ugly quickly, I will paint them or use them as a template for aluminum discs. :)

Oh, since I made these and deleted my passenger side mirror, I have done some testing. I am seeing roughly 2mpg increase both on the highway and at 35 to 40mph areas. To give you an idea of the difference, the best mileage I have ever seem for any real distance was 62.3mpg. That was done at 75 degrees outside. Today it was 56 degrees and misty. This would normally relegate my mileage to the mid to high 50s (maybe 57 or 58mpg max). However, in this inclement weather today I averaged 61.9mpg for the 40 miles of my test. This was averaging 35 to 40mph.

I will know more as I drive the car more.

My hope is to finish my grille blocks, lower pan, and chin spoiler and be able to always be above 60mpg in town and rise from the stock 44mpg highway to 50mpg. That is my goal.

We shall see how it works out. :)


MetroMPG 05-27-2013 11:31 PM

A dedicated thread on those wheel covers would be most welcome.

Alfred State U and its Green Grand Prix-winning Insight is another that would argue you can't go "too deep" with your air dam:

Xist 05-28-2013 12:05 AM


Originally Posted by MetroMPG (Post 373345)
A dedicated thread on those wheel covers would be most welcome.

Alfred State U and its Green Grand Prix-winning Insight is another that would argue you can't go "too deep" with your air dam:

That would be fine if you had a perfectly level track, yet doesn't your nose dip when you brake? Couldn't you potentially brake really hard on a track? Maybe the bottom bit is black because it is rubber.

Recumpence 05-28-2013 09:01 AM

There are so many different opinions on this.

I guess I need to test a few variations and see what I come up with. :)


MetroMPG 05-28-2013 03:35 PM

No harm in that approach.

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