C-Max aero mod success questions.......

[Recumpence]

Hey Guys,

Well, I am nearly at 40,000 miles on my 2013 Ford C-Max and I wanted to ask a question about my findings regarding some very simple aero mods.



First as you can see by the picture, I have blocked the lower and center grilles on my car as well as the fog lights (the right and left black covers visible in the picture). What you cannot see are the clear wheel covers.

Now, here is my question;

I have had the wheel covers for about 6 months now. I saw a slight improvement with them (maybe 1mpg or so). The center grille block gave me 1 to 1.5 mpg gain. The lower grill block gave me nothing what-so-ever. However, when I covered the fog light covers (I also covered the lower grille a bit better at the same time), I saw a roughly 2mpg improvement. This seems way over the top for such a tiny change. However, I have a theory that I want to share and get your opinion;

My guess is, the lower grille, fog lights, and wheels are at roughly the same level on the car. So, I am thinking that the deep fog light wells and the (not so well covered) lower grille were introducing turbulent air to the sides of the car partially spoiling the affect of the wheel covers. However, now the lower grille, and fog light covers are providing smooth airflow to the sides of the car and, with the wheel covers, providing good laminar airflow the length of the car, thus giving a steep boost in FE.

What are your thoughts? Do you think there is anything to my crack-pot theory, or am I totally off my rocker?

Whatever the cause, I am THRILLED with this improvement!

Matt

[MetroMPG]

Congrats on the improvements!

I'd be wary of trying to draw hard conclusions from small changes in MPG, though. I think you said it best: "This seems way over the top for such a tiny change." Trying to assign a value to each mod is going to be tough outside of a lab or wind tunnel (esp. for the smallest ones).

They look great, by the way.

[Recumpence]

Originally Posted by MetroMPG

Congrats on the improvements!

I'd be wary of trying to draw hard conclusions from small changes in MPG, though. I think you said it best: "This seems way over the top for such a tiny change." Trying to assign a value to each mod is going to be tough outside of a lab or wind tunnel (esp. for the smallest ones).

They look great, by the way.

After 40,000 miles driving the same area every day, I know what the car does on a regular basis. It is very consistant. I can tell you my mileage is up 5mpg at the very least with the mods I have done so far, maybe 6mpg. I have gone from working hard to hit 52mpg (in warm weather) to 57mpg being an every day average with my best day of 62.1mpg for 120 miles.

At any rate, I have numerous other mods to do. What I am trying to achieve is 60mpg daily in summer and 50mpg on the worst winter days. That would be an average 8mpg gain over stock. I am 3mpg away from that now. I think I can easily get 1 more mpg easily with an upper grille block, finishing off the rear of the belly pan, and a few other small details. The last couple mpg gains will probably far more difficult to achieve.

Matt

[MetroMPG]

Just to be clear, I wasn't questioning the collective benefit of the mods.

Just saying that assigning an MPG value to smaller individual ones is tricky. But some people have a huge amount of carefully collected trip/commute data and can tease out small signals in the normal amount of noise.

On the other hand, I've seen people abandon (reverse) small mods because they were convinced they did nothing, when it's more likely any real effect was just too small to be seen above normal variation or even if tested (A-B-A).

I think it's great what you're doing with the C-Max.

[Recumpence]

Ahh, gotcha.

It would be cool to take everything back to stock, drive for 1,000 miles and reinstall everything, then repeat the trip.

One thing that I am sure is a factor too is my increased skill at efficient driving technique over the year of owning the car. I would assume at least part of my gains is related to increased familiarity with the car. That being said, I have always driven in an efficient manor. But, I am sure I have adapted to the characteristics of this car and experienced gains from that.

Oh, I am pleased with the look. I was concerned about mucking up the look of a brand new $30,000 car with hand made add ons. So, I must say, I am glad it looks decent.

Matt

[kach22i]

Perhaps your area recently did the change up between summer blend and winter blend gasoline. However, I thought summer blend garnished the greater mpg gain.

http://s184.photobucket.com/user/kac...g.html?filters[user]=48335090&filters[recent]=1&sort=1&o=0


That fog light area already looks sealed up, meaning an air pocket forms of which the actual air flow goes over and around.

I don't get the mpg gains either, other than as people have mentioned that there is a cumulative affect.

[Recumpence]

That's the point to this thread is getting your perspective on this. It has got to be a cumulative affect more than anything.

Oh, in order to create the needed clearance for the covers, I removed the black plastic bezels. When I did that I found the inside around the lights was full of insects, dirt, fuzz, etc. Air was getting into that area and trapped.

Don't get me wrong, as I mentioned, there is no way 2mpg can be attributed to something this small. It has got to be that the fog light covers (as well as reducing the number of openings in the lower grille) made some cumulative affect.

At any rate, I am thrilled with the results.

What do I have left to do to the car? Here is a short list;

--Upper grille block (I already have materials ordered for this)
--New lower grille block with radiused inlets (already have materials ordered)
--Radiused openings for the center grille block
--Wheel spats
--Finish the belly pan (it is hugely open in front of the rear axle)
--Block heater
--Window tint for reduced summer heat

I am hopeful to see another 2mpg with these updates. I have a hard time hoping for anything more. Actually, 2mpg may be a bit high. 1mph is a pretty good bet, though.

Matt

[renault_megane_dci]

I really like the work you did on the front of your car but I am also very much interested in side pics of your car ;-)

[AntiochOG]

^Agreed the modifications look great!

[kach22i]

Originally Posted by Recumpence

Oh, in order to create the needed clearance for the covers, I removed the black plastic bezels. When I did that I found the inside around the lights was full of insects, dirt, fuzz, etc. Air was getting into that area and trapped.

Air getting trapped in a sealed area would be less of a problem than air leaking into a chamber, then leaking back out in another section.

This is because a proper air-pocket would not be formed.

Think of the nose of an electric car or rear engined car (old VW Beetle/Porsche) versus a typical front engine car with radiator up front.

Hence why a grill block works so effectively.

If the area behind your fog light looked anything like this one below, I can see a potential problem.

How to: 08-11 OEM fog light install - Focus Fanatics


Did you take any photos of your work mid-course Matt?

Simple and common weeps which allow moisture and condensation out of a semi-sealed area might be to blame.