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

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.

http://ecomodder.com/forum/attachmen...8&d=1384214964

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

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. :thumbup:

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

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.

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

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
http://i184.photobucket.com/albums/x...psd2655a12.jpg

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.

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

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 ;-)

^Agreed the modifications look great!

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
http://i533.photobucket.com/albums/e...all/step04.jpg

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.

Yup, that is pretty much what the fog light area looks like.

I know what you mean about air leakage. A round parachute has a hole in the top to increase drag by allowing leakage.

There is air leakage through the fog light area into the engine compartment.

Matt

Do you have any details on how you made your grill/fog block offs? They look awesome - very well done!

So you estimate about 10% improvement in FE from the mods? How fast is your typical driving?

The grilles are made from 1/8 inch thick G10 Garolite (Epoxiglass). I used the stock grille and fog light bezels as templates and cut it with a saber saw. I taped the material to prevent surface scratching). The fog light covers are thin carbon fiber I had lying around the shop.

I have done the following mods;

Grille blocks
Fog light covers
Smooth 1/4 inch thick Lexan wheel covers

Beyond that I run 51psi (factory maximum) pressure in my tires rather than the Ford recommended 38.

All of those mods, combined, have upped my FE about 10%. Bear in mind, however, that the car is broken in now. I think 1% or 2% of the FE improvement may have been from additional break in. Of course, I would prefer to take credit for the FE improvement myself.

Oh, I hate to throw this into the equation, but, Gas Pods (vortex generators) seem to make a difference on the C-Max. I know there is a huge controversy regarding them. But, I have run them and removed them and there apears to be a 1mpg improvement with them at highway speed. I have not done specific ABA testing of them specifically to verify the exact change (if any) they make. However, when I install them, I finish my day around 1mpg better than the previous day. This is a pretty consistent finding. I pulled them off the rear "Spoiler" however because I plan on making a modest Kammback.

The majority of my driving averages around 45mph. I do appliance repair with the car and drive town to town in northern Illinois. So, 50% of my driving is 35mph in town and 50% is 60mph on rural highways between towns.

Lastly, I carry 200 to 300 pounds of parts and equipment with me every day.

Matt

Thanks Matt! How did you attach all the pieces to the car?

At freeway speeds you should see an even bigger improvement in FE - your driving speeds are rather modest...

Looking forward to what you have in mind for your kammback!

Interesting material, I've never used it but have a Monopan sample with glass cloth infused into it.

Garolite
Garolite - Wikipedia, the free encyclopedia
About MonoPan
MonoPan :: About MonoPan®
http://www.monopan.ca/images/diagram.jpg
http://www.monopan.ca/images/shaped3.jpg
another lazy Saturday and a piuece or Garolite.. - Telecaster Guitar Forum
http://i110.photobucket.com/albums/n102/Ronkirn/023.jpg

Bakelite and phenolic are much different.

One reason for reduced drag is the location of the foglights: Consider one of those color-coded pressure graphics showing air pressure along a car body, where red is the highest pressure, and blue the lowest. These correspond to the airflow velocity. So, the nose stagnation point is biright red, since the air flow slows and is compressed there, but as the air then accelerates rapidly around the fender and up over the leading edge of the nose, the map shows bright blue.

The air flowing past your lower nose section pretty much stops at the centerline stagnation point, then accelerates but stumbles as it goes past the fog light bay irregularities.

This is a terrible place for any flow disrupters to be, as the airflow there tries to be very fast. Doubling the speed of the flow means 8X the drag, so you want to avoid any shape irregularities in such drag-prone locations. When you covered your foglights, you pretty much fixed the OEM bad shape there. It's a pity the factory designers don't "get it." They should never have botched this shape in the first place.

This reminds me of a conversation I had with a NASA aerodynamicist: He pointed out that on airliners, flashing light fixtures were often put just above the cockpit windscreen, right where the curved shape blends into the tubular fuselage. He said that is the worst place to put a bump for the flashing light, because just there the airflow exceeds the forward speed of the plane. In other words, if the plane is flying at 450 knots, the airflow accerating past the nose if going significantly faster than 450 knots at that particular location, and since drag increases exponentially (2X speed = 8X drag), the drag penalty is very high. Better to put the strobe lights someplace else, such as at the very tip of the nose at the stagnation point.

Not to hijack your thread, but I posted another thread about optimum nose shapes, Hucho's latest findings, etc. This because I'd like to do a nose on my Porsche that (like your modded vehicle) has nice optimally smooth shape, i.e., no fog light holes in the wrong places, etc. Your mods reinforce my hunch that nose shape is very important not just to reduce drag at the nose, but also to smoothe the airflow for as non-tubulent and optimum flow along the body as possible. So, thanks for sharing.

PS: One cheap and easy way to fill these holes would be to put aluminum foil into the nooks and crannies, held in place with tape. Smooth the foil to the body, then fill the foil-lined cavities with Great Stuff expanding foam, let it rise and cure, then sand to match the body contour, then spray with PlastiDip or paint to match the vehicle. With the aluminum foil prophilactic barrier, the foam will not stick to the car, so you can pull it off without a trace.

PPS: Your aero mod shows that the vehicle did not need nearly so large a cooling intake as the factory evidently thought. After all, you covered >~2/3 of the nose intake area without overheating the vehicle, even in summer, right? We may infer from this that you're smarter than the factory guys.

Add a few more low-hanging fruit mods (plastic garden edging air dam, Prius-like wheel fairings, etc.) as are common on this website, and I'd bet you exceed factory fuel economy specs by 20-25%.

This is good information, thank you for posting it.
Doubling the speed of the flow means 8X the drag

I think we can blame every designer on the planet attempting to emulate the upper end Porsche 911's with their twin outboard corners radiators. Everyone except Honda seemes intend on marking those front corners with some type of garnish. Most of it is non-functional.

Porsche 911 Turbo history, photos on Better Parts LTD
http://betterparts.org/images/porsche-911-turbo-01.jpg

Methinks centerline radiators (and everything else that needs airflow through it) at the stagnation point would be better: More pressure to push cooling air through, less drag since the airflow essentially stops at stag. pt. anyway, so you can have a smaller inlet hole, smaller radiator will do the job, better fairing of the outward and upward flow which then goes on over and past the car.

Some say, it's the tail shape that counts, not to worry about the nose. I disagree--apparently Mother Nature does too, which is why a tuna or trout does not have a nose shaped like a brick. If it did have a nose shaped like a brick, the flow downstream would be so buggered that the poor fish would get no traction, and get no breakfast, either. (It would be breakfast.)

Speaking of fast fishes, study their inlet/outlet geometry of mouth and gill. Mother Nature spent the past several hundred million years perfecting that, so we may as well copy the concept for vehicle inlets and outlets, as well as nose shapes. I'm working on that idea for the intercooler cooling air outlet on my Porsche 944 Turbo. Also may redo the whole face of the car, which (I regret to say) too much resembles a brick. Anybody here do Photoshop? If so, can you paste a Porsche Carrera GT face onto a 944 Turbo?

Sounds like you want a Porsche 968.;)

Porsche 968 - Wikipedia, the free encyclopedia
http://upload.wikimedia.org/wikipedi...tenansicht.jpg

944 Porsche White | all porsche images
http://all-porsche.info/wp-content/u..._944_White.JPG

Porsche Carrera GT | Specialist Cars of Malton - Independent Porsche Sales
http://www.specialistcarsltd.co.uk/s...?itok=8552h_Bx

Here is an upper grille block I made today. I have about 45 minutes in it so far.

I have it mounted with a few screws for testing purposes. I will finish mounting it tomorrow.

I used a piece of 3/4 inch 6061 aluminum box tube bent to the shape of the nose of the hood as a support behind the grille to hold the proper shape since there is nothing at the top edge to mount the grille to. Otherwise it would try to flex flat.

The nose finally has that fully rounded look to it.

I will post FE numbers when I have them.

Matt

Good looking modifications.

Very nice numbers for a C-Max. I'm curious to see what you would get in a Prius, with them being rated for better mileage. I'm scared you might beat me.:p

I am very good at knowing exactly how to read this car and how it will react to various road conditions, traffic, wind, etc.

I know the C-Max is rated at lower MPG than the Prius. But, it is different in many ways that seem to compliment my driving style, personal bias, and my type of usage. For example, the car will stay in EV mode all the way up to 85mph. It will charge while accelerating. With such a large engine, this is beneficial. I have driven it using acceleration assist, and with acceleration regen and my FE is far better using accelerating regen, then maximizing EV distance using the added AH I gained by regenning under acceleration.

The vast majority of my driving sees 1/3 of the miles with engine running, and 2/3 EV only. In fact, many of my 10 to 20 mile trips show an indicated 25% engine miles and 75% EV only miles.

I believe Ford has their system (at least in this regard) very well figured out.

In an indicated 40,900 miles, I have seen 24,000 EV only miles (oh, and over 1,000 braking regen miles). :)

Matt

Whip out a black Sharpie pen or indelible Magic Marker, color the screw heads black, and nobody will even notice you have the grill block panels. You did well on the installation.

Matt, I didn't mean to hi-jack the thread with the P-car images, I thought you were through with the tinkering.

Your upper grille block is as nice as the other block installations.:)

No worries. I am fine with people posting whatever they want.

Oh, I have to address the comment made on the last page about fog light position and air acceleration at that point. That was my assumption too. That was one point of my questions earlier in this thread that the fog lights and lower grille are in that area and both are there contributing to the turbulence of each other.

Matt

Why would use this language that you are intimidated by a few naysayers who never tried GasPods. Almost everyone who has tried GasPods and reported back to us has seen the same or better fuel savings than you. Please, have the strength to state the truth and not fall victim to a few who get a kick out of exercising power and control over speaking louder than their intelligence.

Oh... and GasPods are not vortex generators. They are a new and improved technology.

First off, the reason I am cautious about mentioning their use is because of the frequent arguments revolving around them. I do not want to start a pissing match over their use in my thread.

Second, I have seen very little gain with them, certainly less than you claim on your site. Their appears to be a slight gain (possibly up to 1mpg at most).

You need to be careful about using such rude language in your posts. Considering the fact that you are the one marketing these, you need to be very careful how you come across when you post such statements on someone else's thread.

Matt

Bingo.

Bugger the accelerating airflow and you have half angles of turbulence of about 15 degrees all the way back from there, like a boat wake. You want a nice smooth and orderly acceleration of the airlow. In a sailplane, you may get laminar flow most of the way back on the canopy, then turbulent but still attached flow well aft of that. On a road vehicle, pretty much forget laminar flow, but keeping the turbulence as low and attached as possible would be most helpful, so a smooth and well faired nose is key. OTOH, if your nose is shaped like a bulldozer, it might not make much difference how good the shape is further downstream.

Down low where the foglights go is naturally draggy, since much of the stagnant nose air can't flow downward due to the ground, it has to mostly go laterally around the sides or up and over the hood. Then, there's gross buggery due to the effective yaw angle of the spinning wheels/tires, which really screw things up. So, the foglight region gets more air, accelerating even faster due to the concentration, and irregularities or bumps there are even draggier than they otherwise might be. Also, lots of crud accumulates, as well as rock chip damage.

You've done well go fair the foglights, and please report results as able.

I think your theory about the turbulence is correct, at some point perhaps the stock foglight opening is breaking up the smooth air flow, the idea of a open cavity filling in is great if all forward facing, but on the side like yours are could be a factor,

I can tell you all of these changes really add up. I did some 50mph cruise testing by running north, then south repeatedly on the same road with cruise set at 50mph. I eliminated the variable of acceleration and reset my mpg on my scanguage as soon as I hit 50mph on each return trip. This was done on a 2.4 mile road with 12 total trips (6 round trips) and saw an average cruising mpg of 52.25mpg. This was done at a frigid 21 degrees-f. Before all mods, the best I would have seen would have been around 44 to maybe 45 at best. Last winter I saw a couple trips that were 47 in similar areas, but those were rare. I struggled to top 44mpg without mods.

I love this hobby!

Matt

Did not mean to sound rude. Meant to express frustration that some old chatter effects discourse and your posting behavior. Thank you for your participation on all levels.

I just don't want that argument brought into this thread.

Matt

If this holds true that smoothing the foglight opening on the corner is a greater thinng than expected, it could change a lot of designs out there as today almost every newer car had similar openings, what a waste if they dont take advantage of it, on the same vein, I'm thinking of stretching out the outside edges of the front bumper cover on my escort to better fair in teh oversize wheels I have on th ecar now, maybe I can just put a bracket under there to hold it out a bit more,

So, what are your thoughts on sealing up all the gaps around the headlights and hood as well as smoothing out edges as much as possible? I plan on doing it because it is really easy to do. I think any gains would be painfully small. But, since it is so easy, I may as well do it. :)

Matt

think
 

Dr.Wolf Heinrich Hucho measured the drag of an 'ideal' aerodynamic nose,compared to that of the production 1974 VW Golf/Rabbit and saw virtually no difference between the two.

Well, after sealing up the gaps in the nose of my car, I noticed my intake temperature went up 35 degrees. :)

So, if nothing else, sealing everything up will help keep heat in the engine. That will help my FE a touch as well as making my heat work better.

Matt

Well, page 158 (fig. 4.31) of Hucho's 4th ed. book says the optimum shape is 14% less drag than the base shape, does it not?

Perhaps I'm misreading pages 157 & 158. Upon reviewing them, what's your take?