The aero mods begin (Now working on Diffuser) !!!

[ptjones]

Here are pictures of my new air dam.

 

This was made from a 3/4 inch box aluminum tube (14 gauge) bent into the shape shown. Once bent, I rivetted lawn edging along the aluminum every 3 inches or so. It is screwed to the car with four screws untilizing stock holes that would normally attach the plastic belly pan to the fiber pan around 12 inches in from the nose.

 

It took about 2 hours to complete. This was amazing time considering it was 6 degrees F when I started and I did all the work outside. I had to stop repeatedly to warm my hands and warm the lawn edging at my heater.

 

The whole dam weighs very little. If I had to guess, I would say it is about 3 pounds or less.

 

I have not done any ABA testing. However, here is what I did for the few minutes of time I had;

 

I took my average mileage from yesterday (a full day of driving without the air dam), and compared it to a drive today around my area with the dam installed. Yesterday was 18 degrees and I averaged 47.1mpg. In 10 miles of driving today (after I warmed the car up), I averaged 49.3mpg. Now, bear in mind, yesterday's mileage was total mileage including the terrible MPG encountered with warm up. While todays mileage was recorded after the car was warmed up. Yesterday I drove 120 miles. So, the warm up MPG would have averaged in pretty well over those long miles. However, I would assume that I could have had maybe .5 to 1mpg better if I had warmed the car up yesterday before I reset the mileage trip odometer. So, realistically, the dam is probably giving me 1 to 1.5mpg increase (conservatively). This is right in line with what most people get on Ecomodder when they install an air dam (actually most report around 2mpg or more).

 

I will do some ABA testing sometime soon and report back.   :)

 

Matt

I was wondering from an aero stand point wouldn't it be better at the chin as apposed to the underside?  Your location is better from not running into every bump and parking bumper. :) 

 

Paul

[Recumpence]

The short answer is yes. I did it this way for a number of reasons;

 

#1 Simplicity.

#2 Asthectics. A nose mounted chin spoiler would be huge work to make look correct.

#3 Clearance. A nose mounted chin spoiler would hit everything, not just parking curbs, but inclines. In fact, I had one gas station that this dam rubbed a bit when I exited due to a deep dip at the road curb/junction.

 

Actually, the best design from an aero perspective would be chin mounted, with a flat pan under it to reduce turbulence from the dam rearward. That is what I originally has envisioned. However, all of the previous issues came into play and one other thing; Oil changes! I did not want to make it too hard for the poor oil change guy to access what he needs to access. This dam is held on with 4 bolts in factory locations. He would have to remove them to do an oil change anyway. So, no additional time would be wasted to change oil.

 

Lastly, the difference between this and the perfect chin spoiler would be relatively small. I bet there is maybe another 1/4mpg available doing it that way versus this simple dam.

 

Matt

[ptjones]

Somehow I missed the ABA testing, what's ABA? Also was that 4" lawn edging rubber? :)

 

Paul

Edited December 7, 2013 by ptjones

[Recumpence]

ABA testing would be something like this;

 

Group of runs labeled group "A" (without modification)

Run #1 48.1mpg

Run #2 47.6mpg

Run #3 48.3mpg

 

Group of runs labeled group "B" (this would be with a specific modification done that we are testing)

Run #1 48.9mpg

Run #2 51.2mpg

Run #3 49.8mpg

 

Last group of runs labeled group "A" once again because the modification was removed

Run #1 47.6mpg

Run #2 48.7mpg

Run #3 47.9mpg

 

(This is just an example. I did not actually do testing with those results.)

 

So, "A" is without a specific mod and "B" is with the mod. Some guys do AB testing, some do ABA, some do ABAB. The more cycles you do of a given test, the more accurate and reliable the test.

 

Matt

Edited December 7, 2013 by Recumpence

[hybridbear]

Really cool Matt! Your MPGs on the trip to MN were amazing for those speeds. That right there proves the benefits of your aero mods!

Edited December 8, 2013 by hybridbear

[Recumpence]

I am happy with the results so far. Today I drove for 90 minutes at 24 degrees and snowing and I averaged 49.1mpg (50% highway 50% 35mph streets).

 

I cannot wait to get the rear diffuser and Kammback done.

 

Matt

[Jus-A-CMax]

I am happy with the results so far. Today I drove for 90 minutes at 24 degrees and snowing and I averaged 49.1mpg (50% highway 50% 35mph streets).

 

I cannot wait to get the rear diffuser and Kammback done.

 

Matt

 

:worship:  Thats amazingly SICK MPG....in the snow as well :)

[Recumpence]

When is your car going to be done?

 

Matt

[ptjones]

I am happy with the results so far. Today I drove for 90 minutes at 24 degrees and snowing and I averaged 49.1mpg (50% highway 50% 35mph streets).

 

I cannot wait to get the rear diffuser and Kammback done.

 

Matt

That sounds great Matt. Dropped my car at body shop this morning and hoping to have done by end of week. Jus how is yours doing? :)

 

Paul

[fbov]

...Lastly, the difference between this and the perfect chin spoiler would be relatively small. ...

Nicely done; your craft is excellent!

 

While the CMax is not a Fiat Uno, the basic tendencies apply. On the Uno, there's a minima in Cd reduction at 2-3" airdam depth, with additional benefits as one moves the airdam further forward. It would be interesting to know what the curve shape might be for the C-Max.

 

By way of mods, I got tired of choosing between being cold and being efficient, so I tried something new - an inflatable grill block.

 

It's a 20x2" bicycle inner tube, folded in half with the valve at one end, slid between the grill slats and inflated. About 10psi filled the ~4" gap, and it seems the car warms up a bit faster. I'm considering something similar for the lower grill as well. 

 

What an inner tube does not do is affect anything beyond air entry to the engine compartment, and that's a big difference in our approaches. The external panels you've installed are providing aero-benefits two ways, I believe, reduced air infiltration and reduced surface drag, while I'm only addressing air infiltration. The trick with front surface drag is that air flow velocity is very high on either side of the meridian line down the middle of the car, and near the stagnation point, it's virtually all lateral, trying to get out of the car's way by going to the side. You've removed many of the surface details that disturb lateral airflow as you've blocked air infiltration.

 

We'll see if just blocking air infiltration, as I am doing (and Ford supposedly did with the shutters) has much affect on fuel consumption. I'm just not looking forward to the snow tire baseline if these gril blocks really do improve engine warm-up, because I'll have to take them out...

 

HAve fun,

Frank

[fotomoto]

I saw this on another forum and thought it might be of interest to your aero-modders:

 

http://www.greencarreports.com/news/1088990_chevy-volts-wind-thrumming-noise-aero-fix-now-available?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+GreenCarReports+%28Green+Car+Reports%29&utm_content=FeedBurner

[ptjones]

A better solution is to eliminate the side view mirrors entirely. I have been looking at this as a potential solution and some CMAXer's said removing them was easy to do. :) 

 

Paul 

[Recumpence]

Well we are in the single digits with snow and slush on the roads and my day finished with an average just shy of 44mpg.

 

I agree about the air infiltration. I believe that has a greater impact on FE than the surface aero affect. Both contribute, but the faster warmup time is one major aid in this.

 

Oh, I am absolutely LOVING the sealed hood and nose! Even in single digits, the engine stays warm, my heat works great, and my intake air temp is staying 30 to 60 degrees above ambient. The guys on Ecomodder insist that 80 degrees is the ideal intake temperature. I was able to stay around 60 degrees intake temp through the day today with the nose all sealed up.  :)

 

Matt

Edited December 10, 2013 by Recumpence

[Jus-A-CMax]

When is your car going to be done?

 

Matt

Not anytime soon, c the other thread. Well....one good thing is that I get to see all your guys mod away and pick the best one to apply...I like the hood seal but I don't think I will go crazy with the dremel though. I see no gas pods either on your photo...like to see what effect it has (if any).

 

PS everytime I see one CMax drive by I drool....seriously. I miss the MPG game and the saving money bit as this wee lil rental Matrix CHEWS gas. It gets like 30-31 MPG and thats with me having the gas pods on and P&G with the neutral-drive otherwise the MPG on this thing SUCKs like you cannot believe (28 to 29) even for a wee little car.

Edited December 10, 2013 by Jus-A-CMax

[fbov]

...I agree about the air infiltration. I believe that has a greater impact on FE than the surface aero affect. Both contribute, but the faster warmup time is one major aid in this....

I was trying to say the opposite - your surface changes may result in a greater reduction in Cd than reduced air infiltration, per se. The idea is that the air velocity will be much higher on either side of the car's axis as you part the air. I've seen V^4 dependency, V^2 for normal drag, and another V^2 due to increased air velocity at skin level, compared with the vehicle moving in an air mass. As you reduce infiltration, you just add air to this effect. It would explain the benefit from the fog light treatment, for example.

 

Of course, I'm thinking Cd while you're thinking FE. Engine efficiency gains from thermal isolation are a secondary benefit of reduced air infiltration in winter, but they may well swamp out any aero gains. As these last couple sub-30F mornings have shown, it's darn hard to EV when the ICE won't turn off!!

 

Have fun,

Frank

Edited December 10, 2013 by fbov

[Recumpence]

Hey Frank,

 

Sorry, I miswrote what I meant. I was eluding to engine heat affecting FE in winter especially. :)

 

You are correct.

 

Matt

[Recumpence]

Hey Guys,

I have begun the somewhat daunting task of building the diffuser for my C-Max.

This is a difficult task for a number of reasons;

#1 There are precious few areas to mount anything to under the rear of this car.

#2 The exhaust system needed to be lifted 2 inches to provide a proper curve and angle of the diffuser.

#3 I needed to make a subframe for the diffuser because (as I mentioned before) there are almost zero places to attach panels to under the car.

So, you can see that I moved the exhaust up 2 inches. Then I TIG welded together a 3/4 inch 14 gauge 6061 aluminum frame to which I pop riveted 4mm thick G10 panels to form the rear 14 inches of the flat section as well as the vertical fins. Then I used 4mm thick black Coroplast for the forward section of the diffuser.

What you see here is 37 inches long and 22 inches wide. The remaining areas to each side of this center section are roughly 16 inches per side. These side portions will be shaped a little different from the center and will be built as separate parts, bolted to each side of this center section.

I have 7 hours of time into this project total so far. The aluminum frame is very light as is the Coroplast. The G10 is a bit heavy, though. That (and cost reasons) is why I only used G10 for portions of the diffuser, but not the entire thing.

Oh, lastly, I will probably reduce the height of the vertical fins of the diffuser to make it look a bit better.

Being that this thing is only partially done, the results will be minimal until I have it finished. That being said, I have noticed the rear window is vastly cleaner than before. This car has had the worst rear window airflow I have ever owned. I go through a huge amount of washer fluid trying to keep the window clean and, so far, the rear window is drastically cleaner than before I installed the diffuser.

With Christmas here, odds are the remaining portion of the diffuser will take a couple weeks to finish.

Matt

[Recumpence]

Here is the finished diffuser. No I will begin working on the belly pan. The underside of the car has some covers to somewhat smooth airflow. But, it is still far to "Dirty" from an aero perspective. So, I will be fabricating a smooth belly pan to truely smooth out the under car flow.

 

Matt

[obob]

Here is the finished diffuser. No I will begin working on the belly pan. The underside of the car has some covers to somewhat smooth airflow. But, it is still far to "Dirty" from an aero perspective. So, I will be fabricating a smooth belly pan to truely smooth out the under car flow.

 

Matt

 

When I am walking late at night on a road where traffic moves around 50 mph such that a single car goes by every once in a while, it is easy to notice how noisy the turbulence is.  I would find it interesting to listen to your car vs a standard c-max.  I was thinking how measuring the sound from a stationary location could be kind of a poor man's wind tunnel.

 

I am impressed with your work and glad you share in on this forum.  Thanks.

[RaPieR]

Hey Guys,

 

I have begun the somewhat daunting task of building the diffuser for my C-Max.

 

This is a difficult task for a number of reasons;

 

#1 There are precious few areas to mount anything to under the rear of this car.

 

#2 The exhaust system needed to be lifted 2 inches to provide a proper curve and angle of the diffuser.

 

#3 I needed to make a subframe for the diffuser because (as I mentioned before) there are almost zero places to attach panels to under the car.

 

So, you can see that I moved the exhaust up 2 inches. Then I TIG welded together a 3/4 inch 14 gauge 6061 aluminum frame to which I pop riveted 4mm thick G10 panels to form the rear 14 inches of the flat section as well as the vertical fins. Then I used 4mm thick black Coroplast for the forward section of the diffuser.

 

What you see here is 37 inches long and 22 inches wide. The remaining areas to each side of this center section are roughly 16 inches per side. These side portions will be shaped a little different from the center and will be built as separate parts, bolted to each side of this center section.

 

I have 7 hours of time into this project total so far. The aluminum frame is very light as is the Coroplast. The G10 is a bit heavy, though. That (and cost reasons) is why I only used G10 for portions of the diffuser, but not the entire thing.

 

Oh, lastly, I will probably reduce the height of the vertical fins of the diffuser to make it look a bit better.

 

Being that this thing is only partially done, the results will be minimal until I have it finished. That being said, I have noticed the rear window is vastly cleaner than before. This car has had the worst rear window airflow I have ever owned. I go through a huge amount of washer fluid trying to keep the window clean and, so far, the rear window is drastically cleaner than before I installed the diffuser.

 

With Christmas here, odds are the remaining portion of the diffuser will take a couple weeks to finish.

 

Matt

That is some nice looking work!

[frbill]

Absolutely amazing Matt, you really have the aero modding bug! I look forward to seeing your completed mods ( if ever such a thing can be stated)

[mtb9153]

Here are pictures of my new air dam.

 

This was made from a 3/4 inch box aluminum tube (14 gauge) bent into the shape shown. Once bent, I rivetted lawn edging along the aluminum every 3 inches or so. It is screwed to the car with four screws untilizing stock holes that would normally attach the plastic belly pan to the fiber pan around 12 inches in from the nose.

 

It took about 2 hours to complete. This was amazing time considering it was 6 degrees F when I started and I did all the work outside. I had to stop repeatedly to warm my hands and warm the lawn edging at my heater.

 

The whole dam weighs very little. If I had to guess, I would say it is about 3 pounds or less.

 

I have not done any ABA testing. However, here is what I did for the few minutes of time I had;

 

I took my average mileage from yesterday (a full day of driving without the air dam), and compared it to a drive today around my area with the dam installed. Yesterday was 18 degrees and I averaged 47.1mpg. In 10 miles of driving today (after I warmed the car up), I averaged 49.3mpg. Now, bear in mind, yesterday's mileage was total mileage including the terrible MPG encountered with warm up. While todays mileage was recorded after the car was warmed up. Yesterday I drove 120 miles. So, the warm up MPG would have averaged in pretty well over those long miles. However, I would assume that I could have had maybe .5 to 1mpg better if I had warmed the car up yesterday before I reset the mileage trip odometer. So, realistically, the dam is probably giving me 1 to 1.5mpg increase (conservatively). This is right in line with what most people get on Ecomodder when they install an air dam (actually most report around 2mpg or more).

 

I will do some ABA testing sometime soon and report back.   :)

 

Matt

Matt your front air dam design is allot like the approach I took on a 1971 Datsun 240Z I owned back in the 80's.  I lowered the car for autocrossing but there still was too much air getting underneath the fiberglass dam.  So I got the idea of strengthening the lower lip of the dam by filling the backside with cut fiberglass mat.  Then I drilled holes every 3 inches through the lip and mounted with hardware some 4" wide x 1/4" thick x 30" long extruded rubber that I found at  local hardware supply store.  Really added down force to the front end.  Allot of the guys I raced with liked it and copied the design.

 

I'm very interested in seeing the final diffuser design I plan to do this myself at some point.

Edited January 1, 2014 by mtb9153

[Recumpence]

I have a couple changes to make to accomplish two things;

 

#1 Reduce the angle. My final mounted angle is 11.75 degrees. It is best to stay at or below 10 degrees. It was 14.5 degrees. So, I have been able to reduce it somewhat already. But, it needs to be further reduced.

 

#2 The exhaust tip does not exit all the way through the diffuser because I raised the system up 2 inches for clearance. That is melting the Coroplast around the exhaust opening.

 

What I will probably do about the exhaust is TIG weld a short piece of aluminum tube to the diffuser frame to help guide the exhaust through the diffuser opening. This will kick the exhaust all the way out rather than letting it just build up behind the Coroplast aiming toward the hole I cut. I will also probably resheet that area with black G10 as a backing to help heat shield it.

 

It is a lot of work, but fun.   :)

 

Oh, also, a diffuser is maximized when used with a full smooth pan. That is next.

 

What I plan to do is make a light weight frame using the same 6061 3/4 inch box aluminum tube welded and rivited together and sheeted with Coroplast rivetted to the surface of the frame. This entire assembly will mount up to the bottom of the car. It will actually not be very difficult to make. I have plans on how to vent the heat from the exhaust pipe from inside the pan.

 

Also, the pan frame will provide edge mounting ability for side skirts.

 

Basically I want to achieve a smooth tunnel for the air to go under the car as smoothly as possible and exit as smoothly as possible while filling as much of the trailing wake as I can achieve.

 

Honestly, I bet the entire pan, diffuser and side skirts will onlly net around 2mpg gain at best.

 

These cars are so well designed, it is very difficult to see any appreciable gains.  :)

 

Matt

Edited January 1, 2014 by Recumpence

[mtb9153]

Matt, all very interesting and I wish I had your ability to work so fluidly.  I have plenty of idea's but my biggest problem is doing anything about it since my tools are limited to cutting, bending, and shaping material.  I have no access to welding equipment, nor do I have the knowledge to do it if I could.  I had not heard of Coroplast until I did a google search for it.  Very interesting product being a corrugated plastic.  Does it cut easily?  Curious.  Once you have your design finalized and working the way you think it best serves the purpose, I'd be interested in purchasing one if you were interested.

 

I have envisioned using a diffuser made from carbon fiber simply because I love the look, but pricy.  I found one made for the Honda S2000 sports car made by APR.  I felt I could make it work on the CMax while thinking the undercarriage was similar in dimensions to the undercarriage of our car.  But I'm only assuming this with no real concrete proof that it could be made to fit.  Given the cost of $300+ I need to be more sure it will work.