Do you like the spoiler? And what is its aerodynamic impact?

[TonyHzNV]

The PhysLink says "Some cars, like the Ferrari F1 cars, have them front and back; and since they are probably the most scientifically advanced wheeled transportation, I'll use them for the discussion."

 

Obviously there are different types of spoilers and one for a sedan is designed differently than the one on a F1 racer.

 

Wikipedia tells how a properly designed rear spoiler can decrease aerodynamic drag on a sedan or hatchback http://en.wikipedia.org/wiki/Spoiler_%28automotive%29

 

"a spoiler can still be beneficial. This is because many vehicles have a fairly steep downward angle going from the rear edge of the roof down to the trunk or tail of the car which may cause air flow separation. The flow of air becomes turbulent and a low-pressure zone is created, increasing drag and instability (see Bernoulli effect). Adding a rear spoiler could be considered to make the air "see" a longer, gentler slope from the roof to the spoiler, which helps to delay flow separation "

Wikipedia also says this: "Some spoilers are added to cars primarily for styling purposes and have either little aerodynamic benefit or even make the aerodynamics worse." Think about it. How much effect do you think it really has at 45-50 MPH? And how fast was that Ferrari going? 200 MPH?

 

You're thinking from the race car perspective, not the auto OEM perspective. There are two types of race car spoilers, the ones that are upside down wings, and the ones that are vertical or close to vertical walls that generate a high pressure area in front of them. The OEM spoilers like the one on the Fusion is neither of those. Spoilers on sedans reduce drag because they "clean up" the air flow as it falls off the back of the trunk. Essentially they kick up the air so that it flows over the turbulent zone behind the car, which reduces drag a little bit. It may seem counter-intuitive, but most often a sharp edge at the rear of a vehicle will reduce drag. Look at the back of a new Suburban, they have very sharp edges on the D-pillar for the same reason.

 

If you don't believe they are effective at normal speeds, then you also wouldn't believe that the underbody shields or the tire spoilers or the grill shutters would make any difference either. All the pieces have small individual contributions, but they all add up.

Actually, the things you named in your last paragraph do serve valid aerodynamic purposes in the FRONT of the car. Thinking that a rear spoiler on a FRONT WHEEL Drive car that almost never goes 70 MPH on average has some great effect is just silly. As a former pilot, I can tell you that wings don't care if they're right side up or upside down. They don't know the difference. What DOES make a difference is the side of the wing that is creating the lower pressure (the top side thinking of an airplane sitting on the ground). The airspeed over the top of the wing is greater than the airspeed on the bottom of the wing creating low pressure on top, creatng lift (with speed - both relative wind speed and ground speed of the vehicle). All the force is generated on the "bottom" side of the wing, with the high pressure on the bottom overcoming the low pressure on the top and the plane flies! The wings themselves as well as the fuselage and other appendages also create drag. We overcome that by increasing the (forward) speed and pressure (on the bottom of the wing) to lift off and accelerate (retract the gear to reduce drag) while climbing out. My point is that the spoiler creates some amount of drag of its own and at OUR SPEEDS doesn't really do MUCH to "clean up the air" behind the car. Have you ever really looked at OUR spoilers? The underside has a couple of LARGE grooves going across it which disrupt the airflow on the bottom and it doesn't look to me like its designed asymmetrically so as to create high and low pressure areas and, the rear of the car actually has some pretty "sharp edges" without the spoiler. If it has SUCH an effect, does the Fusion with spoiler get a different EPA estimate than one without?

Edited March 9, 2015 by TonyHzNV

[GrySql]

This video has been posted on this website before and is valid now. Near the end of the video watch the wind tunnel smoke as it travels over the top lip of the trunk and listen to what is said.

Ford spent a lot of time getting the rear of the car to be as slippery as possible.

As mentioned, at the speeds we travel there isn't much reason for a spoiler except for styling reasons. They do look nice.

 

[Automate]

 

"some great effect is just silly"

 

Who said it has a "great effect"?

 

All we said is that a rear spoiler "can" reduce drag on some cars if it is well designed.

 

Only Ford or someone who has put the Fusion in a wind tunnel with and without the spoiler knows for sure.

 

You can see from the video above posted by GrySql that small things do make a difference. They make enough difference that Ford spends many, many hours on the small details.

[GrySql]

Small things make such a difference that putting Splash Guards (mud flaps) behind all four wheels that the rear trunk area of the FFH doesn't collect as much dirt as before.

They seem to break up the turbulence directly behind the car and the license plate area stays cleaner.

[TonyHzNV]

 

Who said it has a "great effect"?

 

All we said is that a rear spoiler "can" reduce drag on some cars if it is well designed.

 

Only Ford or someone who has put the Fusion in a wind tunnel with and without the spoiler knows for sure.

 

You can see from the video above posted by GrySql that small things do make a difference. They make enough difference that Ford spends many, many hours on the small details.

I never said that small things don't make a difference or that Ford didn't spend many hours on the small details. What I said, in so many words, is that in OUR CASE, the spoiler is purely aesthetic, not functional. In other words, it's for looks and styling. If it were really functional and made enough difference in fuel economy, don't you think Ford would make it standard on all models? It would be in their best interest to do so because of the better fuel economy numbers. Something about the video you didn't mention is that the car in the video doesn't have a spoiler and the chief aerodynamicist for the Fusion demonstrated how crisply and cleanly the air came off of the decklid minimizing the turbulence at the rear of the car. It was designed to do that WITHOUT the spoiler. If anything, the spoiler would mess up the beautiful airflow shown in the video. I won't argue with you that "a rear spoiler "can" reduce drag on some cars if it is well designed." I would just argue that is not the case with OUR CARS and they are what we are talking about. The fact that Ford is marketing a "Super Fuel Economy Package" on the Focus is just that.....marketing. It's a gimmick to get people to spend more money on the car because it sounds and looks good.

[machoman1337]

Haha I didn't expect this to become a debate about the practicality of a spoiler, though it is getting entertaining and educational!

 

I was just asking about whether the spoiler's appealing or not, but nevertheless, keep the info coming :)

[Waldo]

I went back through the archives and dug up some numbers on the Taurus (I don't have Fusion numbers, so this is just for reference). On the Taurus the rear spoiler reduces the Cd by 0.005. Doesn't sound like much, but compare to the active grill shutters that reduce by 0.015, the under engine shield that's worth 0.005, a 10mm ride height drop is worth 0.010 and the underfloor shields that are worth another 0.005. Each one isn't that big, but add all those up and suddenly you've gone from a Cd of 0.32 down to a 0.28. That is absolutely a noticeable difference at 70mph and even below.

 

So why isn't the spoiler standard? Well that comes down to marketing and the EPA process. Bottom line is the EPA doesn't give points for decimals. If you score a 46.8 or a 47.2, you're getting a 47 either way. Ford obviously figured that the underbody shields and other tricks were enough to get to say 46.8 and the spoiler then didn't make a difference to the window sticker number. Now they could have deleted the underbody shields and put the spoiler on everything but then they lose the revenue generated by the spoiler. Basically the extra revenue earned by selling the spoiler on 20% or whatever it is of the Fusions is enough to pay for the underbody shields on all of them.

 

Yes the Focus SFE is a marketing gimick, it's a package designed to get at least one version of the Focus to have "best in class" fuel economy. Then they can advertise the Focus is "best in class", even though it's only a very small percentage of the cars that are actually "best in class". So the stuff on the SFE is there for only one purpose - to increase the EPA label, and it does work. It's not there to make the SFE look good and sell the SFE, it's there to sell more base Focuses.

Edited March 10, 2015 by Waldo

[murphy]

When I ordered my 2013 Fusion Energi Titanium the spoiler was included. There was an ordering option to delete it if you didn't want it. My car was built with the spoiler but they installed the trunk lid torsion bars for a trunk that did not have a spoiler. The trunk would not stay up. There was a TSB to get the correct torsion bars installed.

[hybridbear]

I went back through the archives and dug up some numbers on the Taurus (I don't have Fusion numbers, so this is just for reference). On the Taurus the rear spoiler reduces the Cd by 0.005. Doesn't sound like much, but compare to the active grill shutters that reduce by 0.015, the under engine shield that's worth 0.005, a 10mm ride height drop is worth 0.010 and the underfloor shields that are worth another 0.005. Each one isn't that big, but add all those up and suddenly you've gone from a Cd of 0.32 down to a 0.28. That is absolutely a noticeable difference at 70mph and even below.

 

So why isn't the spoiler standard? Well that comes down to marketing and the EPA process. Bottom line is the EPA doesn't give points for decimals. If you score a 46.8 or a 47.2, you're getting a 47 either way. Ford obviously figured that the underbody shields and other tricks were enough to get to say 46.8 and the spoiler then didn't make a difference to the window sticker number. Now they could have deleted the underbody shields and put the spoiler on everything but then they lose the revenue generated by the spoiler. Basically the extra revenue earned by selling the spoiler on 20% or whatever it is of the Fusions is enough to pay for the underbody shields on all of them.

 

Yes the Focus SFE is a marketing gimick, it's a package designed to get at least one version of the Focus to have "best in class" fuel economy. Then they can advertise the Focus is "best in class", even though it's only a very small percentage of the cars that are actually "best in class". So the stuff on the SFE is there for only one purpose - to increase the EPA label, and it does work. It's not there to make the SFE look good and sell the SFE, it's there to sell more base Focuses.

Great explanation! Thank you for sharing the details of how different components serve to reduce Cd.

 

 

Small things make such a difference that putting Splash Guards (mud flaps) behind all four wheels that the rear trunk area of the FFH doesn't collect as much dirt as before.

They seem to break up the turbulence directly behind the car and the license plate area stays cleaner.

The mudflaps change the airflow around the wheels. I believe having lot of dirt of the back of the car is a sign of good aerodynamics. We've had a Fusion without the spoiler and now the Energi with the spoiler and I can't see a measureable difference in the pattern of dirt on the back of the car. I would love to see the difference in a wind tunnel between a Fusion with the spoiler and one without.

[hybridbear]

This video has been posted on this website before and is valid now. Near the end of the video watch the wind tunnel smoke as it travels over the top lip of the trunk and listen to what is said.

Ford spent a lot of time getting the rear of the car to be as slippery as possible.

As mentioned, at the speeds we travel there isn't much reason for a spoiler except for styling reasons. They do look nice.

I just watched the video again to refresh my memory of it. There's a portion where the Ford engineer is talking about how the flow sticks close all the way to the back but the camera is only showing the front of the car... Grr... :rant2: :angry22:

 

If you're interested in aerodynamics, check out this thread by a C-Max owner. It's very informative read.

Edited March 10, 2015 by hybridbear

[hybridbear]

Small things make such a difference that putting Splash Guards (mud flaps) behind all four wheels that the rear trunk area of the FFH doesn't collect as much dirt as before.

They seem to break up the turbulence directly behind the car and the license plate area stays cleaner.

Here are some of the posts about the dirty back end and aerodynamics:

http://fordcmaxhybridforum.com/topic/3129-tuft-testing-a-c-max/?p=39543

 

I think that your mud flaps are actually creating turbulence and increased drag and that's why the trunk stays cleaner on your car.

[hybridbear]

I think we should rename this topic since it's really about spoilers and now aerodynamics. There's lots of great information here to refer back to in the future that may get lost with the current title.

[Automate]

Here is a highly theoretical analysis that concludes a rear spoiler on a generic sedan can reduce drag by 1.7%

http://waset.org/publications/10504/a-numerical-study-on-rear-spoiler-of-passenger-vehicle

 

But I'm glad we haveTonyHzNV, Ford doesn't need to spend Millions on wind tunnels and thousands of hours testing, TonyHzNV can tell us by just looking at the spoiler. ;)

[machoman1337]

I think we should rename this topic since it's really about spoilers and now aerodynamics. There's lots of great information here to refer back to in the future that may get lost with the current title.

 

Good call, I like it!

[TonyHzNV]

But I'm glad we haveTonyHzNV, Ford doesn't need to spend Millions on wind tunnels and thousands of hours testing, TonyHzNV can tell us by just looking at the spoiler. ;)

You should also be thankful for Waldo since he gives us so much "real", "inside" information being the Ford engineer that he is! Oh, and I'm glad you said "highly theoretical" up there on your link cuz it surely was! :)

Edited March 10, 2015 by TonyHzNV

[Texasota]

Very interesting posts in this thread but the majority of the information and data cited indicates that the spoiler, by itself, affects the aerodynamic characteristics of our FFHs in a very small way at best. The MPG benefit is so small that none of us would ever be able to measure it at the gas pump where it really matters. It would seem that for all practical purposes the spoiler is a styling component and a matter of personal taste.

 

I'm glad Ford makes it an option for those that like it and for those that don't you can purchase a FFH without it. Makes us all happy, right?

[hybridbear]

Very interesting posts in this thread but the majority of the information and data cited indicates that the spoiler, by itself, affects the aerodynamic characteristics of our FFHs in a very small way at best. The MPG benefit is so small that none of us would ever be able to measure it at the gas pump where it really matters. It would seem that for all practical purposes the spoiler is a styling component and a matter of personal taste.

 

I'm glad Ford makes it an option for those that like it and for those that don't you can purchase a FFH without it. Makes us all happy, right?

Excellent summary of the discussion thus far. SE models can get the spoiler as part of the 501A (Appearance) Package and Titanium models can remove it when ordering.

[Hybrider]

Go, SE Appearance Package!!!

Oh sorry, got a little carried away there.

 

[Iwejun]

Not all spoilers are made to produce downforce, some are incorporated into a design to "push" the low pressure area that is produced by the rearend further away from the car so there is less drag. I have the spoiler and compared to other cars that are producing spray at highway speeds I produce very little and what is visible is very low and back quite a ways before I see it. Throw the BS flag if you want but they were into aero with this car not only for looks but as an excercise.

[machoman1337]

IMO, next time Ford should make the spoiler such that it can be mounted with adhesive by a dealer after delivery without needing to drill into the trunk. That would truly satisfy both camps - people who want the spoiler can ask for it at the time of purchase, and people who don't want it won't have to resort to factory ordering. And people who buy used can manually remove the spoiler without creating holes.

 

I sat in a Titanium at the auto show and after feeling those awesome leather seats, I now know that my next Fusion would have to be Titanium. Just would like a simpler way to avoid the spoiler than factory ordering :)

[jadei]

IMO, next time Ford should make the spoiler such that it can be mounted with adhesive by a dealer after delivery without needing to drill into the trunk. That would truly satisfy both camps - people who want the spoiler can ask for it at the time of purchase, and people who don't want it won't have to resort to factory ordering. And people who buy used can manually remove the spoiler without creating holes.

 

I sat in a Titanium at the auto show and after feeling those awesome leather seats, I now know that my next Fusion would have to be Titanium. Just would like a simpler way to avoid the spoiler than factory ordering :)

 

Or get the SE Hybrid with Luxury package (Equipment Group 502A) includes foglights, an auto-dimming rearview mirror, leather upholstery, heated front seats and driver-seat memory settings.

[machoman1337]

 

Or get the SE Hybrid with Luxury package (Equipment Group 502A) includes foglights, an auto-dimming rearview mirror, leather upholstery, heated front seats and driver-seat memory settings.

 

That's exactly what I have. However, the leather quality in the SE vs the Titanium is quite different, sadly. If the two trims had the same kinds of leather seats I would be very happy.

Edited June 12, 2015 by machoman1337