Aerodynamic analysis of dirty cars that I live near.

[@Charlie1012000]

SAAB 2 stroke already had that spoiler slot, and full width, in 1962 on the model 95 estate cars. Of course because SAAB did it it worked keeping the rear window clean. I think they continued with it all to the end of the V4 model 95 cars. They also had flat floor underside...

[@nelsonphillips]

SAAB, we should all miss SAAB

[@Amy-dq2lg]

flat floor, that's a nice feature

[@MrZyLeXx]

They have a wing for their Aero's in 2004 with a wing that keeps the rear window clean

[@rogerwilco2]

@@nelsonphillips I still drive my 9-3 2001 Aero daily, but I'm really sad they don't make SAAB any more. I still think they are some of the best cars ever made to actually drive. But you have to drive them for a while to really appreciate them.

[@jortsmcpunch2580]

i believe they were one of the only car manufacturers to use wind tunnel testing at the time! benefit of starting out as just an aircraft manufacturer i guess

[@krudmuphinstudioz]

I've always known the slotted/standoff spoilers on production cars to be for keeping the window clean from dust. Often times if you look at the spoilers on SUVs, they are even shaped in a way that channels a LOT of air downward over the rear glass. It's pretty clever!

[@las3k91]

Mini R56 - with slotted spoiler [Cooper S model] or not [Cooper] rear window and whole rear hatch is dirty literally right after washing. So sounds good, doesn't work

[@krudmuphinstudioz]

@@las3k91 At least it has a wiper, lol

[@KmcK]

Same - this has always been my understanding. Very cool to see the fluid dynamic simulations demonstrate it.

[@marcoling2173]

I have heard that the Focus ST spoiler does a good job of keeping the rear windshield clear, as I suspected that it directs air downwards onto the windshield. The difference is very clear when compared to the RS, where a wing further away from the roof is used. The roof extension flap right under it presumably helps keep the airflow clean under the wing to ensure the wing's effectiveness, but as a result it separates the air away from the rear windshield. The RS rear bumper also has a small rear diffuser which I believe is meant to work in conjunction with the factory muffler to form a smooth surface underneath. The air that exits the diffuser and recirculates upwards is strong, with the high speed air leaving between the roof extension and the wing, the tradeoff is severe. The RS has significant debris buildup on the rear windshield compared to the ST. I believe the issue with snow isn't from over the roof, but rather from underneath the car. The air thrown upwards from underneath is so strong that brings a lot of powder snow or water droplets in the case of wet roads, whereas the ST slotted wing directs a sheet of clean air downwards to fend off the debris thrown from underneath the car. Ford engineers claim that they calibrated the RS wing and diffuser so that the car has zero lift at certain speeds, but they made no such claim for the ST model, which indicates to me that the ST wing wasn't designed for performance gains, but rather for aesthetics and street driving practicality.

[@notaboutit3565]

Took an ST to a tad over 150 one time, can confirm that wing was just for show.

[@ryanford5387]

​@@notaboutit3565😂😂

[@TeraAFK]

The purpose of a spoiler is to redirect air to the low pressure zone left by the car to reduce drag. A wing however increases drag as a trade off for more down force to allow better grip at high speeds

[@mtang65]

At what speed? 60, 100, or 120?

[@TeraAFK]

@@mtang65 At all speeds, the faster you go the more air is deflected by the wing and the more downforce will be exerted. You would have to do calculations and simulations for the specific vehicle and aerodynamic properties to specify "at what speed" this down force actually makes an improvement on performance

[@lucashurley7612]

Low speed the Spoilers offten work better. for thinks like auto cross. they can work great, just like the one one the LEMANS nascar commero. @@mtang65

[@markvicferrer]

Looking up options in vehicle brochures, some regular car spoilers state that their function is to direct wind downwards to help clean the rear window. For vehicles meant to actually be sporty, the optional spoiler is actually raised above the roof to catch air to produce downforce.

[@gregochan]

love how you explain the features of these production cars. I have a e36 and always think how the LTW wing really works. people say that the wing introduced a lot more downforce so need to counter it with a front splitter. Anyway love your videos and keep it going!!

[@Palatard]

Thank you for the information. Straight, clear, and to the point. I stumbled upon this looking for hatchback aerodynamics but it is very interesting.

[@meep9935]

I had a 4Runner that had a gap between the hatch and the spoiler and my rear window still got covered with rain water probably because it was a rolling brick

[@martinhann1672]

I have an old V70 Sport - rear Sporer with slot. The rear window very quickly mists up in wet conditions but the slot is there to clear the rear wiper - the sole reason! Oh, aesthetics perhaps. 5:13

[@nelsonphillips]

might work better for snow...... I think the simpsons reference is still more likely

[@allenplant1702]

My tiny hatchback Suzuki Alto Works came from factory with a small spoiler that created that vortex of dirt on the rear window. I swapped to a full-slotted, and longer up swept style to keep it clean. Does this help with aero? I don't care 🤣 the window stays clean for longer and the speedo tops or at 140kph! 😎🤙 Great video lesson!

[@op3l]

I wish my minivan had these slots. I have a near 90 degree rear gate and that thing gets dirty anytime I drive over dust or some moisture as it just sucks up whatever’s on the road and deposits it on the rear window.

[@76horsepower]

The Mazda 5 does. It’s a nice feature.

[@jolladevices]

What about the variant of this wing on the MINI R53 "Cooper S" 🤔 that wing has a stranger shape more curved. I remember on that car I had the rear glass so dirt all the time...

[@CrAzYDr1veR]

my citroen ax has a big gap from the spoiler to the roof to be able to open the hatch, i wonder how bat it is for aero :P

[@cameronfarrell9076]

Before watching thr video. My hypothesis is that the holes are there not for performance, but primarily to prevent water pooling in the spoiler, and secondly aesthetics

[@NuriBass69]

Here I am, high as a mf with my uschanka, smoking my 7am J, watching a video about aerodynamics How did I end up in this situation? Holy hell

[@matthewholt2174]

I'm very late to this but I had a Mazdaspeed 3 (Mazda 3 MPS in the EU) which had a completely pointless spoiler. All it did was increase the drag on the car because it wasn't shaped like an aerofoil, and, even if it was, it was angled in a way that would make it create lift rather than downforce. Of course I didn't know anything about cars or fluid dynamics at the time, because I was still in high school, but in retrospect I find it funny that I thought it was beneficial.

[@Xanderoby]

If the flow following the rear window met a spoiler like that of the Porsche Cayman or Ferrari 296, basically a mid spoiler, could it generate vertical aerial load like on these cars? I have a similar project on a hatchback with an electric spoiler but I still don't understand if it would work.

[@nelsonphillips]

any spoiler will work on a hatchback, that is why every hatchback sold these days has one. It depends on how much work you want it to do.

[@Nando-gc8kb]

could you make a CAD/CFD sim of the Chaparral 2J fan car or the Brabham BT46?

[@jackalseesyouhiding7201]

Ive got a 94 celica and some of them have a roof spoiler. Apart from esthetics, for a liftback to have one is so odd to me. Im sure it has its benefits along side the wing maybe.

[@Vaasref]

So that's why the first version of the MG4 came without rear wiper. MG was saying at first that it wasn't needed due to how the car aerodynamic design. They actually told the truth. And they even never claimed the spoiler to be anything other than aesthetic. I'm kind of shocked that it wasn't a baseless marketing claim to make buyers accept the lack of rear wiper. I mean they put a wiper on the second version but the marketing wasn't baseless.

[@gabrielrugarcia7805]

Do more like this, good job friend💪🏾

[@mihauLOL1234]

I just found Yours channel Man and Ive got to admit I love your content 👏🏼 Hope You will analyse sedan shape one day also!

[@indopleaser]

great video. good info on street car aero!

[@simtalkayak]

So, i have an 05 Honda HR-V and I've always been curious about why they came out with spoilers. Would you be able to look into this model specifically please?

[@Eggyteevee]

Looks cool, doesn't affect performance to an noticeable extent, without it the loss would be bigger and increases practicallity for daily driving. I'm not a professional but I can say that's a clever idea

[@sethmoyer]

I have a Fiesta ST mk7 with the slotted spoiler, and I actually had to buy a riser kit for the spoiler to allow air to go under it so that it would keep the rear window clean. Without the riser it did nothing. As far as I know, the Fiesta ST is too slow to benefit from any kind of wing unless it was absolutely massive, so they generally just put them on because it will make the car look sportier.

[@mc1996]

Aerodynamics start to work at 60kmh or so, a ST is fast enough, any car is. The spoiler is for reduced drag, by creating a smaller area being the car, not for downforce, as with most road cars

[@sethmoyer]

@@mc1996 The wing does nothing, it is for styling purposes only. On the actual racing Fiestas, the wings are much bigger and are actually designed with aerodynamics in mind. The only wind tunnel testing they likely did with the Fiesta/Focus ST wings was to make sure they didn't make overly loud noises at speed.

[@mc1996]

@@sethmoyer noise equals drag, lol. Every hatchback has a spoiler for this reason

[@sethmoyer]

@@mc1996 Yes, that's why the Fiesta and Focus SE have their tiny little spoilers. But the ST and RS with the fancier looking ones have NO benefit. I'm not trying to trash talk these cars at all; I have one and it's my favorite car I've ever owned. But it's naive to think that a company selling a sub $20,000 hatchback (even for the top trim levels) with a top speed of like 130mph is going to put significant R&D into aerodynamics. They didn't even add the little wind deflectors in front of the side mirrors until like 2018 or 2019... Also, the Fiesta ST wings use the same mounting solution as the SE wings, and incredibly thin plastic, so they generally crack after a while. If there was any significant force being imparted to the wing by aerodynamics, they would have needed to use thicker plastic.

[@mc1996]

@@sethmoyer man, just pick up a book. All hatchbacks have a rear spoiler for reducing drag, not making downforce. The spoiler doesn't have any downward forces, it's just to smooth the air after leaving the roof....if you have any doubt that a spoiler like these (and all other models on the road) works, then I don't know what to say. Manufacturers struggle to keep emissions and fuel consumption low on these base models (even with STs) so they can balance with the performance models.

[@NarcoSarco]

My imagination was that it got rid of low pressure zones behind the car, making it more efficient. Good video but noe is want a real world test xD

[@stickman-1]

You are wrong. The answer to the question "do these slot work?" is an emphatic yes. The reason is their purpose it not to make the car go faster, but to clean the rear window. You assumed a purpose. But you assumed wrong.

[@StormÆLnGoFth]

Subaru had a whole extra bar on the the sti and a massive spoiler

[@ThisRandomUsername]

Would the solid centre portion not create a vortex pulling the lower energy inwards? You only tested a continuous slot across the whole spoiler?

[@nelsonphillips]

you are correct. the simulation did confirm that the purpose of the slots as outlined in the paper. There is a lot of detail that you can go into and a manufacturer would, but this is yt.... I'm going for a mildly interesting video that isn't wrong....

[@Muhluri]

This was very informative

[@peanuts2105]

Ive got an ST and it is very stable at high speed (100 mph+). The rear aerofoil section does help to keep the air attached to the rear more by delaying pressure difference (high on the roof to low at rear window). Or what I've just said is complete bollocks

[@nelsonphillips]

The spoiler fundamentally changes the shape of the wak drawing air from under the car up the rear window. this means that there is less pressure under the floor, but more importantly the induced drag from the air above the roof isn't pulling at the rear window creating lift.

[@BigDumbMeRC]

Do you think spoilers make a difference on large SUVs?

[@tsyp40]

I use Suzuki GTI and was exactly searching for this stuff

[@GTSW1FT]

I do like that he use a model of a mk1 gti over the more rounded mk2 gti. I do wish i saw them more offen

[@solomondoors7610]

Do cars like this ever get going fast enough to warrant even needing a spoiler in the first place? I thought spoilers really only made a difference at speeds over 100mph

[@Plokus]

Amazing vid sir

[@lunarthespacecat7772]

i keep getting this answer so the answer is no. they do not work their mainly a cosmetic thing, unless their under an active spoiler like on the mclaren, they are not going to do anything on your B class.

[@fe3bal]

Snow is just cold white dust. But stickier.

[@alekswilde6304]

I suppose it’s possible these lend themselves more to feel making the car feel livelier or aid in rotating the rear of the car. It seems to me newer cars tend to feel lazier and more stable so perhaps this is the most cost effective way to achieve a desired feel?

[@nelsonphillips]

car maker don't want to sell a "lively" car as it would unsettle most drivers.

[@4ae109]

@@nelsonphillipsThe cars with the slotted spoilers are FWD sports cars. The people who buy those would probably prefer a slightly loose tail on a FWD.

[@RandyAugustus]

@@4ae109I own a car with a fwd performance car. I do not want a lively rear end. I want it planted and firm.

[@TiyamatFTL]

true, but the fiesta st for example is anything but not lively. I don't think thats down to a little bit of lift though, so not really relevant here@@nelsonphillips

[@getahanddown]

Is this where some of the extra top speed of 'performance models' come from, not just from raw power? Would like to see real cars side by side then using each others slotted / non slotted spoilers

[@PiDsPagePrototypes]

The slot's not there for performance, it's there to keep the window clean, especially on Stationwagons - search images of the Chrysler Valiant CM wagon, or the earlier VC Valiant Safari, where the air redirection is done from the sides with a chrome peice.

[@Iowa599]

It doesn't look like your program included the airflow through the grill & heated by the engine. I think that is significant… Was that included?

[@RaianF1]

Amazing!

[@SummonerArthur]

Short answer: yes, but not for performance

[@Secretlyanothername]

I've seen snow once. Cold white wet dust.

[@samusaran7317]

Im of the opinion it's *mostly* for a 3rd brake light.

[@nelsonphillips]

the spoiler is definitely for drag and lift reduction. reduces drag by 10%.

[@samusaran7317]

@@nelsonphillips You still missed the word "mostly" in my original comment. Everyday cars *largely* won't benefit much from this...

[@nelsonphillips]

@@samusaran7317 no i got it, that is why i responded and stated that it reduces drag by ten percent. that is why every hatch has some version of a spoiler even if it is just a small numb.

[@DatPenguin97]

Good thing my Fiest ST150 doesn't ye have holes, just sort of indentations haha

[@ebestubbe2177]

Good vid

[@burnzy3210]

"spoilers reduce drag" uh no... they add drag, that's how they work. These gaps reduce drag and turbulent air.

[@nelsonphillips]

spoilers on hatchbacks reduce drag and that is why they are on every hatchback now sold. See my other videos for the experimental reasons. They even work on camper trailers for a easier to watch version.

[@robertsaca3512]

Did you seriously assume Australia has no snow? 😂

[@2LAZY-2EDIT]

I thought he was gonna talk about prostitutes.

[@OttoMatieque]

'speed holes' is that what they are calling them in the age of hookup culture?

[@nelsonphillips]

simpsons reference

[@TaylorPhase]

couldve told you its to keep the window cleaner in the first 4 seconds...

[@CarNerd]

The entire vehicle is the wrong shape.

[@nelsonphillips]

True, it looks nothing like a My Little Pony.

[@dukedub]

Backwards flatbill 🧢

[@sunnohh]

porsche doesnt have it which suggests it doesnt matter