Hatchback Aerodynamics: Improving the rear wing or spoiler
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- Опубликовано: 22 авг 2024
- This video further developments the Golf GTi's aerodynamics by adding a rear element that increase the downforce for a wing. This video contributes to the understanding of hatchback aerodynamics that the general public lack. Rear wings aren't by themselves a great idea for hatchbacks because they aren't supplied with sufficient clean air flow. Adding a spoiler under the wing dramatically increases the effectiveness of the wing and the overall performance of the vehicle.
I guess this is where the Peugeot 205 T16 rear wing design came from.
Exactly what I was thinking too! They sure did tons of wind tunnel testing on the 205 T16. Makes sense why it was the fastest group b car :D
Its cool to finally see why they went with the design :)
Seems a bit like he is rehashing what WRC teams have been doing for a long time.... Its not often WRC teams get Aero wrong
@@nigelsmith7366 The point of the video is that no one outside of the old group b and modern wrc cars does it correctly. Its practically unknown outside CFD circles. I have never seen a hatchback use this design in time attack or other high downforce applications...
I havent seen anyone else talking about this on youtube. Plus, its just super cool to see this actually explained with very well done CFD in a video
Yeah, when people speak about group B cars usually it's about their engines and power to weight ratio, but they forget tge crazy aero those cars had
Already a huge improvement to the thing’s mentioned the other day.
Much better (slower) pace and the pictures/comparisons are easy to understand.
The graphs at the end might still need to be paused and have a closer look at to really digest, but that’s not much you can do about that and not a big deal.
Nice work on the aero and the improved video. 👍👍
"just 20% more drag"
That's what I call an 'aerodynamical heart attack'
This video should get more attention
This is a pretty nice improvement. I do think it's funny that your first solution, the spoiler + wing approach, is basically just fixing the hatchback wing performance issue by giving it a simulated sedan trunk lid.
Make sure you test wings/airfoils seperately and compare them to xfoil or wind tunnel results. When I first started getting into aero I was getting very different results. Turns out that a good transition model is key to get these low reynolds number airfoils working. That's probably one of the reasons why you are always getting so much separation on your wings.
I think it would be worth testing the wing in a setup where the flap extends all the way to under the rear wing. That seems to be the case for the WRC cars and I wonder if provides better support for the rear wing. Maybe even build a slight tail cone off the top of the roof into the flap to keep the flow smoother. Also I’m curious to how the TCR cars are getting their downforce as they all run a traditional rear wing without any window flap to help and those cars are producing pretty respectable downforce
I think the TCR car benefit from contemporary aero, that is the roof slopes down much more at the rear. This means if your regs say a wing cannot be higher than the roof it is a reasonable distance above the hatch. There is a bunch of other this as well, like the wing is far back, the spoiler exists to split the wake and roof air, but is above the window instead of on it.....
This vid was based on some work already done, it was to fit into some regs and other constraints. There is definitely two videos that could follow. Might randomly do a camper trailer next though.
Something of note is that (at least, supposedly, I've not come across an accurate enough model to check via CFD myself) during the development of the modern Fiat 500 (Mid 2000s-Current) the designers wanted to avoid a rear spoiler, the Abarth models in particular though had them introduced purely on merits of drag reduction alone. As a consequence, the electric models of the hatchback sport a similar spoiler as drag reduction is also key in that application.
That explains a lot on why I see some wings in that particular form. Thanks!
Looks like a shift of the wing forward an up at the end of the roof section would work much better, since it will be aligned with the flow on the roof. Though some regulations might not allow wings that high up.
yeah most regs say "not above the roof", but definite improvement options available
Great video. I think this was researched by some teams during group B era and i think some car between renault, peugeot or lancia had a wing that looked similar. With cars also being quite boxy like this example's golf.
dunno why this is not used widely today though.
Oh and btw, quite interesting how bodykit modifications to arches and wings makes cars start looking like group B too - remember the bodykit on audi quattro? uncanny resemblance to this golf.
A lot of people has done the flap before the wing on hatchbacks or similar time attack cars, not to the complete world to know but they do from long time ago ( in pro and in also amateur, me using this idea on my civic around 10 years ago and actually test it around 5) it is amazing to see the cfd on what was on my mind, thank you very much
the videos from this guy are so comfy
There is a 1990's Honda Civic aero kit that has that extra duck tail under a wing.
I always thought it served zero purpose, and it was more for looks, but it all seems to make sense now :).
If we are talking about the same duck tail: It probably has nearly no downforce effect. Probably it is more for the looks and avoiding dirt accumulation on rear window. Look up "Automotive Aerodynamics Ep. 6: Honda Civic Hatchback" from GraysGarage ;)
25 years ago I raced a MKII GTI and Jetta. Accounting for weight, etc, I always felt that I was getting better downforce on my Jetta. Lucky for me my school had a small wind tunnel and I had unlimited access to it. I made scale versions of both cars and tested a ton of different aero modifications. In 2002 the GTI ended up with a lip and wing combo much like your design. Between that and underbody aero I was in love with that car and lost all interest in the sedan. Then I started a family and hung up the r&d/racing chapter so I never developed it any further unfortunately. Oh, and the car went from an r&d platform in autocross, running in events at Laguna Seca, to a canyon racing machine. ok, now I kinda miss those days lol.
This is super interesting and kinda explains ’98 Toyota Corolla WRC wing design. It didn’t attach to the top of the hatch, rather halfway the window
Like the current WRC cars, the 98 Corolla had the mid window spoiler too to improve the wing performance. It seems that the rally car builders have known about this for a while.
Thanks for sharing the video. Your models explain this dynamic very clearly.. The wing options make sense when you show them. Reminds me of the Peugeot 205 T16 with its huge rear wing. and also like you said the current WRC cars use the flap on the rear window to improve the efficiency of the rear wing.
Ford's RS2000 was originally designed with 3 wings - the final production version had only 2.
On Wheeler Dealers, they added the missing 3rd wing.
Hatchbacks like Golf mk1/mk2 benefit a lot from a lower rear splitter. Reduces dirt on rear window, too.
Some race cars had this worked out. Look at the 205 T16 Evo II, that thing had the wing of wings in the hatchback style of car.
An interesting comparison would be the 205 GTi vs the 205 T16 Evo II. Also the 306 S16 vs the 306 Maxi Phase 1. The latter 306 had a shopping trolly style wing on it which from what I can see only generated lift...
Amazing info! Earned yourself another sub. Thanks so much for this!
Why RUclips recommend this to me, I do not know but I'm glad it did.
I didn’t understand 90% of what was said in the video because I’m not versed in this topic, but I enjoyed watching and learning!
That final wing design reminds me of what was used on the Lancia ECV prototype. Maybe they came to a similar conclusion.
the aero of group b and s is surprisingly forgotten or at least underappreciated
Very interesting, I myself made a "drag style" wing for my rover 100. But added a bill/wicker/gerny at the end of it. It made a noticible difference in downforce with the rear being more stable but no idea if it actually reduced drag or its creating a bunch more
yo that was really interesting to watch! hopefully you'll keep doing this type of content, subbed :)
this is fantastically interesting and also really usefull info
Nice video. What cfd software do you use for this analysis? Have you ever done an aero study on common SUVs like Honda HR-V or Toyota Raize?
I believe he's using OpenFOAM
Now I’m curious towards the cosworth double wing design effect.
sweet ass video, subbed, will enjoy seeing you grow soon
Hold on a second. There is a production hatchback that has a spoiler half way down the rear window. That's the EU/JP 2005 Honda Civic. So it's not like this thought doesn't exist.
Obviously it doesn't have a rear wing though.
It's absolutely spectacular in person though. It feels a very similar shape visually from all sides, some sort of optical illusion, it's basically like an UFO floating in front of you, and the design details with smooth polycarbonate grill decoration with reverse side detail and angular handles are very striking as well. And like it stays planted, it turns, it's decent. Futuristic design extends to the dashboard as well.
Fantastic! Thanks!
You should look at FWD RC racing. The last style wing minus the mid section is basically a 1/10 Touring car Spoiler. If the rules allow we usually use those on the back of the body when we need a lot of read down force. Although the aero is pretty diffeerent due to the inner of the body the outside may give you some ideas :)
Love the video...
Subaru hatchback owner here. 1995 Impreza rally car. I feel like I have been denied my god given birth right to a sick ass rear spoiler. If I am gonna have to put up with Subaru mileage and head gaskets, I want a spoiler, dammit. However, all the stock GF8 wings have big time weenie hut junior energy. Another local driver has more or less taken the WRC shelf + spoiler approach on his car. Both of us compete in ARA, which has some pretty clearly defined (and restrictive, depending on who you ask) aero rules, chief among which is how far outside the existing outline of the car you can put a wing. I'll have to consider this approach if I decide to build my own wing, and whether I can fit it into their rules
on the mini R53 people run the standard spoiloer along side the GP wing before this video i was thinking about removing my factory wing for looks when i get a GP one but keeping it as it actually improves the downforce
Good afternoon, please could you do a video on the following. I would like to know the down force difference between the porsches with "Ducktails" and "Whaletails".
I would love to see a sim like this done for a 1987 Toyota Celica GtFour
very interesting, I like this sort of stuff, but I don't understand all the acronyms
Cool! Could you do a video analyzing a Saab 900 turbo? Like the effectiveness of the aero parts, the rear spoiler and the rims.
You just got yourself a new subcriber!!! Please can you make a video for Mazda mx5 mk1 with softop,hardtop and without, also ductail rx7 front lip to see if they do anything and maybe more aggressive aero options simulations?
A few uneducated opinions on how I would solve the extra drag from the 3rd variant
1) roof vortices
2) have a secondary wing/structure that starts at the tip of the C-pillar (not unlike the Ford Cosworth), not for downforce but to channel high pressure air into the main plane and extended winglets
3) either multi-tiered flaps on the main plane for passthrough, or rally style spoiler channelers (the vertical columns seen on modern rally cars, like the 04 WRX STI
Great video! Which software are you using for these simulations? I would love to improve aero on my formula predators pc010, but I have no idea how to get started
I've seen plenty of WRC hatchbacks use a similar dual wing design, so this is clearly no secret in the racing world. See the WRC Fiesta for example.
great stuff.
Ford used a vaguely similar system for the Group A Sierra Cosworth RS500.
The spoiler was at the bottom of the long tailgate glass and the wing was on mounts above it half way up.
The tailgate wasn't as steep as your model.
And they used the same setup on the Escort RS Cosworth.
I feel like there are probably some good high angle of attack flap/slat designs from aircraft that could be advantageous
Sounds like pinderwagon your referring to with the rear wing and wanting more rear aero
Great video, the photos really show your intentions. What kind of program are u using for your CFD?
openfoam
Id be interested to what modeling shows for multi spoiler hatchbacks like the EK civic type r, where it has a roof spoiler and mid-height spoiler at the base of the rear glass I've always been curious if it the second spoiler was just aesthetics or actually reduced lift and/or drag.
Isn't this what the Sierra XR4 did? It's not exactly a hatchback but still
Hey Nelson, try not using a Volkswagen shaped hatchback. I had a hyundai pony (real gutless) that got very bouncy at a quarter tank of gas. I made a wing that mounted on the hatch just above the latch it was flush with the roof line due to the downwash
of the hatch. It had 1/4" Gurney flap that proved way too much and had to be flattened out again. So to say the effect is minimal is due more to the specific vehicle than the wing itself.
The air already did its job flowing around the main shape and it's just leaving, but then you give it an extra obstacle to solve, that's what you're seeing on those graphics. it's the same as having a lot of people leaving a crowded place after the show has ended and then you think it's a good opportunity to do a marketing move right at the exit, you'll only generate an unnecessary congestion right when people want to leave and go home.
Nice 👍
What about something like the 2020 Sonic RS Hatchback? It comes with just a flat lip as a spoiler for an inch or so, but below it, the car is done, completely vertical basically. I've seen people mount wings on them, but it didn't make sense, since the air is already flowing completely straight off the end. Is there any way to improve the aero with this or is the lip the best?
Oooooh. I wish you'd do a Corrado the same way.
This is awesome tech nerdy stuff!
Have you tested what would happen if you lower the secondary flap under the rear window (2:23) like they've done in some aftemarket kits for hatchbacks?
You should have a look at the style of rear wing (more of a spoiler) that drag cars use for hatchbacks. Look at 'Civic EG Drag Rear Wing' in google you'll get an idea.
I don't know how effective it would or wouldn't be for road racing, probably not very given that you don't see it, but I'd love to see some CFD analysis of what it does for a hatchback body shape.
Great content! I will ask you an opinion on how to place a wing on a car that's already pretty aerodynamic but need just some downforce on the rear axle...
Really nice video, i really want to see an investigation on whale tail wings on drag cars and what do they do maybe it could be an idea for a future video
google: "Peugeot 205 T16" your final wing design is basically the same as what they ran in the 80's.
Hello! You are doing amazing job!
Do you have a video for hatchback aerodynamic for the drag race ?
How do you compute/compile the CFD? I recognize paraview from my graduate work using Nek5000, are you using something similar?
Hi, how did you do this simulations ? Nice video by the way.
Could you please do an analysis of a mk7 golf r with full oettinger kit? 😬
So I’ve been contemplating a wing. I have a Zender spoiler on my hatch now and from watching this keeping that and adding the wing would be better than removing the spoiler when adding the wing?
What happens it you dramatically change the leading edge of the wing to "capture" more air and reduce its AoA (or incidence, I never know which is which in English)?
Somehow, even though I generally only watch car teviews RUclips decided I needed to see this... But my question is how much down force ia actually created by a typical wingat 100mph?
That's quite an increase in CdA tho, although I would assume it is a worthy trade off in this kind of competition.
I wonder if this would work on the back of the cab of a pick up?
My Veloster N comes with a flat lip with a small spoiler directly on top of the flat lip, how would/might that style apply to this effect?
Great video, I subscribed.
I've been wondering for a couple of months now, since I stuck one of those little model spoilers on AliExpress to my friend's fiesta, how much downforce does it actually produce. If you think it'll turn into a fun/educational video, I'd love to see it
@GearsandGasoline This might help out the civic
can you do some research for chrysler 300c, station wagon, how to reduce drag and lift of boxy body
some civic 6th gen hatchbacks can be seen with "middle" spoiler aswell ;)
can you please do an analysis of a car with windows up vs windows rolled down
What about just a spoiler ?
So in other words, the spoiler delivers more high energy air across the suction surface. Without it, the downwash from the hatch is not aligned with the airfoil's AOA. I wonder what would happen if the airfoil's suction surface were aligned with the downwash from the hatch. Would it make the same downforce as the hatch with the spoiler?
I'd wager it may help with a reduction in drag as if you were to align the airfoil with the hatch downwash your force vector for downforce would have a fairly significant component pushing towards the nose of the vehicle. Achieving similar raw downforce numbers may be difficult.
@@WeAreChecking If it reduces drag, then that's a win.
then the upper surface is misaligned.... Also the low pressure interacts with the hatch, increasing drag.
@@nelsonphillipsany chance you can add a second element to the wing then, to reenergize the flow with a small slot gap?
@@TheGamingHungary I guess you could. You wouldn't apply it in the same way conventional double element wing are, but more of a guide than another element. That is a big gap between elements.
i think they had something like that in some version of honda civic 6 gen although below the window
Could you test if the first-gen Alto Works (CC72V) cheese grater rear aero element (spoiler? wing?) actually works? The brochures certainly made a point about the aerodynamic drag coefficient reduction it allegedly did.
I want to try this mid flap and spoiler combo on my ek civic now
Hey, have you experimented with adding vertical side profiles to the rear spoiler similar to the GTI Mk7 Clubsport?
It should reduce pressure under the spoiler, as it inhibits airflow along the sides of the car from going to that area.
So the best rear spoiler and overall body kit for mk1 Ford Focus will be '03 Focus WRC?
Hatchback aerodynamics are solved cutting rear bumper and mounting rear wing down low in the vicinity of ground effects and having ramp angled diffuser’ish rear floor that had free flow space over the wing. A rear wake low pressure area must be minimized.
Thought of that also. Beside greater downforce the increased reagion of low preasure on the back is causing more drag.
In my own BMW clownshoe I cutted a lot of lift and drag away. Maybe 150kg less lift and a bit on the downforce side, I had to do front spitter which of underside I made wing ofcourse too to rebalance car. Drag coefficient bettered from 0.37 to about 0.32. I have in same test stretch 20kph more top speed, speeds I have never seen in this car before. @@mateuszkasza
this is huge
Could a vent in the bonnet help reduce front lift?
How effective would the voomeran style spoilers be?
The youtube algorithm provides something interesting for once. Looking at this, Peugeot did their homework back in the day with the setup for the 205T16 E2...and Lancia for that matter with both the S4 and what they came up with later for the Integrale. Having watched this, I was wonder what effect the kind of setup that was on the Pikes Peak 205T16 had, where the wing was on top of the spoiler/flap and the endplates closed the gap between the two....
Also, I wonder if this is the same or related effect which lead to the rear wings on some Group C and IMSA GTP cars going lower and lower and closer to the diffuser exit, eventually resulting in the massive bi-plane wings of the early 90s...and maybe later as well with the LMPs rear wing endplates growing longer and longer to where before the rules were changed there just a small gap between the spoileresque rear bodywork and the endplates.
I was specifically talking about hillclimb and general racers using off the shelf wings. Give a team a factory budget then they should have reached the outcome
Your AoA @1:17 looks it's stalled the wing. Maybe consider setting the AoA relative to the airflow and not the the groundplane. It looks like you've got the wing set at 50* AoA to the airflow. I don't know of any single element airfoil that would do well with that.
So i've run the aoa with wings in another video and this was to illustrate the case of a single wing at that angle then how adding a device like this helps df. It seems that I accidentally made a watchable video this time and a new audience brings an unfamiliarity with what I'm doing, which is fine I probably need to make it more explicit that these are experiments not instructions. Its the "spoiler v wing" vid if your interested.
@@nelsonphillips I just finished up that video. Even in that vid you mention you tested a wing at 0° AoA and showed a graphic. The graphic shows your Airfoil at 0° to the ground plane. Not at 0° AoA to the airflow. It's stalling in that video. No airfoil is going to perform well when you stall it. I'jm just some internet idiot but it seems like with your hatchback you should be using vortex generators to keep airflow attached to the ass end of your brick. With airflow better attached, place your rear wing to help your floor generate more lift (downforce). Don't use the rear wing for downforce. Use it to help your floor generate even more. In other words, think of the car floor and rear wing as a two element wing. The Car Floor is the larger first element. The "Rear Wing" is the second element. Use the Rear Wing to keep flow attached while also adding energy to help evacuate more air from the low pressure side of the Floor to generate more lift (downforce).
What about spoiler on 05 saleen focus. Does it work or just for looks?
eg hatch here. my wing is attached to the car can u do a few lil sims on that variation they have a few options to n peeps run what is called a duck bill would be interesting to see that thing weird'ness.. i have the more drag style where it just runs off the back of the car. im not sure my wing helps wif downforce but should help wif drag a lil bit my car is stable till 110 then i feel like i needs more down force after that n then i run out of gear n tune
Or, you could just do what Porsche, VW, Peugeot and a lot of other car and aftermarket manufacturers did with their kits for hatchbacks in the 80's, and mount the spoiler just beneath the rear window. Essentially turing the car into a more sedan like shape airflow wise. Alledgedly this increases downforce in the rear, but at the cost of increased drag due to the negative pressure pocket created beneath the wing (behind where the numberplate and taillights goes essentially). Though on a race car, this could probably be mitigated by a properly designed Venturi tunnel.
Best option is to mount something that flows straight off the roof, and a sort of rear canard? aleron? arrangement off the back of the boot, just below the rear window glass
yes, but the wing would need to be higher than the roof. TCR use newer vehicles with their roof line sloping down and therefore do this, supplying the wing with sufficient mass flow.
@@nelsonphillips ah.. i see my verbal mistake. the structure of the wing should begin at the roof line and accend. Not flow straightening.. but yes it would be better a little higher in the free stream.
I've started to see a strange ... its not a dimple... its the inverse of that, in the centre of cars above where the license plate is mounted..(base/bottom centre of rear glass, brake light mounting point or bottom mounted wiper blade location. ) I assume that it is some way of organising the flow at the rear, into controllable regions of drag or recircultation. yet i have never seen it visualised.
Adrian Newey would be proud
what program are you using to do these simulations? I would love to do this kind of thing for my sw20
What if the rear wing was placed further up, offseting it from the car's body so it won't interfere as much. Not as elegant of a solution, but it could have a similar effect
Good question, the hatch downwashes air, so placing it higher up will just create more divergence and more separation. I reckon It would have to be comically high, which would then introduce lever effects on the chassis. You can't force air to go where it doesn't want to go, you have to go with it. It's not just about placement, but also aligning the suction surface so it gets plenty of high energy airflow, since that does the bulk of the work.
regulations not allow it to be above roof
what software are you using to measure aerodynamics?
What if you use gradual slope on top of the roof instead of spoiler, something like semi roof fairing but concave
The gr yaris comes with the flap
Check Wheeler Dealer Ford Escort RS Cosworth with triple spoiler or the EScort WRC had some flat wings and also the Fabia mk1 WRC had a double spoiler like the 2006 Focus WRC... there were also some available manufacturer data from SEAT Motorsport about the client track car Seat Leon II with drag and lift for the rear spoiler, it had and awful aerodynamic and only the TDI engine made it succesful so it had to be made slower buy addig weight... but I remember rear spoiler going down meant you could reduce drag by diverting flow to fill the wake and even keep the lift neutral...many road cars have positive lift at high speed on the road... like the Cordoba, TT, Octavia, Toledo... and they need at least a lip spoiler to make it neutral and stable...being sedan body shaped... but hatchback definitely have a rear giant vacuum cleaner with all king of susrprising flows...as you say usual spoilers won't help much other than esthetics neither solve lift or lower drag or reduce wake or anything...
I saw a video of the designer talking about the rs cosworth body kit and how he wanted a triple wing at the back but was only allowed two. Years later they tested the triple and it turned out that it gave better results. As i recall he was just a designer and doing something aesthetic, which happen to be better. This was a few years ago and I didn't really know how it would be better, this I think may explain part of the reason.
@@nelsonphillips I guess there is a point where puting anything filling turbulent and lowest pressure zones on the wake is better than nothing... you can add brick walls or a trailer and lower total vehicle cd or even change the lift... you should do the cfd test of the 2x boxy Golf's bumper drafting to see cd and lift... in Nascar style...
You maybe get more performance out of your wing in that downforce is higher, but you just ruined the airflow to the back of the vehicle creating this massive separation wake that will slow you down like crazy. You won't get more downforce without more drag, but this solution gets you more downforce with WAY more drag. This is why big spoiler solutions are usually combined with big diffuser solutions to make sure that space gets filled with air coming from underneath the vehicle (typically also helping you generate downforce). Any extra time in the corners will be massively outweighed by the time lost in the straights, if your little ol' four-popper can even generate enough thrust to keep you at the grip limit around the turns.
How effective is MINI GP3 rear wing?