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Forget front spoilers - you *want* air to flow under your car!
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- Опубліковано 4 сер 2024
- The idea that you don't want airflow going under your car is decades out of date. Here's why. Note that my most recent aero book (replacing the one shown in this video) can be found here - www.amazon.com/Vehicle-Aerody... or Amazon in your country.
The Insight is a sign this guy is a real one.
Thanks for taking the time to post the video. Perhaps in a future video, you could give us some insight into race car aero, which seems to be a bit of a departure from what you are discussing here for typical road cars. Obviously there are lots of reasons racing teams invest big $$ into protruding devices attached to the front ends of every imaginable car.
While I have an idea, I would love to hear your insights. Great work!
Another great video! About half way through I was hoping you’d show my Passat wagon and sure enough there it was. Keep up the good work
Yep...these videos are great
Was yours the one near the end with the exhaust covered by the under tray? How much exhaust is it safe (for heat build up) to cover up, just the rear section or the mid too?
After watching this video I actually removed the front splitter/lip om my megane 4 RS. I can see the benefit of actually having more air flow underneath (on quite a smooth underside) both for downforce but even cooling of engine bay. Car gets tracked quite a lot so Im hoping on an inprovement of my oil temps as well as intake air temps.
Just removing the splitter lip, without then changing the underside of the car, probably won’t improve things!
Great videos! I’ve been binge watching the entire series.
I’m curious on what your thoughts are on front splitters?
Front splitters have major downsides over properly designed undertrays. Covered in detail in my latest book - www.amazon.com/Vehicle-Aerodynamics-Modification-Development-alternative/dp/B0C87VYVL8
I’m so happy that I found your channel. Loving your video content and just ordered your book. I’ve been planning on making a flat floor for my vehicle for a while. Was wonder if you tested the before and after difference in drag.
My book (page 151 - 152) gives some figures for the drag change resulting from fitting a full undertray, but a lot depends on how bad the underside is to start with!
Great study
Modern cars use the splitter to create a high pressure zone in the front for added downforce, not to stop airflow from going underneath the car.
Sure, did I say otherwise?
You didn't mention it. I felt like it was worth mentioning because otherwise the video implies the splitter isn't beneficial @@JulianEdgar
@@JulianEdgarI feel like a super bird front end would be great for funneling air underneath the car. It just needs wheel vents and some way to create a high pressure zone on top of the car
No, overall, I don't prefer using splitters to gain downforce. Undertrays are far better - covered in detail in my latest book. www.amazon.com/Vehicle-Aerodynamics-Modification-Development-alternative/dp/B0C87VYVL8 or Amaon in your country.
Would be nice to see how you fitted the Insight with that undertray...!
Yes, covered in my book - www.amazon.com.au/Modifying-Aerodynamics-Your-Road-SpeedPro/dp/1787112837
Both Ford F-150 and AMG GT R use active air dam, do they work like front spoiler?
Look at a Rochdale Olympic Phase 1. Totally smooth underneath with recessed exhaust - in 1957.
Yes, and the Kamm cars 20 years before that!
Hi Julian. Do you think there is any value in improving the undertray smoothness in a car like an Ioniq EV with light Mylar tape over the remaining imperfections like stiffening ridges or bolt holes etc?
There might be a fracional (ie unmeasurable) improvement if doing this towards the front of the car, where the boundary layer will be thinner. Do you have a link to any pics of the car's underside?
Hello Julian. I agree with all you say but ask if there is a point where the front of a car, perhaps because of its height from the road, directs so much air underneath that the air cannot speed up enough to create low pressure so a higher pressure 'bow wave' is set up thus, possibly causing lift? There must be an optimum somewhere?
Airplanes miles above the road.
Are still capable of downforce
Will you make video about your DIY air suspension?
ua-cam.com/play/PL52-wxMBN-EizFZL2F6d7XvgYuS-RRce6.html
Mr Edgar; I have added an undertrays (similar to your insight) to my little Toyota 05 Echo (trying to increase mpg). I have also closed the grill openings (mostly). To keep air moving I have shimmed my hood up at the hinges by 9mm. I was hoping you might comment on this as it is different and i cant seem to find any relevant information on this. I feel it would either a) allow air out of the hood (however theres little flow/ pressure from the grill openings) b0 allow air that would build up a high pressure area at the base of the windshield somewhere to go. Id love some learned thought on this. Much Obliged...
Don't guess (and ask others to guess) - just do some testing. What direction of airflow is shown by tufts?
notice the alpine has a couple of open rectangles ahead of the rear axle/engine - air intakes? and if they are, how effective can they be in such a low pressure area?
Flow depends on pressure differential, so it depends on where the exits are.
Purchased the book really enjoying the read and this series content, looking forward to getting my new Toyota Yaris GR4 and doing some basic wool tuft testing on the car, I've actually found a video of the underside of the car, all in Japanese auto translate made fun viewing , it's a comparison between the new HV Yaris and GR4, the front undertray diffuser has an open duct about 300mm back, looks like an inverted bonnet intake, would this be for airflow into the sump area of the engine for cooling? or the opposite ?
Regards Russ...
Can you link to the video?
@@JulianEdgar
Hello, I'm not sure as most of the title and all the wording is in Japanese, I you type ( Toyota Yaris GR VS HV )in your UA-cam search it comes up with all the GR 4 Yaris videos,
with mine it's about the 10th down the list, a young Japanese Girl wearing a Face mask, they have about 10 videos available as I think they are related to a Toyota garage selling all the available models. The GR4 is black and the HV is blue. Just had another look sorry try this www.youtube.com/watch?ve=Fpo1vkrVQ28
Hope this helps Regards Russ....
Looked at the video. The opening is just a cooling duct for the engine sump or gearbox I'd think. The underside of the car doesn't look anything special - should be easy to improve, especially rear half.
@@JulianEdgar
Thanks for the reply, Yes I was very suprised at how little undertray aero they have under the hole car, as I said previously from other videos I've watched, they have a lot of ducting to brakes and front intercooler. as this is long term car for me, I'm sprinting the car at a few events I've competed at for years as standard, then hoping to add underbody mods for the next year.
Regards Russ...
Mr Edgar its hard to change minds some of came from decates ago what are your thounths vacuum cleaner car
Chaparral 2J i still believe less/non airflow under car much better results like you said from 80s :=)
I don't see any connection between what is covered in this video and the Chaparral 2J fan car - completely different approaches.
Hello Julian I have old 944 and it has very rough bottom do you think its worth to start making it flat or just fit spoiler to front and be done whit it? Ordered the books based on these videos, quite good marketing, it gets some time to get here though :)
Thanks, another job for me to do! But happily I know it will be actually beneficial unlike some modifications I made. 🙂👍
I would think the Porsche 944 an excellent candidate for a full undertray, as the upper body aero is already quite good.
Yes, an undertray is one of the few modifications you can be almost certain will make an improvement.
@@JulianEdgar More modded aerodynamic Porsche 924 World record high speed distance car from 1976 isnt too differend from 944, it has some intresting design at the back and way lower cd 0.268 instead of 0.37. I have usa variant of ugly bumpers and worst fitting front so i suspect the cd is even worst than that in my car, i noticed it has air curtains coming for front wheels not sure if they planned it or its just something that they ended up whit that kinda pumper and tire fenders. My english isnt great sorry if my mumble is some what confusing.
what about the groundforce ....upward force throu the compression between road and floor ?
There is none.
Check the panhard CD lm64 race car from the early sixties, drag coefficient of 0.12! , with a big diffuser and smooth floor. The knowledge has been around for ages :)
he mentioned previous videos of that car i dont know wich one than you for remembered
Yes I have always loved this car. But be very sceptical of claimed drag coefficients of the distant past. (But it least it *did* go fast on not much power = low Cd.)
@@JulianEdgar yeah, drag coefficient will change depending on measurement, available wind tunnel technology etc. Even with modern numbers and methods there are alit of variation. The Tatras from old is also pretty meat with completely flat floors etc, jay Leno showed his on a lift on his youtube channel recently, worth a look :)
Can you explain why more ground clearance means less drag
More ground clearance doesn't necessarily mean less drag . It depends on the underbody roughness and the clearance versus the body length. Page 125 of my book.
Babu Moshai having more ground clearance doesn’t = less drag. Having a flat floor and enough room under the car to let some of the air from the front of the car pass under = less drag
I read it had something to do with the body of revolution.
The VW ID-R has a front splitter/spoiler (not sure how to describe it exactly?) and has been quite successful. Equally, with VW behind it, its probably had a fair amount of engineering thought put into it. So are they as obsolete as you suggest? Or am I missing something?
To be clear, I don't say that out of disrespect, it just seems like quite a big discrepancy and I don't know enough to understand if I am missing something, or if yourself and VW disagree.
It's a full competition car, not a road car! Think of the splitter as being an extension of the undercar aero. Now on a road car, how much bigger can you make the floor area by using a splitter? 5 per cent? So why would you bother doing that rather than optimising undercar aero? See also ua-cam.com/video/TVVWo8jylkA/v-deo.html
@@JulianEdgar So if I understand correctly your argument is less about them being obsolete, and more about the lack of practicality on a regular road car, and how they have been misused in the past as a blockade as opposed to a functional item?
@@aljowen Well, the book is called 'Modifying the Aerodynamics of Your Road Car', and every example in the video is of a road car. Did you watch the other video I cited? Usually, following race car aero practice on road cars is going in the wrong direction.
If you are referring just to front *spoilers* (and not splitters), then yes, I think front spoilers are completely obsolete on road cars. Why block the air you can do something very good with?
@@JulianEdgar Ok, thanks for clearing things up :)
I don't have a background in engineering, but as a hobby I do like making cars for a video game. While the game does simulate drag/aero, it uses a much simplified model, so I don't strictly *need* to worry too much about this stuff, as long as it looks and feels convincing to Joe Bloggs. But I am trying to learn as much as I can so that I can design vehicles that are more convincing and stand up to greater scrutiny. If you are at all curious: ua-cam.com/video/AbBNLBTf0OU/v-deo.html
(If only the game could simulate wool and pressure sensors, but alas)
Anyway, I've watched a bunch of your videos, and subsequently ordered a copy of your book. I look forward to finding out more, and understanding more about what I do.
Answering
"...if you haven't optimized the underside. And why wouldn't you?":
because I don't want to drill holes in the floor and have it rust to pieces in no time in my climate ;)
It'd be great if anyone in the comments section suggested reasonable options for securely attaching undertrays without drilling holes in the car
Stainless steel rivnuts and fasteners, inserted in painted holes? Use the existing fasteners to attach a frame to which the undertray is then attached? Use existing fasteners and where new ones are required, use brackets that attach to pads urethaned to the underfloor? Talk to a local body shop about what they do to rust-proof any holes they need to drill?
It’s called thinking outside the box.
The purpose of a splitter is NOT to stop air from going under the car. Judging by some of your videos, I’m not sure you understand the “how” and “why” of using a front splitter. Don’t get me wrong, I enjoy your videos, I just don’t know if you’re dumbing things down for the masses or if you’re actually a bit foggy on some things. Either way, good day!
You do seem confused indeed. Where do I say the *purpose* of a splitter is to stop airflow going under the car? That is one of its outcomes, and if you understand undercar aero, it's not a good outcome.
@@JulianEdgar well, let’s see. You claim a splitter forces more air to go OVER the car...so doesn’t that mean less air under? That’s what you imply and that is NOT the outcome of using a splitter. That is where YOU seem to be a little confused. Without formal education on the matter, no wind tunnel experience, and no CFD experience, we are supposed to take you at your word as the source of all aerodynamic knowledge? C’mon man, you wrote a book, that’s cool and all but don’t let it go to your head and get all bitter when someone points out an inaccuracy. You have a lot of good info, but you’re off the mark on splitters.
@@carportshenanigans5918 You've changed the proposition of your argument. Previously, it was "The purpose of a splitter is NOT to stop air from going under the car.." where I *never said it was*. Now, the proposition you're mounting is: "You claim a splitter forces more air to go OVER the car.." And that's right, it does. It's not its purpose; it's the outcome. And that's a really stupid outcome if you know anything about undercar aero. As I said: "The idea that you don't want airflow going under your car is decades out of date. Here's why."
@@JulianEdgar Apparently, you didn’t properly read my comment. I said, your statements implied that a splitter stopped air from going under the car...which it doesn’t...not even a little. You’re creating circular straw-man arguments in an attempt to discredit me so you can appear more knowledgeable. It’s a childish technique...although not as childish as the name-calling from one of your other responses. Also, there are a few pretty note-worthy caveats to jamming more air under the car, but not once do you address those...and that gives a false impression of what is good and what isn’t. Not because it doesn’t carry truth, but because it’s not the whole story, some qualifiers are left out. I do like your work with flat floors, vortex generators, wool-tufting and instrumentation with pitot tubes. I really haven’t been trying to make things personal, I’ve been trying to engage in an exchange of ideas, but you reverted to some foolishness on another video and it has honestly turned me off to that idea.
Perhaps do some testing on cars so you can see flow directions? Certainly, less air flows under the car with a splitter fitted because it changes the location of the front stagnation zone.
If you think more airflow is good, raise your vehicle suspension and tell me the results, lol
Well, that would reduce airflow speed under the car, wouldn't it? Not the same thing.
Nice content in this channel. I am a bit confused regarding the need of a front splitter. There are so many examples of card using front splitters and being very effective on track.
Why adding a front splitter will prevent air from going under the car? I mean that ok, it will block the air that has reached the bumper from going under the car but the air that hits the splitter will eventually be spitted and go above and under the car.
For example here is an Alpine going to pikes peaks: www.4troxoi.gr/wp-content/uploads/2023/05/Alpine-A110-Pikes-Peak_03-1024x576.jpg
It has quite a big splitter.
Since that video I have done a lot more testing, and yes, splitters can work well. But it's still better to start with a front undertray if you want to reduce lift / gain downforce. Note: my videos cover road cars, not track cars. And it's not the same!