So refreshing to have someone teaching and encouraging real performance modifications instead of just the usual clout chasing flat brim hat flat-line brain crap like you see on Donut. Thank you for the work you do for the car community!
I want to do this with my Prius, but first have to deal with some dodgy exhaust work a previous owner did. Even on a Prius, there is room for improvement in this area.
I got this book a few months ago, as I have used so much of your knowledge with my WRX beetle over the years. The book is amazing, with so much detail and explanation, I highly recommend it. Sits next to another great book on my shelf.. 21st Century Performance. Thanks for ALL your info, it has been applied so many ways in my builds.🙏🙏
Thank you. You may like my most recent book on suspension - www.amazon.com/Vehicle-Ride-Handling-Modification-Development/dp/B0D7327WSB or Amazon in your country.
Hello Sir, since you questioned and made a video about this multiple times I will share my issues with underbody aero: - Yes, I would like to work with my vehicles rear-axle-back aero. It is basically open and exposed on that area, otherwise pretty ok I believe, (it's an All4 F54 Clubman) - I need a prolonged access to a lift and work area, - I need to determine and buy materials, especially determine the type, strength, and thickness of the them, - I need to mock up the cut. It won't be a mostly flat one I presume because the area has many protruding things as silencer box, differential and possible connection spots. - Connection points are protruding or recessed which make things lot harder to comply with. I would need bosses and pokes to work with. Which means I need to be really precise and crafty. - I don't have the complete set of power tools. And this is where I am at.
I did most of my undertrays using just a set of car ramps. Make a template out of cheap material eg cardboard that you can change. You need to test mock-ups anyway - never build a final item when doing car aero (sounds like you intend building the final item first - never do this). You don't need complete set of power tools.
Play with cardboard for shapes, build prototypes out of plastic sheet from the hardware shop, you need only a few simple hand tools and maybe a heat gun and rivets?
An effective undertray can improve flow through the radiator / engine bay. Very easy to measure different mock-ups on the road. Covered in the book - www.amazon.com/Vehicle-Aerodynamics-Modification-Development-alternative/dp/B0C87VYVL8 or Amazon in your country.
Have have you seen the Porsche with the golf ball like indents underneath? I think there was an experiment where if a car was filled with golf ball indents it’s superior aerodynamically and Porsche employed this with the under tray on a few models . Thank you for another amazing video I learn so much from you.
Watching videos on aero design, my current opinion is that you can't haphazardly apply this type of texture without extensive experimentation. I will say i have have heard that high performance sailboats designed for racing opt for paint jobs with a textured finish, rather than a smooth one, because the amount of smoothness required to minimize skin drag without taking advantage of this effect is very difficult to achieve. Supposedly small objects with high surface areas like golf balls are more likely to benefit from this texture than something like a car as well.
The experiment you mentioned was probably an episode of Mythbusters. The effect of golf ball dimples on a golf ball is that of vortex generators. They ensure flow stays attached longer, reducing the size of the ball's wake, which of course reduces drag. On a car it works in much the same way, except they don't need to be dimples, and they don't need to be on every part of the car. You can use many more effective shapes, and only place them where they're needed. They need to be dimples on a golf ball because they need to be unidirectional. On the undertray of a car (especially one as low-slung as a Porsche) it may be useful to use dimples over a more conventional vortex generator in order to prevent any downward protrusions that could be damaged.
I am liking your videos very much! I live in Brazil, so any thoughts about releasing a e-book version, so it would be easier to get a kindle version? Best regards!
Easy to measure the change in pressure difference across the radiator, with and without an undertray. Sometimes in fact flow is improved. Covered in the book - www.amazon.com/Vehicle-Aerodynamics-Modification-Development-alternative/dp/B0C87VYVL8 or Amazon in your country.
I'd really love to do that as mine tries to take off near 160mph, and i really dont want to change the look of the car too much. It is unfortunately not that easy on an old FR setup that already has troubles cooling the engine and drivetrain
Sir, I own an Alfa Romeo Giulia Q4 and track it. It has no aero packages whatsoever. Other than covering more of my undercarriage, I would like to know if a wicker bill would be an effective means of producing downforce.
My book covers in detail modifications to develop downforce. It's simply not hard to do. www.amazon.com/Vehicle-Aerodynamics-Modification-Development-alternative/dp/B0C87VYVL8 or Amazon in your country.
A few questions: If you were to do this on a car that you didn't have time to maintain yourself (and thus took to a mechanic for any larger repairs), would you still put a tray under the engine bay? Would an undertray have the potential to mess up the airflow from the engine bay and reduce the effectiveness of the radiator, or is the air likely to just find another way out? Can you cover the exhaust downpipe without something melting/burning? Should you?
“If you want aero so your mates see it and say oh that looks good, this isn’t for you. But if you want something that just works…” Por que no los dos? It’s getting cheaper almost every day to custom order composite parts if you make the template first, which your book teaches us how to do. You absolutely can use the book to design and test an effective under tray and the flashiest of body aero canards, spoilers, dams, splitters, and diffusers that actually work for your car. Or be sensible and just do the undertray. I just want my fellow silly gits to know they can also use this to make silly but functional mods. As always: don’t guess, Test! It’s surprisingly fun.
@@JulianEdgar URLs almost always get comments auto culled, but there are a few companies that do custom composites for automotive enthusiasts (rock west, protech, etc). Once you’ve tested your template you make it into a mold. Depending on the company, and your budget, they’ll have standards for how much of the molding process they want you to do yourself, how many casts you’ll get, etc. If you’ll pay top dollar, some will take the template and do all the work, but that’s a lot of labor hours to buy. Though, when all the process stuff is in stock, there is a big community for entirely DIY carbon parts. GoFastMatt’s current salt flat build (called “slow car fast” I think) has a few episodes of him trying it out, which is how I yolo’d into it.
@@JulianEdgar Oh, I’m sorry, I wouldn’t really know. I do know that your average village idiot (me) can go from “neat RUclips videos” to a tested and working custom carbon front splitter & removable canards for under $600, including the cost of tools I didn’t have, renting shed space for two days, and your book. If I was into this as a full hobby, I am confident I could get individual parts down to barely more than materials cost pretty quickly, since start-up tools are a fixed cost. But, I just wanted to have more fun in canyons and mountain roads in my hatchback for less than the cost of a single pre-made aftermarket carbon part of dubious functionality, I wasn’t trying to do Pikes Peak or N-Ring times (which it seems some of your audience genuinely might be closer to doing, from other comments I’ve seen on other videos). It really is an era where anyone can make these parts, and they can be as strictly functional and subtle, or as flashy as one likes.
Most of the Honda's modifications weren't aimed at improved mpg. My book covers the likely relationship between changes in drag and mileage on different types of cars.
I have a 1971 Chevelle. My question is is the front bumper too high from the actual level of the undercar for a trey to work? Or should i try to install a semi air dam before the undertrey?
@@JulianEdgar air dam not even down to the plane of subframe? Should undertray then be curved upwards in the front and join the bumper that way? Like a boat.
I would worry about some things. Firstly i wouldn't want my custom undertray to fall off on the road while driving in case a pot hole or pavement or rock contact. Secondly i have my concerns about water accumulation and possible rust "friendly " conditions if i install a big undertray. Thirdly i have worries about where to screw and how to safely secure the undertray and not damage the car underneath in the future. Most of those are probably dealt with in the book i am sure.
Hi Julian, looking at making a front splitter/undertray for my Megane RS track car. Would it be more beneficial to have the downward slope at the front or just have it flat, as I won't be running a complete floor? I'd also be keen to hear your thoughts on the Ferrari 296 GT3 car as it has a very aggressive slope angling into the front undertray. Cheers
Guessing is pointless. Measurement of mock-ups (easy - eg pressures) is the key. Covered in the book - www.amazon.com/Vehicle-Aerodynamics-Modification-Development-alternative/dp/B0C87VYVL8 or Amazon in your country.
My wife just bought a 2014 BMW 328d xDrive. I'm trying to maximize fuel efficiency. Already switched from 225/50R17 tires to 205/60R16 tires. The front of the car has very complete undertray coverage but the back has a lot of open areas, especially below the trunk. Do you think this sort of car would generate less drag with the rear underbody completely closed off with additional panels? Thanks!
Got a new MG HS which has no undertrays, only a small one under the radiators. So lots of room for improvement. Does the height of the undertray make much difference in the downforce generated (the MG HS is an SUV)
Detailed drag reduction techniques are covered in the book. www.amazon.com/Vehicle-Aerodynamics-Modification-Development-alternative/dp/B0C87VYVL8 or Amazon in your country.
This guy reads my mind. I would ask/suggest for a video about under the car aero mods. And boom, he delivers again
So refreshing to have someone teaching and encouraging real performance modifications instead of just the usual clout chasing flat brim hat flat-line brain crap like you see on Donut.
Thank you for the work you do for the car community!
Thank you.
Great topic of discussion, thanks for beating it into us, we're stuck in mythical paradigms and need help.
I want to do this with my Prius, but first have to deal with some dodgy exhaust work a previous owner did. Even on a Prius, there is room for improvement in this area.
I got this book a few months ago, as I have used so much of your knowledge with my WRX beetle over the years. The book is amazing, with so much detail and explanation, I highly recommend it. Sits next to another great book on my shelf.. 21st Century Performance. Thanks for ALL your info, it has been applied so many ways in my builds.🙏🙏
Thank you. You may like my most recent book on suspension - www.amazon.com/Vehicle-Ride-Handling-Modification-Development/dp/B0D7327WSB or Amazon in your country.
Hello Sir, since you questioned and made a video about this multiple times I will share my issues with underbody aero:
- Yes, I would like to work with my vehicles rear-axle-back aero. It is basically open and exposed on that area, otherwise pretty ok I believe, (it's an All4 F54 Clubman)
- I need a prolonged access to a lift and work area,
- I need to determine and buy materials, especially determine the type, strength, and thickness of the them,
- I need to mock up the cut. It won't be a mostly flat one I presume because the area has many protruding things as silencer box, differential and possible connection spots.
- Connection points are protruding or recessed which make things lot harder to comply with. I would need bosses and pokes to work with. Which means I need to be really precise and crafty.
- I don't have the complete set of power tools.
And this is where I am at.
I did most of my undertrays using just a set of car ramps. Make a template out of cheap material eg cardboard that you can change. You need to test mock-ups anyway - never build a final item when doing car aero (sounds like you intend building the final item first - never do this). You don't need complete set of power tools.
Genuine concerns I share too
Play with cardboard for shapes, build prototypes out of plastic sheet from the hardware shop, you need only a few simple hand tools and maybe a heat gun and rivets?
One of the challenges I face is heat retention due to the LS2. The amount of heat that engine and heat output is crazy.
An effective undertray can improve flow through the radiator / engine bay. Very easy to measure different mock-ups on the road. Covered in the book - www.amazon.com/Vehicle-Aerodynamics-Modification-Development-alternative/dp/B0C87VYVL8 or Amazon in your country.
Have have you seen the Porsche with the golf ball like indents underneath? I think there was an experiment where if a car was filled with golf ball indents it’s superior aerodynamically and Porsche employed this with the under tray on a few models . Thank you for another amazing video I learn so much from you.
Could be golf ball indents, could be many other shapes - they all work in a similar way.
Watching videos on aero design, my current opinion is that you can't haphazardly apply this type of texture without extensive experimentation. I will say i have have heard that high performance sailboats designed for racing opt for paint jobs with a textured finish, rather than a smooth one, because the amount of smoothness required to minimize skin drag without taking advantage of this effect is very difficult to achieve. Supposedly small objects with high surface areas like golf balls are more likely to benefit from this texture than something like a car as well.
The experiment you mentioned was probably an episode of Mythbusters. The effect of golf ball dimples on a golf ball is that of vortex generators. They ensure flow stays attached longer, reducing the size of the ball's wake, which of course reduces drag.
On a car it works in much the same way, except they don't need to be dimples, and they don't need to be on every part of the car. You can use many more effective shapes, and only place them where they're needed.
They need to be dimples on a golf ball because they need to be unidirectional. On the undertray of a car (especially one as low-slung as a Porsche) it may be useful to use dimples over a more conventional vortex generator in order to prevent any downward protrusions that could be damaged.
I am liking your videos very much! I live in Brazil, so any thoughts about releasing a e-book version, so it would be easier to get a kindle version? Best regards!
No, never. E-books get pirated within weeks.
Very interested in doing this myself!! Thanks for the inspiration for the average enthusiast!
Be careful though to evacuate the hot air coming from the radiator.
Easy to measure the change in pressure difference across the radiator, with and without an undertray. Sometimes in fact flow is improved. Covered in the book - www.amazon.com/Vehicle-Aerodynamics-Modification-Development-alternative/dp/B0C87VYVL8 or Amazon in your country.
I'd really love to do that as mine tries to take off near 160mph, and i really dont want to change the look of the car too much. It is unfortunately not that easy on an old FR setup that already has troubles cooling the engine and drivetrain
It is actually quite easy with a FR driveline. You just integrate radiator flow into the testing and design.
Do you know when the book will be available again? At least on Amazon in the US, for me it is listed as "currently unavailable".
I’ve contacted Amazon.
It's now available again - not sure what happened.
Sir, I own an Alfa Romeo Giulia Q4 and track it. It has no aero packages whatsoever. Other than covering more of my undercarriage, I would like to know if a wicker bill would be an effective means of producing downforce.
My book covers in detail modifications to develop downforce. It's simply not hard to do. www.amazon.com/Vehicle-Aerodynamics-Modification-Development-alternative/dp/B0C87VYVL8 or Amazon in your country.
A few questions:
If you were to do this on a car that you didn't have time to maintain yourself (and thus took to a mechanic for any larger repairs), would you still put a tray under the engine bay?
Would an undertray have the potential to mess up the airflow from the engine bay and reduce the effectiveness of the radiator, or is the air likely to just find another way out?
Can you cover the exhaust downpipe without something melting/burning? Should you?
All covered in the book. www.amazon.com/Vehicle-Aerodynamics-Modification-Development-alternative/dp/B0C87VYVL8 or Amazon in your country.
Yeah but if other people can't see it, then you won't gain the extra +25 HP! 😂
“If you want aero so your mates see it and say oh that looks good, this isn’t for you. But if you want something that just works…”
Por que no los dos?
It’s getting cheaper almost every day to custom order composite parts if you make the template first, which your book teaches us how to do.
You absolutely can use the book to design and test an effective under tray and the flashiest of body aero canards, spoilers, dams, splitters, and diffusers that actually work for your car.
Or be sensible and just do the undertray. I just want my fellow silly gits to know they can also use this to make silly but functional mods.
As always: don’t guess, Test!
It’s surprisingly fun.
Do you have some links for custom composite parts from templates? I must admit I never thought of taking that approach.
@@JulianEdgar URLs almost always get comments auto culled, but there are a few companies that do custom composites for automotive enthusiasts (rock west, protech, etc).
Once you’ve tested your template you make it into a mold. Depending on the company, and your budget, they’ll have standards for how much of the molding process they want you to do yourself, how many casts you’ll get, etc. If you’ll pay top dollar, some will take the template and do all the work, but that’s a lot of labor hours to buy.
Though, when all the process stuff is in stock, there is a big community for entirely DIY carbon parts. GoFastMatt’s current salt flat build (called “slow car fast” I think) has a few episodes of him trying it out, which is how I yolo’d into it.
Oh, OK - so not much has changed. I was hoping from what you said that the process was now automated to a much higher degree.
@@JulianEdgar Oh, I’m sorry, I wouldn’t really know.
I do know that your average village idiot (me) can go from “neat RUclips videos” to a tested and working custom carbon front splitter & removable canards for under $600, including the cost of tools I didn’t have, renting shed space for two days, and your book.
If I was into this as a full hobby, I am confident I could get individual parts down to barely more than materials cost pretty quickly, since start-up tools are a fixed cost.
But, I just wanted to have more fun in canyons and mountain roads in my hatchback for less than the cost of a single pre-made aftermarket carbon part of dubious functionality, I wasn’t trying to do Pikes Peak or N-Ring times (which it seems some of your audience genuinely might be closer to doing, from other comments I’ve seen on other videos).
It really is an era where anyone can make these parts, and they can be as strictly functional and subtle, or as flashy as one likes.
I did the best I could on the belly of a Durango RT I've built for drag racing.
What sort of improvements do you see in terms of mpg on your Honda?
Most of the Honda's modifications weren't aimed at improved mpg. My book covers the likely relationship between changes in drag and mileage on different types of cars.
I have a 1971 Chevelle. My question is is the front bumper too high from the actual level of the undercar for a trey to work? Or should i try to install a semi air dam before the undertrey?
No air dam - but it needs to be a proper undertray, not just a bit of one.
@@JulianEdgar air dam not even down to the plane of subframe? Should undertray then be curved upwards in the front and join the bumper that way? Like a boat.
I would worry about some things. Firstly i wouldn't want my custom undertray to fall off on the road while driving in case a pot hole or pavement or rock contact.
Secondly i have my concerns about water accumulation and possible rust "friendly " conditions if i install a big undertray.
Thirdly i have worries about where to screw and how to safely secure the undertray and not damage the car underneath in the future. Most of those are probably dealt with in the book i am sure.
Like any car modification, good workmanship is important.
Good stuff!
Thanks for the video
I'd love to buy it but it's 110 USD shipped.. do you have a link for a digital version?
No
What's the benefit for a daily driver?
Better handling and stability at highway speeds. Also, if the car is really bad underneath to start with, better mileage.
@@JulianEdgar My 1993 240sx convertible is horrible underneath
Hi Julian, looking at making a front splitter/undertray for my Megane RS track car. Would it be more beneficial to have the downward slope at the front or just have it flat, as I won't be running a complete floor? I'd also be keen to hear your thoughts on the Ferrari 296 GT3 car as it has a very aggressive slope angling into the front undertray. Cheers
Guessing is pointless. Measurement of mock-ups (easy - eg pressures) is the key. Covered in the book - www.amazon.com/Vehicle-Aerodynamics-Modification-Development-alternative/dp/B0C87VYVL8 or Amazon in your country.
My wife just bought a 2014 BMW 328d xDrive. I'm trying to maximize fuel efficiency. Already switched from 225/50R17 tires to 205/60R16 tires. The front of the car has very complete undertray coverage but the back has a lot of open areas, especially below the trunk. Do you think this sort of car would generate less drag with the rear underbody completely closed off with additional panels? Thanks!
Yes, but it will be a small change in fuel efficiency only. Worth trialling a mock-up.
Hi Julian, do you have any ways of writing to you privately? e.g. by email and such? Cheers
My email address is on this channel under 'About'.
Got a new MG HS which has no undertrays, only a small one under the radiators. So lots of room for improvement. Does the height of the undertray make much difference in the downforce generated (the MG HS is an SUV)
Yes.
How would you improve the aero of a Lotus Elise to make it less draggy?
Detailed drag reduction techniques are covered in the book. www.amazon.com/Vehicle-Aerodynamics-Modification-Development-alternative/dp/B0C87VYVL8 or Amazon in your country.
S2000 owners: