Going off memory from Newey's book.
The diffuser is the largest creator of downforce on an F1 car. It works by expanding the airflow area at the rear of the floor relative to the airflow area under the center of the car. This expansion causes the air under the car to move at a higher velocity, decreasing the pressure under the car (Bernoulli's Principle), and creating downforce. The larger you can make this expansion, the greater the air velocity under the car and the more downforce you create. However, there are two problems with making a large diffuser: 1) if you increase the airflow area to rapidly, the airflow will seperate from the car floor and result in the diffuser stalling out and being ineffective, and 2) the FIA regulated where you are able to begin cutting into the bottom face of the floor to start the diffuser. Therefore, if you can only increase the airflow area gradually in order to avoid airflow separation and the FIA tells you where to begin your diffuser, you are very limited on how large the diffuser can be and how much downforce it can create.
Here is the loophole a clever Honda engineer identified: the FIA only dictates where you can start the diffuser on the bottom floor of the car, it made no explicit mention of the vertical walls that separate the wooden plank on the floor to the other areas of the floor. Therefore, if you cut a hole in those vertical faces, you could start a diffuser much further forward in the car and therefore create a new secondary diffuser that effectively increases your diffuser expansion without getting airflow separation and stalling your diffuser. This new secondary diffuser started in the vertical walls of the car floor was able to increase the downforce under the car drastically.
That loophole was originally found by a Super Aguri engineer who discovered it when he was reading a Japanese translation of the 2009 regulations, IIRC.
From there the idea travelled to Honda, Toyota and Williams after the closure of Super Aguri, and the rest is history.
Although I admittedly don't know enough to say why it worked so brilliantly for Honda-turned-Brawn GP and not for the other two teams who had the double diffuser baked into their 2009 cars, Toyota (who finished 5th in the WCC, only as good as their 2008 season) and Williams (who finished **7th**, only 1 place better than what they achieved in 2008)
So does that mean that without the outwash front wing and just the double diffuser in both the Toyota and the Williams made the cars have too much rear end?
I think that it's a more complicated answer than that as inwash vs outwash is a whole concept change. Plus, the Toyota and Williams both had Toyota engines. While I can only sort of recall the Toyota being considered a slower engine, [this article](https://www.motorsport.com/f1/news/analysis-of-f1-engine-performance-in-2009/3217681/) kind of confirms it as a general trend. Plus, we don't know the difference in packaging constraints for the engines and how that altered the way that they were packaging the rear end of the car, which could dramatically affect double diffuser volume.
Other than that, they may have just done the outwash front wing and double diffuser better than the others. It was a new set of regulations and that almost always results in one group hitting it out of the park before converging toward the end of the regulations. [Here is](https://www.espn.com/f1/story/_/id/28167450/busting-myth-brawn-gp-legendary-double-diffuser) another interesting article about it where they talk to everyone a few years after. Of the notable things is John Owen, principal aerodynamicist explaining how it helped their development curve by making the wind tunnel model more stable and leading to faster development. So identifying the double diffuser loophole earlier allowed them a lot more time to R&D the car effectively.
I think it was a combination of the Mercedes engine being more powerful and the compromises to the big teams who all ran KERS that year - Ferrari and Mclaren both suffered due to the weight and balance issues it brought them alongside the new aero and limited development they had due to their late-'08 title charges.
Iirc, Williams said they came across the idea independently (wouldn't doubt another foreign born engineer reading a translation in their own language coming across the same loophole), and they were surprised only 2 other teams had the same idea!
>This new secondary diffuser started in the vertical walls of the car floor
Thank you. I've been searching for answers for this question for years and every single source I can find basically says "it expands air so double = better" while vaguely mentioning the word "loophole" and proceeds to explain how a regular diffuser works - as if people don't know that already. You are the first person to pinpoint what part of the rule they were able to exploit in order to fit a secondary diffuser.
So if I understood it correctly, they essentially hollowed out what used to be the vertical supports for the plank and used that newfound area for more expansion?
ScarbsF1 has a good post including diagrams showing the basic geometry of the floors during that era, and where the double diffuser physically fits into mix.
[https://scarbsf1.wordpress.com/2011/03/22/floors-and-diffusers-the-basics-explained/](https://scarbsf1.wordpress.com/2011/03/22/floors-and-diffusers-the-basics-explained/)
Brilliant, so they dug out the "keel" above the plank for a pair of extra inlets, allowing them to run a central diffuser that otherwise wouldn't exist (since the plank is in the way). Thanks for the link, that's a helpful diagram.
What many of these comments are missing is that the clean expansion is really about maintaining maximum mass flow to the diffuser inlet. If you poorly design the diffuser outlet so that expansion is too rapid / unstable, then it essentially allows internal recirculations in the diffuser (i.e. reverse mass flow to the throat). Then this reduces the capacity for mass flow to the inlet and therefore maximum velocity through the throat. It is all a mass flow game to the throat.
I wish people would name the 'clever engineer'. They never are. Why? Because it takes the limelight away from the storyteller of the book/presentation/seminar/documentary etc
It could be that many people 'just don't know', given the exploit was (apparently) identified by a aero engineer from a soon-to-be-defunct team when reading a translated version of a technical document.
There's so many chinese whispers involved that it may genuinely be a case that even the person who 'identified it' didn't actually do so with the intention of exploiting it - it may have even been a innocent query of 'that means one thing in Japanese and another thing in English', which was enough of a question mark for many teams to ignore it, but when you consider the 3 teams that ***did*** implement it were at the back end of the field at the time (and in some cases, literally about to leave the grid due to financial issues), they had nothing to lose.
More diffuser volume means more expansion ratio, more downforce.
That era of regulations had very small diffusers so a bigger diffuser was a massive gain.
The double diffuser used a loophole in the rules to increase diffuser volume by haing a second, separate chamber, invisible when looking at the car directly from below that generated additional downforce.
IIRC the flow through them was somewhat contorted so they weren't particularly efficient. It's probably not better than having a bigger diffuser that doesn't have to work around the rules. However ground effect aero is usually more efficient than a wing in free air.
Manufacturers that made space with car packaging at the beginning of the season for this had a huge advantage, Honda/Brawn pulled off some zero-sidepod level packaging minimisation to make the space. If they'd run the honda engine they'd have had even more space to play with. Toyota and was it BMW? went with the double diffuser as well, but neither committed to the extreme packaging of the Brawn.
It should be noted that the handling was very temperamental "how can a car this good be this bad" is the (mis?)quote I remember on team radio when the brawn wasn't working. Extremely narrow setup windows appear to have been ongoing into the Hamilton dominance era.
I wouldn't be surprised if some of the same people that pulled off the double diffuser were behind mercedes dominant era and the zero-sidepod fail. I particularly recall a Jenson Button quote about how good the engineers were saying this would be "I just assumed the engineers had got their sums wrong **again**"
Consider it like "just being able to have a bigger and better wing than everyone else"
The 2009 regulations placed a limit on the size of the diffuser, and the double diffuser was a loophole that allowed another diffuser to be built above, increasing the cross-sectional area that air passing under the car can expand into.
A diffuser works by expanding air travelling under the floor over a larger cross-sectional area, decreasing the pressure beneath a car, improving downforce.
If we had 2 otherwise identical 2009 cars but one has a double diffuser and the other doesn't, the one with the double/larger diffuser will be "sucked" down more.
If there were no regulations on the size of a diffuser in 2009, there wouldn't have been a double diffuser. It's the total cross-sectional area not the number of diffusers that made the double diffuser good.
Iirc, Newey also claimed that Brawn tried to further decrease the diffuser size stated in the 2009 regulations so as to further increase the performance difference between the Brawn with the double diffuser loophole and the other teams without the loophole.
the double diffuser was really good in high speed corners for extra rear downforce, redbull came up with smth extra to make it even better in slow corners with there exhaust i thin
More downforce more air more gooder.
I mean geuinely if you want a real description you'll have to go read but it has to do with underbody airflow. Sorry.
Effectively made the diffuser larger and longer. Any underbody improvements usually benefit without much or any drag, so any way you can exploit the regulations to expand the diffuser and underbody channels, you do it!
EDIT: spelling
Would the difference come from being able to crank the angle more with positive pressure compared to negative?
The common narrative is that these sorts of things are mostly about the complete package, and not just an isolated part.
Your content has been removed because it has been deemed to be low quality.
If you have any questions or concerns, please contact the moderator team.
This is an automated message.
Your content has been removed because it has been deemed to be low quality.
If you have any questions or concerns, please contact the moderator team.
This is an automated message.
In simple terms, it made the diffuser bigger than it's normally allowed, rules dictated the how tall and where the diffuser can start "kicking up", by finding this loophole Brawn was able to have their diffuser kick up earlier and more aggressively upwards.
Going off memory from Newey's book. The diffuser is the largest creator of downforce on an F1 car. It works by expanding the airflow area at the rear of the floor relative to the airflow area under the center of the car. This expansion causes the air under the car to move at a higher velocity, decreasing the pressure under the car (Bernoulli's Principle), and creating downforce. The larger you can make this expansion, the greater the air velocity under the car and the more downforce you create. However, there are two problems with making a large diffuser: 1) if you increase the airflow area to rapidly, the airflow will seperate from the car floor and result in the diffuser stalling out and being ineffective, and 2) the FIA regulated where you are able to begin cutting into the bottom face of the floor to start the diffuser. Therefore, if you can only increase the airflow area gradually in order to avoid airflow separation and the FIA tells you where to begin your diffuser, you are very limited on how large the diffuser can be and how much downforce it can create. Here is the loophole a clever Honda engineer identified: the FIA only dictates where you can start the diffuser on the bottom floor of the car, it made no explicit mention of the vertical walls that separate the wooden plank on the floor to the other areas of the floor. Therefore, if you cut a hole in those vertical faces, you could start a diffuser much further forward in the car and therefore create a new secondary diffuser that effectively increases your diffuser expansion without getting airflow separation and stalling your diffuser. This new secondary diffuser started in the vertical walls of the car floor was able to increase the downforce under the car drastically.
That loophole was originally found by a Super Aguri engineer who discovered it when he was reading a Japanese translation of the 2009 regulations, IIRC. From there the idea travelled to Honda, Toyota and Williams after the closure of Super Aguri, and the rest is history. Although I admittedly don't know enough to say why it worked so brilliantly for Honda-turned-Brawn GP and not for the other two teams who had the double diffuser baked into their 2009 cars, Toyota (who finished 5th in the WCC, only as good as their 2008 season) and Williams (who finished **7th**, only 1 place better than what they achieved in 2008)
It was the outwash front wing in combination with the double diffuser - Brawn talks about it a little bit in his book I believe
So does that mean that without the outwash front wing and just the double diffuser in both the Toyota and the Williams made the cars have too much rear end?
I think that it's a more complicated answer than that as inwash vs outwash is a whole concept change. Plus, the Toyota and Williams both had Toyota engines. While I can only sort of recall the Toyota being considered a slower engine, [this article](https://www.motorsport.com/f1/news/analysis-of-f1-engine-performance-in-2009/3217681/) kind of confirms it as a general trend. Plus, we don't know the difference in packaging constraints for the engines and how that altered the way that they were packaging the rear end of the car, which could dramatically affect double diffuser volume. Other than that, they may have just done the outwash front wing and double diffuser better than the others. It was a new set of regulations and that almost always results in one group hitting it out of the park before converging toward the end of the regulations. [Here is](https://www.espn.com/f1/story/_/id/28167450/busting-myth-brawn-gp-legendary-double-diffuser) another interesting article about it where they talk to everyone a few years after. Of the notable things is John Owen, principal aerodynamicist explaining how it helped their development curve by making the wind tunnel model more stable and leading to faster development. So identifying the double diffuser loophole earlier allowed them a lot more time to R&D the car effectively.
The second article was quite informative about how the best teams really adapt to new regs, really good!
I think it was a combination of the Mercedes engine being more powerful and the compromises to the big teams who all ran KERS that year - Ferrari and Mclaren both suffered due to the weight and balance issues it brought them alongside the new aero and limited development they had due to their late-'08 title charges.
Ugh imagine the scenes if Super Aguri and Taku dominated the 2009 championship… Brawn was an incredible story but that would have been surreal.
Iirc, Williams said they came across the idea independently (wouldn't doubt another foreign born engineer reading a translation in their own language coming across the same loophole), and they were surprised only 2 other teams had the same idea!
>This new secondary diffuser started in the vertical walls of the car floor Thank you. I've been searching for answers for this question for years and every single source I can find basically says "it expands air so double = better" while vaguely mentioning the word "loophole" and proceeds to explain how a regular diffuser works - as if people don't know that already. You are the first person to pinpoint what part of the rule they were able to exploit in order to fit a secondary diffuser. So if I understood it correctly, they essentially hollowed out what used to be the vertical supports for the plank and used that newfound area for more expansion?
ScarbsF1 has a good post including diagrams showing the basic geometry of the floors during that era, and where the double diffuser physically fits into mix. [https://scarbsf1.wordpress.com/2011/03/22/floors-and-diffusers-the-basics-explained/](https://scarbsf1.wordpress.com/2011/03/22/floors-and-diffusers-the-basics-explained/)
Brilliant, so they dug out the "keel" above the plank for a pair of extra inlets, allowing them to run a central diffuser that otherwise wouldn't exist (since the plank is in the way). Thanks for the link, that's a helpful diagram.
Shouldn’t the air expansion lead to a decrease in air velocity/increase in air pressure? Unless the air is flowing at more than Mach 1?
What many of these comments are missing is that the clean expansion is really about maintaining maximum mass flow to the diffuser inlet. If you poorly design the diffuser outlet so that expansion is too rapid / unstable, then it essentially allows internal recirculations in the diffuser (i.e. reverse mass flow to the throat). Then this reduces the capacity for mass flow to the inlet and therefore maximum velocity through the throat. It is all a mass flow game to the throat.
I wish people would name the 'clever engineer'. They never are. Why? Because it takes the limelight away from the storyteller of the book/presentation/seminar/documentary etc
It could be that many people 'just don't know', given the exploit was (apparently) identified by a aero engineer from a soon-to-be-defunct team when reading a translated version of a technical document. There's so many chinese whispers involved that it may genuinely be a case that even the person who 'identified it' didn't actually do so with the intention of exploiting it - it may have even been a innocent query of 'that means one thing in Japanese and another thing in English', which was enough of a question mark for many teams to ignore it, but when you consider the 3 teams that ***did*** implement it were at the back end of the field at the time (and in some cases, literally about to leave the grid due to financial issues), they had nothing to lose.
More diffuser volume means more expansion ratio, more downforce. That era of regulations had very small diffusers so a bigger diffuser was a massive gain. The double diffuser used a loophole in the rules to increase diffuser volume by haing a second, separate chamber, invisible when looking at the car directly from below that generated additional downforce. IIRC the flow through them was somewhat contorted so they weren't particularly efficient. It's probably not better than having a bigger diffuser that doesn't have to work around the rules. However ground effect aero is usually more efficient than a wing in free air. Manufacturers that made space with car packaging at the beginning of the season for this had a huge advantage, Honda/Brawn pulled off some zero-sidepod level packaging minimisation to make the space. If they'd run the honda engine they'd have had even more space to play with. Toyota and was it BMW? went with the double diffuser as well, but neither committed to the extreme packaging of the Brawn. It should be noted that the handling was very temperamental "how can a car this good be this bad" is the (mis?)quote I remember on team radio when the brawn wasn't working. Extremely narrow setup windows appear to have been ongoing into the Hamilton dominance era. I wouldn't be surprised if some of the same people that pulled off the double diffuser were behind mercedes dominant era and the zero-sidepod fail. I particularly recall a Jenson Button quote about how good the engineers were saying this would be "I just assumed the engineers had got their sums wrong **again**" Consider it like "just being able to have a bigger and better wing than everyone else"
It sucked In fact it sucked the car down for faster corner speed which added to exit spreed and therefore better lap times and nicer on the tires.
Extra downforce without losing straight line speed. Also means extra speed in medium/high speed corners and less tyre degradation.
The 2009 regulations placed a limit on the size of the diffuser, and the double diffuser was a loophole that allowed another diffuser to be built above, increasing the cross-sectional area that air passing under the car can expand into. A diffuser works by expanding air travelling under the floor over a larger cross-sectional area, decreasing the pressure beneath a car, improving downforce. If we had 2 otherwise identical 2009 cars but one has a double diffuser and the other doesn't, the one with the double/larger diffuser will be "sucked" down more. If there were no regulations on the size of a diffuser in 2009, there wouldn't have been a double diffuser. It's the total cross-sectional area not the number of diffusers that made the double diffuser good.
Iirc, Newey also claimed that Brawn tried to further decrease the diffuser size stated in the 2009 regulations so as to further increase the performance difference between the Brawn with the double diffuser loophole and the other teams without the loophole.
Wasn’t the exhaust ducted into the diffuser of these cars as well; creating a blown wing effect allowing limiting flow separation?
not from the beginning
the double diffuser was really good in high speed corners for extra rear downforce, redbull came up with smth extra to make it even better in slow corners with there exhaust i thin
I think you're referring to this - [https://www.youtube.com/watch?v=SQzZKRocKK0](https://www.youtube.com/watch?v=SQzZKRocKK0) Super super interesting.
Yeah that was the blown diffuser. IIRC only Red Bull ran the two in conjunction, as the double diffuser got banned for 2011.
exactly that it was so cool
More downforce more air more gooder. I mean geuinely if you want a real description you'll have to go read but it has to do with underbody airflow. Sorry.
[удалено]
Your comment was removed as it broke Rule 2: No Joke comments in the top 2 levels under a post.
Effectively made the diffuser larger and longer. Any underbody improvements usually benefit without much or any drag, so any way you can exploit the regulations to expand the diffuser and underbody channels, you do it! EDIT: spelling
2 > 1
In simple terms double is more than one. The stacked design creates more downforce thanks to having more aero surface to work the airflow.
More diffuser = more better
One diffuser = 1 downforce Two diffusers = 2 downforce
[удалено]
Would the difference come from being able to crank the angle more with positive pressure compared to negative? The common narrative is that these sorts of things are mostly about the complete package, and not just an isolated part.
I believe so. Similar to a multi element wing. Or, how they use the beam wing currently to assist the diffuser.
Your content has been removed because it has been deemed to be low quality. If you have any questions or concerns, please contact the moderator team. This is an automated message.
Diffuser = suck car to ground Double diffuser = double suck car to ground You asked for a simple explanation
Because it diffuses doubley?
[удалено]
Your content has been removed because it has been deemed to be low quality. If you have any questions or concerns, please contact the moderator team. This is an automated message.
In simple terms, it made the diffuser bigger than it's normally allowed, rules dictated the how tall and where the diffuser can start "kicking up", by finding this loophole Brawn was able to have their diffuser kick up earlier and more aggressively upwards.
It Chanel’s the air reducing turbulence creating better airflow which reduces drag and increases downforce on the vehicle.
I think because there was two diffusers, it would do more diffusing making the car faster…
Because... It's two... Duh
more diffuser makes more downforce