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I have no idea... I don’t know enough about fractions.... I think fractions are either characterized as new or late or very common for dem to nominate or / using numbers
Rear diffusers...let's see them!!!
- Thread starter MetalSpikeRacing
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I have no idea... I don’t know enough about fractions.... I think fractions are either characterized as new or late or very common for dem to nominate or / using numbers
I drove on a HUGE MASSIVE Florida rain, in the past I always used to have issues with water hitting my belts, after my Difflow, NONE, no belts slipping .... that is amazing!
Oscar
Oscar
Sorry, I wasn't exactly talking to you specifically. But now that I have your attention, I hope you could share some more information below...
Appreciate the history lesson on the FXMD NSX diffuser.
FWIW, from my limited understanding of diffusers: the strakes are there to straighten the airflow and prevent the higher speed, lower pressure air from spilling into the central tunnel from the sides.
Whatever design parameters Difflow decided to build against was their own decision. My conclusion on what Difflow was designing against is based on the install pictures of the Difflow pictures I have seen: it simply looks like the diffuser angle was determined by necessary clearance for the stock exhaust and the rearmost attachment point. If that is incorrect: only Difflow can clarify.
As far as the divergence angle of the diffuser is concerned: 7 degrees is within the general rule of thumb to optimize drag vs downforce for sports cars. The actual divergence angle is limited by flow separation (which strakes also help limit), depends on the the Reynolds number at the inlet and achievable length of the diffuser itself. Or simply put, how flat of a floor can the car have?
As far as misleading data, may you please clarify the colors in the CFD pressure simulation of the 430 you posted later? In terms of decreasing relative pressure does it is it red, orange, yellow, green, blue? If so, doesn't that mean the green area circled has a higher pressure area?
Just here trying to gain some wisdom from those that know a little more than me.
Oh, and for more diffuser pictures:
http://www.nsxprime.com/forum/showthread.php?t=116208
and
http://www.nsxprime.com/forum/showpost.php?p=1471151&postcount=1373
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if you want more wisdom.. reread my posts and you have all the answers to all your questions... this time try not to get all boiled up inside and you will see them...
and I reffer to and use the term rake as the angle.. not the fins... so no need to use the word strake anymore than you did because I wasnt confusing them at all.
Funny how you know so much but misconfused so much in the first post about fxmd.
and your welcome for the history lesson and the knowledge
and if you think I dont know how to read a CFD pressure chart... he is your color curve ball
if you want more wisdom.. reread my posts and you have all the answers to all your questions... this time try not to get all boiled up inside and you will see them...
and I reffer to and use the term rake as the angle.. not the fins... so no need to use the word strake anymore than you did because I wasnt confusing them at all.
Funny how you know so much but misconfused so much in the first post about fxmd.
and your welcome for the history lesson and the knowledge
and if you think I dont know how to read a CFD pressure chart... he is your color curve ball
I'm not boiled up inside at all.
If anything, I think we both agree the divergence angle and or length of most of the diffusers available on the market are optimistically ambitious especially without a floor to feed them properly.
Hopefully my explanation of why fins are used in diffusers is satisfactory.
My initial post listing the FXMD diffusers was to illustrate the point to the general public effective aluminum diffusers do exist, not to chronologically document of the FXMD diffuser development.
To your point, FXMDs aero package most likely became more efficient with the addition of their aerodynamicist, Andrew Brilliant and their old diffuser evolved into part of a better performing package.
The CFD pressure contour plots are fun to look at, but including a scale to show what the colors represent makes them easier to understand. In both of the 430 plots it seems like they are showing a slightly lower pressure at the inlet of the diffuser relative to the center of the car. However, guessing what the colors mean, it looks like the pressure further decreases along the diffuser. So does this mean even with a highly evolved underbody of the 430, the diffuser is not perfect?
In your opinion, do you think the stock exhaust system of the NSX acts as a sort of diffuser? Given what Honda did for the NSX-R: by not giving the diffuser a steep rake, from a side profile, it seems like if the exhaust acted as a diffuser it would extended the "diffuser" like a multi-element wing?
And for a few more Diffuser picts:
http://2.bp.blogspot.com/-I9f1mQtVGLY/Ty3dCwqLXzI/AAAAAAAADss/fD9T2viwWeM/s1600/HONDA+NSX+GT2_2.jpg
http://img268.imageshack.us/img268/5936/gt2nsx1995museum5big.jpg
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My opinion of your question is a heartbreaker to many users of this website.
IMO - people give honda way to much credit for what they came up with. I feel the diffuser much like the type-r rear wing were esthetics only. I do see your point as the front of the exhaust is the shape of the front of a foil. and that their little cf bolt on thingy creates an upward angle. My opinion on the matter is the car is better because the car is lighter with a more dialed in suspension - end of story
Knowing what I know now... I know that car enthusiasts were over explained aero and its much more simple that it seems. When I first saw the comparison of the size of a foil that creates the same drag as a much smaller circle.. the light went on above my head saying... this is a bg deal.. way bigger than originally assumed.
People know planes have wings and that planes fly... this is why.
This is why a car can create down...
I like diflos video a lot since it does that... he is trying to sell a product and I get that too... but call esthetics what it is or a snowball of performance increases will make it harder for people to understand the simplicity of aero
People would “get it” if they just take pressure, venturi effect, wings, stall, diffusers, f ducts, ect ect ect out of the conversation.. and get an A+ on understanding the 2 pictures above
So considering the car as a whole... they did a good simple job in aero design.. and the stock wing is better than a type r due to its shape and location.
Nuf said on this...
pics of a diffuser
http://www.dome.co.jp/race/images/11hsv_03.jpg
the sickest website link I've never seen anyone on prime ever post... why they havent... just like replacing threads in the forsale with the words sold - no one f&*@ing knows
http://www.dome.co.jp/museum/car_m/index.html
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![ctrp_0707_03_z+aerodynamic_downforce+airplane_wing_diagram[1].jpg](/data/attachments/69/69050-0af0210291e0ab46ff597438dfa573c5.jpg?hash=CvAhApHgq0)
Ross don't forget that Bernoulli never played with wings. There are other ways to create lift/downforce using Bernoulli Principle.
<img src="http://www.formula1.com/wi/0x0/sutton/2011/d11esp2077.jpg" width="600"/>
PS: I agree 100% with you Ross that even a properly designed diffuser isn't truly going to be effective unless you have a flat bottom car or at the very least a diffuser that goes past the rear axle.
"But Honda made a diffuser part of the LeMans GT2 car, Dali and Procar even sells a copy of it."
Yes, they did but they also had a flat bottom car and so is the FXMD. :wink:
HOWEVER anything you can do to increase the velocity of the air AND smooth the transition back to ambient will help as well as help increase the functionality of a top mounted wing as you reduce turbulence at the rear. How much? Debatable without wind tunnel testing. The interaction between a diffuser and top wing is pretty complex and depends on the wing, the diffuser, speed, etc, etc.
So in that respect the Difflow is "functional". But once again it is not as functional as it could be if you had a a full flat bottomed aero package to go with it.
I'm going to have to disagree. If you look at the Type R wing, it is an airfoil. How much downforce is questionable, but it has to be more effective than stock which is not shaped as an airfoil
PS Dave - stickier tires (ie R-Comps or slicks) will give a much, much greater improvement than any aero devices.
<img src="http://www.formula1.com/wi/0x0/sutton/2011/d11esp2077.jpg" width="600"/>
PS: I agree 100% with you Ross that even a properly designed diffuser isn't truly going to be effective unless you have a flat bottom car or at the very least a diffuser that goes past the rear axle.
"But Honda made a diffuser part of the LeMans GT2 car, Dali and Procar even sells a copy of it."
Yes, they did but they also had a flat bottom car and so is the FXMD. :wink:
HOWEVER anything you can do to increase the velocity of the air AND smooth the transition back to ambient will help as well as help increase the functionality of a top mounted wing as you reduce turbulence at the rear. How much? Debatable without wind tunnel testing. The interaction between a diffuser and top wing is pretty complex and depends on the wing, the diffuser, speed, etc, etc.
So in that respect the Difflow is "functional". But once again it is not as functional as it could be if you had a a full flat bottomed aero package to go with it.
I'm going to have to disagree. If you look at the Type R wing, it is an airfoil. How much downforce is questionable, but it has to be more effective than stock which is not shaped as an airfoil
PS Dave - stickier tires (ie R-Comps or slicks) will give a much, much greater improvement than any aero devices.
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PS Dave - stickier tires (ie R-Comps or slicks) will give a much, much greater improvement than any aero devices.
I know I was making a joke with the fractional talk making me fractionally happier but I guess no one got me. LOL...
People know planes have wings and that planes fly... this is why.
This is a gross oversimplification of why planes can fly.
How effective a well an airfoil generates lift is based on how it changes the speed of the air based on it's geometry, angle of attack and velocity; as a result of the varying air velocities (above, below, and along the surface of the airfoil) that are complicated by the viscous nature of air, a pressure gradient is generated (above, below, and along the surface of the airfoil) so that a bound vortex is formed to circulate enough air above and below the airfoil to generate lift.
(Edit: At least to the best of my limited understanding.)
Otherwise, things like a balsa wood glider wouldn't fly because if you looked at a cross section of their wings, they're essentially bricks.
However, I am in agreement, the stock exhaust acting as a diffuser is probably overly optimistic and what makes the NSX-R is the sum of it's parts, not just one single thing.
As far as the functionality of the NSX-R wing, there is probably a marginal benefit. Without a windtunnel, we have to take Honda's word on the change in Cd and increase in downforce based on all the other aero changes made to the NSX-R. Otherwise, if people wanted to see at least what the air is doing, one run a tuft test starting on the rear hatch, over the trunk and the wing to see if there is any change in airflow in each of the following scenarios: no wing, stock wing, NSX-R wing.
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"But Honda made a diffuser part of the LeMans GT2 car, Dali and Procar even sells a copy of it."
Yes, they did but they also had a flat bottom car and so is the FXMD. :wink:
HOWEVER anything you can do to increase the velocity of the air AND smooth the transition back to ambient will help as well as help increase the functionality of a top mounted wing as you reduce turbulence at the rear. How much? Debatable without wind tunnel testing. The interaction between a diffuser and top wing is pretty complex and depends on the wing, the diffuser, speed, etc, etc.
So in that respect the Difflow is "functional". But once again it is not as functional as it could be if you had a a full flat bottomed aero package to go with it.
I'm going to have to disagree. If you look at the Type R wing, it is an airfoil. How much downforce is questionable, but it has to be more effective than stock which is not shaped as an airfoil
PS Dave - stickier tires (ie R-Comps or slicks) will give a much, much greater
The location of a stock wing creates less drag.. and it is the shape of a flat topped foil. IMO There is no beni to either... just styling and "try not to restrict the car"
And the Bernoulli Principle is a little complex untill you understand pressure... but your right.
geometro - right b4 my plane comment I said car enthusiests were over explained aero.
You are completely wrong. You should be in airline management. This is why planes can fly....
You are completely wrong. You should be in airline management. This is why planes can fly....
Haha... Somehow I got that :biggrin:
... getting interesting.
Ross don't forget that Bernoulli never played with wings. There are other ways to create lift/downforce using Bernoulli Principle.
<img src="http://www.formula1.com/wi/0x0/sutton/2011/d11esp2077.jpg" width="600"/>
PS: I agree 100% with you Ross that even a properly designed diffuser isn't truly going to be effective unless you have a flat bottom car or at the very least a diffuser that goes past the rear axle.
"But Honda made a diffuser part of the LeMans GT2 car, Dali and Procar even sells a copy of it."
Yes, they did but they also had a flat bottom car and so is the FXMD. :wink:
HOWEVER anything you can do to increase the velocity of the air AND smooth the transition back to ambient will help as well as help increase the functionality of a top mounted wing as you reduce turbulence at the rear. How much? Debatable without wind tunnel testing. The interaction between a diffuser and top wing is pretty complex and depends on the wing, the diffuser, speed, etc, etc.
So in that respect the Difflow is "functional". But once again it is not as functional as it could be if you had a a full flat bottomed aero package to go with it.
I'm going to have to disagree. If you look at the Type R wing, it is an airfoil. How much downforce is questionable, but it has to be more effective than stock which is not shaped as an airfoil
just looking at that pic reminded me of that carbon fiber panel by downforce that covered the gas tank.
i wonder if a vendor like Difflow could make one and somehow make one that covers the bottom of that engine area to make his diffuser even more effective.
So how fast does one have to drive the NSX to make full use of such diffusers and under panels?
How much difference would it make if someone makes use of diffusers and under body panel. (As in how many secounds would it shave off the lap time?)
Just wondering.
How much difference would it make if someone makes use of diffusers and under body panel. (As in how many secounds would it shave off the lap time?)
Just wondering.
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On an oem NSX... we do not have the ability to start the channels of air soon enought to make a diffuser work 100% the way it should - but drag is a big deal so reducing drag will help in any scenario.
As far as seconds off the lap times... on a working diffuser - this video is the track record at Suzuka (old record that has been taken down)
<iframe width="640" height="360" src="http://www.youtube.com/embed/8Mqoe7YNPEU?feature=player_embedded" frameborder="0" allowfullscreen></iframe>
Depends who's driving. Really. You driving or any non-pro - very little because you are not going to be driving the car 10/10ths at it's very limits anyway. It's not like it's going to suck the car down and let it pull 2.5Gs in a turn. People get all wrapped up in this stuff and unless you are really pushing the car to it's limits then you really don't need to be looking at raising those limits (because you are not using them anyway).
So there are 2 ways that diffusers help, right?
1. create down force (sorta like acting as the bottom part of a spoiler like mines)
2. reduce drag by channeling the air in a more straight stream and further away from the rear of the car's bumper so that there is less "vacuum"
I did notice that when I had a diffuser on the rx7 my rear bumper was ALOT cleaner for ALOT longer. To me that's worth it.
1. create down force (sorta like acting as the bottom part of a spoiler like mines)
2. reduce drag by channeling the air in a more straight stream and further away from the rear of the car's bumper so that there is less "vacuum"
I did notice that when I had a diffuser on the rx7 my rear bumper was ALOT cleaner for ALOT longer. To me that's worth it.
1. yes and no. They don't act as bottom part of a spoiler. They help evacuate the air from under the car. The point where the flat bottom and the the diffuser meet creates a low pressure and thus downforce at that spot.
2. yes, they reduce drag. They do this by smoothing the airflow and slowing it down to better rejoin the static (surrounding air) without creating turbulence. Less turbulence = less drag.
http://en.wikipedia.org/wiki/Diffuser_(automotive)
What Ross and I have been trying to point out is without a flat undertray, a diffuser can't really do it's job correctly. Yes, it will reduce drag by smoothing the airflow and slowing it as it exits but the downforce is actually created ahead of the diffuser where the flat undertray meets the diffuser - which in the case of the NSX is an open turbulent air area - therefore a diffuser on the NSX will not create downforce (unless you seal off the fuel tank and engine area and then add a diffuser - oh and you need a ducted hood and sealed front too.
).see pic below again.
SO TO SUMMARIZE. A DIFFUSER ON A NSX WITHOUT A COMPLETE UNDERTRAY FRONT TO REAR WILL CREATE VERY LITTLE IF ANY DOWNFORCE. YES, IT WILL REDUCED DRAG BUT STILL WITHOUT THE WHOLE SHABANG THAT REDUCTION WILL BE MINIMAL AS THE AIR AROUND THE ENGINE COMPARTMENT IS PROBABLY PRETTY TURBULENT UNLESS IT IS SEALED OFF.
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That's fine for me for now.
I was more concern with drag as you described it and spending less time and frequency clay-barring the top of the rear bumper cover from the rear turbulence depositing gunk.
My RX7 had a diffuser similar in size to the Difflow and it certainly helped in reducing my detailing time and resources on my rear bumper cover and tail lights.
The NSX-R diffuser was proven by Honda to improve aero, reduce drag. Unfortunately, I can't find that tid bit of info at the moment.
Notice the NSX-R diffuser is built with the OEM exhaust in mind. The Exhaust cannister itself aids in the airflow. Look how closely it meets to the can. If it does not, it creates the "Parachute" effect and forces air up and over the diffuser which can work marginally but defeats the purpose in my eyes.
There are a couple reasons why I haven't bought the aftermarket diffusers yet.
1. I don't like the parachute effect and have not seen a proper offering to cover the fuel tank underneath. At this point you're mostly doing it for looks. I'd rather save the weight. Since I can't expect anyone to offer a proper analysis i'm willing to try it out someday (maybe the new DF CF one). I hear the placebo effect is a strong one!
2. Another hesitation is because they sit far too low. I'd scrape that everywhere. I don't like to be concerned about this when driving and would simply just get annoyed. After a year i'd be over it.
Notice the NSX-R diffuser is built with the OEM exhaust in mind. The Exhaust cannister itself aids in the airflow. Look how closely it meets to the can. If it does not, it creates the "Parachute" effect and forces air up and over the diffuser which can work marginally but defeats the purpose in my eyes.
There are a couple reasons why I haven't bought the aftermarket diffusers yet.
1. I don't like the parachute effect and have not seen a proper offering to cover the fuel tank underneath. At this point you're mostly doing it for looks. I'd rather save the weight. Since I can't expect anyone to offer a proper analysis i'm willing to try it out someday (maybe the new DF CF one). I hear the placebo effect is a strong one!
2. Another hesitation is because they sit far too low. I'd scrape that everywhere. I don't like to be concerned about this when driving and would simply just get annoyed. After a year i'd be over it.
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The NSX-R diffuser was proven by Honda to improve aero, reduce drag. Unfortunately, I can't find that tid bit of info at the moment.
Notice the NSX-R diffuser is built with the OEM exhaust in mind. The Exhaust cannister itself aids in the airflow. Look how closely it meets to the can. If it does not, it creates the "Parachute" effect and forces air up and over the diffuser which can work marginally but defeats the purpose in my eyes.
There are a couple reasons why I haven't bought the aftermarket diffusers yet.
1. I don't like the parachute effect and have not seen a proper offering to cover the fuel tank underneath. At this point you're mostly doing it for looks. I'd rather save the weight. Since I can't expect anyone to offer a proper analysis i'm willing to try it out someday (maybe the new DF CF one). I hear the placebo effect is a strong one!
2. Another hesitation is because they sit far too low. I'd scrape that everywhere. I don't like to be concerned about this when driving and would simply just get annoyed. After a year i'd be over it.
If you climb under the rear and actually look at it, the OEM exhaust does NOT meet up close to the Type R diffuser that well. I think you are grasping at straws giving Honda way too much credit.
I'm sure any diffuser, including the Honda OEM version will work as advertized.
The question is really to what degree it helps.
Perhaps 2% :biggrin:
The question is really to what degree it helps.
Perhaps 2% :biggrin:
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