NSX diffuser on a quest?

[Convette]

dude, you're getting a fuel cell for that beast anyhow right? nix the tank and build a diffuser. it really doesn't need to be as fancy as the NSX one either. the grassroots and time attack guys build some DIY diffusers.

 

Yeah the more I think about it, I'll be getting a cell. It will be grassroots style, but still fancy...lol

 

THIS CIVIC WILL BEAT YOUR tail BUDDY!

http://www.honda-tech.com/showthread.php?t=2763036

 

umm, its still a civic, and I doubt it.

 

 

dude, i really like the look of no rear wing, but still retaining the side sections of the wings. almost looks like tailfins or devil horns lol

 

yeah I was just too lazy to put the wing on. I have plans for that as well...

[dmyers151]

Pimp out your lady and buy yourself a diffuser.

[Focus]

I am gonna build that now haha. Ask me if I'm kidding...i dare you. =p

 

and I think I can speak for most of us when I say...i don't care if some guy dumps 60k into a honda just to get a few lengths on me at the track...he still sux in the corners, and you can polish a turd for years but in the end it's still a....

 

Hahaha. No wonder I don't post here much anymore.

 

I agree that RWD>FWD but you guys take s*** a little too far.

 

P.S. Obama rules.

[Convette]

Pimp out your lady and buy yourself a diffuser.

 

 

haha

[conquezzy]

Found them in the 2.6 gallery

 

http://www.26liter.us/gallery/albums/userpics/10105/010.JPG

 

http://www.26liter.us/gallery/albums/userpics/10105/022.JPG

 

http://www.26liter.us/gallery/albums/userpics/10105/09.JPG

 

http://www.26liter.us/gallery/albums/userpics/10105/023.JPG

 

http://img291.imageshack.us/img291/8027/006bi0.jpg

[jwbrocloud]

The first one is LandRocket's car, I think he still has it and is still on the boards somewhere, the other one i have not seen before . . .

[Scotty Dont]

The diffuser on the red car is way to big and doesn't really flow well

[Convette]

The diffuser on the red car is way to big and doesn't really flow well

 

I agree looks like part of a bat mobile... I would like to see the front of that car though. Something different there with the lip....?

[19cturbo]

you are on subaru's nuts so why are you here?

 

 

 

And I think that diffuser would be molehills!

 

 

i meen dont you just love these people! haha

[BrazilBoy]

Yup its Roberto approved...you can go for it John

[Metric-man]

THIS CIVIC WILL BEAT YOUR tail BUDDY!

 

 

http://www.honda-tech.com/showthread.php?t=2763036

 

 

That link was a timesuck hole... please warn people when you put up those kind of links...

 

"honda tech" now that's an oxynoron

 

I've gotta go wash my eyes..

[Komeuppance]

I like it, quite aggressive... but its off the chain!!

 

-Robert

[pure_insanity]

can someone explain the whole rear diffuser to me? i mean like whats the aerodynamics behind it and all that jazz?

[dmyers151]

I remember reading somewhere that it lessens turbulence in the airstream leaving the underside of the car, which helps somehow. *shrugs* Edited May 11, 2010 by dmyers151

[D_Venable]

the rear diffuser, the vertical fins create stability at higher speeds.

 

And ones with the smooth gradual curve upwards will cause a vacuum under the rear of the car, aiding in downforce, similar to an airplane wing turned upside down

[patra_is_here]

yeah helps down force by making a low pressure zone. there was a time attack lotus a few weeks back on speedhunters that changed their diffuser design and it prevented rear tire lift under braking, so, there is a benefit if made correctly.

[JustPaus_88TSi]

aero advantage in smoothing out the airflow and weakening the flow detachment left by a moving car.

 

Like Derek mentioned, straight vertical slats promote high speed stability while general upward curve shapes aide in downforce production.

 

From my 2006 post I quoted above, tapered shapes(the diffuser curve also) like the widebody fenders(rear mostly) limit the flow detachment, which I guess could be described as a vacuum that actually pulls backwards on the moving object.

 

If designed right, diffusers can add stability at speed, promote downforce, and lower a vehicles Cd(drag coeffecient). Lots of other things come into play though, as just adding a diffuser by itself isn't really the idea and it could be used much more efficiently with other things. Things like chin spoilers, engine bay/belly pans, and suspension design/stance(overall rake) all play into it.

 

Assuming the design is correct, a diffuser can add all the benefits Derek and I mentioned, but at the same time it can also allow easier usage of a real deal functional rear spoiler to gain even more downforce. Not sure if that was clear... If someone was thinking about using a rear spoiler, but didn't like the idea of creating more drag(raising the Cd) in the process, they could benefit from adding a diffuser(since it can lower the Cd) to alleviate in the additional drag created by the rear spoiler.

[Komeuppance]

Woah... long post...

 

It looks totally JDM tyte cool yo!!

 

LOL... fixed...??

 

-Robert

[spoolinturbo]

d_venable is correct. It's all about changing pressures and direction of air-flow. Creating stability for the car at high speeds. With a good design you could most likely notice a difference at speeds 80mph and higher.

 

HOWEVER the air flow under 99% of cars is erratic anyways with extreme differences in pressure and airspeeds unless they have a full undercarriage design...the c6 z06 comes to mind

 

so just having a rear diverter serves no purpose, just an awesome look =)

[BrazilBoy]

d_venable is correct. It's all about changing pressures and direction of air-flow. Creating stability for the car at high speeds. With a good design you could most likely notice a difference at speeds 80mph and higher.

 

HOWEVER the air flow under 99% of cars is erratic anyways with extreme differences in pressure and airspeeds unless they have a full undercarriage design...the c6 z06 comes to mind

 

so just having a rear diverter serves no purpose, just an awesome look =)

have been wondering about getting everything from the airdam on back flattened out like this..obviously this would take mega calculating to get right and not fly off the pavement..

 

This is a Ferrari F430

http://articles.motortoday.com/feature/firstimpF430/F430_press-underbody.jpg

This is an Enzo undertray..

 

http://img84.imageshack.us/img84/9071/ferrarienzoyn4.jpg

[BrazilBoy]

Good article

 

Aerodynamics

• Drag and Lift
  Drag http://www.autozine.org/technical_school/aero/tech_pic_aero_911.jpg
   
  Aerodynamic efficiency of a car is determined by its Coefficient of Drag (Cd). Coefficient of drag is independent of area, it simply reflects the influence to aerodynamic drag by the shape of object. In theory, a circular flat plate has Cd 1.0, but after adding the turbulence effect around its edge, it becomes approximately 1.2. The most aerodynamic efficient shape is water drop, whose Cd is 0.05. However, we cannot make a car like this. A typical modern car is around 0.30.
   
  Drag is proportional to the drag coefficient, frontal area and the square of vehicle speed. You can see a car travelling at 120 mph has to fight with 4 times the drag of a car travelling at 60 mph. You can also see the influence of drag to top speed. If we need to raise the top speed of Ferrari Testarossa from 180 mph to 200 mph like Lamborghini Diablo, without altering its shape, we need to raise its power from 390 hp to 535 hp. If we would rather spend time and money in wind tunnel research, decreasing its Cd from 0.36 to 0.29 can do the same thing.
   
  Fastback
   
  http://www.autozine.org/technical_school/aero/935_78.jpgIn the 60s, motor racing engineers started to take aerodynamics seriously. They discovered that if they reduce the slope of the back of a car to 20 degrees or less, the air flow will follows the roof line smoothly and dramatically reduce the drag. They termed this design as "Fastback". As a result, many racing cars, such as the Porche 935 / 78 "Moby d***" shown here, added an exaggerately long tail and lower the back.
   
  http://www.autozine.org/technical_school/aero/tech_pic_aero_fastback.jpgFor a 3-box car, air flow leaves the car straightly at the end of roof line. The dramatic drop of rear screen creates a low pressure area around, this attracts some air flows back to complement, thus creates turbulence. Turbulence always deteriorates drag coefficient.
   
  However, this is still better than something between a 3-box and a fastback. If the rear screen angle is around 30 to 35 degrees, the air flow will be very unstable. It could greatly deteriorate the high speed stability. In the past, car makers had little knowledge about this and created many cars like this.
   
  Lift
   
  Another important aerodynamic factor is Lift. Since air flow above the car travels longer distance than air flow underneath the car, the former is faster than the latter. According to Bernoullis Principle, the speed difference will generate a net negative pressure acted on the upper surface, which we call "Lift".
   
  http://www.autozine.org/technical_school/aero/tech_pic_aero_911.jpgLike drag, lift is proportional to area (but surface area instead of frontal area), the square of vehicle speed and Lift Coefficient (Cl), which is determined by the shape. At high speed, lift may be increased to such an extent that the car becomes very unstable. Lift is particularly serious at the rear, you can easily understand, since a low pressure area exists around the rear screen. If the rear lift is not adequately counter, rear wheels will become easy to slip, and that is very dangerous for a car travelling at something like 160 mph.
   
  Fastback is particularly bad in this aspect, because it has a very big surface area in contact with air flow. It seems that good drag and good lift are mutually exclusive, you can't have both of them. However, as we did more research on aerodynamics, we found there are some solution to achieve both of them ....

• Aerodynamic Aid
   
  Wing (rear spoiler)
  In the early 60s, Ferrari's engineers discovered that by adding an air foil (we simply call "Wing") to the rear end, lift can be dramatically reduced or even generates net downforce. At the same time, drag is only slightly increased.

http://www.autozine.org/technical_school/aero/tech_pic_aero_wing.jpg

• The wing has the effect of directing the majority of air flow to leave the roof straightly without going to the back, this reduce lift. (If we increase the wing angle, a hundred kilograms of downforce may even be available.) There is still a little bit air flow follows the back and leave the tail under the wing. This avoid turbulence that appears in non-fastback car, thus remain drag-efficient. Since there is too little air follows this route, its contribution to the lift can be easily cancelled by the wing.

• http://www.autozine.org/technical_school/aero/tech_pic_aero_escort.jpgWing must be installed high in order to be benefited from the majority air flow. Escort RS Cosworth is right .... Cougar, well, seems to use wing as decoration only.http://www.autozine.org/technical_school/aero/tech_pic_aero_cougar.jpg
  The first wing car was Ferrari 246SP endurance racer in 1962. Just one year later, 250GTO road car incorporated a small duck tail rear wing, a first for road car of course. However, wing did not get popular until Porsche launched its 911 RS 2.7 in 1972, whose big duck tail reduced lift by 75% at high speed. Just one year later, 911 RS 3.0 used a "Whale tail" wing which completely eliminated lift. It became a trademark for the later 911s. Porsche's new 996 Carrera offers us some useful data :

Front lift (at 157mph)Rear lift (at 157mph)Wing down64 kg136 kgWing up5 kg14 kg

• </H1><H1>Spoiler
  http://www.autozine.org/technical_school/traction/tech_pic_traction_impreza.jpgSpoiler is the aerodynamic kit that alter the air flows underneath the car. We call those installed at the bottom edge of front bumper as "Chin Spoiler" or "Air Dam", and those installed at the bottom edge of the car's sides as "Skirt". To understand its principle, we must first talk about underside air flow. Air flows underneath the car is always undesirable. There are many components, such as engine, gearbox, driving shaft, differential etc, exposed in the bottom of the car. They will obstruct the air flow, not only cause turbulence which increase drag, but also slow down the air flow thus increase lift. (Remember Bernoullis's Principle ?).
   
  Spoiler is used to reduce underside air flow by encouraging air to pass either side of the car. As a result, drag and lift caused by underside air flow could be reduced. Generally speaking, the lower the spoiler locates, the better result obtain. Therefore you can see endurance racing cars having spoilers nearly touching the ground. Of course road cars cannot do so.
  
   
   
   
  Smooth Undertray

http://www.autozine.org/technical_school/aero/tech_pic_aero_flatbottom.jpgWe can also reduce the influence of underside airflow by covering the car's bottom by a smooth undertray, as shown in this Ferrari F355. This avoid turbulence and lift.

• Ground Effect

http://www.autozine.org/technical_school/aero/tech_pic_aero_ground_effect.jpg

• To motor racing engineers, wing might be a good solution to lift, but still far away from what they really want. A typical formula one racing car corners at around 4g lateral acceleration, that requires substantial downforce to keep the tyres firmly on track. Install a huge wing with high angle can satisfy this requirement, but also deteriorates the drag coefficient.

• In the 70s, Collin Chapman (again) invented a completely new concept to provide downforce without altering drag - Ground Effect. He incorporated an air channel into the bottom of his Lotus 72 racer. The channel is relatively narrow in front and expand towards the tail. Since the bottom is nearly touching the ground, the combination of channel and ground forms virtually a closed tunnel. When the car is running, air enters the tunnel in the nose and then expands linearly towards the tail. Apparently, air pressure is reducing towards the tail so that downforce will be generated. Ground Effect is so superior than wing that it was soon banned in Formual One. In 1978, Brabham's Gordon Murray tried again with different means - instead of expansion channel, he used a powerful fan to create low pressure near the tail. Of course FIA banned it again.
   
  Ground effect is not too suitable for road cars. It requires the bottom to be very close to the ground to form a closed tunnel. For racing car, this is no problem. But road cars should have much higher ground clearance to suit different rough roads, up hill and down hill etc. This greatly reduce the effectiveness of Ground Effect. McLaren F1 road car followed Brabham's trick by using 2 electric fans to create ground effect, but honestly speaking, no tester had ever praised its down force. Dauer 962, a so-called "road car" but it is actually a road-legal Porsche 962 endurance racing car, use conventional air-channel ground effect as the race car. Adjustable ride height allow it to run in rough road (slowly) and make good use of Ground Effect in Germany's Autobahn. Nevertheless, it can barely generate 40% downforce of the racing car.

Edited May 11, 2010 by BrazilBoy

[spoolinturbo]

yea mid-engine/rear-engine designs are wayyy easier due to the exhaust layout obviously. You could use metal...but it would be crude and probably make some noise if they were connected in some flexing areas of the vehicle. It would def be a project roberto!

[BrazilBoy]

I was thinking to side exit the exhaust, then the center channel could be created which lead to the diffuser.. we could make a redirect from the ic down into the channel. But the IC may need to be upright for this to flow right...I may be way off on my thoughts on this but its an idea none the less..

 

 

EDIT:

Sorry just realized something...ENGINE HEAT venting where, duh.....its 1am here sorry..

Edited May 11, 2010 by BrazilBoy

[lmwii]

diffusers built without data are for looks. period.

[Convette]

I have the pans ready to flat the bottom of car, I just got a lot of other stuff that needs to go in first..lol. I sometimes work in the wind tunnel at work and get to see what actually works and doesn't. If I could only get my car in there for a run or two....that would be great.... a little too $$$ for me tho.. ($2500 per hour)