Underbody evacuation downforce

[kachok25]

there was a promptly banned device used back in the 1970 a fan was used to suck the air out from under the car, the edges of the car were sealed with a sliding skirt to allow maxamum downforce, unlike other means of downforce it was not in any way related to the speed of the car. I am sure that most of you are familuar with the story. It was so effective one of the cars was only allowed in one race before it was banned (Needless to say he won by miles) anyway I was wounering why nobody has applied this to a street car (yes I know the Mclaen F1 has underbody evacuation fans but to a very limited extent with no ground skirts) This technology could drasticly increase the cornering, breaking, 0-60, and stability of a roadgoing car. what is preventing manufactures form using this? I know they don't take that much power, one of them had a little 250cc motor driving its fans and it cornerd at 1.7g this could revolutionize the sportscar as we know it why has nobody tried it? Yea I know that the ground skirtrs would eventualy wear out and have to be replaced but that would probably take longer to wear out than your tires, and would not be hard to replace, and I know that you would have to use stiffer that avrage springs but most sports cars use that anyway to increase adgility. Could anyone give me one good reason why this woud not work?

[Alastor187]

Originally Posted by kachok25

there was a promptly banned device used back in the 1970 a fan was used to suck the air out from under the car, the edges of the car were sealed with a sliding skirt to allow maxamum downforce, unlike other means of downforce it was not in any way related to the speed of the car. I am sure that most of you are familuar with the story. It was so effective one of the cars was only allowed in one race before it was banned (Needless to say he won by miles) anyway I was wounering why nobody has applied this to a street car (yes I know the Mclaen F1 has underbody evacuation fans but to a very limited extent with no ground skirts) This technology could drasticly increase the cornering, breaking, 0-60, and stability of a roadgoing car. what is preventing manufactures form using this? I know they don't take that much power, one of them had a little 250cc motor driving its fans and it cornerd at 1.7g this could revolutionize the sportscar as we know it why has nobody tried it? Yea I know that the ground skirtrs would eventualy wear out and have to be replaced but that would probably take longer to wear out than your tires, and would not be hard to replace, and I know that you would have to use stiffer that avrage springs but most sports cars use that anyway to increase adgility. Could anyone give me one good reason why this woud not work?

I think the most obvious draw back of any underbody aerodynamics on a street car is ride height compromise. Generally speaking lower is better for the underbody aerodynamics, however the opposite is better for street-ability. See last week’s Top Gear episode for example:

http://media.putfile.com/Top-Gear---...stuck-in-Paris

How much worse would it be if one of these three cars had a dedicated underbody aerodynamic system?

Also, packaging is going to be an issue and more so in a sports-car (as apposed to a super-car). Where is the system going to fit and will there still be sufficient room for passengers and cargo?

Yet it could have to do more with the most unpredictable component of all, the driver. A high downforce vehicle will handle significantly different from a non-downforce dependent vehicle. Is the average driver capable of safely operating this type of vehicle?

Could this be why the majority of sports-cars and super-cars lack a full high downforce top body package? Would it not be easier just to add a front diffuse and large rear wing, and offset the increase in drag with more power?

[Moppie]

Imagine your super car with its suction downforce is being driven on the limit pulling 1.5g's round a corner, when all of a sudden it goes over a stormwater grate?
All that downforce is very suddenly removed.

A race track is a very controlled environment, a road isn't. And there are too many things could very easily cuase the system to loose vacuum making the car literaly fall off the road.

[kachok25]

Originally Posted by Alastor187

I think the most obvious draw back of any underbody aerodynamics on a street car is ride height compromise. Generally speaking lower is better for the underbody aerodynamics, however the opposite is better for street-ability. See last week’s Top Gear episode for example:

http://media.putfile.com/Top-Gear---...stuck-in-Paris

How much worse would it be if one of these three cars had a dedicated underbody aerodynamic system?

Also, packaging is going to be an issue and more so in a sports-car (as apposed to a super-car). Where is the system going to fit and will there still be sufficient room for passengers and cargo?

Yet it could have to do more with the most unpredictable component of all, the driver. A high downforce vehicle will handle significantly different from a non-downforce dependent vehicle. Is the average driver capable of safely operating this type of vehicle?

Could this be why the majority of sports-cars and super-cars lack a full high downforce top body package? Would it not be easier just to add a front diffuse and large rear wing, and offset the increase in drag with more power?

Your reasoning is flawed on a few different levels first all of those cars in that video have some type of undertray downforce desighen, that in every case I have seen involves a long front overhang which was one of the the causes of their problem, secondly all undertray downforce cars that I have seen have an extreamly low ride hight to reduce the migration of air from the sides of the car, The sucker cars do not depend on either of those to create downforce since it has a flexable skirt surounging all encloseable areas of the car it depends in neither a long nose (throat) to smooth out the uncoming airs passage under the car and through its defusers, nor an air spliter or front air dam to block the air creating a slight low pressure area behind it. Basicly it needs no long overhangs. secondly since the flexable side skirt is all the protection it needs to protect aginst air migrating from the sides of the car it does not need to have the body of the car all but scraping the ground, in fact it could have a regular ride hight just make the skirt a little longer, does that all make sence? And the reason that I would profer an underbody evacuation system over a large multi element rear wing and a front air splitter is because it whoud not have the same problems that we just saw with the air splitter, and it could create an even greater amount of downforce withouth having to travel at high speeds to do it. Not to mention the reduction of aerodynamic drag you get by removing the wing and splitter. And one more factor if the evacuation fans direct the air they removed behind the car the can partialy fill in the vacume that the car creates behind it, remember that drag is not just air molicules slaming into the front of your car it is the difference of two pressures one in front of the car and the other behind it. By giving that vacume some of it's air back we reduce that difference. sounds a whole lot better than just punching a slightly vertilcal hole in it right, and usualy a car with an air dam and a spoiler is not actualy creating downforce anyway it is just negating the lift that is all but inharent in the shape of an automobile. Example the the 1969 camaro ss for all its aero work still creates 300 lbs of lift on the front end alone at 100mph, and the modern 350Z track edition for all or it's trick body work is completly nutreal creating no lift or downforce. Even a NASCAR racing machine with it's extreamly low ridehight, comprehensive front air dam, and rear spoiler creates only a slight amount of downforce if any at all. Are you starting to get the picture right now unless a car has venturi tunnels or at leased a good dispoiler downforce is all but a myth in production cars. Underbody evacuation could change that, now is it any wounder that I am so intrested in it. If you evacuate just .1psi out from under the avrage sized sportscar you are creating a thousand lbs of downforce, and unlike venturi tunnels it would not compromise suspension geometry in any way. The system should not take up that much space especaly since it can be used in conjunction with the cooling system so really it would be not be much larger than the electric motor that drives the fans itself plus a little ducting.(one of the infamus sucker cars did that in fact that is how he got it through tech! He told them they were the fans to his radiator which they were) seeing as this car would not have to use trick body work to negate lift it would probably have more room than a standard sporscar now. That being said is there any other problems that might come up I cannot think of any that would out weigh the benifits.

[kachok25]

Originally Posted by Moppie

Imagine your super car with its suction downforce is being driven on the limit pulling 1.5g's round a corner, when all of a sudden it goes over a stormwater grate?
All that downforce is very suddenly removed.

A race track is a very controlled environment, a road isn't. And there are too many things could very easily cuase the system to loose vacuum making the car literaly fall off the road.

It would not be a catostrophic loss of downforce becaus the air moving through the storm grate would have to be moving very fast meaning that it too would be at a lower perssuer. The same kind of thing was said when the suckers first came out but the big thing was if one of the skirts got riped off during a race the car would loose control. well one day it happend, but the car did not loost control it continued on it's mary way because the air that did migrate under the car was still moving very fast thus at a lower pressure. Did the car loose some downforce yes was the outcome fatal or even dangerous clearly not. They kept running it from what I heard missing a whole side skirt, now maby that story was exadurated i was not alive back then so I can certanly not clame to have seen it but that is the way the story has been told, and untill somone is willing to recreate this event we cannot know for sure, besides even if the car lost downforce altogther would it be any worse of than any other proformance machine and remember that even the supercars with tunnels face the possability of stalling the tunnels creating the same effect no downforce plus the cars with tunnels have a less effective suspeneion geometry. And who is going to be pulling 1.5G turns in the middle of town anyway, people that stupid don't usualy live long enough to get their drivers license and another tid bit of info for you, the first time they got a car to hold togeather with air dispoilers (same downforce system found on modern supercars) the dirver was killed prosumably by the dispoiler stalling out, and how many drivers died when the vinturie tunnels were first introduced by the same thing? Now how many dirvers have been killed in a suckercar NONE to my knowlage, so which one is safer do you think? A tunnel can be stalled out by an increase in rake due to breaking or even a sharp downgrade. Getting the car too far sideways or even a strong crosswind from what I understand can also stall the tunnels and defusers. The sucker is not subject to having its downforce affected by any of those things. Just a little somthing for your brains to chew on.

[Moppie]

Originally Posted by kachok25

And who is going to be pulling 1.5G turns in the middle of town anyway, people that stupid don't usualy live long enough to get their drivers license .

And there you have just ansewered your own question.

There are simply no conditions where a road going car would need that much grip. It would make it far to dangerous to drive.

[kachok25]

Originally Posted by Moppie

And there you have just ansewered your own question.

There are simply no conditions where a road going car would need that much grip. It would make it far to dangerous to drive.

Wrong I don't know about you but when I have a car run a stop light in front of me I want as much grip as I can get for a sharp turn or for breaking! just think about that for a sec, plus it would be nice to get that kind of grip off teh line during the 1/4 mile, When you think about it almost all mesurments of a sportscar are mostly related to traction breaking, cornering, accelaration, slolom, skidpad...ect puls think about the additional stability at highway speeds, or autoban speeds.

[Moppie]

Have you ever seen a Hovercraft lose its skirt and nose dive? Or side slip and roll over?

Or, have you ever seen a Le Mans car hit a small bump, get lift and flip over, or a F1 car lose one of its wings and take off?

Just because a single race car lost pressure and didn't crash dosn't mean that every car that loses pressure will not crash. In a race car your in a controlled environment, wearing safety gear, surounded by a roll cage. On the road your not.
I see what your saying about more traction = more safe, but your not thinking about what happens when you lose that traction.


And have you ever driven a car at over 100mph?
Or one that can corner at close to 1 G in an environment that lets you drive it on the limit and experiance what it feels like?
Im talking very high performance sports cars and race/super cars here, not your mates Honda Civic with some aftermarket suspension racing on some back raods.
It requires a huge level of skill and concentration to keep one on the road at its limits. It is beyond the limits of what the average person is able to control.
Now could you image if there was a road car, capable of even greater levels of handling and accleration, not just beyond what the average person can handle, but beyond what even experiance race drivers can handle?
There would be a lot of death on the road.
More grip dosn't automaticaly mean an easier, safer car to drive.



And I think you will also find that the cars that used vacum to hold them to the road required quite a lot of airflow running past the car (from high speed) to help produce a pressure differential before the there was an increase in downforce.
The effect did not work at a stand still, or at low speed.

[curtis73]

Originally Posted by Kachok25

Could anyone give me one good reason why this woud not work?

Kachock25, take a look over your posts. You asked us a question, some experts answered it and now you're arguing with them; even blatantly telling respected veteran members that they're wrong. Let's just take a step back and relax.

The first problem I see here is a reason. Street cars can pretty easily be designed to outdrive 90% of licensed street operators without the engineering associated with fans to create suction. The other big problem that we may be skirting here (no pun intended) is that the more downforce you have, the greater drag you create. As long as we're splitting hairs here its a valid point.

The difference between a .5g car and a 1.0g car is not too far off from a design standpoint. However, the difference between a 1.0g car and a 1.5g car is immense. Simply adding fans to a BMW won't generate any downforce unless (like someone said) you have sacrificial body skirting of A) sufficient rigidity to hold a vacuum, B) close enough to the ground, and C) doesn't contact the ground which is darn near impossible with any WalMart parking lot entry. Once you've created this body skirting you have to engineer fans of sufficient draw (which will cause a huge shift in the design of the electrical system) and then be able to duct that air to the top of the car. We're not talking about a few 3" pipes, either, we're talking about consistent 2-foot diameter stuff. After all, we're not talking about a 1500-lb race car, we're dealing with a 4000-lb M5 here.

Once you've occupied the entire trunk with ducting, removed all but 3/4" of ground clearance, beefed up the electrical system with twin 150-amp alternators which will draw about 12 hp at full load, completely altered the look of the car with funny skirting, you'll still be left with a 4000-lb car that can now achieve .87g instead of .85g stock. 99% of drivers won't be able to tell a difference and they sure as heck would rather give up that in favor of being able to cross speed bumps without $1700 worth of damage and it would be nice to carry at least a couple bags of groceries.

Plus, Moppie is right. Every time you cross a dip, there will be a huge gap between the skirting and the road. One of the things that race cars can benefit from is almost zero suspension deflection and a nearly flat track. If you suddenly offered this technology on a Camry, they may as well replace the springs with solid steel to prevent suspension movement. That makes it a bit tough to latch doors on a hill. Sometime run your vacuum over a floor vent and then tell me that driving over a storm drain won't change the suction under that car.

Let's be realistic. With current technology its just not a marketable thing for the street. Just because its a faster thing or a better handling thing doesn't mean that anyone will pay for it or get any benefit from it. AND your arguing with us after you asked the question won't solve anything.

[kachok25]

Originally Posted by Moppie

Have you ever seen a Hovercraft lose its skirt and nose dive? Or side slip and roll over?

Or, have you ever seen a Le Mans car hit a small bump, get lift and flip over, or a F1 car lose one of its wings and take off?

Just because a single race car lost pressure and didn't crash dosn't mean that every car that loses pressure will not crash. In a race car your in a controlled environment, wearing safety gear, surounded by a roll cage. On the road your not.
I see what your saying about more traction = more safe, but your not thinking about what happens when you lose that traction.


And have you ever driven a car at over 100mph?
Or one that can corner at close to 1 G in an environment that lets you drive it on the limit and experiance what it feels like?
Im talking very high performance sports cars and race/super cars here, not your mates Honda Civic with some aftermarket suspension racing on some back raods.
It requires a huge level of skill and concentration to keep one on the road at its limits. It is beyond the limits of what the average person is able to control.
Now could you image if there was a road car, capable of even greater levels of handling and accleration, not just beyond what the average person can handle, but beyond what even experiance race drivers can handle?
There would be a lot of death on the road.
More grip dosn't automaticaly mean an easier, safer car to drive.



And I think you will also find that the cars that used vacum to hold them to the road required quite a lot of airflow running past the car (from high speed) to help produce a pressure differential before the there was an increase in downforce.
The effect did not work at a stand still, or at low speed.

First of all the you obvously have never seen the Chaparral 2J race car because it did create downforce at a standstill you could see it when the system was engauged it litraly sucked itself down to the ground LOOK IT UP no better yet let me get you a quote ¶ The beauty of the powered-fan Ground Effect system was that it generated its downforce independent of vehicle speed. The “sucker” stuck to the road nearly as hard in slow turns as in fast ones." that's from http://www.petelyons.com/Monterey%20...esofSeven.html Secondly any car can loose traction I would really like to see one that could not so I fail to see how your traction=death equation work, did you say the same thing when ABS came out? Just think about that for a minute. A stupid driver will be a stupid driver and could kill himself in anthing with wheels on it, that is no excuse to not build a proformance car. Just my

[TheSilentChamber]

I'm not as nice as moppie and curtis so I will tell you what everone else is thinking.

You may be young but that is no reason to think you know everything. You asked a question it got answered, the bubble in your head burst because everyone didnt worship you. Its now time for you to shut the hell up or start posting logically. The design is not even safe for racing, there is no way in hell it would be safe for street use.

[kachok25]

Originally Posted by curtis73

Kachock25, take a look over your posts. You asked us a question, some experts answered it and now you're arguing with them; even blatantly telling respected veteran members that they're wrong. Let's just take a step back and relax.

The first problem I see here is a reason. Street cars can pretty easily be designed to outdrive 90% of licensed street operators without the engineering associated with fans to create suction. The other big problem that we may be skirting here (no pun intended) is that the more downforce you have, the greater drag you create. As long as we're splitting hairs here its a valid point.

The difference between a .5g car and a 1.0g car is not too far off from a design standpoint. However, the difference between a 1.0g car and a 1.5g car is immense. Simply adding fans to a BMW won't generate any downforce unless (like someone said) you have sacrificial body skirting of A) sufficient rigidity to hold a vacuum, B) close enough to the ground, and C) doesn't contact the ground which is darn near impossible with any WalMart parking lot entry. Once you've created this body skirting you have to engineer fans of sufficient draw (which will cause a huge shift in the design of the electrical system) and then be able to duct that air to the top of the car. We're not talking about a few 3" pipes, either, we're talking about consistent 2-foot diameter stuff. After all, we're not talking about a 1500-lb race car, we're dealing with a 4000-lb M5 here.

Once you've occupied the entire trunk with ducting, removed all but 3/4" of ground clearance, beefed up the electrical system with twin 150-amp alternators which will draw about 12 hp at full load, completely altered the look of the car with funny skirting, you'll still be left with a 4000-lb car that can now achieve .87g instead of .85g stock. 99% of drivers won't be able to tell a difference and they sure as heck would rather give up that in favor of being able to cross speed bumps without $1700 worth of damage and it would be nice to carry at least a couple bags of groceries.

Plus, Moppie is right. Every time you cross a dip, there will be a huge gap between the skirting and the road. One of the things that race cars can benefit from is almost zero suspension deflection and a nearly flat track. If you suddenly offered this technology on a Camry, they may as well replace the springs with solid steel to prevent suspension movement. That makes it a bit tough to latch doors on a hill. Sometime run your vacuum over a floor vent and then tell me that driving over a storm drain won't change the suction under that car.

Let's be realistic. With current technology its just not a marketable thing for the street. Just because its a faster thing or a better handling thing doesn't mean that anyone will pay for it or get any benefit from it. AND your arguing with us after you asked the question won't solve anything.

Ok sorry I am not trying to step on anybodys toes here but I have had a few oppions thown in my face with no fact behind them. If your respected veteran is way off I will let him know, there is no shame in not knowing alot about this technology there are probably fewer than a dozen of these sucker cars ever built making this a very understudied subject since they were banned so quickly, I just wanted to put the facts out here and see if anyone has any useful FACTS or oppinions bassed on facts. Insted I am getting taunted by people who don't know a fliping thing about what I am saying. Did you read Moppies last post?! that is exactly what I am talking about he might know more than me about every other subject on the face of gods green earth but he does not know heads from tails about evacuation fans or ground skirts and insted of doing some reserch on the subject he just blerts somthing negetive out assuming since i am a noobie that he has to be right I have been studying this stuff for about eight years now reading every article I could find on it and even reading the books of people that do not like it (like Carol Smith) and finding out why I came here expecting someone might know somthing about a possable street aplacation but insted I get stuff like the now infomus traction=death equation how scientific is that? Your take on the ground skirts is realilistic if you assume that they are paper thin strips if rubber, but there was more to them even back in the 1970s I am sure we could come up with somthing much better now. even the 2j had a decent ride hight prob three and a half or four inches are you telling me that it would be inpossabe to create a ground skirt 1 1/2 or two inches longer? I am not saying that the underbody evacuation fans are the anwser to everything pertaining to grip but they just might be an intresting place to start. And remember that the S7 makes enough downforce at 155mph to drive upsidown with no ground skirts remember that before you assume any tiny air gap will break the suction completly.

[kachok25]

Originally Posted by TheSilentChamber

I'm not as nice as moppie and curtis so I will tell you what everone else is thinking.

You may be young but that is no reason to think you know everything. You asked a question it got answered, the bubble in your head burst because everyone didnt worship you. Its now time for you to shut the hell up or start posting logically. The design is not even safe for racing, there is no way in hell it would be safe for street use.

Listen here you pathetic phsycic wanabe you don't know jack about me so quit with the wiser than thow speech, and if you want me to shut the hell up tell me to my face 2411B gulf Ave Gumlport MS if you got the balls you..... I better leave it at that before I get banned you are not worth it, not even close. And since you seem to such a freeking experet on the subject how do you come to the conclusion that the suckercars were unsafe? They never had an accedent in the races or test runs they did, i personaly have not even heard of a close call. So enlighten us oh master of butting into conversations that you know nothing about, What is the fatal flaw inharent in the desighen? This had better be good I woke up with a really bad tooth ach this morning and I am not in the mood for BS.

[kachok25]

Does anybody know a site where sombody else might actualy understand the basic principal of what I am talking about? You guy have been great and all for all my other threads but nobody here can help me with this one.

[CBFryman]

kachok25
FYI
i read your first post and gathered what you said in all your other posts because i didnt feel like going near-sited from your lack of paragraphs. This isnt a newspaper column, its ok to hut that enter key every once and a while.

[/rant]

Ok, I see what you are saying and on your average street car it just isnt feasable to include such technology. Greater downforce is more easily and safely acheived through the use of properly designed spoilers. Your average track/street car isnt going to need all that downforce at speeds so low that a spoiler will be produceing none.

The speed at which you have to move to create 1g lateral isnt exactly slow either. Remember, 1 lateral G would mean that a 1000kg car would have to withstand 9800 Newtons of Centripital force.

However im not completely agianst this on an application on a "stretable" car. Future vehicles similar to the Buggati Veryon (sp probably, i know TSC will get on to me for something anyway ) could benefit from such a device. Many highend sportscars and virtually all new super cars have settings on htem for "street" "sport" and "race." Street has the highest ride height, softest suspension and often no downfoce fro mthe spoiler and a limited top speed and all the little elves to keep you in controll and safe.
Sport takes it a step further, spoilers are engaged, ride lowers and stiffens, and the little elves lax their controlls.
Race has the lowest right height and stiffest suspension and maximum downfoce and often no little elves to help you when you get into a bind. it would be assanine to put a car in Race on a public road.

On up comming cars it would be feasable to put the technology that you speak of on the car and have it engage (skirts drop and air pumps engage) when the car is placed into "race" mode. The car could be equipted with little elves (lol, dont you love my name for tracction assist?) to help you controll the new downfoce. This would oly to be engaged when you are at the track and never on the street. it would probably never be used by 90% of the vehicles sold with it...but it would be quick to move the things off the lot when the salsemen shows the phompous assed buyer what the car will do.

However on your daily sport/luxury car. there is no need for such technology.