Hard "on the right front". Why?

[timcole421]

Accidentally posted this in the "gossip" section, thought I should repost this here.....

Just curious to the theory of being hard on the right front, in addition to the tons of camber on the RF?

I'm only asking as I am not sure I understand the physics of what is involved and what the goal is. It makes you wonder.....most track records are 10-15 years old, set back before these types of setups, exotic shocks, etc.

Should this theory work the same on a modified or stock car as well?

Thanks in advance!

[mab475]

Most of those records were set when tracks were wet and heavy and used a lot of chemicals that are banned now by the EPA not like todays track prep

[keeks]

Don't mean to hijack, but what kind of chemicals were being used back in the day for track prep?

[mab475]

Some used calcium some used soap and even brine water was used a lot.

[hpmaster]

7 tears ago or so there were tracks that used so much brine the cars would start oxidizing after a weekend show. Yea they were fast, tacky and would hold a ton of torque. Now all that torque is a game killer on an untreated track.

[Matt49]

Accidentally posted this in the "gossip" section, thought I should repost this here.....

Just curious to the theory of being hard on the right front, in addition to the tons of camber on the RF?

I'm only asking as I am not sure I understand the physics of what is involved and what the goal is. It makes you wonder.....most track records are 10-15 years old, set back before these types of setups, exotic shocks, etc.

Should this theory work the same on a modified or stock car as well?

Thanks in advance!

Your post on the gossip section got some pretty good answers from guys that frequent this tech section. I personally have nothing to add on the subject that the others didn't point out other than not ALL cars like the RF pinned down like that. Older front suspension geometry designs don't see as much gain in doing it and start to have some negative affects, not the least of which is bottoming out the frame and/or rack and pinion.
If you want anything technical answered, start in this section. The gossip section is 90% a complete waste of Internet bandwidth and server hard drive space thanks to a handful of people that could really use a good country ass whooping. It used to be a good spot to talk racing from a fan perspective but by the time you weed through all the garbage it just isn't really worth it anymore. But I digress...

[manwplan]

Matt49 and Mastersbilt, What do you guys think about some on the gossip page saying the cars are flatter these days? I disagree, they are hiked more than ever just in a different, calmer, more drive-able way. Flat to me is a 1980's leaf spring car. Those babies were flat.

[MasterSbilt_Racer]

Matt49 and Mastersbilt, What do you guys think about some on the gossip page saying the cars are flatter these days? I disagree, they are hiked more than ever just in a different, calmer, more drive-able way. Flat to me is a 1980's leaf spring car. Those babies were flat.

Some cars are really jacked in the back. Some are not. There are guys running real well without a lot of lr drop.

[mab475]

Its mostly driver preference. Some guys like the feel of being up on the bars and some don't. My driver prefers to be up on the bars. That's his comfort zone.

[Matt49]

10 years ago the entire left side of the car was coming off the ground and guys were carrying the LF 2 feet in the air. Things are different now. Keeping the nose down is where guys have found more speed for many different reasons. I think in most cases the LR is hiking up just as much as it always was but having the nose down is making it look "calmer". Also, look at the difference in the wheel well cutouts now and how some even cover the LR tire at ride height. That is done for several reasons but one is to disguise how much hike they are getting when the LR drops down.
As MBRacer said, some guys are running less than 12 inches of drop and having success. LR drop is all about a compromise between rear steer and LR drive.

[SR444]

10 years ago the entire left side of the car was coming off the ground and guys were carrying the LF 2 feet in the air. Things are different now. Keeping the nose down is where guys have found more speed for many different reasons. I think in most cases the LR is hiking up just as much as it always was but having the nose down is making it look "calmer". Also, look at the difference in the wheel well cutouts now and how some even cover the LR tire at ride height. That is done for several reasons but one is to disguise how much hike they are getting when the LR drops down. As MBRacer said, some guys are running less than 12 inches of drop and having success. LR drop is all about a compromise between rear steer and LR drive.In what ways are guys today able to keep the left front down and still have drive and rotation? is it in the j-bar or rear angles of the 4-bar

[hpmaster]

Some very fast cars are limiting the right front movement and in doing so are making the cars look flatter. It is just another way of controling how much weight is applied to the right frt wheel. Maybe someone figured out how to turn a tight race car.

[Ltemodel]

Soft springs can give the illusion of weight transfer, but things aren't always as they appear. I believe it is a definite advantage to keeping the left front on the ground. Any air passing under the car creates lift and takes away traction. The less air under the car the more air over the car = more traction, side bite, whatever you are looking for.

The key is getting a good balance in the car. If you picture a perfect race car. It would be: put as much horsepower and traction it it as possible and drive it as smooth as possible to not loose momentum. On dirt this is not possible, so we start backing up from that perfect car and create something that is as close as we can get it. We cut horsepower, lift off the gas entering the corner, use the brakes, etc.; but the same mindset should still apply. How close can we get to that perfect race car and still be drivable enough to win races.

Guys liked picking the left front years ago, when four bars were young, because it felt good. Tons of traction off the corner. Now as guys progress, shocks got better, aero becomes more important; the cars are getting more calmed down and maneuverable. Nowadays drivability seems to be the main focus while getting maximum downforce on the entire car.

[Ghopper]

Center of gravity position and lateral acceleration determine all Left-to-right weight transfer. Nobody disagrees with this.

Front and rear roll stiffness determine how the weight is distributed over the tires. Nobody disagrees with this.

As Ltemodel mentions, soft springs can make this transfer look exotic. Because of ride height rules, the static body position of the car is much different than the dynamic race body position. It has been learned that low INITIAL front roll/ride stiffness will create a desired transition from static body position to race body position. Then bumpstops or staged springs increase the roll/ride stiffness to create desired dynamic wedge rates.

.....and to add to your left front tire on ground discussion. LF is needed for entry/middle, but not really on exit. These are rear drive cars. The more load we can get on the rear tires the better. This is usually related to keeping load on the LR tire. X weight will be transfer anyway because of CG height and Lateral acceleration. You would rather unload the LF and load the LR with what weight is remaining on that side.


Ghopper

[Brian Gray]

you cannot have downforce without air getting under the car. downforce is created by equal amounts of air moving at different speeds . without air under the car all you have is drag

this aero influence does contribute to the setups many teams use and is partly the reason we try to keep the frontend relitive to the race track.

[MasterSbilt_Racer]

you cannot have downforce without air getting under the car. downforce is created by equal amounts of air moving at different speeds . without air under the car all you have is drag

this aero influence does contribute to the setups many teams use and is partly the reason we try to keep the frontend relitive to the race track.

Downforce is a difference of air pressure on opposite sides of a surface. Can be achieved by having different speed airflows on each side or by simply having much less air on one side. The advantage of a vacuum under a race car was demonstrated in the 1960s with the Chaparral 2J.

[Matt49]

Downforce is a difference of air pressure on opposite sides of a surface. Can be achieved by having different speed airflows on each side or by simply having much less air on one side. The advantage of a vacuum under a race car was demonstrated in the 1960s with the Chaparral 2J.

Exactly! There's a lot to be said for keeping air OUT from under the car yet letting it escape out the back. Thereby creating a huge low pressure area. I'd love to get some pressure readings from just under the decking of a late model at speed on the track compared to just above the decking.

Remember a few years ago when some guys were trimming their LF quarter panels almost completely off? With the way the LF QPs are tapered in at the back, it creates a major hindrance for air trying to evacuate out the back (especially when the car is yawed out). I guarantee they weren't doing that because they thought it looked cool. Somebody figured something out and I'm guessing officials put a stop to it.

[Brian Gray]

Take air away from the high speed area of an airplane wing and tell me if it will still stay airborne.

If the air isn't under the car there is nothing to escape out the rear. You can disagree all you like but the physics don't lie.

[Ghopper]

Take air away from the high speed area of an airplane wing and tell me if it will still stay airborne.

If the air isn't under the car there is nothing to escape out the rear. You can disagree all you like but the physics don't lie.

Brian - The high speed side of a plane wing is the top (longest side) to create lift. I think your argument is not going the right way for a late model application. If applied to a latemodel, with equal flow above and below the car would also cause lift, as it is a longer distance over the top than the bottom.

We get much of our downforce from high pressure areas (nose, spoiler). More like angle of attack for airplane wings. In this case you want minimal air under the nose of the car. In cases when you have a splitter (like NASCAR), a small amount of air can be beneficial.



Ghopper

[hucktyson]

As usual Brian Grey is a toss off , wind tunnels don't lie Brian

[Brian Gray]

Brian - The high speed side of a plane wing is the top (longest side) to create lift. I think your argument is not going the right way for a late model application. If applied to a latemodel, with equal flow above and below the car would also cause lift, as it is a longer distance over the top than the bottom.


We get much of our downforce from high pressure areas (nose, spoiler). More like angle of attack for airplane wings. In this case you want minimal air under the nose of the car. In cases when you have a splitter (like NASCAR), a small amount of air can be beneficial.



Ghopper

The physics don't change because its a late model.
And Huck you obviously haven't spent time in the tunnel.

The effects created by a splitter are the exact reason the xd4 front end out perform every available nose on the market.

[Brian Gray]

Please revert back to post 18.

[Brian Gray]

As far as answering the question I believe you are asking originally. Why the cars are so pinned over on the right front? Rephrase .

My opinion is most cars now days are so hooked up with the 4 bar spring behind they are trying to eliviate the left rear drive to help the car turn while attempting to retain forward drive which is why typically the cars that are fast stay straight and flat through the corners. Just my opinion.

[hpmaster]

Comparing an airplane's wing generating lift to a car's surfaces generating down force is like trying to trim your hedge by flying a helicopter up side down.

[Matt49]

Please revert back to post 18.

You don't want air going under the car. If air is going under the car, then the air evacuating out of the back is just creating air FLOW and NOT a vacuum/low-pressure area. If you can stop air from going under the car, the openness of the back of the car creates a vacuum. That in combination with the high pressure areas above created by the nose and spoiler (and decking if your attitude is correct) is what gives us downforce. If we wanted air under our cars, then why do ALL of the top teams run valences that leave almost zero clearance between the nose and the ground when the car is at racing stance?

[Ghopper]

The physics don't change because its a late model.
And Huck you obviously haven't spent time in the tunnel.

The effects created by a splitter are the exact reason the xd4 front end out perform every available nose on the market.

Brian - Please.....we have all been off the mark and had to study hard to find answers. Unless you were on a rolling floor tunnel with minimal blockage, then I don't think you were getting good answers for your stall point of the front splitter.

I am on the shaker and compliance rig side of the automotive/race engineering. My friends are in the CFD/physical tunnel side. So I have to rely on what they tell me over beer. For my humble comment: I can also say my wife did better in physics than I did, so I was not the rock star student and have been wrong before.


Ghopper

[hpmaster]

The Bernoulli principle, only about 300 years old, explains and validates what Matt49 is saying. Nuff said.

[Ghopper]

The Bernoulli principle, only about 300 years old, explains and validates what Matt49 is saying. Nuff said.

HP - Bernoulli applies to airplane wings in a flow field, were the same flow is on both sides of the wing. (Maybe that is your point). At least that's how I remember it, but maybe I need straightening out.

Overall I am with Matt49. But I would not apply Bernoulli as the primary downforce to a latemodel as the flow never the same on top and bottom. I am sticking with flow that is not horizontal to the surface (mostly used in Bernoulli principle ), creating high pressures against angled surfaces, and hopefully as little pressure under the car as possible, through road surface interaction and venting (back of car, wheel wells, left side higher than right with a 10-15 body slip angle).


Ghopper

[hucktyson]

Brian you could sell everything you own racing related and still not afford wind tunnel time. I have seen real data from a well respected high level engineer who has been there and done that.

[Brian Gray]

I believe we are in an argument just for the sake of argument. I am simply stating you cannot have one without the other. Air under is a requirement. Like I said the physics don't change. Without air under the car the down force is simply drag. Not free tire loading. Does that clarify?

[Brian Gray]

Huck you may have seen it but you clearly don't understand it.

[hpmaster]

I used Bernoulli as a first step in understanding a fluid, air, reacting on one surface as it flows horizontally along one surface. Key here is first principal. The number of know principles that come into play when trying to figure out how to generate "down force" on a car as it travels in changing directions on different surfaces at variable speeds while changing angles attack and then have braking forces, suspension reactions changing the distance of the car to the ground while going thru air is mind boggling. When confronted with a statement that a race car is like a wing or bullet I frankly lose it. This is partly because of my work in the 1980's on developing what are know as VLD bullets. Bullets and wings are completely surrounded by the air they are traveling thru making the predications on the reactions on them infinitely more predictable. Even then it took years of work field testing, development of computer technology and programs to get where we are today. My input was to attempt to get people to make the first step to understanding there are no simple solutions to where down force is generated on a car rolling on the ground. Now lets look at the drag created. Time to start drinking.

[Brian Gray]

I used Bernoulli as a first step in understanding a fluid, air, reacting on one surface as it flows horizontally along one surface. Key here is first principal. The number of know principles that come into play when trying to figure out how to generate "down force" on a car as it travels in changing directions on different surfaces at variable speeds while changing angles attack and then have braking forces, suspension reactions changing the distance of the car to the ground while going thru air is mind boggling. When confronted with a statement that a race car is like a wing or bullet I frankly lose it. This is partly because of my work in the 1980's on developing what are know as VLD bullets. Bullets and wings are completely surrounded by the air they are traveling thru making the predications on the reactions on them infinitely more predictable. Even then it took years of work field testing, development of computer technology and programs to get where we are today. My input was to attempt to get people to make the first step to understanding there are no simple solutions to where down force is generated on a car rolling on the ground. Now lets look at the drag created. Time to start drinking.

Agreed. But even as your thought process develops the basics apply to every variance you encounter. The amount of mis information in racing is astounding. I just wanted to make it clear so as not to be misleading that when you approach an aero issue you remember how it works.

[Ghopper]

My input was to attempt to get people to make the first step to understanding there are no simple solutions to where down force is generated on a car rolling on the ground. Now lets look at the drag created. Time to start drinking.

I agree. Good clarification.

Ground interaction is lost in most persons view of downforce. There is air under car (for brian), just not enough flow to talk about a wing as HP mentions in the above post. Having to bodies (car and ground) with differential velocity is huge for sucking air from under the car.

Testing for aero could be done on a moving road tunnel ($$$$) or with data acquisition ($$) on an open road with load sensors in body or spring mounts. Many papers have be produced to show procedures and comparison of results for other types of racing.....but when it comes down to putting these in practice...we (I) don't have the time or extra money to do this.


Ghopper

[hpmaster]

One of the best mechanical engineers I ever knew, my father, said Yea, BUT Yes, BUT or Agreed, BUT translated is Yes you are right BUT I want to continue to argue.

[Matt49]

Brian,
I don't think this is an argument for the sake of argument. I am disputing your theory that you must have air flowing under the car to create down force. You keep referring to physics but you're ignoring the physics presented that debunk your theory. Wing physics don't apply to race cars on a race track for the reasons already mentioned by others. But to summarize; wings are in complete interaction with the fluid through which they flow. Cars (unless they are flying) are not. The same physics and aerodynamic principals do NOT apply.

Take this example:
Imagine the body was all the way down against the race track and NO air was allowed under the car from the front. For the sake of this hypothetical we'll have to assume that the body is touching the race track but with zero coefficient of friction between the body and the track to eliminate the variable that would be introduced there. The variable I'm isolating is the amount of air allowed under the car from the front and I want it to be ZERO. But there is still a big opening in the back of the car and the rest of the boy has the same general shape (wedge nose, spoiler, etc.).
Down force comes from three places in this example. A high pressure area over the nose, a high pressure area over the spoiler, and a low-pressure area (in this case a vacuum) under the body. This low-pressure area occurs despite the fact the NO air is flowing under the car. Therefore, air flow under the car is not required to create down force. In fact, the less air flow, the better.
Of course there is drag but ALL down force creates drag. It's a trade-off. Identifying how much drag is acceptable for the amount of down force you are producing is an entirely different problem that brings motor and speed into the equation. What most people don't understand is that the force required overcome aerodynamic drag increases exponentially as speed increases. Compared to the force required to overcome other types of drag (like component drag) which increases linearly with increases in speed. But suffice to say in most short-track situations, we'll take all the down force we can get. We spend a lot more time trying to get the car to stick in the corners than we do drag racing.

[FlatTire]

http://aprperformance.com/index.php?option=com_content&task=view&id=174&Itemid=44

Check out the diagram showing the high pressure/slower velocity air flowing over the top of the car and the low pressure higher velocity air flowing beneath and the effect the splitter has.
We essentially have a splitter on all the modern day late model noses but I don't get the feeling it was put there based on engineering data. Maybe Bentley from Dominator can tell us? Or Brian Gray can you shed some light on the splitter you are talking about? got any pics?

I've often thought about designing my own splitter and testing to determine size/placement. A lot of the roadcourse guys use simple manometers to measure pressure differential/determine effectiveness and seem to have a better handle on this stuff than we do. There is no reason that couldn't be done on a late model.

Another question I have is when you begin to add front down force and make these cars more "aero balanced", are you not taking away from rear down force? What effect does a front splitter have on the rear spoiler? Does it not act like a teeter-totter? Will adding more downforce to the front end decrease downforce at the rear spoiler in effect reducing forward bite?

On a side note, has anybody ever thought about installing hinged flaps on the deck to let out any high pressure that might be underneath?

[Ghopper]

On a side note, has anybody ever thought about installing hinged flaps on the deck to let out any high pressure that might be underneath?

We put strings around the deck with a camera mainly to look at turbulence and flow direction. All the strings near the opening, like oil cooler, go straight down into the hole. i would say that there the pressure is clearly lower there. Which is why I think scopes are overkill for oil coolers.


Ghopper

[keeks]

Correct me if I am wrong, but don't F1 cars create a combination of high pressure areas and low pressure areas producing enough downforce to overcome the entire weight of the car? Thereby in theory allowing said car to actually drive upside down at speed? Sure doesn't seem to be a drag issue negatively affecting performance. (that being said I know it's a huge balancing act).

[hpmaster]

F1 cars use a drag reduction system, DRS, the box like wing system on the rear of the car. There are rules to when, where, how and how far from a competitor it can currently be used. Frankly if you have an hour or three read the official F1 rules, not the short version, you will soon realize an F1 car is closer to an F16 flying on 4 tires than a LM dirt car.

[EAMShater]

Not trying to get in the thick of things here, but I think what Brian is mainly trying to say is there has to be air under the car in the first place to be sucked out to create the downforce/vacuum. Not necessarily air flowing under from the front.

[Brian Gray]

You would be correct.

I can clearly see there is no point to further discuss this topic some people can't think past their old philosophy s

[Ghopper]

:) Brian stepped in it the moment he said "wing" and used it as an example.

We will not be able to stop air from entering the car from the front. Air is present as we are not working in a vacuum. No body is arguing against that. However, you shouldn't think that increasing air flow under the nose helps with down force on a latemodel. Seal that nose to the ground best you can and still be able to cool the car.


Ghopper

[Brian Gray]

Where did I imply you should try to increase air under the car?

Im pretty sure I said you cannot have down force without air under.

[FlatTire]

In order to generate an aero force, there has to be a pressure differential betwen the air above the car and air under the car. When the pressure above is higher you have down force. The other way around and you have lift.

But the idea is not to flow more air beneath the car which would cause higher pressure resulting in more lift. The idea is to speed up the airflow that already exists under the car, reducing its pressure(Mr. Bernoulli's Law) to help aid in downforce. Its the whole reason they use diffusers on F1 cars & redirected exhauast gas flow to help evacuate air under the car, and they've even used fans.

[Matt49]

I'm going to move past the whole "air under the car" aspect because I think we're agreeing but perhaps not having a common understanding of the "why" that makes it work.

Moving on...

I think one thing that gets lost in all of this (remember the discussion was about pinning down the RF) is that it does a lot more than just seal off the nose to help create vacuum under the car. Because we are also hiking the LR up with shocks and bars, having the RF down in combination with the yaw that the car travels in, creates a drastic change in the angle of attack of the decking and the roof. The decking is a huge amount of surface area so presenting it at even a slight angle of attack is going to generate considerable downforce. The same can be said for the roof. I also think getting the nose out as far as the rules will allow (lessening the angle a bit) will maximize the downforce/drag ratio.
Has anybody ever thought about putting vortex generators right at the curve where the angle of the nose goes on to the hood? I'd be interested in knowing how much flow separation there is in this area to determine if vortex generators would be at all beneficial.
That being said, I think you could probably find something in most rule books that wouldn't allow something like a vortex generator even though it might not come out and call it that.

[FlatTire]

Brian is this you??? I want to know more about this XD-4 nose you designed.

http://www.youtube.com/watch?v=0x_OZs_wzEQ

https://www.google.com/search?q=brian+gray+racing&source=lnms&tbm=isch&sa=X&ei=5MXrUs_YFKmqyAGp5oHwAw&ved=0CAoQ_AUoBA&biw=1384&bih=732

[hpmaster]

Be careful comparing a 1400 to 1600 pound, depending on the year, F\1 car capable of reaching over 220 mph with a completely purpose built belly pan used with in some cases with mechanically driven fans, plus varying degrees of perimeter controlled sealing of the surface it operates on that is smoother than almost any highway, while on a suspension that's total movement is closer to a go-kart than any late model dirt car, in conjunction with anti drag designed into it along with dedicated wings to a late model dirt car weighing 2300+ pounds with NO belly pan or wings operating at half the speed, while yawing, lifting, bouncing on a almost infinitely variable surface. As for Bernoulli's Law, while correct in as far as it goes, is not detailed enough to support the precise calculations required for engineering a purpose built race car with it alone. Sorry for the run on sentence.

[hpmaster]

Matt49, vortex generators, open sail panels, an angle here, a bump there. I now go to my corner and say no more.

[Ghopper]

FlatTire, Brian: The moment anyone says Wing or Bernoulli they are implying air speed differential to create a pressure difference.

We all agree that we want this pressure difference on our DLMs that builds downforce. I want to focus on the nose part of this discussion as it applies to the thread topic. The roof can be more closely treated as a wing, so you can Bernoulli that.

Dirt Noses: The "splitter" designed into all of these dirt noses is not speeding up any thing....Especially if you are using the something like the valence kit for the MD3. It does make a nice big surface to take advantage of the high pressure built up at the front of the nose.

My neighbor works for TotalSim (http://www.totalsim.us/). Maybe I can pick his mind for more ideas. We kicked around crunching some numbers if I had better CAD or 3D scan of my car, but in all reality that would still be cost prohibited.


Ghopper

[Ghopper]

HP - you crack me up

[FlatTire]

Lets talk about this nose situation, why is the "splitter" surface of a late model nose above the air dam/skirt/valence? Should it not be below instead like every other type of race car that uses a splitter?

Why not drop the splitter surface lower so its closer to the race track and get rid of the blunt air dam/valence/skirt.
You could even move the leading edge further forward.

[Ghopper]

We can't control our splitter height as well as asphalt cars to design our application the same way. NASCAR splitters can generate better down force a small distance off the track because they can work in the correct range of heights to apply your Bernuolli skills. In that case, sealing the nose by putting the nose ~2mm off the ground can stall the air vs ~10mm and have measurable down force changes. They also have a very different body cavity after the splitter and are usually at speeds 2x what we are driving at.

Since we cannot play in the same spitter game, we need to look elsewhere. The dirt valence is a durable solution to minimize air under the nose and not rip it off on our highly variable dirt surface. But if you can get it lower, you should have more area to generate the high pressure on top. It would have to be better, as long as you don't rip the nose off racing.

Ghopper

[Brian Gray]

In order to generate an aero force, there has to be a pressure differential betwen the air above the car and air under the car. When the pressure above is higher you have down force. The other way around and you have lift.

But the idea is not to flow more air beneath the car which would cause higher pressure resulting in more lift. The idea is to speed up the airflow that already exists under the car, reducing its pressure(Mr. Bernoulli's Law) to help aid in downforce. Its the whole reason they use diffusers on F1 cars & redirected exhauast gas flow to help evacuate air under the car, and they've even used fans.

Ding ding ding we have a winner!!!

[FlatTire]

Look at what was done with a splitter here:

http://www.katechengines.com/street_performance/downloads/Katech%20wind%20tunnel%20data%20report.pdf

The video of this car in the wind tunnel is on youtube if you care to see more.

So which one of you nose manufacturers has done your home work like the company I mentioned above and tested your product and collected actual data?

[FlatTire]

"Matt49: I think one thing that gets lost in all of this (remember the discussion was about pinning down the RF) is that it does a lot more than just seal off the nose to help create vacuum under the car. Because we are also hiking the LR up with shocks and bars, having the RF down in combination with the yaw that the car travels in, creates a drastic change in the angle of attack of the decking and the roof. The decking is a huge amount of surface area so presenting it at even a slight angle of attack is going to generate considerable downforce. The same can be said for the roof."

Totally agree and have thought the same thing. Just take a look at all the dirt on dirt pics from out in Tucson. The faster cars have got the noses glued down, the spoiler/deck is up in the air more so than ever before to take full aero advantage of whats there. The front suspension trend isn't the only reason these cars are tighter than ever before.

Now we gotta figure out how to get air to the center of the rear spoiler to better utilize that. I think hpmaster alluded to that with his open sail panel comment.

Sometimes I think it would be smart to take a year off racing and just go test. You guys got my wheels turning........thanks.

[keeks]

The reason I brought the F1 car was not to compare the two obviously different cars. I brought it up to compare the F1 car to Brians example that with no air under the car the whole thing turns to drag. There is far less air under an F1 car than a DLM. So I thought his drag issue was bunk.

[tworrick]

Sorry off the subject just a bit. Does anyone sale a good open sail Panel ? I can make one but do not have the right tools to make it rigid enough . Any help ? I believe it is very important to this subject.

[Brian Gray]

Keeks. Post 54
True f1 cars have less air under them , let's say less room for air, which is why they use the exhaust and various air inlets to blow air into the diffuser at the rear. This adds volume to the diffuser which aids in increasing the air speed under the car. The faster the air moves the more air volume that passes under the car. There is more downforce generated by increasing the air speed under the race car than both of those wings combined . This I learned from a very good aero engineer at lotus. One of the key rules in f1 pertains to the diffuser. Very critical to handling

[Brian Gray]

You can test this by taking a piece of paper and laying on a table. Just blow air across it horizontally you will find some interesting results

[adamsraceshocks]

I think we need to remember that these race cars are more of a wedge than they are a wing. Think of sticking your hand out the car window while going down the road. If you put the front of your hand down the force of the air on the top of your hand pushes it down, if you put the front up it goes up. The bottom of these cars is too irregular to efficiently use the air traveling underneath so we put the nose as close to the ground as we can to minimize the air and therefore turbulence under the car. The attitude of these cars going down the track maximizes the surface area used for down force.

[RRR_Products]

Very interesting topic I finally finished reading through. Now I know coming from asphalt aero grip is the best grip to have for certain conditions. For example a car that had the Hp and tq we wanted maximum downforce to an extent of track configuratin(straight aways vs corners). With lower Hp cars this made a huge difference on aero set ups. I am not a late model racer on dirt but a modified guy and just finished building our new body for this year. The vacuum under the car is very interesting and after reading about the string theory we may just try this and film. Another question I think would be great to answer is a general or close to accurate scale as to how to measure down force by surface area, angle, and speed. Now I know air density plays a factor but not sure as to how much. I know for our modified when we get down on the rf the hood lines up with the tire with a 45* trying to alleviate getting air under the car even if its a minimal amount. Also, with sail panels are you guys seeing a huge difference removing them handling wise? I can see that this may cause an issue on cars possibly to tight in corner due to the side force generated. In the end though I believe on dirt maximum down force is what any car should have balanced of course.

[Ghopper]

Guys,

Nose people: I was chatting for 10 mins with my local aero guy yesterday about basics of splitter sensitivities. For the Bernoulli people - To find out how much effect the under splitter flow has on down force, he quickly focused on the position of the Stagnation point. This point will determine how much air is going to be forced under versus going over the car if we were just looking at a 2D plane. If the stagnation point is low, then less volume of flow will be directed under the car....kind of like a Y in the road. Basically blunt noses like NASCAR/street cars will force more under the car than a wedge nose DLM.

So we are different than Cup data, and look a little closer to some other forms of racing, but without tight clearance control. Then the conversation turned to valence on or off......and his distraction looking at picture of our standard rear spoiler designs.


Ghopper

[Bubstr]

I have thought on this subject more than a couple times. It is the difference in pressure that creates down force. We could not or even want to eliminate all under car air, that is what cools the engine. With that said, the efficient evacuation of this air with a venturi effect is what creates more or less down force. The same thing that sucks your gas out of the float bowls and into the rapid moving air of the carb throats. You have two maybe three areas where you have rapidly moving air converging with the under car air. The front and top of the front wheel wells, the rear spoiler and to some extent the left rear quarter area. If these spots promote evacuation, you will have down force and a better cooling car to boot. If the car cools better, you can use that bonus to cut down under car air.

I should remind you that Chad Kanaus got a 30 day vacation for reshaping the front fenders of Jimmy Johnson's car in precisely this area. Just something to think on.

[Matt49]

Check out these pics of Bloomers car from Batesville last year:
www.latemodelphotos.com/2013/Batesville-Speedway-AR-815-18/i-w9KmHg4/A
www.latemodelphotos.com/2013/Batesville-Speedway-AR-815-18/i-w9KmHg4/A

Notice anything interesting about the fender flares? Not exactly a matching set.
Makes sense if you think about what he's trying to do with that.
Also notice that his center spoiler brace is trimmed down so that it doesn't block air from getting to the spoiler when the car is yawed.