ok, well I drag race the car which most people know. The question is simple and the answer is kinda tough. The stock wing looks cool in my eyes but would it help me to remove it when running the car at the track? I assume the stock wing creates downforce and drag but at the same time it may be pulling some 'outside' air into the void behind the car at higher speeds, thus helping the CoD I think. So at high speeds I guess the wing might be technically helping the airflow by making less backpressure but the extra downforce is in essence making the car much heavier I would assume. If it can produce say 200lbs of downforce at 120 its making the car the same as being 200lbs heavier. So... with all that in an equation, does the wing help or hinder top speed in a drag race?

This is my belief: The stock wing will slow the car down an insignificant amount (MUCH less than 1%) at speeds less than 50ish. But at 120-130mph the additional downforce may be slowing it down by a few percents but at the same time by the wing pulling air into the very very low pressure zone behind the car it should be helping aerodynamics.

To finish the topic is the vortex generator.... Its designed to disturb the airflow and help pull air into the low pressure zone behind the car and thats it... As another note it lowers the low pressure zone behind the car so that more aerodynamic air can hit the wing, helping the wing provide more downforce. So, is the best way with the VG and no wing? That would help pull air into the low pressure zone but wouldnt have the negative side of the greater downforce.

Also, does anyone have any experience in making a pass with the wing on and a pass without the wing? Did it slow you down, speed you up? I guess we could all theorize what the effect would be but would help if someone just did it and got results.

 

curious too

 

I will offer this, as you say, once the wing becomes effective it creates down force which means it has drag. Up until it becomes effective it has drag just because it is out in the air stream.

Since in a drag race down force is not necessary (is it?) I would pull it. weight, drag, more weight and more drag when when it is working.

I don't think you can figure the wing cleans up the aerodynamics.

 

The RS has no wing that should give you a clue. The VG cleans up the air to the wing which means it may not clean up the air to the rear of the car if there is no wing. In fact it may make it worse. To me weight is the enemy not your friend. Look at an F1 car if it loses its back wing it immediately pulls more than 500 rpm amd top speed goes up accordingly. This is at 180 mph but should also give you a clue, not that the EVO wing is as effective as F1 but you get the gist.

 

Try this sight and type in wings for the technical forum and the archive and you will get more than you asked for from engineers and enthusiasts

http://forums.autosport.com/forumdis...p?s=&forumid=8

 

Just to clarify something, DOWNFORCE and MASS are NOT the same.

This is one of my pet-hates, so let me explain...

If your car if your car is 1700kg (3740lbs) and your downforce amounts to say 20kg (miraculously) then ultimately what your tyres will 'see' is 1720/4 = 430kg pressing on them (going straight, level etc.). And that's about as much relation that downforce has to mass.

To short explanation to this is that the more mass your car has, the slower it will be able to go round a corner. But also, the amount of lateral force (pointing sideways to change your car's direction or turn a corner) is roughly proportional to the vertical load (the harder you're pushing down on it).

What downforce does is increasing the vertical load on your tyre WITHOUT increasing the amount of side force your car needs to go around a corner.

If we assume that your un-winged car creates no lift then if you dirve it around 130R at Suzuka circuit (legendary) at 120kph will need about 1700 x(120x1000/3600)^2 / 130 = 14,530N of force. If your tyres have a coefficient of friction of say 0.9, then the total load on your tyres need to be roughly 1646kg which is almost the weight of your car. So going any faster, the car will begin to slide, etc. Actually, according to this, our max speed around this corner is 121.9kph.

If you make the car heavier say 1800 and see what speed you can go at, if you go through the maths, you'll just get the same number of about 120kph.

If you add downforce to the car, you'll end up needing the same amount of sideforce of 14,530N but now your car will be further away from the limit as it can now generate 1720kg x 9.81 x 0.9 = 15,186N, in essence, the car's top speed through this corner is now about 122.7kph. So a 1.8kph increase isn't a lot (0.66%) but here we're adding a relatively little downforce comapred to the car's mass like 1.1%.

Anyway, downforce is not the same as weight. Aerodynamicists and giant supercomputers are not employed to do something that can be achieved by adding a lump of steel (or tungsten).

p.s. I understand that in a real corner, there are weight transfer and other effects that limit your cornering speed. However, this is just for the sake of a simple demonstration.

 

-Any wing will need a certain velocity of air to start 'working' so at relatively low speed, it will stall and not do much. At over a certain speed things can also go wrong. But I don't this this applies to the speeds here.

-The wing will generate some drag. While this is true, the amout of drag can be (and usually is) much different from the downforce. A good starting point in wing design is to generate as much downforce as possible for as little drag as possible. Another point is to make it do so over a range of speeds.

-The thing about the wing pulling air behind the car is I think a misconception. The wing and the rear end of the car does something to the air and getting the right flow over the end of the car is important. I think the important bit here is to get the flow so that you are not throwing away energy or ruining the flow on to the rear wing. I will get back to you on this...

 

The vortex generator, I think attempts to cut drag but the way it does it I think spoils the air flow to the rear wing. Which is strange. What would be good would be something that tidies up the airflow before the air gets to the wing.

I don't think there's a lot of information on making a pass with/without the wing. There are some very complex cfd models regarging flows coming off the rear of a car.

Anyway, when I pass lorries on my motorbike, you notice a low pressure zone when directly behind it and as soon as you pull out (relatively close to the lorry's rear end) you'll be hit by a whoosh of air which will push you sideways a little bit. Now you don't get things as big as lorries on the strip. So is you're behind and to the right, you might slow down. But I think most of this effect is nullified as the barrier between the lanes will stop this air flow.

 

ok.. so more engineers are needed

Simply, what is the best for top speed/acceleration (Drag Racing). Cornering isnt too needed when going straight and traction on an AWD car is not really needed once you hit 80+ MPH and if it is an issue... you probably have too much torque steer to notice

I just figured by adding downforce you are technically slowing the car down by making some energy being used to push the car down instead of forwards. But I also figured that without the wing the low pressure zone would be worse (making some of the energy actually trying to push the car backwards instead of forwards).... so, is no wing better or worse for drag racing? Or is this a question for a wind tunnel and hugely complex math where I am better off just yanking the wing and giving it a go?

 

short answer would be: drag racing in a stock-shaped car = no wing. Not really needed in our case (AWD). Your car generates some lift but it's nothing dangerous (over a 1/4mile blast).

while the drag exists, its effect is not really significant if you compare it to say losing weight or rotational mass (like lighter flywheel, alloys).

So, just going straight, take the wing off, lower the car and go.

 

According to Mitsubishi the VG directs air to the spoiler and
"VGs create streamwise
vortices, the vortices mix higher and lower layers of
boundary layer and the mixture causes the flow separation
point to shift downstream, consequently
separation region is narrowed. From this, we could
predict that VGs cause the pressure of the vehicle’s
entire rear surface to increase therefore decreasing
drag, also the velocity around the rear spoiler to
increase, and the lift to decrease."

For some actual figures :
"Application of the VGs of the optimum shape determined
through the abovementioned analyses to the
Mitsubishi LANCER EVOLUTION showed a 0.006
reduction in both the drag coefficient and lift coefficient."

More info and the research is here: http://www.mitsubishi-motors.com/cor...004/16E_03.pdf

Mitsubishi puts a lot of research into getting there aerodynamic aids right but that is right for the car's purpose which is rallying, and in particular the Group N class of the WRC so everything on the car is affected by those rules as well. Everything to do with the exterior of the car is the way it is for a purpose, not for show. BUT obviously drag racing has different requirements. The VGs sound ok but the wing could probably be removed.

 

Ahh.... so that's how it works. So the standard wing setup (w/o the vg) is pretty much too low and the separation (w/o the vg) mucks up the flow. If it presents the wing with a nicer flow, then the wing will work better and looks like they've managed to reduce the drag too.

I had misunderstood how it works cos I read somwhere that the vg 'creates turbulent air flow' which would be a rather silly device to have before your wing. And there is some drag to be lost if you can trap a vortex in the back sloping surface so that's what I took to be how it works.

Thanks for the info, man.

I've got it on my MR however even before I know that it actually works though!!!

 

It does create turbulence (which is beneficial at the boundary layer) as it increases stability of airflow over a vehicle. Google "laminar flow breakdown".

 

It creates streamwise vortices which effectively delays the flow separation. From the look at the plots, I wouldn't say that turbulent air is hitting the wing which is what I thought happens.

 

Take a look at the stock RS 1/4 mile time (13.1) vs. the GSR 1/4 mile time (13.6?).