Spoiler aerodymics rear spoiler design and construction

[obi_waynne]

We look at how spoilers work? We also explain the difference between a spoiler and a wing. Spoilers are generally closer to the body of the car and help diffuse the air. Wings are mounted much higher up and have an aerodynamic effect of creating downforce

Continue reading... or post your comments below on this article.

 

[bax]

On this topic at what speed do Wings/Spoiler affect the performance ?

 

[old-git]

They affect downforce and drag immediately the car starts to move. However, it won't be noticable on a road car until around 60mph and then only on back to back comparisions. Above 100 there is a marked effect, but this will be both downforce and drag. Basically, on a 'normal' road car they are only for show. On high performance cars where they have been incorporated into the overall aerodynamic package they have a place.

Any wing bought from eBay or a 'performance' outlet and bolted on is simply a drag inducing appendage.

To prove my point, when high performance Jap cars do high speed runs they remove the huge rear wings because of the drag they produce.

 

[bax]

Out of curiosity ,lets say i have a car that was able to hit 120Mph as a top speed would adding a Spoiler reduce that top speed to 118Mph ?

 

[old-git]

Out of curiosity ,lets say i have a car that was able to hit 120Mph as a top speed would adding a Spoiler reduce that top speed to 118Mph ?

How long is a piece of string?

Are we talking spoiler or wing?

A spoiler does what it's name implies, spoils the air flow, usually over the rear of the car. The idea is to reduce lift.

A wing, properly designed and installed will increase downforce at the expense of increased drag. The ratio between downforce and drag depends, again, on design and location.

So, in answer to your question, I have no idea. However, in my experience, fitting a badly designed wing in the wrong place (most add-on wings fall into this category ) will result in more than a 2mph loss.

 

[bax]

i guess i should give you more details .. the spoiler was ermm how should i say it .. we basically took some cars Original spoiler and cut it on the sides in order for it to fit on our 2 Ton 186hp Suv ... we didnt take into consideration Aerodynamics and such we just did it for looks ... but ive noticed that i can no longer achieve Top speeds like i used to .. now it could be due to age of the engine and such but im curious if a bad spoiler can cause such a drop on a car with such attributes

 

[old-git]

These are spoilers:




This is a wing:



If you are doing it just for looks, then any aerodynamic or performance consequences are immaterial.

Take it off and try a top speed run. If the top speed increases then you will know that the spoiler or wing is causing the speed loss.

What angle did you set it at, one that looked the best?

Post a photo.

 

[old-git]

Pages 33-41 should give the reader an indication as to why simply slapping on an after market wing from eBay or from another car won't work very well or even not at all:

http://www.strangeholiday.com/oops/stuff/annurev.fluid.38.050304.092016.pdf

 

[bax]

mmmmm .. its kind of a hybrid between the two but its more like a wing than a spoiler i guess ... ill try to take a pic when i can .. as for the test run , Unfortunately i only get to test out top speed like one in a number of months ..Traffic wont allow it (Law aside hehe)unless i decide to get up at 3 am and go for it ... But sooner or later ill solve this mystery , doubt ill take it off though not after getting used to seeing it >.<
The angle id have to say maybe 45 .. cant think straight .. ill just take a pic when i can and save us the trouble of guessing

 

[SLEEPER]

The rear "spoiler " on the stagea is a genuine nismo item. (nissans equivelant of AMG )
I have no idea if it decreases the speed as have never done back to back tests.
However it is by far the most stable stagea I have driven at speed (170+ on marham airfield) . I must try it next time we have a 30-130 day there with and without.
I have driven quite a few stageas with no spoiler and some with the equivalent of OGs ebay wings .
Neither were as stable , Of course it may be the car is set up better but Im leaving it on till I have proof it does nothing

 

[obi_waynne]

The whole car shape is a basic wing and tend towards lift, not ideal when you are travelling at speed.

I think a lot of people disregard this fact and crank their cars upto 100mph without realising that the handling will be dramatically different when this lift kicks in.

 

[bax]

i was wrong about the Angle lol ... well anyway this is what it looks like , think this can reduce my top speed ?

 

[old-git]

Well, it is an extra obstruction to the air so certainly won't increase your top speed, IMO.

 

[bax]

yes but will it Reduce the top speed ? the Vehicle weights 2 Tons and is Rear wheel drive , in some countries it comes with an original spoiler/wing like this ...... this seems to be less obstructing no ?

 

[T9 man]

^^ To be honest with you, not sure I would want to take a car that size and riding that high up to the end of it's speed limit.

 

[bax]

i know what you mean though the top speed of this Vehicle is under 200Kph ... plus i dont attempt such runs anywhere except straight even empty roads , dont like doing risky things but like all car fanatics i love to test my Rides capabilities and limits .. i dont get to drive at Top speed often , reason im curious about it is because i recall being able to hit 193Kph before installing the Spoiler and doing the Remap .. now with the Remap and the Spoiler it can barely get to 190Kph , the Remap itself tested by over a hundred owners proved to allow the car to reach slightly above 200Kph , so the blame is shifted towards the Spoiler at the moment

 

[old-git]

I think that you have just answered your own question

Anything put on a car that gets in the way of the air passing over it will create drag. The total drag on the car dictates its maximum speed. More drag eqauls less speed. QED

 

[bax]

i guess ill have to do a couple of runs with and without the spoiler and prove our theory , and if it does prove to be right the way to fix it will be to straighten the spoiler with the roof ? like on the same line straight spoiler no angles ....

heres another question that may seem silly but does the shark fin also cause obstruction ? pr its too thin and sharp to block any air ?

 

[old-git]

Yes, it does cause obstruction to the air. However, they arer a necessary evil as they are designed to house the various antennae bristling from today’s cars. Think about the signals moving through a car: AM/FM radio; satellite radio; cellular voice and data. All of those need independent receivers or emitters, but if they were separate, the car would look like a porcupine driving down the street. This way, the antennae are consolidated outside the steel roof, free from interference, but under a shark fin to reduce drag.

 

[bax]

actually we built that fin .. in this vehicle the antenna is in the front windshield somehow , the fin is just a piece of metal folded into a triangle and then covered with that material they use to fill gaps when repairing parts of the car , and then shaped and painted to look like a fin (fathers idea xD ) , so the fin is only for looks has no real purpose

 

[T9 man]

Well from the picture the fin looks like factory

 

[old-git]

It won't make a noticable difference compared to the spoiler/wing thing.

 

[bax]

what about Rims ? does Negative alignment of Rims affect the performance compared to the stock one ? (in a straight road)

 

[old-git]

What do you mean by 'negative alignment'?

 

[T9 man]

What do you mean by 'negative alignment'?

x2

 

[bax]

ermmm .. oh my bad hehe , Rim offset >.< currently i have Ones with Negative offset (they give the Ride a wider more aggressive look ) i know the weight of the Rim itself has a slight effect on performance but what about the Offset ? put aside the extra strain on the suspension does it have any effect on performance ?

 

[old-git]

An interesting question.

Asssumming weight and stresses are equal, I am struggling to think of a reason why a wider track would affect top speed, apart from if the wheels protrude outside the body line they will increase drag.

 

[bax]

thats what i had in mind ..With the tyres sticking out and spinning at high speeds Forward while air slams into them in a way that would spin them backwards , so in a way the air should be reducing the spinning speed of the tire ... i cant help but wonder what if the air slamming into the front of the car is redirected further away from the side in a way where the clash with the protruding tires is minimal and with small to no effect on the spinning speed , cant imagine the air blowing that close to the side of the car after slamming with the cars front it will probably disrupt the air thats supposed to pass on the sides of the car ... (im just guessing here , nothing to base these claims on )