I've recently noticed on late nights at the track that once I hit 100+ mph, my back end seems to get loose. I use to have a 98 2dr EX with the factory spoiler (taller Si type) and I never had the wagging problem. I now have a 99 EX and no spoiler.

I've done a little more to the engine on this car than I had with the 98.. but It still feels different.
Would getting an OEM spoiler help at all? I hate aftermarket crap that doesn't look like it belongs.

 

I'm pretty sure the OEM spoiler is just pretty much cosmetic.....


I could be wrong though

 

bump for a couple more answers.

I've been looking at the angles.. and it's maybe a 1-2deg down angle.. would that produce enough down force to help?

 

another bump

 

I have the taller spoiler on my EX and it came stock. I think it's just cosmetic myself. I do know that there is a stock looking spoiler that Wings West makes that, I am pretty sure, offers some down force because I think it is adjustable.

 

I highly doubt you'll get any downforce from most OEM spoilers. If you do, it won't be noticeable enough to be worth the money.

 

no they're cosmetic. its a fwd car anyway so even if it did......

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rniederlando &raquo;</TD></TR><TR><TD CLASS="quote">no they're cosmetic. its a fwd car anyway so even if it did......</TD></TR></TABLE>

I'm always amused by these types of comments, as if FWD cars have no need for reduced lift, or downforce over the rear wheels.


To answer your original question John (though unfortunately not directly), some factory wings are indeed functional. The ITR wing is a prime example of this. However, I have not seen any data to either confirm or deny that the Civic optional wing is a functional piece. Its design is somewhat similar to the ITR's, and its height suggests that it was perhaps designed to be positioned in the air stream where it could provide some form of effectiveness. That being said, tall wings are also popular with many people from a purely cosmetic standpoint, so it's not possible to draw a conclusion based solely on the wing's immediate appearance.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Padawan &raquo;</TD></TR><TR><TD CLASS="quote">

I'm always amused by these types of comments, as if FWD cars have no need for reduced lift, or downforce over the rear wheels.


</TD></TR></TABLE>


Word

 

"Using a Subaru for example, the stock wing on a STi will slow you down at the strip, but just removing it altogether might not be the best solution. Air loves (and I mean LOVES) to lift up on round surfaces. Without the wing on the back of the STi to force the air up and away from the shapely roof and rear window, the lack of something on the rear to spoil the air fl owing over it will cause the wind rushing over your car to pull the car upwards.

This dynamic, aptly named "Lift," is great for a Boeing, but not a Subie. If your car has a fairly well rounded body top surface (more like a Beetle than an xB), you'll need to look at adding something to spoil the air fl ow and lightly defl ect it upwards and away from the roof and back window. We're not looking for downforce here: helping the air to fl ow over and away smoothly without pushing down or pulling up is the goal.

Allowing air to lift your car off the ground, even just a little bit will take enough weight off of your tires to cause instability at anything over moderate speeds."

http://www.tprmag.com/issue/13...shtml

 

A lot of Type R owners swear it makes a difference. I'd like to see all the people who say it doesn't make a difference give a decent explanation as to why, because I think it definitely could make a difference.

 

Most spoilers reduce lift and drag (it was a tech question at the back of a Road and Track issue a few years ago), but with the chords and angle of most OEM spoilers they probably don't work well at low speeds.

 

2 or 3 months back when SCC previewed the new SI they quoted honda that the spoiler increased downforce and decreased drag by soem rediculous percent.

 

Define low speeds though..

I only notice the rear end wag at around 90mph or higher.
I love keeping my car as oem as possible... so I really don't cherish the idea of putting on an aftermarket spoiler.

Is there any kind of chart that lists degree of the spoiler vs speed equals how much down force you get?

 

http://www.insideracingtechnol...t.htm

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by johnecon2001 &raquo;</TD></TR><TR><TD CLASS="quote">I've recently noticed on late nights at the track that once I hit 100+ mph, my back end seems to get loose.</TD></TR></TABLE>

What else is going on? Are you simply going straight? Any elevation or camber changes? Are you turning or braking... possibly lifting or feathering the throttle?

Need more facts to accurately answer the question.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by johnecon2001 &raquo;</TD></TR><TR><TD CLASS="quote">Define low speeds though..

I only notice the rear end wag at around 90mph or higher.
I love keeping my car as oem as possible... so I really don't cherish the idea of putting on an aftermarket spoiler.

Is there any kind of chart that lists degree of the spoiler vs speed equals how much down force you get?</TD></TR></TABLE>

aero doesn't really start to come into play untill 80mph+ (appx).

Offten times the spoiler doesn't need to have a nice air foil and actually create downforce, some times it can just smooth the air out and reduce the turbulance that happens at the back of the car.

maybe J mac will come in here and explain every thing alot better then me

 

OE wings, like the ITR wing and STI / EVO wings, really don't produce net downforce. I believe that the 911 GT3 and GT2's have zero lift as a product of their kitchen table sized spoilers.

The real problem in 3 box aerodynamics is that whole rear window and decklid area. That tends to produce alot of lift and turbulance. This is why you look at the new EVO and STI and they have all sorts of neat airflow smoothing devices to try and fix that.

Essentially all OE spoilers can do is reduce lift a little and smooth out the airflow which makes more of a difference in high speed stability.

Annother bit that helps out alot is to over that whole underside lip off the rear bumper otherwise it tends to act like an uneven parachute. Vishnu racing I think makes a neat peice for the EVO to cover that hole and in back to back testing made for a good boost in confidence in it's high speed stability (EVO 8 RS)

 

What else is going on? Are you simply going straight? Any elevation or camber changes? Are you turning or braking... possibly lifting or feathering the throttle?

Need more facts to accurately answer the question. [/QUOTE]

Yeah, I read the first post and thought of when I went to the drag strip with torn up TA bushings. Booty shakin' fun.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sdcivic549 &raquo;</TD></TR><TR><TD CLASS="quote">OE wings, like the ITR wing and STI / EVO wings, really don't produce net downforce. I believe that the 911 GT3 and GT2's have zero lift as a product of their kitchen table sized spoilers.

The real problem in 3 box aerodynamics is that whole rear window and decklid area. That tends to produce alot of lift and turbulance. This is why you look at the new EVO and STI and they have all sorts of neat airflow smoothing devices to try and fix that.

Essentially all OE spoilers can do is reduce lift a little and smooth out the airflow which makes more of a difference in high speed stability.

Annother bit that helps out alot is to over that whole underside lip off the rear bumper otherwise it tends to act like an uneven parachute. Vishnu racing I think makes a neat peice for the EVO to cover that hole and in back to back testing made for a good boost in confidence in it's high speed stability (EVO 8 RS)</TD></TR></TABLE>

not exactly...you want turbulence to reduce drag...hence vortex generators

 

Most factory spoilers do provide some benefit, whether it be drag reduction or lift reduction. Actual numbers are difficult to find, and you'll usually only find them in the manufacturer's marketing literature.

My advice would be to check your alignment and make sure that your suspension bushings are all in good shape (as others have mentioned). If that all checks out, then it does sound like you could be having an aerodynamics problem, so by all means try the OEM spoiler to see if it makes a difference. If you get it used, you should be able to sell it and break even if it doesn't help.

 

isn't under body aero more effective than a spoiler at [considerably] lower speeds? like having a fron splitter and rear diffuser would create more downforce than just a rear trunk mounted spoiler could. case in point is the new C6 corvette; it has considerable underbody aero versus the C5. Also many of the GT Aston Martins have considerable underbody aero.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mugenpowered &raquo;</TD></TR><TR><TD CLASS="quote">"Using a Subaru for example, the stock wing on a STi will slow you down at the strip, but just removing it altogether might not be the best solution. Air loves (and I mean LOVES) to lift up on round surfaces. Without the wing on the back of the STi to force the air up and away from the shapely roof and rear window, the lack of something on the rear to spoil the air fl owing over it will cause the wind rushing over your car to pull the car upwards.

This dynamic, aptly named "Lift," is great for a Boeing, but not a Subie. If your car has a fairly well rounded body top surface (more like a Beetle than an xB), you'll need to look at adding something to spoil the air fl ow and lightly defl ect it upwards and away from the roof and back window. We're not looking for downforce here: helping the air to fl ow over and away smoothly without pushing down or pulling up is the goal.

Allowing air to lift your car off the ground, even just a little bit will take enough weight off of your tires to cause instability at anything over moderate speeds."

http://www.tprmag.com/issue/13...shtml
</TD></TR></TABLE>

In a rather unscientific trial, i ran back-to-back sessions (well there was 1-hour of cool down between sessions to rest the motor/breakes/tires/shocks, all of which are upgraded very agressively) in my '01 RS - one with the spoiler, one without, as the removal of the spoiler would see a pretty good weight savings. I had always surmised that the spoiler offered an aerodynamic advantage, as it is shaped "interestingy" with a small uptuned lip on the trailign edge and a generally upside-down wing shape to the element. In any case, the rear end of the car felt quite loose without the spoiler, almost alarmingly so. The spoiler went back on after that session and never came off again.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by johnecon2001 &raquo;</TD></TR><TR><TD CLASS="quote">I only notice the rear end wag at around 90mph or higher.
I love keeping my car as oem as possible... </TD></TR></TABLE>

That would be around when aero would come into play on a 'street' vehicle.

The following is all speculation coming from an engineer doing computational fluid dynamics and numerical analysis on some of these types of problems; so take with a grain of salt:

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Outrun &raquo;</TD></TR><TR><TD CLASS="quote"> but with the chords and angle of most OEM spoilers they probably don't work well at low speeds.</TD></TR></TABLE>

But the 99-00 civic 'high' spoiler is also pretty broad, so something else comes into play. It may not be producing alot of downforce because of the rake, but it does seem like it can deflect the air coming off the roof and reducing recirculation; in effect reducing the low pressure zone and lift.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slammed_93_hatch &raquo;</TD></TR><TR><TD CLASS="quote">it can just smooth the air out and reduce the turbulance that happens at the back of the car.
</TD></TR></TABLE>

Turbulance is somewhat of a misnomer. At the rear of the vehicle, there is a huge recirculation zone (low pressure) above the trunk area. With an OEM type spoiler on the rear, the flow can pass over the it and reduce the recirculation zone, reducing the lift. This then moves the recirculation zone to the rear of the car, thus increasing drag. A highly raked spoiler will actually increase downforce by bluntly using the airstream to 'push down' the rear of the car.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sdcivic549 &raquo;</TD></TR><TR><TD CLASS="quote">OE wings, like the ITR wing and STI / EVO wings, really don't produce net downforce.

The real problem in 3 box aerodynamics is that whole rear window and decklid area. That tends to produce alot of lift and turbulance. This is why you look at the new EVO and STI and they have all sorts of neat airflow smoothing devices to try and fix that.

Essentially all OE spoilers can do is reduce lift a little and smooth out the airflow which makes more of a difference in high speed stability.
</TD></TR></TABLE>

Couldn't have said it better myself.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by igyloo &raquo;</TD></TR><TR><TD CLASS="quote">
not exactly...you want turbulence to reduce drag...hence vortex generators </TD></TR></TABLE>

Turbulance increases drag, smooth airflow decreases drag.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by chrisw85 &raquo;</TD></TR><TR><TD CLASS="quote">isn't under body aero more effective than a spoiler at [considerably] lower speeds? </TD></TR></TABLE>

Underside aero can be very important. This straightens flow, and increases it's velocity, which is basically the opposite of lift (where airflow is speeded up above a wing, reducing pressure, to get a plane off the ground). I'm not sure about what speeds this takes effect though. The other problem is that it's almost impossible to get any sort of good aero on any street car.

I've been wanting to do a simulation on my civic with the high spoiler, because it does appear as it will do something, but I didn't want to get all the dimensions off the car and build the model. Anyone want to send me a CAD file? Maybe I'll do a 2D estimate of the centerline of the car, and see what happens.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by igyloo &raquo;</TD></TR><TR><TD CLASS="quote">not exactly...you want turbulence to reduce drag...hence vortex generators </TD></TR></TABLE>

Less turbulence means less drag, almost without exception.

What vortex generators do is prevent or reduce separation of the airflow from the surface. So, when properly designed, they actually REDUCE overall turbulence.