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ex-Super *********
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Discussion Starter #1
hello,

I was wondering how to create downforce/decrease lift, in a 4 door B14. I have questions like - how tall would a rear spoiler have to be to be effective, would venting the top of the hood reduce lift. stuff like that. can any one help
 

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Since our cars are FWD, a wing in the rear won't help you. If you do put a wing (that's meant to create down force) it will hurt your plans to create effective downforce. That's why most FWD cars with big wings are classified as RICE since the wing does nothing for a FWD car other than maybe lifting your front in teh process? I'm not sure what you can do to create downforce in the front (where you really want it.) Short of putting a wing in the front (LOL.. we all know that won't work) and as far as I know there aren't any front facia's built to do create downforce like the F1 racers - well none commercially available anyhow.

I'd like to see if anyone else has any good ideas with respect to creating effective downforce on a FWD car.
 

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what?
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Hmm,
Well, the best place (and untapped) is the underbelly of the car. There is where alot of air is rushing in and can be harnessed (venturi effect). Getting this to really work can be tricky since not everyone has a wind tunnel. But basically the first two things you need are front and rear valences that channel the air correctly. Then on the underside you need vents and deflectors that can also channel the air properly. Bolting on a piece of aluminum under the car shouldn't be too hard, and the off-roading boys can hook people up with places that will pound it to the right shape.
To find a decent shape (as in an educated guess as to what it will look like) copy the design from books that show what effective underbellies look like, and modify the dimensions to fit the Sentras.

Seth
 

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Icy Hot Stunta
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Brainstorm said:
Since our cars are FWD, a wing in the rear won't help you. If you do put a wing (that's meant to create down force) it will hurt your plans to create effective downforce. That's why most FWD cars with big wings are classified as RICE since the wing does nothing for a FWD car other than maybe lifting your front in teh process? I'm not sure what you can do to create downforce in the front (where you really want it.) Short of putting a wing in the front (LOL.. we all know that won't work) and as far as I know there aren't any front facia's built to do create downforce like the F1 racers - well none commercially available anyhow.

I'd like to see if anyone else has any good ideas with respect to creating effective downforce on a FWD car.
That is not true at all!

Mike
 

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Nissan Freak
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pat i saw this thing on the tv about spoilers, supposedly the only thing they were invented for was commercials, since there was no more place on the body, a spoiler was added for more ads on a race car
downforce counts if u are in the triple digits....but barely
 

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Icy Hot Stunta
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XtremE said:

pat i saw this thing on the tv about spoilers, supposedly the only thing they were invented for was commercials, since there was no more place on the body, a spoiler was added for more ads on a race car
downforce counts if u are in the triple digits....but barely
Spoilers make a huge difference starting from about highways speed.

I don't have the time to argue aero theory on this forum, but on our se-r race car for instance, it is good for about a second a lap on most tracks.

Mike
 

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what?
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Well,
To comment on the above 3 threads:
First a disclaimer: these are short anwers. Don't expect too much.

FWD, RWD, 4WD, it doesn't matter. The shape of the car dictates aerodynamics, not the drivetrain. In drag racing where a load is produced on one end of the body, where the power goes makes a difference, but that is more of a suspension issue than aero. Aero comes in farther down the 1320.

Small lip spoilers on cars do nothing since they are not in the air path coming over the roof and hence do more swirling the air behind the car creating drag. In some correctly placed lip spoilers this swirling air helps diffuse the rear end lift and even smooths out the air sometimes coming off the roof maiking the car more efficent. It all depends.

Big wings. These need to be tall enough to hit the oncoming air from over the roof of the car. Depending on the shape of the car and the amount of lift generated, the spoiler would have to be so high and at such an angle to counteract this lift without creating too much drag. It isn't effective at slow speeds (below highway) since the sheer weight of the car and the design do not permit airflow problems to be created and therefore amended.

The main notion of aerodynamic enhancement is only viable at high speed where stability gets sketchy. You have to know where the air is going at these speeds, and be able to move it accordingly.

No one knows how to perfectly do this since much of fluid dynamics is still theory. Computers, even nowadays, can barely hack out the functions to properly map airflow. However the science is moving along and is fairly sophisticated right now. Still, unless you race, or speed alot, cooling is the only real airflow problems you should worry about.

Seth
 

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in^3,N20,RPM,PSI
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forget all that mumbo jumbo. a spoiler is designed like an upside down airplane wing. instead of creating lift up it pushes you down. you need to be a pretty fast speed to get a significant amount of force (airplanes don't take off at 35 mph do they?)... they work alright, everything said in the above posts are correct.

venting the top of the hood? no, i don't think it will reduce lift as much as it will increase wind resistance.
 

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Brainstorm said:
Since our cars are FWD, a wing in the rear won't help you. If you do put a wing (that's meant to create down force) it will hurt your plans to create effective downforce. That's why most FWD cars with big wings are classified as RICE since the wing does nothing for a FWD car other than maybe lifting your front in teh process? I'm not sure what you can do to create downforce in the front (where you really want it.) Short of putting a wing in the front (LOL.. we all know that won't work) and as far as I know there aren't any front facia's built to do create downforce like the F1 racers - well none commercially available anyhow.

I'd like to see if anyone else has any good ideas with respect to creating effective downforce on a FWD car.

Well I have a good idea that might be pretty affective BUT, I don't have the money for a mold. :)
 

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what?
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(airplanes don't take off at 35 mph do they?)...
...ummm...actually, they do. 2 seater Cessnas take off at 55, and ultralights can take off at a jogging pace. However you're thinking of a 747 which weighs 200,000 pounds, or 80 SUVs. There, takeoff is around 160mph or so.
"rotate"

Seth
 

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Found an interesting bits of info on aerodynamics and the role of spoilers and body kits...

here
 

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ex-Super *********
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Discussion Starter #14 (Edited)
Whoa!!... Here are my replies to each one of you.

Brainstorm,
Read Mike's second post in this thread...Nuff said.

setwas,
I think we are on the same wave-length(under-body stuff).

morepower2,
We ARE on the same wave, thank you.

XtremE,
Just for adds? I dont think the worlds best/fastest race cars would sacrifice the weight and areo drag of a wing to get more adds. D-force counts in triple digits..Thats where I am going.

James,
Venting the hood wont help you say, you know those big openings for air in the front of cars..to let air hit the radiator??? what do you think that air does after that..disappear? No it creates a high pressure bubble under the front of your car effectively lifting the front end(making a understeer prone FWD even worse). Tottaly tape off the front of your car(leave a small opening for cooling air) and go for a high speed run, you will know what I am talking about.

Here are some of my other thoughts on car aero.

Lips/splitters: Put low enough they help divert air, stopping some from going under the car and becoming hella turbulent. Creating some "weird happenings" and lift down there at high speeds. This is where under-trays and diffusers come into play.

Under-body stuff ie. trays and diffusers: designed properly will smooth out that "dirty" air, and possibly create "suction". Do you think an F1 car gets enough down force to squash hella stiff springs and theoreticly run upside-down, from its front and rear wings? I don't. Wings that good would create hella drag.

Rear spoilers: depending on the tilt of the rear window(20deg I think) air will not "stick" to it and flow down to a oem(read useless) spoiler, and if it does the air will be so "dirty(read tubulent) the spoiler doesnt do a hell of a lot. Think of this.. cars with a rear window less than 20deg, that have a wing and a rear wiper dont utilize the wing because the wiper "dirtys" the air. For a sedan like say a B14 you need a wing that will peak up into the "clean" air over the roof of the car. I may look "rice", but its less rice than riding around on Sportlines with stock length struts(I'm guilty on that one).

Did I forget anything???
For those that think I am "ricing" or not going to acomplish anything with my aero ideas, remember this when a Charcoal Mist 99 Sentra XE blows by you on a corner because its sticking and your sliding.

"We mock what we dont understand"

P.S. Every "real" racing B14 I have ever seen has a wing.
 

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ex-Super *********
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Discussion Starter #15
morepower2,

Got any pics/specs on that spoiler? Id like to see.
 

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in^3,N20,RPM,PSI
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ok let me digress...

you're right, it does create the high pressure you are talking about. I said "i think", i'm not an expert on aerodynamics i just know the theory.

well here's a question for you then, do you think a car driven on the road daily will suffer more (whether that be from power, cd, or gas mileage, blah blah blah) from the high pressure under the front of the car or from the increase in drag in cutting holes in your hood?
 

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ex-Super *********
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Discussion Starter #17
James,

Not every day is a road day.

Drag from hole/vents in hood. Expain as I am not aware of that, If there is I would imagine that it is slight and the benifts could out-weigh the costs
 

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in^3,N20,RPM,PSI
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well i have no proof and no evidence. this is something that can only be known if we could test it and i don't have the equipment here. i'm only going by the logic that it's like opening your window, it creates enough disruption in the flow of air that it can affect your car...
 

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ex-Super *********
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Discussion Starter #19
James,
I see your point, but in that case the air is going in to the car, in mine its comming out. I agree that it would have to be tested.
 
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What does your car run where you would need the downforce especially in a sentra....
 
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