C7 Corvette

[r0tor]

Functional front splitter... It bolts to the chassis


Cosmetic aero... It bolts to the bumper

[r0tor]

Spoilers don't make downforce.  They reduce lift.  Also introduce drag.

Spoilers make downforce and ridiculous amounts of drag - See NASCAR

[CaminoRacer]

Spoilers make downforce and ridiculous amounts of drag - See NASCAR

It's a math equation. Channeling air out from the under car reduces lift, therefore increasing downforce even if the plastic piece does nothing to push the car down. Same with flat bellies.

[r0tor]

It's a math equation. Channeling air out from the under car reduces lift, therefore increasing downforce even if the plastic piece does nothing to push the car down. Same with flat bellies.

Spoilers create downforce based on deflecting airflow.  Undercar "ground effects" work by creating low pressure under the car.  Completely different principles

[r0tor]

Stick on aero looks so cool though

[CaminoRacer]

Spoilers create downforce based on deflecting airflow.  Undercar "ground effects" work by creating low pressure under the car.  Completely different principles

Low pressure doesn't need to play a factor at all - simply redirecting the air so it can't go underneath and push up on the car is good enough.

You're the one calling it a spoiler and then saying it doesn't fit your definition of a spoiler.

[MX793]

Spoilers make downforce and ridiculous amounts of drag - See NASCAR

An airfoil or wing creates lift/downforce, spoilers don't.  A spoiler "spoils" airflow, causing it to break away cleanly from the surface, triggering what is generally referred to as a "stall".  This results in a reduction in lift on the top surface of the car (or whatever, planes use them too).  On a stock car, the spoiler doesn't direct any airflow upwards.  It traps a pocket of air behind the rear windscreen and forces air to separate higher up, kind of like the tailgate of a pickup truck traps a pocket of air in the bed and forces the airflow over the truck to behave almost like it has a cap (and drag in a pickup is worse at speed with the tailgate down or removed than up).  Depending on vehicle shape, it may even reduce overall drag by reducing turbulence (see:  pop-up spoiler on the roof of 1st generation New Beetles).

Besides the traditional NASCAR tail spoiler on the trunk lid, the pop-up flaps that were added to NASCAR vehicles ~20 years ago that prevent the cars from going airborne when they spin around are also spoilers.  Low pressure on top of the car when it's not traveling straight ahead pulls them up and then upset the airflow to prevent lift from hoisting the whole car in the air.  Many aircraft, particularly those with really efficient wing forms, also utilize pop-up spoilers on the tops of their wings to cut lift during landings.

All of the "downforce" on a NASCAR is generated by the front of the vehicle and underbody ground effects.  That spoiler isn't generating any actual downforce.  It's simply reducing, or completely canceling, the amount of lift on the tail.

The fastback shape of a Corvette would also make the rear prone to generating lift, so a tall spoiler on the back results the air breaking off in a manner that cuts the lift on the hatch.

This is a pretty good article (with pictures).
https://www.quora.com/How-much-downward-force-does-a-spoiler-produce-and-is-it-significant-enough-to-make-a-positive-impact-on-acceleration

[MX793]

Low pressure doesn't need to play a factor at all - simply redirecting the air so it can't go underneath and push up on the car is good enough.

You're the one calling it a spoiler and then saying it doesn't fit your definition of a spoiler.

You need low pressure to actually generate positive downforce, which is what underbody ground effects and diffusers do.

[CaminoRacer]

You need low pressure to actually generate positive downforce, which is what underbody ground effects and diffusers do.

Absolutely. I was just saying that the Corvette pieces can improve downforce without generating it. Most street cars do it that way, since diffusers are expensive and not speedbump friendly.

[r0tor]

An airfoil or wing creates lift/downforce, spoilers don't.  A spoiler "spoils" airflow, causing it to break away cleanly from the surface, triggering what is generally referred to as a "stall".  This results in a reduction in lift on the top surface of the car (or whatever, planes use them too).  On a stock car, the spoiler doesn't direct any airflow upwards.  It traps a pocket of air behind the rear windscreen and forces air to separate higher up, kind of like the tailgate of a pickup truck traps a pocket of air in the bed and forces the airflow over the truck to behave almost like it has a cap (and drag in a pickup is worse at speed with the tailgate down or removed than up).  Depending on vehicle shape, it may even reduce overall drag by reducing turbulence (see:  pop-up spoiler on the roof of 1st generation New Beetles).

Besides the traditional NASCAR tail spoiler on the trunk lid, the pop-up flaps that were added to NASCAR vehicles ~20 years ago that prevent the cars from going airborne when they spin around are also spoilers.  Low pressure on top of the car when it's not traveling straight ahead pulls them up and then upset the airflow to prevent lift from hoisting the whole car in the air.  Many aircraft, particularly those with really efficient wing forms, also utilize pop-up spoilers on the tops of their wings to cut lift during landings.

All of the "downforce" on a NASCAR is generated by the front of the vehicle and underbody ground effects.  That spoiler isn't generating any actual downforce.  It's simply reducing, or completely canceling, the amount of lift on the tail.

The fastback shape of a Corvette would also make the rear prone to generating lift, so a tall spoiler on the back results the air breaking off in a manner that cuts the lift on the hatch.

This is a pretty good article (with pictures).
https://www.quora.com/How-much-downward-force-does-a-spoiler-produce-and-is-it-significant-enough-to-make-a-positive-impact-on-acceleration

Only partial credit on that answer


The air does get directed upwards and there is forward force on the car created from the change of momentum of the air upwards.  This portion of the downforce is no different then the angle of attack on a wing.

That dude is in the right church, just not exactly the right pew

[MX793]

Only partial credit on that answer

Might want to brush up on how to read CFD charts...

If the spoiler (picture on top) were generating actual downforce, you wouldn't see all of that blue (which is low-pressure, turbulent air) several inches above it.  The Wing (CoT style) on the lower car is actually generating downforce as the airflow is actually hitting it.  There's also a clear pressure gradient (higher on top, lower on the bottom) between the top and bottom of the wing.  Don't confuse wake with airflow direction.  That plot is showing pressures, not airflow direction.

Here's one with actual flow lines.  You'll note that the flow lines aren't, overall, diverting upwards.  Those that are are the same ones that were pulled downwards (which indicates lift) by the slope of the roof, so the spoiler is merely correcting those and canceling that lift..



Another side-by-side.  Again, you'll note there's no meaningful upward diversion of air with the spoiler.  The wing, on the other hand...

[r0tor]

I understand cfd... Thanks

What the author fails to conceive is that despite the net effect of the streamtubes not going dramatically verticle, the streamtubes have been effected in a vertical nature.  To displace airflow requires a force... I really don't have the time to write a thesis on why the author doesn't have a complete handle on what is going on

Back 30years ago Nascar teams made the rear spoiler flimsy enough​ they would lay down at straightaway speeds and stand back up at turn speeds.  They now require supports every so many inches to keep the spoiler up.  There is a tremendous force on their rear spoiler that if integrated balances out the change in air flow.

[12,000 RPM]

r0tor is drunk again guys tread lightly

[CaminoRacer]

Bumpers are bolted to the chassis genius.

[r0tor]

The bumper cover isn't structural genious

[r0tor]

Legit front splitter... Not fastened to a bumper cover

[CaminoRacer]

http://www.pro-touring.com/threads/101460-Designing-Aerodynamics-for-Track-Performance

Air Dams / Spoilers:
A front spoiler is typically an add-on piece partially for style & partially for function. They come in a gazillion shapes & dimensions. Many known as "chin spoilers" mount at a rake angle. An air dam is typically a vertical panel either added on, or built into, the nose bodywork of the car. The shape of this vertical panel typically follows the shape the nose bodywork. In racing, extender lips are often added to the air dam that can be adjusted to just touch the track to better seal off air.

Both air dams & front spoilers are designed to reduce airflow underneath the car, to reduce lift. Air dams are more effective at sealing the car's bodywork to the track, so they are capable of almost eliminating airflow getting underneath the front of the car in the corners. Spoilers don't usually get this low, nor cover all the way across the front of the car as well. For this reason, I think of spoilers as "under car airflow reducers" & air dams as under car airflow eliminators."

A well designed front spoiler or air dam reduces the volume of air getting under the car. This creates a low pressure area & vacuum effect to help hold the front end down through the corner. Front spoilers & air dams don't create downforce in the typical sense. They do so by reducing lift & creating a low pressure vacuum area, helping to suck the front of the car down to the track.

A well designed front spoiler or air dam ... combined with a sizable splitter ... reduces lift, creates a low pressure vacuum area ... and adds downforce on the splitter ... creating more net downforce than the spoiler or air dam would create on their own.

Splitters:
Attach at the front of the car, under the air dam or nose bodywork, and have a flat surface typically ranging from 1-5" running parallol with the ground line. Their role is to split the airflow that goes underneath the car ... from the airflow that goes up & over the hood or around the side of the fenders. Very short ones split the airflow to a degree ... and reduce lifting force ... but create very little downforce. This is a nice, solid gain in front downforce by reducing the lift. Short splitters can be mounted without braces if well attached to the air dam or bodywork.

Longer splitters split the airflow more positively and create downforce on the front of the car. This is a big gain in front downforce, increasing front tire grip, making the car run flatter, improving turning ability, increasing corner speeds. Because the airflow is actually putting downforce on the longer splitter, the splitter needs supports to prevent it from buckling under.



If you want your Pro-Touring car to be a serious track car, adding a quick on/off splitter you can run at the track is a big gain. Take it off to load in the trailer, dive on the street, etc ... and just put it on at for track days.

[r0tor]

Do you read your own crap?  Short splitters do nothing, long ones create downforce and then give you a picture of a race car with serious bracing on the front splitter to keep it from breaking.

My original point - hey look at the crap stage 3 aero GM brags up and down creating class leading downforce and it's a small ass piece of stuck on crap that does shit.


...Also their theory understanding is poor...

[MX793]

I understand cfd... Thanks

What the author fails to conceive is that despite the net effect of the streamtubes not going dramatically verticle, the streamtubes have been effected in a vertical nature.  To displace airflow requires a force... I really don't have the time to write a thesis on why the author doesn't have a complete handle on what is going on

Back 30years ago Nascar teams made the rear spoiler flimsy enough​ they would lay down at straightaway speeds and stand back up at turn speeds.  They now require supports every so many inches to keep the spoiler up.  There is a tremendous force on their rear spoiler that if integrated balances out the change in air flow.

Not to be the guy who likes to play this card, but you seem to forget that I was an aerospace engineering major with a grad degree in aero/mech, and all of the aero/fluid dynamics background that goes with it.

[CaminoRacer]

Do you read your own crap?  Short splitters do nothing, long ones create downforce and then give you a picture of a race car with serious bracing on the front splitter to keep it from breaking.

My original point - hey look at the crap stage 3 aero GM brags up and down creating class leading downforce and it's a small ass piece of stuck on crap that does shit.


...Also their theory understanding is poor...

The second post in the thread I linked to has this bit:

2.   If we see it different ... let's just agree to disagree & go run 'em on the track. Arguing on an internet forum just makes us all look stupid. Besides, that's why they make race tracks, have competitions & then declare winners & losers.

[r0tor]

Not to be the guy who likes to play this card, but you seem to forget that I was an aerospace engineering major with a grad degree in aero/mech, and all of the aero/fluid dynamics background that goes with it.

Seems like you don't know I also took a couple aero classes...

[MX793]

Seems like you don't know I also took a couple aero classes...

Your teachers weep...  That spoilers are not lift/downforce generating devices is Aero 101.

[Cookie Monster]

Legit front splitter... Not fastened to a bumper cover

I need to build me one of those. Waiting to get new bumpers though.

[Gotta-Qik-C7]

Last Stingray.........
https://www.youtube.com/watch?v=3TbVryDQIxU