Nice add-on or air brake?

[black mamba1]

I really love the rear wing on the Gen 4 ACR. I am wondering if it is available seperately and if so where can I buy it, and also wondering if the rear wing creates enough drag to increase 1/4 mile and 1/2 mile times.

I had a Vette years ago, before I put on my rear wing it had a top speed of 158 mph. After the rear wing the top speed dropped to 147 mph.

Does this gorgeous wing on the Gen 4 ACR act as an air brake?

Anyone got enough technical knowledge to chime in?

 

[wastntim]

Air brake. Rear spoiler won't have any effect until a minimum of 120mph. With MOST vipers running a max mph on a quarter mile in the 130's, the rear spoiler will only add additional drag.

 

[AviP]

I really love the rear wing on the Gen 4 ACR. I am wondering if it is available seperately and if so where can I buy it, and also wondering if the rear wing creates enough drag to increase 1/4 mile and 1/2 mile times.

Yes it will create additional drag. Why put a spoiler on a drag Viper? It's pointless. As to the spoiler not having any effect until 120mph, that's not true. Most factory spoilers generate a decent amount of downforce even at highway speeds.

 

[black mamba1]

Yes it will create additional drag. Why put a spoiler on a drag Viper? It's pointless. As to the spoiler not having any effect until 120mph, that's not true. Most factory spoilers generate a decent amount of downforce even at highway speeds.

Yeah, that is what I was worried about. I noticed that in some car mag speed comparison tests, drivers remove mirrors and even change wheel design to milk out every possible drag reduction.

The wing is a sporty add-on, but the additional drag factor which counteracts horsepower is a deal killer for me. Especially when you consider how much horsepower is needed to overcome even the slightest increase in drag at high speeds.

I would, however like to see some 1/4 mile and 1/2 mile performance data to see how the Gen 4 ACR stacks up to stock Gen 4's w/out that wing. I know the ACR is lighter, but 80 lbs can be offset by how much gas is in the tank and how much the driver weighs, should be a good test.

 

[M. ROD]

Spoilers provide downforce at speeds of around 50mph but it’s not until about 70mph that this becomes significant.


The truth is that the viper is a “circuit car”. Design to handle twisties, and that wing is very important.


The principles which allow aircraft to fly are also applicable in sports cars. The only difference being the wing or airfoil shape is mounted upside down producing downforce instead of lift. The wing of an airplane is shaped so that the air moving over the top of the wing moves faster than the air beneath it. Since the air pressure under the wing is greater than that above the wing, lift is produced. The automotive version is inverted with the more curved surface on the bottom. More load is placed on the four tires to provide more overall grip. The more grip we have, the faster we can drive through the turns.

The aerodynamics of a car are very sensitive to change. Airfoils are also used in the front of the car in an effort to generate more downforce. And yes, there is a price for this amount of downforce. Drag. Redirecting the energy of the airflow to hold a car down creates more resistance for the car to push against. But that's OK. Although drag reduces top speed somewhat, the increase in cornering speeds makes for faster lap times. A correctly designed aerodynamic package will add the right amount of downforce without sacrificing much drag.


The Viper, with enough power to approach 200 mph, needs to have an aero package that can maintain aerodynamic balance and stability throughout the car's considerable speed range. On the hood, louvers keep air pressure buildup from producing front-end lift, and the rear spoiler adds downforce at the back. Under the car flat belly pans fill in the underside of the body and frame at both ends. Where the rear belly pan curves up to meet the bumper cover, there are four long vertical stakes(diffuser) that straighten the airflow under the car. This abbreviated version of race-car flat-bottom aerodynamics ensures that the SRT-10 will stay planted at high speed. The shape of the underbody creates an area of low pressure between the bottom of the car and the racing surface. This ***** the car to the road which results in higher cornering speeds and reduces wear on the brakes.


This new Viper ACR is beautifully balanced!


Canards

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Also known as dive planes or dive plates, help generate downforce in two different ways. First, the canard redirects the oncoming air's momentum upwards, which causes a downward force on the canard. Canards generate strong vortices that travel down the sides of the car and act as a barrier. If the canards are positioned correctly, these strong vortices act to keep high-pressure air around the car from entering the low-pressure underbody region, thus maintaining more downforce. If air was allowed to enter the underside, the pressure would inevitably rise, reducing downforce. Therefore, these strong vortices act like a virtual curtain or dam, restricting higher-pressure air around the car's sides from entering the underbody region. As a result, the low pressure under the car is maintained and downforce is maximized. Unfortunately, canards are not very efficient, since the strong vortices create a significant amount of drag. They are more useful for fine-tuning aerodynamic balance.




Side ducts

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Side ducts are primarily seen on race cars for two reasons, because brake and engine cooling is crucial, and because most serious race cars will use a front underbody diffuser that channels airflow toward the rear of the front wheel well. The hot air moving through the engine bay and brakes generates drag. Side ducting not only provides a smooth outlet for these hot and turbulent gasses, but also turns the flow to exit smoothly along the side of the car instead of directly outward, which would interfere with the turbulent curtain generated by the canards. This reduction of air stagnation inside the bay also helps pull more fresh air through the cooling system.




Splitters

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Since the front of the car is a blunt shape, the oncoming air is slowed substantially, resulting in a high-pressure zone known as a stagnation point. By placing a horizontally protruding splitter plate right in the thick of this high-pressure zone, a large amount of efficient downforce can be generated. The splitter, hence its name, splits the high-pressure zone from the low-pressure high-speed flow moving under the car. Pressure varies with the car's speed squared, so downforce increases quickly as the speed increases. Generally, the effects are felt at speeds over 75mph. Downforce can be increased or decreased, depending on the amount of exposed splitter area.




Diffusers

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Diffusers work in conjunction with other aerodynamic components of a car to help produce downforce. Because a car displaces air as it moves forward, the air molecules in the rear of the car get disrupted causing a vacuum of low pressure air. To help channel the high speed air flow coming from underneath the car, diffusers redirects the high speed air flow to transition smoothly into the low pressure vacuum in the rear. This encourages a smoother flowing air flow underneath the car and allows better performance from other aerodynamic components such as aerodynamic wings.




Race enthusiasts will really enjoy this machine!

 

[Vipermann]

I agree completely.

I recall driving at Las Vegas speedway last year and being told 'don't lift' (off of the gas) as I came to the end of the straight and entered the banking. That goes against instinct. But think about the implications for the ACR's aero characteristics.

The reason why I couldn't lift going into the corner, was because that would cause the load on the rear tires to lighten up (shift to the front) and the rear of the car to break loose -- and then I could go a$$-end into the wall. So thinking about that, with the ACR, I would go FASTER down the straight (with less caution about the upcoming banking and my foot firmly to the floor), because I would rely on those aero characteristics to keep my car planted as I entered the banking (maybe even if I did 'lift' a little bit).

And that doesn't even yet take into account the benefits of the 1.5gs from that suspension and tire set up.

This ACR is going be a monster on the tracks!!!