Engineering Explained: 5 Incredible Facts About The Dodge Viper ACR

The Dodge Viper ACR is one of the most sophisticated track machines from North American soil. So what is it that makes it so special?

1. All The Downforce

Engineering Explained: 5 Incredible Facts About The Dodge Viper ACR

The 2016 Dodge Viper ACR with Extreme Aero Package produces more downforce than any other production car. At top speed, this is nearly 800kgs of downforce created through the use of a front splitter, dive planes, a carbonfibre rear diffuser, and a massive dual-element carbonfibre rear wing. The number remains impressive even at lower speeds, with around 545kgs of downforce at 150mph.

Extreme aerodynamics don’t come without a penalty, of course. The drag coefficient of the Viper goes from 0.37 on the base model to 0.54 on the ACR. For reference, Tesla’s latest SUV, the Model X, has a drag coefficient of 0.24 (it’s the best SUV Cd in the business). The street snake’s drag is so significant it shaves 29mph off the top speed, from 206mph down to 177mph. But chances are on the race track you’ll be wanting grip more than top speed, which brings us to the next point.

2. 1.5-G Lateral Grip

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FCA claims that the Viper can hold and sustain 1.5 g during high speed cornering thanks to its suspension, aero kit, and ACR specific tyres. The simple maths checks out, assuming the tyre can hold 1 lateral g (these are custom summer tyres, it shouldn’t be a problem). If you add 1700lbs (771kg) of downforce to a 3400lb (1542kg) vehicle, you’re looking at a normal force of 5100lbs (2323kg) divided by the car’s weight, 3400lbs (1542kg), which gives you exactly 1.5. That’s pretty special.

So how does the ACR handle all of this downforce? Super stiff springs and lots of negative camber, that’s how. The front springs on the ACR are three times the stiffness of the base model, and the rear springs are more than double. Why so stiff? Here’s an easy way to find out: call ten of your friends and tell them to stand on your car (fewer, if they’re American). This is the kind of downforce the Viper is dealing with. At speed it’s the equivalent of four adult male lions or 170 pit vipers lounging on top of the car. Obviously, then, stiff springs are needed so the Viper doesn’t rest on its chassis at speed.

And as for the negative camber, the Viper ACR doubles the negative camber of the base model, from -1.4 degrees to -2.8 up front. Why such a serious camber spike? With higher g-force turns, the tyre contact patch will be forced to sustain greater stresses. The high camber ensures an ideal contact patch as the tyre is warped from the lateral grip.

3. Live Horsepower & Torque Display

Charger Hellcat display shown.
Charger Hellcat display shown.

The first and only thing you can think when you discover this display is just how high can I get it to read? The Hellcat has the same display, which I managed to read 692 horsepower during a short lived pull. The amount of information included is sure to satisfy any petrolhead. Along with instantaneous horsepower and torque readouts, there are acceleration timers, braking calculators, oil temp and pressure, battery voltage, steering angle, lateral and longitudinal g-forces, speed, gear selection, and boost pressure. Best not to geek out at the display while driving the Viper over 200mph.

4. All The Torque, All The Litres

Photo Credit: Doug Berger, NWAPA Run To The Sun Event 2015
Photo Credit: Doug Berger, NWAPA Run To The Sun Event 2015

The power plant of the beast is an 8.4-litre V10 producing 645hp and 600lb ft of torque. That’s more torque than any other naturally-aspirated engine in a production sports car. That may sound impressive initially, but much of this is due to the fact that it’s also an enormous engine; I don’t know of a larger one in production. Even the Bugatti Veyron’s W16 was an amateurish 8.0 litres. Are its power and torque levels impressive? Not exactly. A V6 Toyota Camry makes nearly identical power and torque per litre. It’s big, it’s bold, and it provides you with 12 miles per gallon in the city. That’s less than 200 miles of range if you’re not careful. But who’d drive one of these in the city? Someone must have gotten quite lost on their way to the circuit.

5. Incredibly Customisable: 1 of 1

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If you opt for the Viper GTC, you’re getting unbelievable customisation from the factory, including 8000 exterior colours to choose from, 24,000 racing stripe colours, 11 wheel options, 16 interior trims, seven aero packages, three brake packages, and four suspension options.

According to Dodge this gives the buyer over 25 million ways to customise the Viper. I don’t know who does the maths at Chrysler, but when I multiply it all together I get something like 2.8 trillion. I suppose that is indeed more than 25 million, so I guess technically they’re correct. Fair play Chrysler, you win this time…


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