The speedometer in the 2016 Audi S8 plus creeps towards 140 mph as I barrel down the back straight on Daytona International Speedway's road course. My sedan feels planted, which isn't surprising for a model bred for bombing down the autobahn at triple-digit velocities, but there's a tight "bus stop" chicane at the end that I have to navigate all 4,700 pounds of Teutonic sedan through. I mash the brake pedal to scrub speed and turn in, transitioning left and then right, feeling understeer briefly before the rear end comes around, proving the torque-vectoring rear differential is doing its job. The exercise is without much drama, and it's wildly entertaining.

The speed, the brakes and the handling are traits you'd expect from a sports car, but find them in an otherwise coddling full-size sedan is a little shocking. The S8 Plus builds speed at an alarming rate and then slows quicker than it seemingly should, all with its air suspension keeping things tidy in high-speed turns. But this is the reality of the modern high-dollar sport sedan, where engineering and technology are pushing performance boundaries to result in cars like this new-for-2016 Plus, a model even faster and more capable than its S8 predecessor.

Following visual updates in 2015, Audi has unlocked an additional 85 horsepower from the S8 Plus' 4.0-liter turbocharged V-8 engine to push output to 605 for 2016. Torque also climbs from 481 pound-feet to 517 pound-feet available at just 1,700 rpm and all the way up to 6,000 rpm. If that's still not enough twist, an overboost function ratchets things up more to 553 pound-feet between 2,500 and 5,500 rpm if you so desire. A new turbo, engine software changes, exhaust valve enhancements and upgrades to the cooling system help make the output increase possible. To cope with the additional power, Audi gave the eight-speed automatic transmission stronger clutches and the mapping program from its RS 7. This results in an official 0-to-60 mph time of 3.7 seconds.

An optional dynamic package adds carbon ceramic brakes, sport exhaust system, carbon fiber rear lip spoiler and raises top speed to 190 mph on the S8 Plus.

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What else necessitates the decision to change the model's name from S8 to S8 Plus? There's a new available $11,000 dynamic package that raises the Plus' performance IQ even further, including carbon ceramic brakes, sport exhaust, and a carbon fiber rear lip spoiler. The coup de grâce? Increasing the top speed limiter from 155 mph to 190 mph.

My test car had these features, making the S8 Plus sound lovely at wide-open throttle, while the brakes confidently slow the car for the Daytona road course corners. How many people considering a vehicle like the S8 Plus plan on hitting a racetrack? Probably none, but at very least they can count on the S8 Plus being more than decent when dancing around on winding back roads.

For normal street driving on Florida's flat and straight roads, the S8 Plus is a wonderful cruiser with the Audi Drive Select system set to Comfort. The engine is quiet and delivers its wave of power smoothly, with cylinder deactivation keeping efficiency in mind, helping the V-8 receive a better-than-expected EPA fuel economy rating of 16 mpg in the city and 26 mpg on the highway. The only times I notice the engine operating in four-cylinder mode is on the expressway, when leaning onto the throttle a touch more results in a slight but noticeable engine vibration. Ride quality from the air suspension is cushy even on the high-performance 21-inch Dunlop tires, yet it doesn't feel floppy. That sensation is aided by steering that offers a light feel, but quick response to inputs, with a small dead spot on center.

For 2016, the 4.0-liter turbocharged V-8 engine sees output increase to 605 horsepower thanks to a new turbo, engine electronics tuning, exhaust valve enhancements and cooling system upgrades.

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Punch the Drive Select system into Dynamic mode, and the sport exhaust note gets throatier -- noticeably so, even at idle. Power is livelier to quickly propel you above legal speed limits, steering feel tightens and the suspension firms up some, yet everything remains pleasantly comfortable. In fact, rolling at 90 mph down the expressway is entirely too easy to do unawares, your butt speedometer pampered into thinking you're traveling about 60 mph. Sorry, officers.

Worrying about cops didn't last long on my drive, though, as sheets of water began falling from the sky, dramatically limiting visibility and causing me -- and everyone else on the road -- to add a few hours on the way from Miami to Daytona Beach. Standard features like blind-spot monitoring came in handy when changing lanes in the blinding downpour, and the head-up display kept my eyes on the road as much as possible -- a good thing when white-knuckling it in tough driving conditions. Props also go out to the Quattro all-wheel-drive system for helping me stay surefooted on very wet pavement, never once feeling out of sorts.

The navigation system in the 2016 Audi S8 Plus features Google Maps imagery.

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The slow going let me appreciate the S8 Plus' cabin features more, too. The front sport seats proved supremely comfortable, with a massaging function to keep me loose while sitting in hours of bumper-to-bumper Orlando traffic, and the available 19-speaker Bang & Olufsen audio system sounded wonderful, as it should for $6,300. The Audi Connect system's Wi-Fi hotspot capabilities kept my passengers busy surfing the Web on their mobile devices, while real-time traffic information popping up next to the navigation's Google Maps imagery let me know how much more congestion-induced suffering lay ahead.

Other available features include adaptive cruise control, active lane assist (side cameras monitor lane markings and gently steer the car back into one's lane when the driver inadvertently wanders) and night-vision assist that uses an infrared camera and thermal imaging to warn of pedestrians or large animals ahead in the dark. What isn't available is either Apple CarPlay or Android Auto, and worryingly, a company spokesman says neither feature is in the immediate plans for Audi's A8 family.

So the S8 Plus now boasts more than 600 horsepower, cruises even more effortlessly at high speeds, and can confidently rocket around a race track -- or dispatch horrendous weather -- like few other machines. What's more, it does so in a practical large sedan package that offers superlative cabin comfort. Simply put, there's not much it can't do.

Better still, the Plus' extra power comes at no extra cost compared to last year's model, with Audi holding the model's base price steady at $114,900 for 2016. It's still a lot of money, but in this rarified air, it's also something of a deal when compared to the $143,000 Mercedes-AMG S63, a rival that only has 577 horsepower and needs 3.9 seconds to hit 60 mph. Consider that little nugget as yet another thing to smile about as you race home from work...or if you somehow find yourself shooting down the back straight toward the "bus stop" at Daytona.