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Can a Viper ACR take on A McLaren Senna on track?


Yes, I have mentioned a Dodge in the same breath as a McLaren, and a McLaren that was named after no one other than Ayrton Senna. You might get angry. You might think I've gone mad or lost my bearings. But before you do any of that, consider this: What is arguably the most outrageous metric or aspect about the Senna? Power? Construction? Brakes? No, in my opinion, it's aerodynamics. The power, the brakes, the suspension, the attention to detail, everything is very impressive, but none is ground breaking, especially for McLaren. The aerodynamics, though, are what resulted in the menacing and brutal function-over-form styling of the Senna which makes an Alien vs Predator battle scene look like child's play in comparison.

So if it's aerodynamics, the amount of downforce must be huge (it is). You know the 911 (991) GT3 RS? It makes do with just 262 kg (622 lb.) at 150 mph. The insane 991.2 GT2 RS generates a maximum of 450 kg (992 lb.) at its 211 mph top speed. That's more than even the Porsche 991 GT3 Cup race car. But all of those Porsches are dwarfed by the Senna, which produces a staggering 800 kg (1,764 lb.) of downforce at 177 mph. Impressive, isn't it? It is very impressive, although not compared to the Viper ACR. That has more downforce than all of those cars with 907 kg (2,000 lb.) at 177 mph.


You may not want a relatively archaic Viper mentioned in the same breath as a tour-de-force McLaren hypercar, but the numbers don't lie. And a lot more numbers are now available since Car and Driver has just tested a McLaren Senna, just like they tested a Viper ACR a couple of years ago when it went on sale. If you just want to read the test numbers, scroll down to "Test Numbers". If you want to read how very different approaches in each car achieve very similar results, read on.

Aerodynamics

I've already given away the punchline. The Viper not only matches the insane Senna, it actually exceeds it and generates more downforce; the Viper has 907 kg vs the Senna's 800 kg at 177 mph. With that said, the Senna does have a few tricks up its sleeve.


The Senna has active "front aero blades" as well as an active rear wing. Those elements allow the car to not only change how much downforce is produced, but also optimize the aero balance. In other words, the car can change front-to-rear downforce balance in real time to "tune" the car for more front end or rear end grip, depending on the track and the corner. The adjustable components also allow the car to produce useful downforce at a wider window (i.e. presumably, a wider range of speeds), according to McLaren. The adjustable rear spoiler could also be used as an air brake.


The Viper could generate that much downforce... if you set it up right. Everything on the Viper is adjustable. Various aero bits are removable, some air inlets/ducts come with pop-in panels so you can block them if you want to change the aero balance of the car. The front splitter and rear carbon fibre wing are adjustable so you can tune how much downforce you have. There is a rear underbody diffuser with six removable strakes. You can set the car the way you like and change it from track to track for maximum performance. Trouble is, you have to know what you're doing. The Senna, on the other hand, will do it for you.



Suspension

The Viper ACR, again, gives you all the adjustability in the world. Coil overs using adjustable Bilstein monotube dampers are used at all four corners. The dampers are two-way adjustable (i.e. adjustable in compression and rebound) with 10 different stiffness settings for each. Moreover, the coil-overs are camber and height adjustable with a ride adjustment range of 76.2 mm (3 in.). That's nearly the same height adjustment range that you get out of a Ranger Rover Sport.


Suspension stiffness and height on the Senna are adjustable like the Viper, but actively; while you are driving. The same hydraulic suspension McLaren pioneered on the MP4-12C and has been using since then is in the Senna. But this car is utterly focused on performing on a track so, instead of balancing comfort and performance, it balances performance and, well, more performance... it allows the Senna to actively change stiffness and height to balance mechanical grip at low speed (i.e. more compliance to allow the tires to follow road imperfections) vs aerodynamic grip at high speed (stiffer to withstand downforce, avoiding bottoming out, and lower for better aero). Once again, the Senna is always working in real time to make you faster.

Brakes



Both cars use monoblock (fixed) braking calipers. Both cars use six-pistons in the front brake calipers and four-pistons in the back ones. Both cars use two-piece brake discs/rotors for better thermal management and resistance to fade, and both of them use carbon ceramic materials. Both cars use 15.4 inch front discs (although the McLaren uses the same size all around whereas the Viper makes do with "only" 14.2 inch discs in the back). Finally, both Dodge and McLaren will gladly tell you that the materials and components are bespoke to their cars, although only McLaren can brag about its F1-inspired technology and discs that take 7 months to create (each).

Tires

Once again, both use bespoke barely-street-legal track tires. The Senna uses Pirelli P Zero Trofeo R tires that were designed specifically for this car. They are sized 245/35/19 front and 315/30/20 rear tires. I have personal experience with those tires and I can tell you that, once heated, they stick like super glue on a dry track.


The Viper sources its tires from a much more humble name - Kumho. A version of the Kumho Ecsta V720 tires were developed for this car. They are called the Ecsta V720 ACR tires (yes, the tire model includes ACR in the name). Kumho can't claim the pedigree of supplying F1 tires and only when compared to the almost-slick Trofeo R do those tires appear road friendly with a UTQG wear rating of 200 AA A vs the silly 60 AA A of the Trofeo R's. But the Viper's tires are sized 295/25/19 in the front - nearly the same tires as the McLaren's rear tires - and a comical 355/30/19 in the back.

Drivetrain

This is one area where there are no similarities. The McLaren uses a state-of-the-art 4.0 litre, twin turbocharged V8 with twin-scroll turbochargers, electronic waste gates, anti-lag systems, and variable valve timing. It uses a dry sump system to improve lubrication at high cornering loads. It makes 789 hp at 7,250 rpm and 590 lb-ft. torque at 5,500 rpm and sends that power through a 7-speed dual-clutch gearbox. McLaren claims the lower hp versions of this engine have the heighest hp-to-CO2 emissions of any engine, meaning it should be one of the most efficient (burning) high hp engine out there. Dodge makes no such claims.


The Viper uses a giant, push-rod OverHead Valve (OHV) V10 displacing 8.4 litres. It is on its 5th iteration based on the original Viper V10 that debutted in 1992 (and was originally developed with a little bit of help from Lamborghini). It makes 'only' 640 hp, but at a lower 6,150 rpm, and 600 lb-ft torque, again at a lower 4,950 rpm. It does, however, use variable valve timing, making it one of the first and few OHV engines to utilize the technology (but that's because the majority of OHV are retired, telling World War 2 stories). The Viper doesn't even use a rear transaxle like its main crosstown front-engine rival - the Corvette - and relies on a traditional 6-speed manual transmission bolted to the engine.

Test Numbers

Although very similar in focus and function, the Senna seems to have an advantage everywhere, as you'd expect. It is several years newer, packed with technology and the collective knowledge of an F1 team, and - despite the similarities - seems to solidify advantages in every aspect. But you can't ignore the test numbers...

Grip? 1.12 g for the Senna vs 1.15 g for the Viper

Braking? 136 ft for the Senna to go from 70-0 mph vs 134 ft of the Viper

Both numbers are based on actual instrument tests done by the same publication - Car and Driver - using the same sort of test equipment (Vmax) and the same lateral g force test; a 300 ft skidpad. If you want to be even more astonished, the Senna should generate higher grip levels at the relatively low speeds possible on a 300-ft skidpad. This is because the aero elements are active and allow a wider window of performance according to McLaren, unlike the Viper that is designed to work at track speeds and should rely almost exclusively on mechanical grip at lower speeds.


Even more impressive are the brakes. The Viper's slightly smaller (rear) brakes and lack of F1 knowledge and tech hasn't hurt it one bit. Call it a tie and chalk the 2 ft Viper advantage in braking to different test days and different weather. They have, as close as makes no difference, equal braking performance, despite the McLaren discs taking seven months to make, each. The Viper brakes are likely made in a little shop, overnight, probably over a couple of beers.

But when it comes to speed, the Viper is licked. The Senna is packing nearly 150 hp more, backed by a lightning-quick dual clutch gearbox, and weighing nearly 170 kg (370 lb.) less, making it far quicker.



0-60 mph in the McLaren happens in 2.8 seconds. A lot of sports cars take around 5 seconds to reach 60 mph, but the McLaren takes roughly that long (5.1 seconds) to reach to 100 mph. The Viper looks slow in comparison. It takes a lethargic 3.3 seconds to get to 60 mph - half a second longer - and doesn't get to 100 mph until 7.5 seconds have passed, over 2 seconds longer.

1/4 mile in the Senna passes in 10.1 seconds at a 147 mph trap speed. The Viper takes all of 11.5 seconds to cover a 1/4 mile and is going 126 mph by that time. You could walk faster than that! (at least that's what a Senna might say if it could talk).

Pick Your Poison



There is no denying the Viper's capabilities. What it lacks in speed, it makes up for in handling. When tested by the same professional racing driver on the same track - Randy Pobst at WeatherTech Raceway Laguna Seca in California (previously Mazda Raceway Laguna Seca) - it beat cars like the McLaren P1, Lamborghini Huracan Performante, and Porsche 918 Spyder.

It set 13 different lap records at various tracks in the US, including Laguna Seca, Road Atlanta, and Virginia International Raceway (VIR). It is certified by the Sports Car Club of America (SCCA) to hold more track records than any other production car. The SCCA is a lot more than just a car club. It is a sanctioning body for multiple road racing, autocross, and rallycross series in America from grassroots level motorsports to professional.

I think it's clear that the Viper has the advantage in outright grip, both mechanical and aerodynamic, but it has a serious power deficit in comparison. It wouldn't stand a chance against the Senna on longer tracks, chief of which is the Nurburgring, of course, where the Senna should have a great advantage. Each has strengths and weaknesses that make each better suited for different tracks.


Every detail, every technology, and every component in the Senna is magnificent. I think all the tech and active components will make it much more approachable. It will take much longer to set up the Viper properly for each track, and will take more effort, more trial and error, and some "POO HAS COME OUT" moments when you get it wrong... but when you get it right, it will be massively satisfying. And beyond that, the far more analog Viper with its steam roller, understressed V10 engine would make it a much lower maintenance track weapon. My brain is mesmerized by the Senna, but my heart? THAT is falling for the Viper...

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