The Inside Scoop on How Chevy’s New ZL1 Cup Car Won the 2018 Daytona 500 by Michael Accardi February 23, 2018March 12, 2018 Share Comments There’s no way of saying this nicely, but if you weren’t running under the Chevy banner during the 2017 North American racing season, you didn’t really stand a chance. Last year brought an embarrassment of riches to the bowtie brand – Chevrolet propelled Josef Newgarden to the IndyCar Driver’s Championship and proved themselves more dominant than rival Honda. Over in IMSA, Corvette Racing won the GTLM Driver’s championship with Antonio Garcia and Jan Magnussen, they also gleefully trounced Ford to the Manufacturer’s championship; meanwhile in the Pirelli World Challenge, the new Camaro GT4.R took Lawson Aschenbach to a GTS Driver’s Championship during its debut season. Take a breath, because what Chevy did to the NHRA in 2017 was utterly disgusting: They were the first brand to ever sweep all five categories of championships, from Top Fuel to Stock Eliminator and everything in between. Which brings us to NASCAR, where the new Chevrolet Camaro SS propelled William Byron to the Xfinity Series Championship along with another coveted Manufacturer’s championship. You’ll notice one glaring omission from Chevy’s dominant 2017, a Monster Energy NASCAR Cup championship. Well, after finishing last in the Manufacturer’s championship despite fielding the largest contingent of cars, Chevy isn’t interested in making the same mistake in 2018– they’ve come prepared, very prepared. Enter the new Camaro ZL1 Cup car. You’re forgiven for thinking the new car is just a fascia update to the outgoing Chevrolet SS teams raced with last year, but from nose to tail it’s all brand new, and that also includes the philosophies used to bring it from drawing to Daytona. The decision to extend the use of the Camaro to the Cup program was an easy one for Chevy, since it allowed them to continue as the only manufacturer that could boast a mild semblance of a connection between its race car and its road car. Think about it, the new NASCAR is a rear-wheel-driven, fuel injected V8 backed by a manual transmission with roughly 650 horsepower. So, on paper, it’s basically the same as the ZL1 you can buy from your local Chevy Man. “For me, this is a dream job to be able to first work on the production ZL1 and then take that same essence and translate it to the NASCAR.” said John Mack, one of the Design Managers at the Chevrolet Performance Studio. “The main emphasis of the car is the one face, and we were able to capture that in 3D, not just stickers, this is all really well developed and defined.” Obviously there are going to be significant differences between the two. For example, NASCAR mandates a 100 mm hold point from the base of the windshield, which complicated getting the hood surfacing of the street car to translate, plus the belt line on the race car is significantly lower to allow the drivers to climb in and out the window. But the body of a modern NASCAR is so much more than a vessel for advertising decals and fake features. It needs to produce downforce to push the car into the track surface. It needs to generate side force to help it tip into the turns. But it should also cut through the air as thinly as possible. Pat Suey, who works as the NASCAR group manager within Chevrolet’s motorsports competition group, is more acutely aware of this than anyone else. “Downforce is used to maximize the grip of the tires in order to corner faster, while side force will combat any looseness in the chassis setup in order to give the drivers a better feeling of stability when turning left, while lower drag will help it travel as fast as possible down the straight. “Within NASCAR’s figures we needed to figure out where to attribute those values, so we worked with our drivers in the simulator down in Charlotte to determine how much downforce we should have on the rear, versus how much we should have on the front, and that was actually the first time we’ve ever done that to develop one of our Cup cars.” A consortium of aerodynamicists from Hendrick Racing, Richard Childress Racing, and Chip Ganassi Racing started working with Chevy’s internal aero group early in the 2017 season and have continued to go back and forth all the way up to its competition debut during Speedweeks in the lead up to the 60th running of the Daytona 500. “Starting with the design John created, we tweaked it to fit NASCAR regulations before the aero development really started using Computational Fluid Dynamics, which is basically a wind tunnel on your computer. It can simulate the air particles moving over the body of the car, and allows you to see in depth where the air hits and how it travels across the surface of the car far better than you can in the wind tunnel. “We ran more CFD than we ever have before which allowed us to start subtly reshaping the car in order to adjust the airflow to get the forces you want and provide a good starting point for our teams to go racing.” Once the CFD work was done, work moved to a conventional wind tunnel, starting first with a 40 percent scale model, which allows the team more flexibility to run through design iterations before moving to a larger scale format. “Ultimately though, NASCAR has to approve the design before we can get it on track. They have dimensional criteria and they have aerodynamic performance criteria. We’ve seen our competitors struggle to get through the submission process, and when you have to re-body 15 race cars per car number for our main teams, it’s important to get through that process as quickly as possible.” Suey emphasizes this point. “The longer it takes us to get the car through the submission process, the longer it takes us to start making parts. and the longer it takes for our teams to start building race cars.” Team Chevy’s pretty proud of themselves because they punched the ZL1 through upon first inspection, and kicked off tooling immediately after receiving NASCAR approval in July of last year. NASCAR allows tolerances between the design homologated by Chevy and what the teams ultimately bring to the race track– .150-inch tolerance on metal surfaces and .200-inch for glass. That gives teams the ability to subtly shape the car’s body in order to make profound changes to it’s aerodynamic properties. That’s doubly important following the debut of NASCAR’s new Hawk-Eye inspection system which replaces the old laser inspection station and claw template that cars had to satisfy before and after races in the past. When the car now goes through Hawk-Eye it’s evaluated by eight projectors and seventeen cameras which create a 3D model of the car’s dimensions in order to compare it with a CAD model of the car’s homologation spec, determining how far away the car is from tolerance. “You gotta know the rules in order to figure out how to take advantage of them, at least that’s what racers do,” Suey says with a wry smile. “When we started designing the ZL1 we knew Hawk-Eye was coming, so some of the decisions we made give us an advantage, at least for now, until our rivals bring out new models optimized for the new rules.” So far, the car has succeeded in every possible way: Hendrick’s Alex Bowman took pole for the 500 in the No.88, and the No.9 of teammate Chase Elliot won one of the mid-week Can-Am Duels. Then, on Sunday, after all but three of the brand new ZL1’s had been lost to typical restrictor plate carnage, it was Austin Dillion in RCR’s sacred No.3 that ran a rival Ford into the wall at 200 mph at Turn 3 and scampered safely home to win the Daytona 500 nearly 20 years to the day that Dale Earnhardt took his first and only trip to victory lane at Daytona It really doesn’t get much better than that.