JAMES: Finding the GT3's sweet spot

JAMES: Finding the GT3's sweet spot

Blancpain GT World Challenge

JAMES: Finding the GT3's sweet spot

What’s the downside to homologated cars? While they can be made pretty equal – depending on the track – teams can’t make wholesale changes to the car to make it work; there are pretty strict limits on what you can do. 

“We can change the springs; there are certain rates of springs we’re allowed,” explains John Ward, engineer for the GAINSCO Bob Stallings Racing team which fields a Porsche 911 GT3 R for Jon Fogarty in Pirelli World Challenge. “The damper settings can be changed. Then we go to ride height … we can change ride height, rake, camber, toe, all of that. And we can change rear wing angle. There’s nothing you can do on the front aerodynamics; that’s basically fixed.”

Ward is engineering his second GT3 car in the team’s second season of World Challenge competition; last year the team competed in a McLaren 650S GT3. Before that, he engineered the Falken Racing Porsche in the American Le Mans Series, and previously worked in Indy cars and prototypes in Grand-Am and ALMS. But it was his design work at Dan Gurney’s All American Racers that earned him notoriety. He designed Eagle Indy cars and the all-conquering Eagle MkIII GTP car. He is the proverbial guy-who-has-done-it-all and has a pretty good idea of how to set up a car.

Once the car is on track, the driver can only make a few adjustments, such as the anti-lock braking system and traction control. Beyond that and tire pressures, there’s not a whole lot a team can do to make a car fast.

“It sounds simple, and in some ways your choices are narrowed down,” Ward says.

But you need to get the choices you have very close. It’s a homologated series and it’s a Balance of Performance series; they get better and better at balancing the performance of all these different cars. What that means to me and Jon and anybody operating in this series is the difference in getting at the front or sixth in qualifying can be measured in tenths of a second. So the requirement is pretty exacting to get the car just right.”

If a team has raced at a track before – and if they arrive with the same car – it should offer a head-start on setup. But any number of changes – a new car, track repave, weather – could render that useless. So how does a team get the car as quick and as comfortable for the driver as it can be?

“We’re always trying to be in qualifying mode, so the first thing a driver will always complain about is understeer,” he explains. “They’re always right, no doubt about that, but sometimes you get it all out and you go slower. But typically we’re working on understeer. We’ll use things like rake, for example. Changing springs front to rear doesn’t change the balance as much as you might think; changing roll stiffness ratio front to rear is not as powerful as you think.

“Rake is a reasonably powerful tool. In general, most cars I have worked with respond to aero more than they do mechanical. A Porsche GT3 R may not have a huge of ground effects, but they are still aero dominated, it appears. So you’re working on things that change aero for balance. Mechanical, too – it turns out that rake does everything. Rake gives you some mechanical changes to the center of gravity, some roll centers, and just by changing the rake, you change the aero. It’s probably one of our primary tools.”

On the mechanical grip side, the first thing Ward will turn his attention to is dampers. Like adjusting rake by changing the ride height front to rear, changing the damper settings is a pretty simple task compared to changing springs on a GT3 car. And, surprisingly, it’s often more effective.

“They’re pretty responsive to dampers of all things, and that’s not normal in my experience,” Ward says. “All cars will respond to dampers, but these will respond with just a few clicks. In years past, if I’d have told a driver I’m going to change the front low-speed compression two clicks, they’d go, ‘What? You don’t understand. I’ve got a problem here!’ But nowadays they know. Jon and I know that a couple of clicks is significant. GTs are maybe alike that way, probably because they’re sprung softer than a prototype or an Indy car. They move and they roll, and the movement and rolling you can control with dampers. How you control that movement and roll is crucial to how the car feels to the driver.”

To lower lap times, look to the corners. The goal for almost any corner on the track is for the driver to brake later than the other guy, carry more speed through the middle of the turn, and get to full throttle sooner. There are a lot of variables to get there, though.

“You can get understeer out, but the car might be terrible to drive, so you have to find a way to get that to happen, to get neutral, so he can roll speed through the middle and still put the power down,” Ward summarizes. “Those are the keys, right? If you can roll the middle but can’t put the power down, you’re not going anywhere. It’s all about how long the throttle is open.”

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