Improving the Indy 500 – IndyCar’s superspeedway tech tweaks

Last October’s six-car test at IMS saw Will Power, Scott Dixon, Alexander Rossi, Graham Rahal, Ed Carpenter and Tony Kanaan running a revised aerodynamic package and a different Firestone tire compound. The purpose? To try out some changes in specification to Dallara’s universal aerokit [UAK18] and to the tires, a combination of alterations that should allow the cars to run closer and more predictably at 220mph-plus lap speeds on race day.

Tino Belli and Bill Pappas, IndyCar’s VP of competition, first tackled the task in a test with Dixon and Power last August, but it was the six-car post-season test that confirmed IndyCar was heading in the right direction. We asked Belli what was done, how it was done, and why it should work.

DM: What was the prime instigator of these changes?

TB: Following a race, we always look at polls rating the on-track competition. We thought last year’s Indy 500 was quite good, we asked Chevrolet and Honda what they thought and they were happy – but the fan ratings were down a little bit. Now, we have to keep our safety hat on too, so we don’t want pure drafting races, like restrictor plate races in NASCAR. And so for a first go around, this Dallara kit, which had been produced in quite a short timeframe, had done OK.

Nonetheless, we wanted to look at what could be done to improve the on-track product. Another point was that teams had complained to us that it was difficult to get identical front wings, so when they set up the front wings on their tools, they were getting slight differences in the aero balance; some teams got a handle on that, but some of the smaller teams were struggling a little bit. And then the third point we wanted to address was that we noticed from the onboard cameras that there was a little too much front-wing vibration.

So we did some CFD [computational fluid dynamics] studies. It’s quite a high-cambered and short-chord wing, and that’s for a reason – we have very stringent aero stability criteria. So as well as being designed to enable certain speeds and enable the car to race well, our car is designed so that if it goes nose-up, it shouldn’t backflip unless it’s extremely nose-up. (Obviously we can’t cover for absolutely every situation.) We do CFD tests at 5 degrees nose-up and we had to specify that the UAK18 was no worse than the manufacturer aerokits [of 2015-’17] in that situation. So, for example, when Takuma Sato hit the back of James Davison’s car, he went nose up but it came back down. So we couldn’t slacken our safety criteria, and one of the only ways we could hit the same number with UAK18 was to shorten the cord of the front wing, so it doesn’t catch the air so much.

To get a bit more front downforce for the Pocono race last year, we looked at lengthening the cord outboard and also inboard, and when we lengthened it outboard, we got into some bad situations because the trailing edge was stalling and the shape of the endplate was also stalling because the air’s expanding in front of the rear wheel. So we tested these revisions at Indy with Dixon and Power just before the Pocono race, and Scott liked them and Will didn’t. But between that test and the group test we did in October, we went back to the CFD and studied its effects, and felt like we could get the same effect by chopping a little notch out of the trailing edge outboard part of the mainplane. It just shoots the air through the end of the wing and energizes all of the airflow on the outboard section.

The new notch in the front wing, and how wickers must be trimmed flush to the notch.

Is it a massive effect? Probably not. Most of the drivers’ responses varied between “I can’t feel any difference,” to “it’s a little better”. But we did check it with accelerometers on the tips of the endplates to measure the shake, and we noticed a significant reduction in shake. We never got a negative response on track, the CFD flow studies looked better and that was checked via two different sources, and possibly one of the benefits will be that the wing will be more consistent on setup for the teams.

We scanned a whole slew of these wings to check it wasn’t a quality control issue, and it was well within the acceptable parameters. We also checked the wing wasn’t bending under load, and I can tell you it was extremely stiff so we don’t think that was a problem either.

There was clearly a lot more than just tires that gave the positive outcome to that test…

Yes, but Graham [Rahal] was right: Firestone have done a pretty major front tire revision. These tires were pretty much designed for the previous manufacturer aerokits and can therefore cope with very, very high levels of downforce. No one chose to run those very high levels of downforce, but they could, so Firestone had to cover for that possibility. So the tire becomes quite hard and non-compliant and we certainly have been working closely with them to try and produce more compliant tires. They did a very good job at Indy and did make a big step forward.

Firestone's new tire for Indianapolis Motor Speedway has helped make each car far more predictable in the wake of another.

That test was carried out with the track having been covered with a new sealant so the surface was very black and there were a lot of worries that the surface was very slippery. We did assess the grip of the track, by measuring surface roughness, and had people go around with a machine that tows tires, and the result of this study was that the grip level would not change. It’s a fairly new technology still, so we have to be careful about firmly stating that the surface coefficient is exactly the same as before, but judging by the testing, I would say that the level of grip had not been changed by the coating. And now that it’s been through a winter cycle, it’s even more likely to have deviated toward 2018 levels of grip.

As well as having more predictable behavior from the tires and greater consistency from front wings, there has been an increase in downforce for the superspeedways too, correct?

Yes, when we did the group test with six cars last October, we also tested with a bit more downforce. Because it’s fair enough for the guys at the front to say the downforce level was sufficient last year, but our target with UAK18 was to match the downforce levels of the fastest Honda and the fastest Chevy from the previous year, complete with their respective manufacturer aerokits. Which by its nature means that we’re measuring off the guys at the front, the ones trimmed out the most because they’re running in the cleanest air. So we decided to allow two rear wing wickers for this year, to give the guys in the middle of the pack a bit more range to run more downforce to make them a little bit more comfortable. And because we have them, the teams will be allowed to run the Pocono parts, the wing extensions and the +2deg wing angle.

How much difference does the rear wing make? I’ve had a couple of team owners/engineers say it’s just a 200mph advertising hoarding.

Three superspeedway rear wing wickers are available for 2019; one is a ‘+50lb’ downforce, the second one ‘+100lb’ downforce, the third is a full length wicker ‘+200lb’ of downforce.

Well it does a whole lot for downforce, it doesn’t do a whole lot for altering the drag. So when they’re trying to trim out for qualifying, you don’t get much drag reduction for a very big downforce reduction. It makes the car very, very difficult to drive without making the it go a lot faster in qualifying. But it only takes a few tenths of 1mph to offer quite a big difference. It’s just that the driver, to find those few tenths of an mph, now they have to be very ballsy.

The problem was that we wanted qualifying to be a 230mph four-lap average – we didn’t quite achieve that, but a big thank you to Mr. Carpenter who did manage two laps in the 230-plus range which probably saved my job! I mean, I did want to err on the lower side with our calculations, but yes, we wanted to get to 230. And when removing the rear wheelguards for UAK18 increased the drag a lot, the only way to achieve that speed was with this tiny rear wing.

Fans are, I’d say, broadly in accordance with you – that 230mph is the magic number that we want to see in qualifying. But there are some fans who regularly raise the subject of beating Arie Luyendyk’s 1996 record – 237mph average, give or take a tenth or two. Is that even feasible?

We will not get to that speed without more horsepower. We are expecting the engines will be a little bit better this year, but not a big step because last winter there were not many areas for the manufacturers to develop. On the years when they are allowed, we see a little bit more of a jump – around 1mph – and the ‘in-between’ years, we see about 0.5mph improvement. But the teams will have rubbed on the cars a little bit more and learned a little more, so we might get to 231, unless it’s a really hot day.

The other thing you’ll remember last year, is that some of the teams tried taking the sidewalls off the diffuser exits, or at least trimming them. I think Oriol Servia [then running a third Rahal Letterman Lanigan Racing-Honda] did it in the cool of the morning and then decided to run it like that for qualifying and had a disastrous time because the day had warmed up. We really should get blood-pressure monitors on these drivers to see how much effort they’re putting in…

Last year we made the teams run them symmetrically but this year we’ll allow them to run these sidewalls asymmetrically. There’s also a trim option on the sidewall – standard and short – so that’s open to the teams, as it was in the manufacturer aerokit era. I mean these things are very much in the same range of efficiency as the rear wing – a big loss in downforce for a very small reduction in drag – but if you’re going for pole or trying to get into the Fast Nine or you think you’re about to be bumped out of the field altogether, it’s something that you’re going to have to consider doing.

I will say this, though: in qualifying those cars are very, very on edge, and those drivers are very, very brave. The ballsiest racecar drivers in the world.

So with all these tweaks and options, the cars are as on edge as last year in qualifying, but the handling will be more predictable in the draft come raceday, which was the criticism from some quarters?

Yes on qualifying, absolutely. For the race, we hope to have significantly reduced that unpredictability, yes. And based off the tire test in October when the teams cooperated and worked very closely with each other and us, I think they were all very pleased at being able to run together and make moves. The ones running at the front will, I’m sure, still trim out a bit more for running in clean air, but now provisions have been made for guys running 20^th or 25^th to have enough downforce to make their way forward. Then they’ll be able to trim out a bit more in the final stint or two, providing they’re nearer the sharp end.