Like the pit stops where “energy” has replaced fuel in determining time spent in the pits as well as stint lengths, there are a few other things about the LMDh cars in GTP that could alter strategy. Like the pit stops, however, the changes will largely be invisible to the casual observer.
“On the inside, when you look at all the numbers and energy saving versus fuel saving and all that, it’s it’s quite different,” says Ryan McCarthy, strategist for Meyer Shank Racing with Curb Agajanian for drivers Tom Blomqvist, Colin Braun, Helio Castroneves and Simon Pagenaud. “But on the outside from a fan’s perspective, what the cars are actually going to do during the race, it’s very similar – saving energy is the same as saving fuel.
“Our stints are longer, we have a larger fuel tank, although we’re now running to an energy rule, rather than just until we’re empty on fuel. So we go from 35 minutes stint last year in a DPI car to a 50 minute stint now. The stint’s longer, and IMSA has mandated a longer time in the pits during the pit stop for us to fill up our our energy tank. So it kind of calms things down, it really gives the guys a little bit more time to get the job done.”
With stints around 50 minutes in green-flag running, that adds up to 28-ish stints depending on how many laps are run under caution. Teams will have 21 sets of Michelin tires to use during the race. That means up to eight sets of tires will need to go two stints. But exactly how those tires are double stinted is up to the team, and there are several possibilities, including double stinting one side or the other, or even taking a set off after a stint, and putting them back on later.
“I think you’ll see a variety of approaches,” explains Hans Emmel. Michelin’s manager for the series. “When you talk about double stinting, the first thing you think about is you put a set of tires on, you go out, you do a stint, you come in you feel the car and you go back out on the same set of tires, but that’s not necessarily how it has to be done every time.
“You can look at approaches like double stinting the left side tires then double stinting the right side tires, depending on the weather conditions we’re dealing with, the teams might want to keep at least part of the tires on the car warm, and then benefit from new tires on one side.
“You can also see some approaches of running tires for a stint, pulling the whole set off, putting another set on, and now the set you took off are four tires that could be used as two separate sets of left-side tires or two separate sets of right-side tires, depending on how they want to use the tires that have already seen a heat cycle. So I think it’ll be interesting to see. And I think, certainly, there will be a variety of approaches.”
Adding a new variable, there are now two compounds of Michelin tire. Call them harder and softer if you like, but the teams and the series typically refer to them as a warmer-weather tire (SHT in Michelin’s designation) or a cooler tire (SLT). In reality, it’s a daytime tire and a nighttime tire as, for Daytona, IMSA has restricted the use of the softer compound from 7 p.m. to 8 a.m.
“We have a little bit of a of a new twist where there’s two compounds available,” says McCarthy. “We have a low temperature tire, which is only meant for and allowed to be run at night. And then we have our standard Daytona tire, which will be the preferred tire except for the very dark and cold parts of the race. The amount of each of those is limited, so we have to balance that a little bit.
“But you don’t want to use up all of your low temperature tires and then from 3 a.m., you don’t want to have to be putting on the daytime running tires, and vice-versa. You don’t want to run too late onto your your daytime tires into the night because you might get a little bit of surprise there.”
The LMDh cars are using wider tires at the rear and narrower at the front than the DPis did to account for the different weight distribution with the hybrid system. The LMDh cars are heavier, so in that respect they’re harder on brakes and tires. On the other hand, the electricity regeneration has the effect of taking some load off both. When it comes time for a team to conserve energy, especially when trying to extend a stint at night, that last fact could cause throw some unexpected curveballs.
“When we start saving energy, the car cools off a lot. So we we use the brakes less, we use the tires less. So our tire temperatures come down a lot, our brake temperatures come down a lot. It can be very significant. So sometimes you might make an adjustment in the race, if you know you’re going to go into an energy saving period of time maybe over the over the night hours or something like that, you add some tape to your brakes to bring everything up because you know you’re gonna go conservative for a while,” McCarthy elaborates.
“Tires are really difficult to manage here; IMSA has mandated a minimum tire pressure at all times. So if you’re meeting that minimum tire pressure on normal, pushing hard laps while racing other people, and now you go into an energy save mode, you’re not going to be legal anymore. So you have to consider how much energy saving you can do and still still be legal. Or do you have to plan ahead and say we’re going to save energy on this next few stints, so we’re going to increase our tire pressures to start with. That’s going to be difficult to manage. That was still a consideration in the DPI era, it’s just more much more significant now than it was then.”
The ratio of fuel to electric energy the GTPs are using is largely automatic, but there are different maps to choose from. Changing the balance will result in greater or less energy usage as the 920 megajoule limit counts down. Mike O’Gara, team manager for Chip Ganassi Racing and strategist for the No. 01 Cadillac driven by Renger van der Zande, Sebastien Bourdais and Scott Dixon, says that’s going to be a new factor to take into account.
“There may be situations where teams use a little extra electric power during a stint, which means their stint could be shortened, or it could mean that they’ve used electric power, but not all of their fuel in the car. So we may be pitting with laps of fuel still left in the car that we can’t use, because of we’ve used up our virtual fuel tank. So it’s going to be a balance of how much electric assist you use during during a stint,” he explains.
There will still be short fills to try to leapfrog competitors in the pits and top-offs at the end of long yellows. But it’s going to take a lot of calculating on the pitbox, as will determinations on how to manage the balance between petrol and electric energy.
“The strategy is really the same. We’re looking at how long can we make sets of tires last. When can we start single-stinting at the end of the race? But there’s this new layer of complication with the electric energy available in the car that goes along with the actual tank of fuel so I’m not sure how much more I know beyond that, because we haven’t done it yet.
“You run ‘full rich’ and go faster, but you’re gonna pay the penalty by not being able to go as long. It’s just now you’re not just burning fuel, you’re burning electricity at the same time. So what I’m not sure a lot of teams have their heads wrapped around yet is the balance between saving fuel saving energy, what knobs affect each of those.
“I expect teams to be pretty conservative here early on and just kind of figuring each other out and how far everyone’s going go on a tank of fuel.”
Those that are going into the Rolex 24 at Daytona with a better understanding of all that may be the ones out front in the end. But surely all of them will leave Daytona with much more knowledge of how it’s all going to work.