IMSA Roar test leads to new Rolex 24 At Daytona BoP adjustments - GT

IMSA Roar test leads to new Rolex 24 At Daytona BoP adjustments - GT


IMSA Roar test leads to new Rolex 24 At Daytona BoP adjustments - GT


Marshall Pruett photos

The TUDOR United SportsCar Championship’s dress rehearsal last week at the Roar Before The 24 has helped IMSA tech boss Scot Elkins to gather the final data points needed to lock down Balance of Performance adjustments.

Now, with practice set to begin in two weeks for the January 25-26 Rolex 24 At Daytona race, RACER looks at the tweaks that are being readied for the GTLM and GTD portion of the TUDOR Championship paddock.
(Read about the Prototype and PC BoP changes HERE).


With many of the Prototypes and all of the PCs, IMSA works from a set of rules that are unique to the TUDOR Championship. Even the P2s, which conform to ACO specs, have been slightly modified to work within the combined Prototype class, but balancing the competitors within the manufacturer-laden GT Le Mans class is done with the ACO in mind at every step. Elkins has done plenty of ALMS GT performance balancing, so it’s far from a new process to undertake, but there’s a built-in need to stay close to the ACO’s specifications for each car.

Based on the times from the Roar, Porsche’s new 991 chassis isn’t hurting for overall speed, and Corvette’s C7.Rs, which made their public debut at Daytona, were close behind with the second- and third-fastest laps during the test. The SRT Vipers and the lone Aston Martin ran within a half-second of the leading Porsche, while the BMW Z4s, which struggled last year on tracks with long straights, were well off the pace. That 1.3-second gap to Porsche, as Elkins explains, came after BoP concessions were made, and more could be in the works.

“We’ve been working with BMW ever since the November test, honestly,” he acknowledged. “And we’ve helped them out a little bit. We reduced a little bit of weight, reduced the rear wicker from 25 mm to 15. And gave them a little bit of aerodynamic change in terms of the door sills, the actual lower area below the door, we’ve allowed them to kind of expand that a little bit, similar to what the Aston has, if you remember that. We’ve allowed them to do some things just for this event to try to reduce some of that drag and help them get their V max up a little bit. So we’re working with those guys.”


As RACER documented in our Roar analysis, the GTD cars were blindingly fast on the straights, which is nothing new, but such speed and performance disparities between the GTD cars and the vehicles in the other three classes, 24 hours of tense passing attempts can be expected in the braking zones.Taking some of the top speed advantage away from the GTDs would reduce the number of divebomb passes, and after adding rear wing wickers to slow the cars at the Roar, IMSA will be taking another stab at the process for the Rolex 24.

“We would like to definitely try and slow them down a little bit,” he confirmed. “The problem is, the initial thought was the wicker would do a lot of that It wouldn’t slow them down 10 miles an hour but it would slow them down quite a bit. And then what we discovered this weekend and after we got the cars in tech and kind of looking over everything because the bulk of those cars in that class are brand-new cars we sat down and started looking at that and started realizing that there were a couple of existing rules that we carried over from Rolex GT that minimized the wicker.”

Some GTD teams, noting a loophole in the rules, adjusted the height of their rear wing end plates to offset the intended effect of the wicker, which resulted in higher top speeds than IMSA expected.

“The teams have the ability to actually move the end plates on the up or down on the [rear wing] main plane; there wasn’t a fixed location for that so we’ve actually changed that regulation on that and tweaked that to make the wicker a little more effective. It’s not going to solve the problem but it’s going to help us when we get back to the race.

“We also found a couple of other experiences in terms of the height of the roof and the height of the rear wing in reference to the roof, so we’re trying to tweak a couple of those things. But anything else we do isn’t going to have the same effect across the board. We can’t just reduce 200 RPM across the board in the class because it won’t affect each car the same because of the homologation that they have and how cars are using different gear ratios and things like that won’t have a universal impact.”PIT STOP RULE CHANGES

For TUDOR Championship teams coming into the series from Grand-Am, the 2014 pit stop rules are very familiar. For ALMS teams, however, a fundamental change is in order. Where Grand-Am allowed its teams to refuel and change tires simultaneously, ALMS teams, just as the ACO requires at Le Mans, had to wait on refueling to be completed before swapping tires.

Grand-Am’s process has been carried over into the new series, although some ALMS practices have been incorporated, and with the massive car counts and the prospect of packed pit lanes in mind, IMSA has reduced the number of personnel allowed over the wall.

“Grand Am had always done fuel and tires at the same time, and I everybody in the building here in Daytona thinks of that as an American pit stop,” added Elkins. “At ALMS, we had always done fuel and tires as two separate operations, which made the stop longer but it also provided the opportunity to do some strategy where you could think about double stinting tires and it created some more strategy in the race. The Grand Am rule, because the fuel took quite a bit longer than changing tires, it seemed like you were changing tires every time.

“So, we’ve adopted the changing tires and fueling the car at the same time for the TUDOR Championship but what we were trying to do is mix it up a little bit. The guys are now only allowed to use two guns, and as you rightly noted, we’ve limited the number of crew over the wall. So it’s a combination of trying to slow the tire change down a little bit and then, by utilizing the [refueling tank] fuel restrictors that we have, we’re going to increase those some to try to speed the fuel delivery to try to have a balance of where the tire change and the fuel delivery are of a similar time.

“Or at least to where the tire change is a little bit longer than what the fuel delivery is, so that we can build that ability and strategy of going back in and double or triple stinting a set of tires into the event, because that actually makes the event more interesting. It makes it more interesting for the strategist, and honestly, I think it makes it more interesting for the fans because it’s not just the same thing every time.”ANTI-SANDBAGGING RULE

IMSA sent out a bulletin prior to the November tests that rankled quite a few people. In it, the series outlined its intention to penalize those who run at slower speeds than they are capable of with the goal of having IMSA make performance balance adjustments in their favor.

With BoP determinations serving as the top priority for IMSA from November onward, the series reminded TUDOR Championship team managers and key personnel of the anti-sandbagging rule at the Roar, which led to more grousing. A time-based penalty has been suggested so far, but throwing the proverbial book at anyone who gets caught will likely be the outcome if and when it happens.

“In November we published a bulletin that stated any falsification or anything that we didn’t use the word sandbagging but that’s what we meant anything that happened, there’d be a penalty during the event,” Elkins explained. “So the idea behind that was to put some teeth to it. We have the ability and have always had the ability as a series to go in and pull data from teams, directly from their data systems to validate and verify. So the combination of that, the combination of the data that we have from the [embedded timing & scoring] loops that we’ve always used for analysis gives us plenty of data and plenty of opportunity to prove or disprove whether the team is actually performing to their ability or not.

“You know it as well as anybody, I look at throttle traces, I look at everything to see whether they’re lifting; I can tell if guys are on the rev limit. You can see all of those things if they’re giving their full performance or not. The fact is the data from this test is what we’re using to set expectations for the Rolex 24. So if you want to come and sandbag at this test, then I guess you need to sandbag for the 24 Hours because if you show a performance that’s different from that, you will receive a penalty.”

Tales of sandbagging away from the track have made the rounds in Grand-Am circles for years, especially with DP engines undergoing benchmarking tests held at NASCAR’s R&D center, but with IMSA’s efforts to gather its own data, to put the TUDOR Championship cars through wind tunnel tests and the recent anti-sandbagging bulletin, the series is making its greatest effort to date to bring its technical affairs under control.We’ll soon find out if any of the teams or manufacturers have been able to circumvent IMSA’s edict, and if they get caught, look for Draconian penalties to follow.

“And it’s a unique thing in motorsports, and especially from the organizer’s standpoint, where this is the type of rule we really only have to act on it one time and everybody realizes that we’re very serious,” Elkins stated. “So there’s even the possibility I’m going to probably change the regulation there’s even the possibility that we could penalize the guys prior to the event if we find that there’s been something nefarious going on. And I think that adds more teeth to what’s going on.

“There might be a revision of that bulletin shortly. I stood up in the managers meeting [at the Roar] and reminded everyone of what the bulletin was and they probably should take a read of it. And the best way that it works and the only way that it works is full transparency on the side of us and the side of them. And that’s what everybody wants. Everybody wants a fair playing field. So that’s all we’re asking for. We’re just trying to do it by legislating it through a penalty if possible. It’s the best thing that we could come up with.”