INSIGHT: Sebring test lessons

INSIGHT: Sebring test lessons

IMSA

INSIGHT: Sebring test lessons

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Lots to digest from Sebring’s two days of testing. (Marshall Pruett photos)

A few major lessons came out of the first-ever TUDOR United SportsCar Championship test at Sebring last weekend. The first was obvious: Despite the high number of brand-new cars (or teams working with cars they were unfamiliar with) in the GT Daytona class, lap times were fairly close and there were no glaring deficiencies among the leading manufacturers in the pro-am category.

Some degree of performance balancing will take place before the TUDOR Championship kicks off its inaugural season at Daytona, but as a whole, none of the GTD cars in attendance were woefully lacking in any major performance area.

The second item, which is a bit more nebulous, involves what we learned about the very first attempts at establishing parity between Daytona Prototypes and P2s. By the numbers, the 2014-spec Action Express Racing Corvette DP, which carried all of the available high-downforce additions and carbon brakes, was significantly faster than the near-2014-spec Extreme Speed Motorsports HPD ARX-03b, which lacked the required low-downforce body kit.

The Corvette DP recorded a best lap that was a full 4.1 seconds better than its P2 counterpart while sharing the track at the same time.

The 1:53.74 set by AXR’s Sebastien Bourdais on Sunday was well clear of the 1:57.947 posted by ESM’s Ryan Dalziel, but the gap would have been halved, according to the Scot, had they been working from the same testing objectives.

?Sebring was only meant to be a shakedown for us; we were only going to test at Daytona, but went to Sebring to work out some kinks first,? Dalziel told RACER. ?More than anything, we were wanting to get the drive-by-wire throttle sorted out and to turn a few laps to make sure everything else was good, so the intention wasn’t to go flat out; that’s what we have planned for tomorrow and Wednesday.

?But if we’d bolted on a set of sticker tires and really tried to go for it, I’m confident we’d have gotten into the 55’s, but with the air restrictor and the weight we’re carrying, there’s no way we’re capable of going any faster than that right now. The biggest thing to remember is this is just the first test for all the performance balancing, so there’s no reason to get upset about anything.?

As Dalziel noted, the 2014 rulebook, along with the respective DP and P2 regulations that are in place for Sebring and the Tuesday/Wednesday Daytona test, is far from being set in stone. Sebring, like Daytona, will provide IMSA rules boss Scot Elkins and his team with data to make necessary adjustments leading into January’s Roar Before the 24 test, the final dress rehearsal before the Rolex 24 at Daytona.

Within the Prototype class, vehicle weights and horsepower outputs are likely to be the first changes made once testing concludes this week. The 2013-spec DPs weighed a minimum of 2325 pounds (1055 kilos), and that has been decreased by 40 pounds to 2285 (1036 kilos) for 2014, but that figure is expected to be adjusted prior to the final rules being locked into place.

2013-spec P2 cars weighed in at 1984 pounds (900 kilos), and that has been increased to 2116 (960 kilos) for 2014 ” at least during the November tests ” as a starting point.

Sonic restrictors have been employed for the first time on all TUDOR Championship cars, and with the DPs, an increase in power has been made in concert with the weight loss to keep pace with the P2 cars. An estimated horsepower figure of 625, an increase of 60 or so from 2013, along with a significant spike in torque, said to be up by 90 lb-ft over last year’s spec, has given the DPs a noticeable acceleration and top-speed advantage at the moment.

Based on private figures supplied to RACER from pre-2014-spec DP and P2 testing at Sebring, a top P2 speed of 160mph was seen entering Turn 17, while 166mph was reached in the DP. Based on what this writer captured via radar gun, the AXR DP reached a peak of 165mph before braking into Turn 17, while the ESM P2 topped out at 155.9, a difference of 9.1mph.

For the sake of comparison, Pickett Racing’s PC car posted a 155.0, Aston Martin Racing’s GT Le Mans V8 Vantage reached 154.8 and NGT Motorsport’s GT Daytona Porsche GT America recorded a 152.4.

?Although we didn’t put down an ultimate lap time, and we weren’t pushing 100 percent, the one thing that won’t change is the trap speeds ” especially down into (Turn) 17,? added Dalziel. ?[IMSA’s VP of competition and technical regulations] Scot Elkins was there, the gun doesn’t lie and we were very honest about what kind of outright lap time we could do. We were sitting there at top speed maxed out riding down the back straight…

?They definitely achieved what they desired with the DP, but now we need to make the (P2 and DP) cars race well a nine or 10 mile-an-hour difference at Sebring is going to equate to closer to 20 (mph) at Daytona. Safely, it will be 15 (mph) difference, and I don’t know how we could all race together at that big a difference. Still, we’re not panicking; it’s a performance balancing test, and it’s an ongoing process.?

Given the chance to tweak the P2 specs, Dalziel thinks uncorking more P2 power ” something over the 450hp the twin-turbo Honda’s currently allowed ” would improve laps times and draw down the top speed disparity. Simply pulling the extra 60 kilos of ballast from the car would not do the trick, as he shares.

?Of course reducing the weight will help, but not as much as bringing up the power,? he said. ?The DP car has more acceleration off the corners, it gets up to speed faster and carries it down the straights. We’re quick off the corners, if not faster, but we just don’t have the horsepower to build up that same acceleration curve. And then by the time we get to the end of the straight, we’re still that much slower than the DPs. It’s about power, not weight.?

ESM got to work with Continental tires on the car for the first time after using Michelins in the ALMS, and for Dalziel, who has used Continental rubber in DP and PC, the changes weren’t as big as some might have expected.

?I’m a big fan of theirs; they got a lot of grief in the beginning, but they’ve developed a really good tire and it worked well for us in DP last season,? he explained. ?Degradation was a bit of an issue at Sebring, but we’re still learning them on the P2 car, obviously, and the extra weight didn’t necessarily help the situation. The only issue is that the tire we used at Sebring, the 2013 tire, was never developed on a P2 car, and I know we’re going to be on a different tire next year, so we didn’t waste too much time tuning on the car.

?The tire, regardless, is going to make for good racing. This is the first time we’ve been on track with proper P2 and DP cars ” you can ignore that test at Daytona last year ” and Continental has something good coming for 2014.?

Dalziel also gave praise to the AXR team for showing up in 2014 trim and going hard at Sebring.

?I’m really glad it was them at Sebring, because they don’t mess around; they go hard and you can count on them for being straightforward,? he continued. ?I’m pretty close with (AXR driver) Joao Barbosa, and we both talked after the test and were really honest about what we’re doing. What’s really important is to have two teams like this being serious about what they’re doing, giving the right effort and feedback to the series so they can do their job to balance things, and make the racing as good as possible. It doesn’t help the sport to have cars that aren’t racing well, and when we get to Daytona, we’ll be pushing as hard as we can now that we have our car shaken down and ready to go.?

For Sebastien Bourdais, who sampled the 2014 Corvette DP for the first time on Sunday, the performance increase was noticeable from his very first laps in the car. It’s possible the AXR car could have gone even faster, but with the team having to wait for more downforce-generating pieces to add to the front of the Coyote chassis, a few setup compromised had to be made.

?The car is definitely quicker, although it’s hard to compare at Sebring because I’ve never been there in a DP,? Bourdais told RACER. ?Two things jumped out at me: the car is pretty draggy with all the extra aerodynamic stuff on the car; and, two, we really couldn’t extract the potential of the car because there’s nowhere near the aero we need on the front. Until we can put everything on the front that we need, it will be hard to know what downforce level to run to be comparable to the P2.?

With a marked increase in downforce for the DPs ” something intended to be a 60 percent jump from 2013, seeing the AXR car reach 165mph into Turn 17 was a bit of a surprise. Even with the extra horsepower and torque, pulling the additional downforce and drag through the air should have impacted top speed. Simply put, and despite the jump in downforce and drag, the 2014 bodywork appears to have cleaned up a lot of the aero inefficiencies that hampered the previous generation of DPs.

?We were flat-out; it was all we had,? Bourdais admitted. ?We couldn’t run more rear wing because we couldn’t balance it (at the front). The thing is, if we ran max rear downforce, we’d be missing six or seven percent CoP (center of pressure). It’s not going to work, so we had to run the car with only some of the downforce intended with the update. The general direction of the new DP aero makes sense, and once we can rebalance the car ” move that CoP forward where it needs to be ” I think you’ll see a better idea of what the car is capable of.

?It was also interesting for me because the last time I was at Sebring in sports cars, I was in a Peugeot and we were doing 42’s and 43’s?so it took some getting used to in the DP. But I have to be honest and say the DP car is very enjoyable and has a lot of development ahead of it. It was a good test, we had no issues and I really liked the discipline of the team. They work very hard and have a very good idea of what to do and where to go.?

IMSA’s Scot Elkins told RACER he’s happy with what came from the Sebring test, and has started to craft the series’ next set of plans to balance the Prototype class. The GTD and GTLM classes, for the most part, will require some internal balancing, but setting the overall speed differences between the classes will serve as the greater priority.

?GTD was pretty close right out of the box, but it should be because we’ve been working with those manufacturers for some time, and with products that are mostly known to everyone,? he said. ?There’s still some things to be refined; a lot of the Audi guys are using the bigger rear diffuser so there’s some stuff to be learned there, but everyone was pretty close at Sebring.

?There’s a little bit of concern at Daytona that the GTD cars might be as fast as the GTLM cars, so maybe they’ll need to have a small wicker added or something to separate those two classes, but that’s about the only thing I’ll have my eye on there. We want to make sure there’s a separation between those two.?

Switching to Prototype balancing, Elkins knows he’ll need to come up with something to bring DPs and P2s closer together on top speed, and especially at Daytona. Current simulations show the 2014-spec P2 cars reaching an unassisted top speed of 182mph at Daytona, while the exact DP figure, regardless of speculation, won’t be known until all of the are pieces are finalized and run at the “Roar Before the 24” test.

?We’re actually in the wind tunnel today with the Corvette, just like we were with the Ford, to run through all the downforce settings and to see what kind of pieces we’ll need to make to balance the front,? said Elkins. ?Some of the simulations we’ve seen have said we might need to come up with a Daytona [DP] spec to shed some of the rear downforce, and we’ve always said the 60 kilos we put on the P2 cars was just a trial. We’ll keep it on for Daytona just to keep the car the same as it ran at Sebring, but I can see that coming back off after Daytona.

Most of the Prototype changes for 2014 have fallen to the DP camp, but Sebring revealed the P2 class will need more attention as well.

?I think the extra [P2] weight was affecting the tires yesterday,? Elkins remarked. ?We’ve always held that we could make a restrictor bigger for the P2 cars ” give it some more power ” to help. The idea was that the DP weighed so much more, we needed to add weight and generally try to slow the P2 car where we could, but we may need to tweak on that approach a little. It’s the first time out for our performance balancing, so there’s a lot of tweaks to come to get things where they need to be. It’s just first steps right now.?

Final weight for the DP cars will also take a little while longer to set, according to Elkins.

?We dropped 40 pounds to the DP from 2013 with the carbon brakes and the new (lighter) battery regs, but we added some back with the rear downforce pieces,? he noted. ?The diffuser is particularly strong because it has to be, but there might be some weight we could save there because we added some back. We hope to get it to a 60-pound reduction.?

The last item of note for Prototype balancing to come from Sebring ” and it will be a topic of interest leading up to the first race ” is fuel mileage.

DPs and P2s share the same fuel capacity of 19.8 gallons (75 liters), but with the inherent thirstiness of turbocharged powerplants, a team like ESM can expect to get approximately 45 minutes of running per tank. With less power, downforce and drag in 2013, DPs could stretch to 50 minutes or more, but with power/downforce/drag on the rise, fuel consumption has also gone up.

It will take more running at the Roar to get a proper handle on how the various naturally-aspirated and turbocharged DP and P2 packages fare on mileage, and with the fixed 20-gallon DP fuel bladder, any balancing required will likely come from removing capacity from the P2 cars, if such a move is deemed necessary.

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