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Multiple BoP Changes for Lime Rock

Multiple changes in IMSA BoP for Lime Rock…

Photo: Jake Galstad/IMSA

IMSA has confirmed multiple Balance of Performance adjustments for GT Le Mans and GT Daytona class cars ahead of next weekend’s Northeast Grand Prix at Lime Rock Park, including power cuts for both the BMW M6 GTLM and Ferrari 488 GT3.

The BMW, which claimed its second consecutive GTLM class win last weekend at Canadian Tire Motorsport Park, has received a significant reduction in turbo boost across all RPM levels, as well as a 1-liter fuel capacity cut and refueling rig height adjustment.

After struggling in the last two rounds, the Corvette C7.R has been given a 0.2 mm larger air restrictor and 1-liter fuel capacity increase for Lime Rock, along with a 1.5mm larger refueling restrictor.

Refueling restrictor adjustments have also been made to the Ford GT (+0.5 mm) and Porsche 911 RSR (-1.0 mm)

In GTD, the Ferrari has also received a reduction in turbo boost, along with corresponding adjustments to fuel capacity (-1 liter) and refueling restrictor (-3 mm).

Other changes in the class include a 20kg weight break for the Lamborghini Huracan GT3, 10kg reduction for the Porsche 911 GT3 R, a further 20kg added to the Mercedes-AMG GT3 and a 1 mm smaller air restrictor for the Lexus RC F GT3.

The Northeast Grand Prix is scheduled for July 21-22.

John Dagys is the founder and Editor-in-Chief of Sportscar365 as well as the recently launched e-racing365 Web site for electric racing. Dagys spent eight years as a motorsports correspondent for Channel, and contributes to other publications worldwide. Contact John



  1. Mike S.

    July 14, 2017 at 12:24 pm

    Not surprised by BMW move. But were the Vette’s that slow? They seemed to stretch fuel. More surprised by how much Vette has been given. These are small changes though not drastic.

    • tracer

      July 14, 2017 at 12:47 pm

      Agreed that the Vettes were hard to judge at Mosport, but between watching on boards at that race and Watkins Glen it appeared that they were down on power a bit compared to the rest of the pack. I’m not sure how much the boost cut to the Bimmers will affect them at Lime Rock, as the track layout should favor the Porsches and Fords anyways.

    • Max

      July 14, 2017 at 12:51 pm

      There’s a chance they felt they were just not competitive on pace so they ran at 80% the whole time to save fuel in the hopes of winning on strategy. Perhaps with the telemetry IMSA has they believe they’d run short on fuel at 100% with the restrictor increase.

      Pure conjecture of course, but seems within the realm of possibility.

    • JEZ

      July 14, 2017 at 1:46 pm

      The Corvettes have definitely been slower recently. Last three races, they have qualified P6 and P8 (COTA) P6 and P8 (Glen) and P7 and P8 (Motorsports) Race lap times have generally been down as well, and without the yellow flag, the #4 was about to be lapped at CTMP.

      At CTMP though, the Fords were equally slow for some reason. Hopefully they can get their pace back, or they’ll be left at the back of the pack with no adjustments

      • Wheeeee

        July 14, 2017 at 4:36 pm

        Surprised nothing for the Fords. They were way off the pace at Mosport. BMW takes the suitable wack after their wins and now Porsche gets to win. Everyone gets a turn!

    • DEJ

      July 14, 2017 at 3:35 pm

      Not to fret Vettes will be on an above pace… a sure win .

  2. WBrowning

    July 14, 2017 at 12:50 pm

    The Vettes always seem to have the fastest pit stops, not sure I get the fueling restrictor increase for them.
    Just checking the boost changes, but they look to be about a 0.75% decrease in boost ratio, not sure that’s enough, but it can’t hurt in bringing them back closer to the rest of the class.

    • tracer

      July 14, 2017 at 1:05 pm

      The P&M guys are definitely at the top of the pit stop game, but it did appear that their refueling times were a good bit slower than the Porsches and Fords. I think that played a major part in their long-run strategy at Mosport.

      • JEZ

        July 14, 2017 at 1:22 pm

        The Corvettes changed fueling gear for Le Mans (I believe as required) and the new gear is slower than what they were using earlier in the year, which is why they went from quick stops earlier in the year (maybe too quick) to longer stops the last couple of races.

      • DEJ

        July 14, 2017 at 3:37 pm

        don`t forget “lil Dougies DEEP pockets !

        • Loser's love the internet

          July 14, 2017 at 9:42 pm

          Fehan has accomplished more and experienced more in life than you will in three lifetimes. Funny how internet ‘Losers” such as yourself find power in their parent’s basements attempting to belittle those soo much more successful in life. You’r penis will always be very tiny, and no amount of anonymous internet wailings will change that.

          • DEJ

            July 14, 2017 at 10:14 pm

            Sure am glad you got that rant off your mind

      • Georg

        July 14, 2017 at 4:23 pm

        Pitstop times are limited only by the refueling. All teams can change tires easily within the time it takes to fill the tank, when it’s done after a full or nearly full stint.

  3. tracer

    July 14, 2017 at 12:52 pm

    GTD Porsches and Lambos were in need of some help, but surprised to see the AMGs get slapped with 20 more kilos.

  4. Jake

    July 14, 2017 at 1:32 pm

    BMW needed an adjustment, whether in HP or weight. They are the lightest in class by a good margin.

    Trap speed wise Corvette werent off a whole lot. Data showed they were losing their time through the corners more than the straights. I would have thought a weight adjustment would have been more appropriate.

    As mentioned above, they switched fueling rigs to one that is compliant at Le Mans and fueling was drastically slower.

    • juneracer

      July 17, 2017 at 9:30 am

      BMWs need less wt to make up for the high CG and they need more power to push the brick through the air. but a power reduction for them was required…adding wt to them would appear to have been the wrong choice…

  5. jason

    July 14, 2017 at 1:54 pm

    Warning…about to complain big time…….What the H-E-double hockey sticks! More weight increase on the Mercedes AMG! That p!$$es me off big time!! Very Very bad move IMSA. You need to reverse that immediately. That would justify Cooper and Ben to take their AMG’s and run off to PWC again like last year. Mercedes is the coolest-a$$ race car in the series. Again I call you to immediately reverse this horrible call.

    • Rocket J. Squirrel

      July 14, 2017 at 2:25 pm

      Yes, IMSA, you should always make decisions based on which are the coolest-a$$ cars in the series.

      • welp

        July 15, 2017 at 11:46 am

        and which rich people are going to through little hissy fits and leave the series. (something both ben and cooper are known for)

        • Ryan

          July 16, 2017 at 6:15 pm

          Cooper and Ben didn’t leave. The team employing them left.

          • Mike

            July 17, 2017 at 5:41 pm

            Actually, Cooper did leave. WeatherTech money was funding his AJR car & seat and he cut it off in complaint.

            Correction on Keating. Ben was not the other one that left. Park Place left (and then Magnus left after the VIR DQ and the “miscommunication” on the Petit drive times.

  6. Andrew

    July 14, 2017 at 9:51 pm

    The hamfisted BOP against the AMGs continues and gets worse with the 20 kg weight increase. As noted, IMSA did a BOP smaller restrictor adjustment the night before the Daytona 24 Hours and Porsche 911s blew by them on the banking all race long. These small restrictors were re- instated at Watkins Glen, Mosport and possibly at Detroit, plus will be in effect at Lime Rock. The AMGs no longer have any competitive horsepower, are qualifying at the back in all qualifying sessions, are running at the back of the GTD grid during races (save for attrition), have poor race results and have been taken out of the championship; the AMG teams had to run the cars trimmed out with no downforce in order to get any speed at all which meant all handling and braking disappeared from the Mercedes-AMG GT3s, hence the very poor on-track performances. The racing has truly become ‘show’ only, WWF wrestling anyone?

    But, at least IMSA got its $500,000 mandatory entrance fee. It is a joke for fans and for AMG or other mfrs considering running in the series. By this point, IMSA should have learned from Blanc Pain GT3 series and WEC on how to do even-handed BOP adjustments, but instead it is instead IMSA sledgehammer BOP techniques and whatever flavour of the week appeals to the officials. What a mess.

    • Andy Flinn

      July 15, 2017 at 5:29 pm

      Andrew, the #33 Mercedes hit a wall at Detroit. The #75 Mercedes hit the VFR prototype.

      Was that BoP?

  7. CD

    July 14, 2017 at 10:48 pm

    Only Corvette can Win 5-6 in a row before BOP adjustment kicks in. BMW wins two in a row and they get hammered. If GM doesn’t win, OMG something must be wrong! If BMW doesn’t win for the next 2 years, oh well they weren’t trying hard enough.

    • Larry

      July 16, 2017 at 3:28 pm

      What’s amazing is that the ‘vette is the second lightest car in the class while having the biggest engine, 5.5 liters.

      It weighs 1240kg while the Porsche with its 4 liter 6 banger weighs 1250kg.

      The lightest car is the BMW with a 4 liter also except it’s turboed.

      Seems there should be a sliding scale equating weight to displacement with a factor built in for turbos.

      • JEZ

        July 17, 2017 at 8:34 am

        All these cars can make more power than they are “allowed” to. The engines are supposed to be production based (but limited to 5.5 liters, which is why the Corvette has a smaller than production motor), but they want the cars at roughly equal power. So the theory behind any sliding scale doesn’t really apply if we’ve balanced a 4.0 liter and a 5.5 liter to have roughly the same output. The extra displacement advantage is taken away by BoP.

        They then tweak engine power and weight to primarily balance for the car’s architecture that impacts handling and aerodynamics. The problem with having production looking cars (with production-based architecture)is you get a highly aerodynamic Ford GT, with a mid engine going against a big brick of a front-engined car like the BMW. If they weighed the same, and had the same motor, the Ford would crush the BMW because of its other efficiencies. So you make one lighter, maybe give it a little more power and off we go.

        So weight in the category has more to do with handling and aerodynamics over displacement.

  8. Luna

    July 15, 2017 at 3:22 pm

    IMSA is trying hard to make everyone happy, to make every manufacturer win at least one event. Customer satisfaction exercise.
    They are NASCAR, don’t forget. They tried so hard to have Danica Patrick in Victory Lane…..
    In GTD its going to be difficult with the clowns of Lamborghini and the Gentilozzi’s gang. But they paid money and will get something.
    Maybe Kevin Buckler can send some bottles of wine…

    • Andy Flinn

      July 15, 2017 at 5:44 pm

      Yes, Luna, it’s far better to be the ACO and the WEC and watch Oreca walk away with the 2017 LMP2 “world championship.” WEC LMP2 theoretically has no BoP.

      The Tockwith Ligier, the only non-Oreca even competing (on a limited schedule) in the WEC LMP2 championship this year, qualified dead last behind all of the Orecas for tomorrow’s Nurburgring round.

      If Tockwith quits, WEC LMP2 will be just another spec series. It’s very close to being that as it is.

      So Luna, IMSA/”NASCAR” BoP versus ACO/FIA WEC LMP2 non-BoP?

      Based on the on-track product and COMPETITION I’ve witnessed so far this year, I’d prefer the IMSA model AND day.

      The IMSA BoP whiners can whine….

      • Mike

        July 17, 2017 at 5:44 pm

        In fairness, it is easier for AMs (and Pros for that matter) to have tighter lap times in GTs than Protos because of the nature of the car.

        Not saying I disagree with you, but there is a drastic difference in both Pro and Am P2 driver quality across WEC. Same exists in GTE-Am… look at Christian Reid (and his 1 win since 2012) compared to, say Paul Dalla Lana and “Silver” Mattias Lauda), and it definitely plays a factor, along with the longer races, in the performance gaps.

        If IMSA’s races were 6 hours and they didn’t have SCs, there would probably only be 2-3 GTDs on the lead lap then too.

  9. Limeglen

    July 15, 2017 at 7:06 pm

    Not great news for Mercedes but it would be nice to see the Porsches be competitive again.

  10. juneracer

    July 17, 2017 at 9:37 am

    IMSA contends its a data driven BoP. and they seem to do what they can with what they collect. not perfect but far better then what the ACO/FIA do currently. the Cadi Dpi’s and the Merc’s in GTD have big displacement over the balance of the field. that’s a hard one to match up. can’t kill low end torque easily…

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