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IMSA Issues Prototype BoP Changes for Rolex 24

DPs given reduction in power in final round of adjustments for Rolex 24…

Photo: John Dagys

Photo: John Dagys

IMSA released Friday Balance of Performance (BoP) adjustments for the Prototype class in advance of next weekend’s TUDOR United SportsCar Championship season-opening Rolex 24 at Daytona.

The biggest change come with revised air restrictor sizes, which sees a reduction in power for Daytona Prototypes and clarifications for P2 cars, following data from the Roar Before the Rolex 24 as well as dyno testing performed earlier this month.

DPs will have roughly a five percent reduction in power, with the Chevy-powered entries now utilizing a 2.5 percent smaller air restrictor in diameter, and the Ford EcoBoost-powered Rileys running 33.1 mm openings.

Nissan-powered P2 cars have been confirmed with 41 mm sized restrictors (in diameter), while the turbocharged HPD engine will have two 31 mm openings.

Both are in line with IMSA’s proposed five-percent performance increase over the current ACO LMP2 regulations.

DPs led the way in testing at Daytona, with the quickest P2 car, the No. 1 Extreme Speed Motorsports HPD ARX-03b, ending up with a best time that was 1.2 seconds slower than Christian Fittipaldi’s 1:38.630 lap set in the No. 5 Action Express Corvette DP.

“Working with the engine builders, we took the engines to the dyno after the test. It helped us determine some of the other items we were looking at,” IMSA’s Scot Elkins told Sportscar365.

“The testing at the Roar enabled us to get the final adjustment of performance for the prototype class, which we published today.”

Fuel capacities for both platforms are now confirmed, with gasoline-powered P2s allowed to carry up to 72 liters, with DPs at 76 liters.

The clean diesel-powered Mazda SKYACTIV-D entries will be permitted 70 liters, while the DeltaWing will run at 48 liters, with also a 10 kg reduction in minimum weight.

Boost pressures were also defined for the turbocharged HPD, Ford and Elan-tuned DeltaWing powerplants.

“We had data from the Roar and we reduced the power of the DP cars, which should help the fuel mileage,” Elkins said. “We did a very slight increase in the DP fuel capacity, just to max out the fuel cell.

“To compensate for the difference in fuel economy, we’ve reduced the P2 [capacity]. To compensate the flow going to a smaller capacity, we also reduced the [refueling] restrictor to try and balance that as well.”

Elkins estimates the change in the refueling restrictors will result in 3-4 second quicker fuel fills compared to last year.

Minor adjustments were also made to the spec Prototype Challenge class, which will see a revised rear wing placement.

The Oreca FLM09’s Chevy-based powerplant had been hitting the rev limiter around Daytona, and while a taller gear was tested at the Roar, Elkins said it didn’t entirely solve the problem.

“We are just basically trying to [tweak] the aero setting and not let them have a setting under the “hole 6″ wing position on the car,” he said. “That will obviously induce drag and hopefully it will solve this rev limiter problem.”

Elkins said he expected BoP changes for GT Le Mans and GT Daytona to be released later tonight.

P& PC BoP Changes: Click Here

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. rissas dad

    January 17, 2014 at 4:17 pm

    My season of fandom used to begin with Sebring, very much looking forward to this race. I cant remember at any point in the last 18 years that Ive followed sportscar racing that there are so many unknowns/possible winners in each class. You could really see any of 10+ in EVERY catagory as a possible class winner. Cant wait. Im looking forward to the Petit already!

  2. Jason

    January 17, 2014 at 5:13 pm

    There are so many classes of cars so the overall dynamic will be interesting to watch too. For one I do predict that the GTLM winner will be the LMPC winner overall and finish perhaps as high as 5th overall. I think prototype attrition will be pretty darn high.

    Plus this BoP debate between all of the classes starts all over again for Sebring!

    • Jack

      January 17, 2014 at 6:50 pm

      lmpc could have a podium if there clean, but the gtlm might get a top ten

    • Bakkster

      January 18, 2014 at 9:11 am

      The diffuser for the DPs should help them catch up the last bit on cornering, so they might just get a little less motor again. I’m pretty well at ease about BoP at this point, it shouldn’t be much worse than any other recent year.

  3. Vance

    January 17, 2014 at 5:17 pm

    This should make this pretty wide up open now. P2 cars should dominate through the infield. Man I’m excited for this

    • Jack

      January 17, 2014 at 5:29 pm

      IMO there are 3 1/2 p2’s that are competitive while any dp besides highway to help can win

      • Seth

        January 17, 2014 at 6:46 pm

        I wish the AC/DC guy was racing with Highway to Help Racing

        • Jack

          January 17, 2014 at 6:49 pm

          yea, i means its a charity team and it would bring more money if he raced

        • Chad

          January 17, 2014 at 7:13 pm

          Sadly the insurance agreement with his record label does not allow Johnson to go racing.

          • Bobke

            January 17, 2014 at 7:23 pm

            I guess he will be there with the team even though not behind the wheel?

          • Lanky Turtle

            January 17, 2014 at 7:23 pm

            He ran in 2012 and still races HSR so I don’t see how that would be an issue. He was there last year to promote the team and I suspect he will this year too even though he won’t be driving.

    • Bakkster

      January 18, 2014 at 9:10 am

      The P2s weren’t that much faster at the Roar. The cars are actually pretty well balanced in all the non-oval sectors, within 0.3s for fastest DP, P2, and DW sectors. It will definitely be a good race with cars having strengths without being so different it hurts the racing.

  4. Mikessp

    January 17, 2014 at 5:35 pm

    Jake is correct. The P2’s were not nearly as fast as many assumed they would be. Some were just so slow it was hard to watch.

    My opinion is the P2’s will have reliability problems (rear suspension, drive, tires) from so many hours on the high banks, and they will also have aggressiveness issues with the DP’s, which are rock solid and will play hard ball (as always).

    The GTD field will be the series to watch.

    • Jack

      January 17, 2014 at 6:15 pm

      the ford dp will explode and the Chevys will crash out

      • Chad

        January 17, 2014 at 7:16 pm

        Not likely… If it doesn’t rain I think a DP will win.

        • Jack

          January 17, 2014 at 8:46 pm

          its either a corvette, star works or a p2, fords will go kaboom and i think the dp drivers will be a little to aggressive through the gt field

    • Ben

      January 17, 2014 at 9:39 pm

      I disagree. These P2 cars have run at Sebring for several years. They are built solid. The tires however will be a different story. The continentals are really designed DPs and I don’t know if they have done much development.

  5. Timo

    January 17, 2014 at 5:52 pm

    When did the DeltaWing get a 2.3 litre engine? I always thought the Mazda based engine had a capacity of 2.0 litres.

    • Jack

      January 17, 2014 at 6:48 pm

      not 100% sure but i believe they upped it when they went to the coupe

      • Bakkster

        January 18, 2014 at 9:19 am

        Good catch Timo! It was actually destroked to 1.9L last year. Sadly IMSA never had the DW on the BoP sheet last year, so no way to check when they swapped engines.

        I would expect any change was more for reliability rather than pace.

    • Bakkster

      January 18, 2014 at 9:35 am

      I just asked them, they say it’s still the 1.9L

  6. Larry Joseph Morgan

    January 17, 2014 at 8:39 pm

    Don’t kid yourselves! The P2’s were sandbagging at the Roar Before!!!

    • Jack

      January 17, 2014 at 8:47 pm

      so were the dp’s, ganassi loves to find a second right after the roar, in 2013 the 01 car did a 42.4 at the roar, in the race it did a 41.2, so dont say the p2’s were sandbagging,

      • (The Real) JT

        January 21, 2014 at 12:11 pm

        The good teams always find .5 to 1 second between practice and qualifying

    • Bakkster

      January 18, 2014 at 9:21 am

      If they were off pace, and IMSA didn’t know, they’ll get a minimum of 5 minute stop and hold to be served in the last 30 minutes of the race. It isn’t worth it to be guaranteed to finish laps down, I doubt we saw sandbagging to the level we’re used to.

  7. andy

    January 18, 2014 at 9:49 am

    Ive been leery of all of this merger since it was announced but I cant forget it all right now !!! This race is hopefully going to be terrific! Im going to go with history in that either Ganassi car will be on top they just do their homework the best. BUUUT if the P2s can keep out of any traumas wow who knows. GTLM will see the usual hot shoes out front . GTD will see the hottest action way to many great teams there happy racing all

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