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IMSA Sets Initial Balance of Performance

IMSA releases initial Balance of Performance for WeatherTech SportsCar Championship season…

Photo: Rick Dole/IMSA

IMSA has set the Balance of Performance for next weekend’s Roar Before the Rolex 24, having released Friday the initial table for the 2018 WeatherTech SportsCar Championship season.

It comes following extensive testing and analysis conducted both on and off-the-track, including evaluations at Daytona International Speedway earlier this month during an IMSA-sanctioned test.

While the GT Le Mans and GT Daytona classes remain relatively unchanged compared to this year’s end-of-season BoP, adjustments have been made to several Prototypes. 

The Cadillac DPi.V-R, which features a smaller 5.5-liter V8 engine, has seen the biggest change, with a 10kg minimum weight increase along with a 1.8mm (x2) larger air restrictor. 

Wayne Taylor Racing took part in the recent IMSA-sanctioned test with the updated powerplant, which was sent to NASCAR’s R&D facility in Concord N.C. for further evaluation.

Both the Nissan Onroak DPi and the new-for-2018 Acura ARX-05 will also now run at 940kg, compared to 930kg for the LMP2-spec machinery and the Mazda RT24-P.

No power-related adjustments have been made to either of the turbocharged Nissan and Mazda powerplants, although IMSA has implemented aero-related changes for some P class cars.

Initial performance levels for both the Acura DPi and BMW M8 GTE, the two all-new cars for next year, have been established, with the BMW running at a 1250kg minimum weight and with a revised turbo boost curve than its M6 GTLM predecessor.

No performance-related adjustments appear to have been made to any other GT machinery since this year’s season-ending Motul Petit Le Mans, although IMSA holds the right to issue a revised BoP table prior to the season-opening Rolex 24 at Daytona.

UPDATE: IMSA released a revision to the BoP late Friday, confirming a 1mm larger air restrictor for the Mercedes-AMG GT3 and newly defined maximum RPMs for all classes.

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. Socialist

    December 29, 2017 at 10:15 am

    I agree with balance of performance because it is more important to create equal outcomes than to have equal rules with unequal outcomes.

    • SS

      December 29, 2017 at 10:18 am

      The horse is down to dust, you can stop beating it now.

    • Mo

      December 29, 2017 at 10:50 am

      In case you missed it, even with BOP, there are unequal outcomes. I have yet to see a three way tie on the top step of the podium, or a three way tie for the drivers, team, or manufacturer’s championship. There are no equal outcomes with BOP.

    • Andy Flinn

      December 30, 2017 at 12:08 pm

      Socialist, there was no BoP in WEC LMP2 this year. You know, the chassis that IMSA DPis are based on. Of course, Oreca/spec-Gibsons won ALL the WEC LMP2 races and the WEC LMP2 championship.

      With you being a “socialist” I could see why you would prefer the series-mandated spec Gibson engine (for ALL WEC LMP2 class competitors) and the WEC LMP2 Orecafest over IMSA.

  2. Sol Shine

    December 29, 2017 at 10:49 am

    BOP meeting #1.

    OK boys, how much do we have to give to Caddy to make sure Generous Motors wins a lot again this year? We sure do wanna keep Nascar’s, er, Imsa’s buddies at Generous Motors happy.

    • Mo

      December 29, 2017 at 10:55 am

      How do you know this, but the other manufacturers are apparently oblivious to GM’s preferential treatment? As the previous poster stated- that dead horse has been beaten to dust.

      • lookattheGMfanwhine

        December 29, 2017 at 12:28 pm

        They are not oblivious to it, they just wanna race.

        Why do pro ‘rasslers (and their wheeled versions NASCAR) keep participating.


        And the previous poster wasn’t talking about the Government Motors favoritism. Every time it gets brought up, you GM fanbois rush to their defense. Talk about beating a dead horse………..

        • Tom

          December 29, 2017 at 1:45 pm

          I think you misspelled a word… it’s not whining it’s winning. GM is winning not whining, now on the other hand… you may be whining.

          • Andy Flinn

            December 30, 2017 at 12:27 pm

            Exactly, Tom. Great post!

          • Jordan

            January 1, 2018 at 10:04 pm

            Just some basic facts.

            Chevy has never won a Le Mans Prototype race.

            Chevy had to be bailed out by the US government.

            Andy Flinn precedes to whine like a bitch over basic facts.

            Why can this be predicted?

            Because losers are very predictable.

        • Mo

          December 29, 2017 at 6:57 pm

          Nonsense! The other manufacturers would not waste time and money in a rigged series. You conspiracy theory nuts act as if GM just fell off a turnip truck and don’t know how to go racing. The other manufacturers don’t race just because they want to race.

          • jakester

            January 2, 2018 at 12:35 pm

            Fact? As you have stated it, not fact.
            In fact, Chevy has ‘won’ every LE MANS PROTOTYPE CHALLENGE race (both ALMS/IMSA and ACO/FIA, as every LMPC FLM09 chassis carried a Chevrolet crate engine amidships. 😉

    • Barefoot in the Tower

      December 29, 2017 at 11:17 am

      BOP Meeting #2:

      Why haven’t we BoPed Beaux’s Lack of Shoes during a race?

    • Moan and groan and cry

      December 29, 2017 at 8:51 pm

      Once a moron, always a moron! You must be a very miserable person to be around. Constantly moaning and groaning. How does your boyfriend stand being near you?

      • Andy Flinn

        December 30, 2017 at 12:32 pm

        Moan, does your therapist know you’re using his computer?

    • Andy Flinn

      December 30, 2017 at 12:25 pm

      Sol Shine, replace GM, Caddy, IMSA and NASCAR with Oreca, Gibson, ACO and FIA and your absurd, tinfoil hat conspiracy theory plays out EXACTLY the same way.

  3. David Chaste

    December 29, 2017 at 1:20 pm

    We can all talk bad about GM, but they have the most involvelent in the series. Corvette DP, Cadillac DPi, Corvette GTLM.

    I too hated how much coverage they cadi dpi’s had at last year’s rolex 24. But someone has to put the money in to make it work and attractive. And GM does that. Their strong involvement is what attracted acura to bring a full fledged factory effort by calling up Penske. And the chance to go against Penske and possibly beat them is attracting many privateers.

    There’s downsides to the nascar GM collusion. But dont forget about the upsides as well.

    • TF110

      December 29, 2017 at 3:36 pm

      Acura is just a name that HPD is using. The same HPD that was in the series a couple of years ago but were pushed out over them not being allowed to race their own car. So they put a beak and headlights on the Oreca and threw in the engine. That’s some huge manufacturer involvement for ya. It looks like GM has the series by the nuts to a lot of people. The reasons why are spoken here.

      • David Chaste

        December 29, 2017 at 3:49 pm

        Well, there own car wasnt cutting the mustard, and ESM has a top notch operation as we can see now.

        When they finally fixed it they didnt want to pay for a team to race it. But those were not full fledged efforts like this Penske deal.

        I heard at a race that the fast hpd 3.5 twin turbo engine was faster in the ligier than in the Hpd chassis. Even after the updates.

      • Nick

        December 29, 2017 at 5:51 pm

        Correct me if wrong pls. Weren’t all the old arx-0xx chassis re branded from a unspecified mfg. not exactly their own car

        • David Chaste

          December 29, 2017 at 6:52 pm

          Wirth research was building it for Hpd/acura. But the 2007-2008 acura’s had more developments (factory). From 2009 on the aco started cost capping p2 cars and spares and required a gentleman driver at lemans.

          In my opinion wirth couldnt quite design cost capped cars as well as the unlimited budget chassis of 2007 and 2008 they had churned out.

        • Jackson P

          December 30, 2017 at 4:30 pm

          They featured a few redesigns over the years, but yes, at the heart the ARX (01 and 03) cars were Courages…

      • Mo

        December 29, 2017 at 7:11 pm

        @TF110, Yes, that is huge manufacturer involvement. A two car factory Acura Team run by Penske is huge manufacturer involvement. Not to mention bringing in drivers like JP Montoya and H. Castroneves. Yes, they put their brand styling cues on the LMP2 and put their engine in it- That’s what a DPi is. That’s the beauty of DPi.

      • Andy Flinn

        December 30, 2017 at 11:52 pm

        TF110, are you so used to seeing spec-Gibson/Orecas dominating WEC LMP2 this year that you can’t tell the difference between a spec-Gibson/Oreca LMP2 and an Acura/Oreca DPi?

        Even if you completely ignore the different Acura DPi bodywork, they’re still not the same race car (engine).

        And nobody (aside from a frustrated Toyota LMP1 Le Mans fanboy) cares if people call it an Acura or Honda. It will still always be more than just another spec-engined WEC Oreca.

      • Dave

        January 1, 2018 at 3:16 am

        You always have really bad opinions. Acura is just a name HPD is using? Yeah, what do you expect? Of course it’s not the actual factory making Acura road cars that is working on the racing program!

  4. pierre

    December 29, 2017 at 6:09 pm

    can’t remember, has imsa applied any bop post qualy like the fia/aco do for lm24?

    • WesGTR

      December 31, 2017 at 11:23 am

      Not that I know of, but to be fair, the post Le Mans qualy BoP adjustment was so public that it may have robbed light from any other such event.

  5. Jason

    January 2, 2018 at 7:53 am

    Kind of lame no coverage of the qualifying but they’re covering the prototype challenge race. Doesn’t make much sense!

  6. Bert

    January 2, 2018 at 9:53 am

    Another year of keeping Risi choked out….

  7. fourloko

    January 2, 2018 at 12:28 pm

    i would be surprised to see the bmw stay at 1250kg, considering the corvette is 1240.

    • fourloko

      January 2, 2018 at 12:55 pm

      2.18 bar max for bmw holy cow

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