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Cadillac to Debut Updated 5.5-Liter DPi Engine

Cadillac to roll out with smaller 5.5-liter V8 powerplant for IMSA WeatherTech SportsCar Championship season…

Photo: John Dagys

Cadillac will head into its IMSA WeatherTech SportsCar Championship title defense with an evolution of its championship-winning engine, featuring a smaller, more optimized powerplant for 2018.

Sportscar365 has learned that IMSA has approved the use of a 5.5 liter normally aspirated V8 engine instead of Cadillac’s 6.2-liter unit that took Ricky and Jordan Taylor to the Prototype championship this year.

The change, which has been months in the making, is understood to provide a more balanced torque curve and power output, and expected to help aide IMSA in its Balance of Performance process, which the Cadillac DPi was at the subject of throughout the 2017 season.

The No. 10 Wayne Taylor Racing Cadillac DPi quietly debuted the updated engine package at this month’s IMSA-sanctioned test at Daytona International Speedway, which saw the sanctioning body conduct extensive power-related evaluations prior to impounding the engine for additional dyno testing at NASCAR’s R&D Center in Concord, N.C.

DPi rules allow manufacturers to make engine updates at any time, but are subject to IMSA’s re-certification process, which includes dyno and track testing.

All four of the Cadillac DPis, including newcomer Spirit of Daytona Racing, will have the updated ECR-built engine for next weekend’s Roar Before the Rolex 24 at Daytona.

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. David Chaste

    December 29, 2017 at 10:31 am

    So that’s why WTR’s engine was inpounded.

    But inpound is such a strong word in this situation. It’s more like taking the engine to a controlled environment for performance testing.

    Seems like the 5.5 already in the Corvette, probably with tweaks for more cooling, less weight and higher output.

    • David is still a moron

      December 29, 2017 at 10:51 am

      No, impound would be the correct term as they took a participant’s equipment as it was used to not be modified in anyway.

      Just because you think there is some implied restriction to the use of impounded does NOT mean it is the wrong word to use. They have to follow the actual English language, not David Chaste’s impressions of the language.

      • Patrick Laurent

        December 29, 2017 at 11:06 am

        Why do you hate David? He’s a cool guy and is very knowledgeable on this stuff, perhaps you should get a life and stop hating users behind your keyboard.

        • KV

          December 29, 2017 at 1:39 pm

          CADILLAC DNA spells V8 POWER !

          • Avery

            December 29, 2017 at 9:21 pm


      • Webster

        December 29, 2017 at 2:54 pm

        Impound….to seize and take legal custody of something because of a infringement of law or regulation.

        Deffinetly the wrong word as to the situation at hand. You sir are a ____

        • Webster is a fucking moron too

          December 30, 2017 at 8:16 pm

          Nice try dumbass but definitions are included in the rule book from IMSA. The rules state taking an engine for inspection is impoundment. So by the rules they did exactly what the rule states with the verbage used.

          And bs definition you used. Try actually using a correct definition next time

          • Travis McBee

            December 31, 2017 at 8:05 am

            Had a shit Christmas bud? Hope you have a happy new year!

          • Nick

            December 31, 2017 at 6:53 pm

            Are you Cooper McNeil? Cuz no one like cooper and that’s whit I am gathering here.🐑🤛

    • Jake

      December 29, 2017 at 4:24 pm

      Doubtful that its the C7-R lump. The C7-R’s engine is still based on the 7L LS7. Which was an LS based motor. This one is likely still LT based. Just reduced displacement.

      • KV

        January 2, 2018 at 1:16 pm

        LT or LS based,direct,and port injection ,will recoup any performance losses due to Bop. GM is only scratching the surface !SYONARA HONDA,NISSAN,and GIBSON !MAZDA GIVE ME MORE !

  2. Zaphod Beeblebrox

    December 29, 2017 at 11:15 am

    I liked that the teams used the 6.2L motor. It was the same displacement as the block in the CTS-V, which at least hinted at some sort of road car connection. I doubt that change will affect the quality of the racing, so not a big deal.

    • Max

      December 29, 2017 at 11:19 am

      The drivers will probably appreciate not having to struggle around the hairpin at Long Beach with the exceedingly tall first gear they were given.

      • N8

        December 29, 2017 at 12:33 pm

        I think that’s the key. They weren’t going to get a break on the gearing unless they reduced engine output.

    • fourloko

      January 2, 2018 at 8:15 am

      the c7r uses the 7.0 block, ive seen the casting mark in person. why would they go through the additional development for the 6.2 production block?

  3. Av

    December 29, 2017 at 11:15 am

    Full of anger people.

  4. Mike D

    December 29, 2017 at 11:17 am

    Is it still built by ECR? Any idea on internal dimensions to get to 5.5L? (I’m just nerdy and like to know this stuff)

    Corvette still builds their own 5.5L, unrelated to this one… I think.

  5. Max

    December 29, 2017 at 11:17 am

    Is this just the 5.5L Corvette DP spec LS7R motor?

  6. gmsucks

    December 29, 2017 at 12:11 pm

    I guess NASCAR finally said “you had your year, now dial it back”.

    • juneracer

      December 29, 2017 at 3:38 pm

      exactly. same issue IMSA had with the Viper and still have with the Merc. can’t properly BoP low end torque. all you can do is curb total power with restrictor and fuel/air. easy with Turbo cars. with the DPs they’d spec out cams… i’m sure IMSA persuaded them to change…

    • Mo

      December 29, 2017 at 7:15 pm

      It’s not NASCAR, it’s IMSA. Brian France runs NASCAR.

      • Sold me out for chicken change

        December 30, 2017 at 11:56 am

        Who owns IMSA? oh yeah, nascar

      • jaysfan

        December 31, 2017 at 10:18 pm

        And guess who runs IMSA? 3 guesses, first 2 don’t count, Does the name Jim France sound familiar?

        • Keep the trend going

          January 1, 2018 at 12:42 pm

          Well clearly Bill France has the word France in it which means the country France makes decisions on IMSA. Le Mans is run in France which is run by the ACO which means the ACO runs IMSA…

          • jaysfan

            January 1, 2018 at 12:55 pm

            Try again junior!

  7. Bjones

    December 29, 2017 at 12:58 pm

    Pratt & Miller are GM built units, Cadillac 5.5 are ECR built units. It is a racing motor built utilizing NASCAR type blocks. Other words those engines are special blocks and parts made specifically for racing.
    The vette engines supposedly come off the shelf ( So to Speak). They are not the same only share the 5.5 capacity. Just to explain in a different manner The only thing the ECR motor shares with a stock motor is its shape.
    Personally my belief is IMSA could not figure out how to stem the torque or they did and Caddy used an ole NASCAR trick and went lower cubes to get more power in a different power band. Remember the late sixties and early seventies and those nasty 302s from ford and chevy. If you do then you understand what they are up to.

    • KV

      December 29, 2017 at 7:28 pm


      • Avery

        December 29, 2017 at 9:22 pm


    • FactsAreOnTheNet

      December 29, 2017 at 9:37 pm

      This comment about NASCAR style blocks is not correct. The Cadillac DPi uses a aluminum LT-R (GM LT racing version). The “NASCAR” block is cast iron and is complete different (larger bore to bore centers, longer, different oiling layout, different lifter bore locations, r07 head bolt pattern). So they are nowhere close to the same or compatible.

      • Bjones

        December 30, 2017 at 10:15 am

        As usual I expected someone to go on the net and start quoting specs, I stand
        by what I said and to help you out it is a built aluminum block by nascar engine builders, that is why I said style. It is not a 4 cam motor and as usual someone wants to start getting tech through google. Every damn motor built by a different builder has different designs. With that said I was wondering if ole NASCAR had went to aluminum but was not sure. Point is, the motor is a purpose built racing as like a Gibson, but push rod design aka NASCAR because the motor (blocks and heads) are purpose built for racing. Are we clear.


          December 30, 2017 at 10:49 am


        • Put down the shovel BJ

          December 30, 2017 at 8:19 pm

          But what you said is NOT what you meant or what you said in the second post. Don’t try to double down with stupidity when you were wrong the first time. There’s VERY little between this engine and NASCAR style engines. Other than they are 8 cylinder engines that burn gasoline. Just because it’s push rod doesn’t make it NASCAR style, the C7 uses the same style

        • Jake

          December 31, 2017 at 12:36 pm

          So wait, where is it defined that any non DOHC engine is to be declared NASCAR based?

          Sounds like your simpleton mind cant wrap itself around the fact that a pushrod engine can provide all the performance that a DOHC can (and do so while being more efficient, and packaged smaller and lighter than its DOHC equivelant)

        • kv

          January 1, 2018 at 11:18 am

          CRYSTAL clear Bjones !

  8. Passenger

    December 29, 2017 at 5:13 pm

    New 5.5 could be base new LT engine or rumor of new C8’s DOCH engine.

    • KV

      December 29, 2017 at 7:38 pm

      THE DOHC TT V8 FOR THE C8 IS LS BASED ,and can be bought as a crate engine under code SB 4 FROM MERCURY MARINE !

      • Avery

        December 29, 2017 at 9:20 pm


  9. Matt e

    December 29, 2017 at 6:27 pm

    SPortscar racing rules!

  10. speedy

    December 31, 2017 at 5:32 pm

    Corvette C8 engines are DOHC engines code names LT6 and LT7, they have nothing to do with MM. They are in house build, this could be on of them behind these Cadillac DPI’s. Cadillac will have a new V8 TT engine coming up in there line-up.

    • kv

      January 1, 2018 at 11:31 am

      The NASCAR model of having multiple engine builders to develope a package for what the application is not new,but it works !

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