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    • Comparing BMW F80 M3 & F82 M4 S55 engine design and output to the Porsche 991.2 9A2 Carrera

      The BMW M3/M3 and Porsche 911 have quite a bit in common this generation. Why? Because both have twin turbocharged and direct injected 3.0 liter six-cylinder powerplants. You can also get either with a dual clutch or manual transmission with power sent to the rear wheels.


      Let's look over the specifications of the motors:

      9A2 3.0 991.2 Carrera

      Horsepower: 370
      Torque: 332 lb-ft
      Boost Pressure: 13.1 psi
      Bore x Stroke: 91mm x 76.4mm
      Redline: 7500 rpm
      Compression Ratio: 10.0:1
      Intercooler: Air to Air
      Turbos: 49mm compressor/45mm turbine
      Piston Speed FPM: 3759.842

      BMW S55

      Horsepower: 425
      Torque: 406 lb-ft
      Boost Pressure: 18.1 psi
      Bore x Stroke: 84.0mm x 89.6mm
      Redline: 7500 rpm
      Compression Ratio: 10.2:1
      Intercooler: Water to Air
      Turbos: 51mm compressor/43mm turbine
      Piston Speed FPM: 4409.449

      Obviously, we all know the S55 engine is highly underrated by BMW. Recently, when Porscheboost was doing some testing at VF-Engineering on their Mustang dyno the opportunity presented itself to overlay a stock S55 with the stock PorscheBoost project 991.2.

      Here is the result, both dual clutch examples stock on 91 octane pump fuel:


      What is interesting to note is that the spool on the 991.2 Carrera 9A2 is much better than the BMW S55. The Carrera is spooled by 2400 rpm and the S55 has more lag by roughly 1000 rpm. That is significant.

      You will notice once spooled the curves are fairly similar. The S55 does have more peak torque and horsepower but the difference is not as large as one would expect.

      The difference in torque is only 3 lb-ft at the wheels. A wash. Not bad for what on paper is supposed to be 74 lb-ft. The 911 is making more torque than Porsche is letting on by quite a bit.

      The difference in peak horsepower is 15 at the wheels. This is attributed to the S55 making power to 6850 rpm while the 9A2 is tailing off past 6400 rpm. Both torque curves are dropping hard but the S55 maintains a top end edge from 6400-6800 rpm.

      Revving either engine out to their 7500 rpm redline does not gain anything and short shifting is preferred for maximum performance.

      It is interesting that the 9A2 engine with less boost and slightly lower compression is so close. It is also interesting the spool is so much better but Porsche likely concentrated very hard on quick spool down low to appease naturally aspirated purists who would complain about lag. The engine comes on strongly and quickly. It is no wonder the 9A2 knocked out the S55 in its category at the 2016 International Engine of the Year Awards.

      In an ideal world we would be able to toss a Carrera S and a GTS onto this dyno to see how Porsche is really separating their 9A2 motors. We do have Dynojet numbers posted for the Carrera and S but the GTS is the variant we are all eagerly awaiting to see. This is the difference between the turbocharged 991.2 Carrera S 3.0 and the naturally aspirated 991.1 Carrera 3.4:


      BMW of course has the Competition Package version of the S55 and now the CS version in an even higher state of tune essentially doing what Porsche does in offering the same motor in different flavors. The main difference though is that Porsche changes the turbochargers and not just the software offering greater differentiation and tuning value in this respect.

      What is clear is that the turbo era is elevating power and torque to heights we have never seen and it will result in a far greater proliferation of tuning for Porsche and BMW models than ever before.

      This article was originally published in forum thread: Comparing BMW F80 M3 & F82 M4 S55 engine design and output to the Porsche 991.2 9A2 Carrera started by Sticky View original post
      Comments 24 Comments
      1. quattr0's Avatar
        quattr0 -
        Thanks for this Sticky. Wonder if should try Eurocharged now, they use Dynojet though IIRC, as I had my M4 base run there with 93 oct.
      1. M_terkait's Avatar
        M_terkait -
        big bore small stroke, should be a happy revving motor.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by quattr0 Click here to enlarge
        Thanks for this Sticky. Wonder if should try Eurocharged now, they use Dynojet though IIRC, as I had my M4 base run there with 93 oct.
        Eurocharged doesn't have a tune for the 991.2's yet.
      1. quattr0's Avatar
        quattr0 -
        No, I meant for a dyno run for my C2
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by quattr0 Click here to enlarge
        No, I meant for a dyno run for my C2
        Ah. Yeah, they have an all wheel drive Dynojet. That's a good choice.
      1. BlackJetE90OC's Avatar
        BlackJetE90OC -
        Porsche took the 2.5L to 3.0L class win in the 2016 International Engine of the Year awards.

        Ousting the S55, after only a one year reign. For comparison, the S54 won it's class 6 straight years and the S65 won it's class 5 straight years.

        http://www.ukimediaevents.com/engine...sults.php?id=6
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by BlackJetE90OC Click here to enlarge
        Porsche took the 2.5L to 3.0L class win in during the 2016 International Engine of the Year awards.
        I made sure to mention it:

        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        It is no wonder the 9A2 knocked out the S55 in its category at the 2016 International Engine of the Year Awards.
        I think it indeed deserves the spot. How long will it reign though?
      1. BlackJetE90OC's Avatar
        BlackJetE90OC -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        I made sure to mention it:



        I think it indeed deserves the spot. How long will it reign though?
        That is what I get for skimming the article. Click here to enlarge
      1. Torgus's Avatar
        Torgus -
        It would be neat to see how the dynos look tune + 91 only, tune + 100% e85 only, FBO + 100% E85 with whatever FBO means for both platforms.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by Torgus Click here to enlarge
        It would be neat to see how the dynos look tune + 91 only, tune + 100% e85 only, FBO + 100% E85 with whatever FBO means for both platforms.
        Agreed. I can't guarantee I will do them all but I can at least do a tune vs. tune comparison.
      1. Eleventeen's Avatar
        Eleventeen -
        What I don't really understand is, why would Porsche underrate this engine so drastically?
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by Eleventeen Click here to enlarge
        What I don't really understand is, why would Porsche underrate this engine so drastically?
        Why did BMW underrate the S55 so drastically?

        For Porsche it makes sense as the last thing they want is GT3 and 911 Turbo owners getting their panties in a twist. Let them think they are soooo much faster for the money.

        Also, mine seems to be strong for some reason. I didn't follow break in. I just hammered it off the lot.

        A tune only 991.2 Carrera S will beat a 997.2 Turbo.
      1. KEMA's Avatar
        KEMA -
        Thanks Sticky. Great piece. Very interesting to see how the two engines arrive at their output.
        13.1 vs 18 psi. 49mm compressor/45mm turbine vs 51mm compressor/43mm turbine.

        Is it a stretch to assume the Porsche has more on the table in terms of bolt on potential? Given that it's running lower boost?
      1. Sticky2's Avatar
        Sticky2 -
        Click here to enlarge Originally Posted by quattr0 Click here to enlarge
        No, I meant for a dyno run for my C2
        Go schedule that dyno. We need more data.
      1. Sticky2's Avatar
        Sticky2 -
        Click here to enlarge Originally Posted by KEMA Click here to enlarge
        Thanks Sticky. Great piece. Very interesting to see how the two engines arrive at their output.
        13.1 vs 18 psi. 49mm compressor/45mm turbine vs 51mm compressor/43mm turbine.

        Is it a stretch to assume the Porsche has more on the table in terms of bolt on potential? Given that it's running lower boost?
        The Carrera certainly has a lot of room to grow. When tuned vs. a Carrera S on the stock turbos I don't see a huge difference. Maybe 20 whp? I mean what does the extra 2mm give it at the end of the day?

        Ultimately, the 9A2 is a better motor. The S55 is a powerhouse don't get me wrong but look at what the 9A2 is doing in its lowest state of tune at less boost. I think the S55 on the factory turbos will probably make more power up top than the Carrera as the Carrera is tuned to go come on very quickly. The spool advantage is embarrassingly large.

        The S will be a wash probably and the GTS will top them all.

        Ultimately, the 9A2 will be the stronger power plant. Plenty of room to gain bore or stroke, better design for revs, and the turbos are much easier to replace with far more room to work with. Plus it's based on the 9A1 in several areas meaning it is overbuilt. Combine all of that with no crank hub issues and it wins.
      1. Bowser330's Avatar
        Bowser330 -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        A tune only 991.2 Carrera S will beat a 997.2 Turbo.
        Beat at what exactly? 1/4 mile e.t.? trap? 1/2 mile?

        Either way that's a bold claim my man and i want it to be true so that it might help to reduce the resale value of these 7 year old 997.2 Turbos i'm checking out for $95K!

        I'm inclined to think the cars would be close but I still think a stock 997.2 Turbo will take the win over a tune-only 991.2 C2S
      1. Sticky2's Avatar
        Sticky2 -
        Click here to enlarge Originally Posted by Bowser330 Click here to enlarge
        Beat at what exactly? 1/4 mile e.t.? trap? 1/2 mile?

        Either way that's a bold claim my man and i want it to be true so that it might help to reduce the resale value of these 7 year old 997.2 Turbos i'm checking out for $95K!

        I'm inclined to think the cars would be close but I still think a stock 997.2 Turbo will take the win over a tune-only 991.2 C2S
        It's not a bold claim. The 991.2 Carrera S with a tune is dynoing more than the stock 997.2 Turbo at least according to Champion and GIAC.

        Lighter car plus more power? Simple.
      1. subaru335i's Avatar
        subaru335i -
        Click here to enlarge Originally Posted by Bowser330 Click here to enlarge
        Beat at what exactly? 1/4 mile e.t.? trap? 1/2 mile?

        Either way that's a bold claim my man and i want it to be true so that it might help to reduce the resale value of these 7 year old 997.2 Turbos i'm checking out for $95K!

        I'm inclined to think the cars would be close but I still think a stock 997.2 Turbo will take the win over a tune-only 991.2 C2S
        997.1 6MT is where it's at. Mezger engine ftw. Though the new engines are looking good we still don't know 100% what the long term reliability will be. I'm just gun shy of DI from the 335i.
        There are several examples of Mezger turbo engines going strong to 500-600k miles lol which is a crazy feat for a performance motor.
      1. Bowser330's Avatar
        Bowser330 -
        Click here to enlarge Originally Posted by Sticky2 Click here to enlarge
        It's not a bold claim. The 991.2 Carrera S with a tune is dynoing more than the stock 997.2 Turbo at least according to Champion and GIAC.

        Lighter car plus more power? Simple.
        http://www.porscheboost.com/content....an-997-1-Turbo

        Please show me where its more powerful than 997.2 Turbo... dynos please? im very interested. Your previous article was referring to the 997.1 Turbo....
      1. Bowser330's Avatar
        Bowser330 -
        Click here to enlarge Originally Posted by subaru335i Click here to enlarge
        997.1 6MT is where it's at. Mezger engine ftw. Though the new engines are looking good we still don't know 100% what the long term reliability will be. I'm just gun shy of DI from the 335i.
        There are several examples of Mezger turbo engines going strong to 500-600k miles lol which is a crazy feat for a performance motor.
        I want a PDK model, too bad there wasn't a PDK that was made for the mezger....