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    • Comparing the Porsche 991.1 3.8 X51 powerkit to the 2017 on 991.2 Carrera S 9A2 3.0 X51 powerkit

      With the release of the X51 powerkit for the turbocharged 991.2 Carrera S Porsche is offering a tremendous power upgrade at a great value. Think of it as a factory hybrid turbo upgrade with factory backing, testing, and a warranty.


      Now, there are many out there who do not really understand what it is you are buying with the X51 package. If you read other forums (why would you?) there are some Porsche fans who believe paying $7500 for 'only' 30 horsepower is a bad idea and a poor value.

      Well, let's start with the fact that Suncoast already dropped the 991.2 X51 Powerkit price to $6800 (is it a coincidence this happened after PorscheBoost stated the individual OEM turbo price?). That makes it cheaper than ordering the GTS/X51 turbochargers alone from Porsche directly. Not to mention it includes the entire kit with brake ducting and software.

      The X51 powerkit for the 3.8 liter 991.1 models runs $11k from Suncoast. An additional $4200. It also is said to add 30 horsepower. This is where things really diverge however.

      The 3.8 liter 991.1 is naturally aspirated and the gains only come up in a certain part of the rev range. Look at Porsche's dynograph:


      There is power added from 6500 rpm to 7500 rpm thanks to the new cylinder heads and cams. This does not come without a sacrifice. There is a dip in torque from 4000 to 4500 rpm as well as 6000 to 6500 rpm. There is a tradeoff for more top end pull due to the new cam profile.

      The 991.2 X51 kit on the other hand does not change anything internally in the motor. That is the beauty of it. In theory, it will apply to every 991.2 911 model. They all share the same 3.0 liter twin turbo 9A2B6 engine.

      The only difference between the 991.2 Carrera, S, and GTS? The turbo sizes and the software tuning.

      The X51 kit gives you GTS turbos which offer a 3 mm larger turbine and 4 mm larger compressor over the Carrera S. Boost pressure is also increased to 18.0 psi from 16.0 psi.

      This is the result:


      You will notice there are gains throughout the curve. Is there a slight penalty? Yes, roughly 300 rpm in spool. There is a nice torque kick down low though and torque gains carry through redline.

      In other words, you are not just getting 30 horsepower in a short rpm range as you do with the 991.1 X51 package. The 991.2 provides greater gains throughout the entire rev range for far less money.

      Things do not end there though. For some reason, people are not taking into account that Porsche is providing larger turbo wheels. The upgrade is fairly robust. There is, conservatively, another 100 horsepower in these turbos.

      Suddenly the upgrade goes from adding 30 horsepower to 130+ horsepower once tuned. A quality tuner will likely be able to provide even more but this will range with supporting modifications, fuel quality, etc. For reference, the 991.2 Carrera gains 100 lb-ft of torque at the wheels at 3000 rpm with a tune. The GTS turbos will show a large torque increase with a tune but also provide more top end flow.

      As a matter of fact, for an aftermarket hybrid turbo upgrade to exceed the Porsche X51 upgrade it will require some quality hardware components. PorscheBoost has some inside information regarding the factory turbo housings. There is room to go bigger than Porsche did but not by as much as you might think.

      Porsche knows all of this. The 991.2 GTS with a tune will perform like a 991.1 Turbo if not slightly better. The 991.2 Turbo can then get a tune to exceed it. Everything is specifically designed to maintain the model hierarchy stock and tuned. That is why the Carrera has smaller turbos than the Carrera S and the Carrera S has smaller turbos than the GTS. They all then have less displacement and smaller turbos than the 991 Turbo/S.

      Never before has Porsche offered such 911 tuning value from the factory. The 991.1 powerkit simply can not be compared. It offers less torque through the curve at a higher cost with less headroom. The install is much more complex and labor intensive:


      Frankly, why bother? Seriously, why? If one wants a strong naturally aspirated flat-6 just get a GT3 and be done with it. The 991.1 Carrera S 3.8 simply will not match the GT3 no matter what parts from Porsche you stick on it:


      If you want power, well, the GTS turbo upgrade and a tune is going to be incredible. We're talking an easy 10 second car.

      PorscheBoost has more information on the factory turbochargers coming as well as another 991.2 turbo upgrade option which will outperform the GTS/X51 turbochargers. Stay tuned.

      This article was originally published in forum thread: Comparing the Porsche 991.1 3.8 X51 powerkit to the 2017 on 991.2 Carrera S 9A2 3.0 X51 powerkit started by Sticky View original post
      Comments 2 Comments
      1. quattr0's Avatar
        quattr0 -
        Great stuff man!!! Im just shocked the lack of tuners that are willing to invest and take this bad boy to the next level!
      1. Sticky2's Avatar
        Sticky2 -
        Click here to enlarge Originally Posted by quattr0 Click here to enlarge
        Great stuff man!!! Im just shocked the lack of tuners that are willing to invest and take this bad boy to the next level!
        Thank you, feel free to share it!

        Tuners are investing it is just the ecu being a problem. Big things coming I promise.