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    • AMG M157 turbocharger upgrade analysis, comparing tuners turbo upgrade approaches - Journal Bearing versus Ball Bearing and A/R

      There has been a bit of discussion in the BenzBoost M157 engine forum as to which tuner is using what turbo setup for their M157 turbocharger upgrades. There are three major M157 turbo upgrades all from BenzBoost supporting vendors. Those three are AMS with their Alpha 9 package, Renntech's turbo upgrade, and Weistec Engineering's M157 turbo upgrade. Confusion arose as to who was doing what CHRA (center hub rotating assembly) and why.


      To clear this up all these turbo upgrades are not the same. Renntech chooses a custom Garrett GTX2870r based setup. AMS also uses a GT28 based setup. Weistec goes with a GT22 CHRA and exhaust wheel. Tuners and users chimed in with their opinions and a tuner from the BimmerBoost.com side stated his belief that the Ball Bearing CHRA of the GT28 is superior to a journal bearing based setup as in the GT22. Garrett's own position is such:

      Garret Turbo: "The journal bearing has long been the brawn of the turbocharger, however a ball-bearing cartridge is now an affordable technology advancement that provides significant performance improvements to the turbocharger.

      The ball bearing cartridge gives better damping and control over shaft motion, allowing enhanced reliability for both everyday and extreme driving conditions. In addition, the opposed angular contact bearing cartridge eliminates the need for the thrust bearing commonly a weak link in the turbo bearing system."



      Now the Weistec choice is the GT22 from the Garrett gasoline turbocharger family which is a newer design over the GT28 and they believe it is the better choice. This is due to lower inertia and its more compact size which allows it to flow close to the GT28. This is their position:
      http://www.weistec.com/turboupgradefaq.html

      Weistec Engineering:
      "It is slightly smaller, but more efficient, and proof that bigger is not always better. The process of adapting the GT28 into the factory Mercedes exhaust housing requires extensive machining of the volute profile, an increase in radius and flow width to install the larger, older exhaust wheel. This reduces the A/R of the already small housing, as well as reducing the yield of how much exhaust gas actually drives the exhaust wheel forward via the volute.

      Machining to fit a larger wheel into the same exhaust housings effectively reduces the AR even further and with it, the flow potential and turbine efficiency of the GT28. The result is operation at an even lower level of efficiency than the OEM configuration at multiple points. Although the wheel is larger, less exhaust gas will flow through the turbine. This is reducing the efficiency of the system. In the performance world, efficiency is power, drivability, time to torque, response, back pressure and again Power!"

      There are two different perspectives at work here and both have merit. When going to a GT28 based turbo upgrade it will require running new oil and water lines. Since the Weistec setup is identical on the outside to the OEM setup a dealer will not know the turbos are upgraded which is handy for those who are concerned with warranty work or like to keep their mods hidden. A GT28 based setup will be noticeable. Again, pluses and minuses here.

      Each company here chose the setup they believed was best for their customers. All are good choices and are an upgrade over the stock turbos. It would be great to have a shootout between all of them but due to distance that is not possible. Keep in mind these upgrades use the stock housings and manifolds. The M157 is a fairly tight fit which varies based on the chassis it is in. This motor will see much more development over the years.

      For now, let's enjoy having options.

      Journal Bearings:


      Ball Bearings:

      This article was originally published in forum thread: AMG M157 turbocharger upgrade analysis, comparing tuners turbo upgrade approaches - Journal Bearing versus Ball Bearing and A/R started by Sticky View original post
      Comments 27 Comments
      1. LZH's Avatar
        LZH -
        Nice writeup and a good comparison for those looking to upgrade the M157. I sure wish someone would do this for the M156. I'd be all over that...
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by LZH Click here to enlarge
        Nice writeup and a good comparison for those looking to upgrade the M157. I sure wish someone would do this for the M156. I'd be all over that...
        You mean turbos for the M156? Would be nice but... well, whatever happened to that? Click here to enlarge
      1. LZH's Avatar
        LZH -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        You mean turbos for the M156? Would be nice but... well, whatever happened to that? Click here to enlarge
        Yeah, the M156....or, the M159 would be sweet too Click here to enlarge
      1. m54b25's Avatar
        m54b25 -
        Hey Joe! Nice write up & it brings up some good points about the stock GT22 (MGT2260xxx) turbine wheel & housing. When modifying the M157 turbine for RT, we took into consideration more than anything in machining precisely the TIP height & modified surface to fit the BB GTX28 turbine complete CHRA as how OEM Garrett would have intended. Also, a private flow & velocity testing was done =). Since exhaust gases behaves much different from intake charge flows... I can say the GTX28 using M157 modified A/R has not much changed, other than have similar or even better spool up time. The end results will be a car that performs consistent at the track & will not expect any early CHRA failure under extreme duty uses for at least 5-7 years using MB regular service guidelines.

        BTW, we already tested some stock MGT22 to it's limit & it will fail under extreme duty using Dynojet numbers of around +720ftlb in enduro test.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by m54b25 Click here to enlarge
        Hey Joe! Nice write up & it brings up some good points about the stock GT22 (MGT2260xxx) turbine wheel & housing. When modifying the M157 turbine for RT, we took into consideration more than anything in machining precisely the TIP height & modified surface to fit the BB GTX28 turbine complete CHRA as how OEM Garrett would have intended. Also, a private flow & velocity testing was done =). Since exhaust gases behaves much different from intake charge flows... I can say the GTX28 using M157 modified A/R has not much changed, other than have similar or even better spool up time. The end results will be a car that performs consistent at the track & will not expect any early CHRA failure under extreme duty uses for at least 5 years.

        BTW, we already tested some stock MGT22 to it's limit & it will fail under extreme duty using Dynojet numbers of around +720ftlb in enduro test.
        I appreciate your perspective Lenny.
      1. Jacob502's Avatar
        Jacob502 -
        This Article helped clear things up. Good stuff @Sticky
      1. m0v30v3r's Avatar
        m0v30v3r -
        So which setup will help give more HP for those that opt to do engine builds also?
      1. nawlinstornado's Avatar
        nawlinstornado -
        Click here to enlarge Originally Posted by LZH Click here to enlarge
        Nice writeup and a good comparison for those looking to upgrade the M157. I sure wish someone would do this for the M156. I'd be all over that...
        How about an upgrade for the M278? Anyone know what turbo is in this engine? I haven't been able to find it.
      1. yage202's Avatar
        yage202 -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        There are two different perspectives at work here and both have merit. When going to a GT28 based turbo upgrade it will require running new oil and water lines. Since the Weistec setup is identical on the outside to the OEM setup a dealer will not know the turbos are upgraded which is handy for those who are concerned with warranty work or like to keep their mods hidden. A GT28 based setup will be noticeable. Again, pluses and minuses here.
        Good write up! None of the statements vendors made were inconsistent.

        Apples to apples, the ball bearings will outperform journal bearings, but the other factors of cost, durability, reliability, failure mode etc. have to be weighed. Journal bearings have been around forever in mission critical uses.

        Thought experiment: imagine an engine where all journal bearings are replaced by ball bearingsClick here to enlarge
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by m0v30v3r Click here to enlarge
        So which setup will help give more HP for those that opt to do engine builds also?
        These setups don't appear to be capable of maxing the stock engine internals.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by nawlinstornado Click here to enlarge
        How about an upgrade for the M278? Anyone know what turbo is in this engine? I haven't been able to find it.
        I don't know. That's a great question and I can look into it for you.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by yage202 Click here to enlarge
        Good write up! None of the statements vendors made were inconsistent.

        Apples to apples, the ball bearings will outperform journal bearings, but the other factors of cost, durability, reliability, failure mode etc. have to be weighed. Journal bearings have been around forever in mission critical uses.

        Thought experiment: imagine an engine where all journal bearings are replaced by ball bearingsClick here to enlarge
        Don't forget the size of the housing as well. There are several factors here.
      1. PianoProdigy's Avatar
        PianoProdigy -
        What are the chances the turbos can be swapped without dropping the motor by a skilled shop in, say, an ML63. ;-)
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by PianoProdigy Click here to enlarge
        What are the chances the turbos can be swapped without dropping the motor by a skilled shop in, say, an ML63. ;-)
        ML63 should have more room but I don't know. From what I hear it's a compact design and likely labor intensive. Hopefully one of the tuners chimes in.
      1. m54b25's Avatar
        m54b25 -
        Click here to enlarge Originally Posted by nawlinstornado Click here to enlarge
        How about an upgrade for the M278? Anyone know what turbo is in this engine? I haven't been able to find it.
        It's a MGT1752xx with both A/R .52 52mm compressor & turbine. Shares same turbine wheel shaft diameter used in the M157 MGT2260xxx with A/R .50 60mm compressor & A/R .64 turbine
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by m54b25 Click here to enlarge
        It's a MGT2256xxx with both A/R .52 56mm compressor & turbine. Same turbine wheel used in the M157 MGT2260xxx with A/R .50 60mm compressor & A/R .64 turbine
        Will there be turbo upgrades for the M278?
      1. m54b25's Avatar
        m54b25 -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        Will there be turbo upgrades for the M278?
        For the M278 biturbo it uses MGT1752MS.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by m54b25 Click here to enlarge
        For the M278 biturbo it uses MGT1752MS.
        I see but what I meant was will Renntech do M278 turbo upgrades?
      1. m54b25's Avatar
        m54b25 -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        I see but what I meant was will Renntech do M278 turbo upgrades?
        There's a 99.9% possibility to use same same M157 GTX turbo upgrade for the M278 as well. So problem solved with some validating turbo calibration!
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by m54b25 Click here to enlarge
        There's a 99.9% possibility to use same same M157 GTX turbo upgrade for the M278 as well. So problem solved!
        Excellent! That makes the 550 models quite a bargain.