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    • Variable compression engine possible thanks to articulated connecting rods? Porsche files patent for eccentric articulated stem

      This sounds absolutely fascinating but frankly the engineering involved is way beyond our pay grade. In essence it seems this articulated rod can move and change the position of the piston which then impacts the compression ratio.


      Here is the technical explanation:

      Porsche is developing a variable compression engine, a puzzle that has been tried by many but is not yet possible in the automotive industry.

      To this end, the German brand has applied the patent of an articulated connecting rod.

      Sketches show that the room can change the volume of the burning chamber by alternating the compression rate.

      Porsche has submitted a patent for an eccentric articulated stem, whose VA-ET-VA movement (controlled by two oil pressure bars) changes the position of the piston to change the volume of the burning chamber by changing the rate of Compression.

      The component has been developed in partnership with hilite international and the great advantage of this engineering solution is to generate efficiency gains, especially in turbo and / or flex engines, as the compression rate is so far fixed and unique. Optimized for maximum power. Thanks to this articulated connecting rod, it would be possible to increase compression when the turbo is at a minimum pressure, thanks to the variable length of the connecting rod, thus compensate for less power and yield less than lower speeds.

      On the other hand, the reduction of the length of the connecting rod reduces the compression rate and prevents the bang from happening when the turbo blows at maximum pressure. In the case of flexible engines, the use of methanol, gasoline and mixture of both would be optimized, which, with a correct compression rate for each fuel, would result in consumption and performance gains.
      That all sounds amazing, right? Now, is this added complexity going to add weight to the rotating mass? Additionally, will the rod be weaker? Is this going to translate into a performance technology or one primarily centered around efficiency?

      It certainly will be interesting to watch how this technology develops.


      This article was originally published in forum thread: Variable compression engine possible thanks to articulated connecting rods? Porsche files patent for eccentric articulated stem started by Sticky View original post
      Comments 12 Comments
      1. Stevenh's Avatar
        Stevenh -
        Sounds like a lot of things to go wrong... For what it's worth, I think Saab patented variable compression a few decades back but never put it in production. I think their version accomplished it by raising and lowering the cylinder head.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by Stevenh Click here to enlarge
        Sounds like a lot of things to go wrong... For what it's worth, I think Saab patented variable compression a few decades back but never put it in production. I think their version accomplished it by raising and lowering the cylinder head.
        https://www.boostaddict.com/content....-to-witchcraft
      1. 7to3_enthusiast's Avatar
        7to3_enthusiast -
        aftermarket tuning a variable compression engine would be a nightmare
      1. nito822's Avatar
        nito822 -
        Doesn’t the 2019+ infiniti qx50 have a variable compression engine?
      1. maxnix's Avatar
        maxnix -
        Can anyone say, "Increased reciprocating mass?"

        DOA.
      1. Sticky2's Avatar
        Sticky2 -
        Click here to enlarge Originally Posted by nito822 Click here to enlarge
        Doesn’t the 2019+ infiniti qx50 have a variable compression engine?
        Click the link I posted
      1. welwynnick's Avatar
        welwynnick -
        This is a very much neater solution than all the other variable compression engines proposed so far.

        However, what's the point when you can simply retard the ignition?

        Nick
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by welwynnick Click here to enlarge
        This is a very much neater solution than all the other variable compression engines proposed so far.

        However, what's the point when you can simply retard the ignition?

        Nick
        You can increase compression at low speeds and rpm on the fly to reduce lag.
      1. F87Source's Avatar
        F87Source -
        Very interesting...

        Aftermarket support for rods will be a PIA, and engine builders + tuners will probably struggle for awhile before they adapt.
      1. Mortagnais's Avatar
        Mortagnais -
        Strange "Porsche" is patenting such an old thing...
        this is being developped by the (also-) german company FEV :
        http://www.auto-innovations.com/actualite/2063.html
        sorry it's french, but you'll translate it or just watch the pics!! Click here to enlarge

        The earlier version of this rod is adjusting CR automatically, thanks to engine speed (making the rod longer) and cylinder pressure (shortening the rod)...unless they didn't explain everything at that time and there was also a valve on conrod's hat??
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by Mortagnais Click here to enlarge
        Strange "Porsche" is patenting such an old thing...
        this is being developped by the (also-) german company FEV :
        Probably some minor differences as to how they are going about it but interesting that there is more than one group working on this.
      1. Mortagnais's Avatar
        Mortagnais -
        I would say just buy aluminium rods and stop worrying about knock damaging the bearings...but then these rods become consumable, and it's not a solution!Click here to enlarge

        As this idea started 10years ago, I hope some OEM will use it soon, in order to see the benefits in real life! Click here to enlarge