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Technical variable compression connecting rod; just an interesting pic

Discussion in 'The Hokey Ass Message Board' started by atch, Sep 23, 2022.

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  1. atch
    Joined: Sep 3, 2002
    Posts: 5,168

    atch
    Member

    Don't know anything about this. Saw it on FB and thought y'all might also find it interesting. Perhaps you'd like to discuss it. Perhaps not.

    variable compression connecting rod.jpg
     
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  2. 19Fordy
    Joined: May 17, 2003
    Posts: 7,620

    19Fordy
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  3. 34Phil
    Joined: Sep 12, 2016
    Posts: 392

    34Phil
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  4. G-son
    Joined: Dec 19, 2012
    Posts: 1,045

    G-son
    Member
    from Sweden

    SAAB also worked on a variable compression engine, but with the upper part of the block "hinged" so the cylinders & head would move up and down. Turned out the benefits were nowhere near as big as the theory suggested, so the project was scrapped. Could have been an interesting engine otherwise.
     

  5. There was another effort, with actual running motor, that used a two-piece fixed-length rod. But this one didn't have the crankshaft directly connected to the piston. Instead, the rod from the crankshaft connected to a lever at one end and there was another short rod connected from the lever roughly in the middle to the piston. The lever pivot was at the other end. The variable ratio was accomplished by moving the lever pivot point back and forth. Worked rather well, as fuel economy was markedly increased. The idea was to raise the compression ratio under light-load conditions for better efficiency, but the expense of building it was too high for the benefits.
     
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  6. Tow Truck Tom
    Joined: Jul 3, 2018
    Posts: 724

    Tow Truck Tom
    Member
    from Clayton DE

    You make a, my head hurt
     
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  7. Budget36
    Joined: Nov 29, 2014
    Posts: 9,449

    Budget36
    ALLIANCE MEMBER

    That’s wild looking.
     
  8. indyjps
    Joined: Feb 21, 2007
    Posts: 5,090

    indyjps
    Member

    Variable valve timing benefits make sense, but, variable compression- WTH. I'll read thru the links and theory.
     
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  9. MCjim
    Joined: Jun 4, 2006
    Posts: 549

    MCjim
    Member
    from soCal

    You can change your compression by thinking about it...
     
  10. Johnny Gee
    Joined: Dec 3, 2009
    Posts: 10,303

    Johnny Gee
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    from Downey, Ca

  11. Rickybop
    Joined: May 23, 2008
    Posts: 8,289

    Rickybop
    Member
    from Michigan

    Variable ignition timing
    Variable fuel delivery
    Variable cam timing
    Variable stroke/compression

    Now all we need is an infinitely variable transmission.
     
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  12. jaracer
    Joined: Oct 4, 2008
    Posts: 1,709

    jaracer
    Member

    There were some variable compression lab engines built back in the 30's of 40's to test fuel octane rating.
     
  13. Tow Truck Tom
    Joined: Jul 3, 2018
    Posts: 724

    Tow Truck Tom
    Member
    from Clayton DE

    They Are available in models from Japan:)
     
  14. Budget36
    Joined: Nov 29, 2014
    Posts: 9,449

    Budget36
    ALLIANCE MEMBER

    I think it’s already here. CVT on small cars. Well, stands for constantly variable transmission, but not sure if the same as what you may be thinking.
     
  15. G-son
    Joined: Dec 19, 2012
    Posts: 1,045

    G-son
    Member
    from Sweden

    DAF had it in their cars in the 70's, maybe earlier. We have it in several cars and all scooters today.
     
  16. Rand Man
    Joined: Aug 23, 2004
    Posts: 4,432

    Rand Man
    Member

    My wife bought two daily drivers with CVT. I thought they totally sucked as a driving experience. Idea is good but the functionality is ridiculous.
     
  17. Call me old fashioned but seems like an awful lot of extra parts to be thrashin' around inside the cylinder. I've had enough trouble in my life keeping regular old connecting rods in one piece. :D
     
  18. Blues4U
    Joined: Oct 1, 2015
    Posts: 6,739

    Blues4U
    Member
    from So Cal

    There are CVT transmissions for some of the smaller heavy equipment; but hydrostatic transmissions, also infinitely variable, have been in use in agriculture equipment and some material handling and road building equiment for many decades. Hydrostatic transmissions offer incredible performance advantages, but you have to deal with reduced efficiency, a lot of heat generation, and if using external oil lines there is always the issue of leaks.

    Variable compression? I'm still not seeing any real advantage. Other than making an engine easier to start, what performance advantage is there from being able to temporarily reduce compression?
     
  19. Rand Man
    Joined: Aug 23, 2004
    Posts: 4,432

    Rand Man
    Member

    “what performance advantage is there from being able to temporarily reduce compression?”

    they want to reduce spark knock or detonation. That’s a big engine killer. A lot of modern engine control systems have anti-knock sensors as high priority.
     
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  20. 302GMC
    Joined: Dec 15, 2005
    Posts: 7,308

    302GMC
    Member
    from Idaho

    Do a quick search for Cartercar ...
     
  21. Rickybop
    Joined: May 23, 2008
    Posts: 8,289

    Rickybop
    Member
    from Michigan

    I suspected that some of you were going to say it's been done.
    LOL
    Interesting.
    To be clear, I was thinking of how a belt driven torque converter works... no steps in between gear ratio changes. And controlled according to load, RPM and throttle position for optimum gear ratio.
    But we've stepped too far into the future. The space-time continuum is eroding.
    Mr Wizard...
     
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  22. Mike VV
    Joined: Sep 28, 2010
    Posts: 2,671

    Mike VV
    Member
    from SoCal

    Interesting, but.
    It would defiantly be a lower rpm engine !!
    With that much weight at the top of the rod, would surly limit the rpm capability.

    Lower the ratio for normal driving, raise the ratio for high speed (?) driving.

    Mike
     
  23. Truckedup
    Joined: Jul 25, 2006
    Posts: 4,547

    Truckedup
    Member

    What Mike said, too heavy and complicated for highrpm....Variable cam timing changes compression ratio or more accurately cylinder pressure...
    Modern sportbikes make 3 hp per cubic inch off the show room floor with all the complication.Some even have variable injector location...
     
  24. Budget36
    Joined: Nov 29, 2014
    Posts: 9,449

    Budget36
    ALLIANCE MEMBER

    Like the Comet clutch I built for the kids 4 wheeler from a old Polaris chassis? The drive pulley would be small and the driven pulley large at idle/rest. As engine accelerated the dive pully would open up and the driven would as well, but be smaller.
     
  25. 31 Coupe
    Joined: Feb 25, 2008
    Posts: 328

    31 Coupe
    Member

    Similar principal to a BRIDGEPORT type mill variable spindle speed.
     
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  26. KenC
    Joined: Sep 14, 2006
    Posts: 801

    KenC
    Member

    Here's a cutaway showing the Nissan implementation with a metallic belt and pulleys.[​IMG]
     
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  27. Moriarity
    Joined: Apr 11, 2001
    Posts: 24,144

    Moriarity
    SUPER MODERATOR
    Staff Member

    The Hamb is no place for a discussion on what modern new ideas are being used in new cars
     
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