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Thread: Discuss! cylinder deactivation & GM's "skip shift" system

  1. #11
    Senior Member Fummins's Avatar
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    I agree the cylinder deactivation is just another thing to fail. The one hemi I tore apart had a needle bearing on the end of the lifter start to squeak. eventually it would have seized and chewed up the camshaft.
    We have a few 07 5.3 Chevys with the afm crap. One of them has close to 700,000km on the stock engine. It’s never been opened up. Still has the stock timing chain and oil pump. It’s had the transmission replaced twice but the engine keeps on ticking, sometimes literally.


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        click to view fuel log View my fuel log 2014 Mirage SE wussie cvt edition. 1.2 automatic: 37.7 mpg (US) ... 16.0 km/L ... 6.2 L/100 km ... 45.3 mpg (Imp)


  2. #12
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    Quote Originally Posted by 7milesout View Post
    That may have been the dumbest feature GM has created.
    Not in my opinion! At least a match with the 2-4-6-8 scheme for some V8's. How bout 2 different keys for the same car?
    Karl

  3. #13
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    Quote Originally Posted by 7milesout View Post
    That may have been the dumbest feature GM has created.
    Not in my opinion! At least a match with the 2-4-6-8 scheme for some V8's. How bout 2 different keys for the same car?
    No, how bout off-set connecting rods? That really cost GM a bundle for a boo-boo!
    Karl

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    Quote Originally Posted by Pimp_Daddy_Patty View Post

    As for cylinder deactivation. I'm skeptical about how well it works in real life. You still have parts moving and creating parasitic losses. I guess it helps keep the engine in a more efficient load range. That being said, my 94 Ranger had a 2.3L 4 cylinder, a 4.0 V6, and now a 5.0L Turbocharged V8. Most of these combinations have been used with 3.08 and 3.73 gears out back and each engine had a different version of the same transmission behind it. Highway fuel mileage has been 28mph for all engines. I guess you still need a certain amount of energy to keep the vehicle moving regardless of the engine setup.
    The cylinder deactivation also reduced pumping losses. The cam shafts on the deactivated cylinders would "disconnect" to prevent the cylinders from needlessly moving air around. Mitsubishi also made a variable displacement engine for awhile: https://en.wikipedia.org/wiki/Variab...#Mitsubishi_MD
    please consider checking out my Mirage related youtube channel: https://www.youtube.com/channel/UC6c...IEViRFw/videos

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    Senior Member MightyMirageMpg's Avatar
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    For cylinder deactivation you'd want to cut spark and fuel so you don't run ultra lean for a second. Ide think a double contact relay could do both?

    Wonder what the fuel savings would actually be. We've all driven cars with a miss before, but not sure a 3cyl could do much more than idle.

    Seems there's a chance the computer would compensate and overfuel the other two cyl in an effort to raise idle rpm and not die.

  6. #16
    Senior Member Fummins's Avatar
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    I had a driver limp a Mirage back to the shop with 2 cylinders. It had dead miss at all speeds when one injector wire broke. I was surprised they drove it like that but it made it from 10 or so miles away. It was very noticeable lol

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        click to view fuel log View my fuel log 2014 Mirage SE wussie cvt edition. 1.2 automatic: 37.7 mpg (US) ... 16.0 km/L ... 6.2 L/100 km ... 45.3 mpg (Imp)


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    Quote Originally Posted by mohammad View Post
    The cylinder deactivation also reduced pumping losses. The cam shafts on the deactivated cylinders would "disconnect" to prevent the cylinders from needlessly moving air around. Mitsubishi also made a variable displacement engine for awhile: https://en.wikipedia.org/wiki/Variab...#Mitsubishi_MD
    mitsubishi is really a very technologically advance company during their days, until now they still trying to be the first they made the first diesel engine with MIVEC thats in the current pajero sports. ive heard the cylinder deactivation first i think is on the honda accord.

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    Quote Originally Posted by allrock View Post
    mitsubishi is really a very technologically advance company during their days, until now they still trying to be the first they made the first diesel engine with MIVEC thats in the current pajero sports. ive heard the cylinder deactivation first i think is on the honda accord.
    I think Mitsubishi as we know it is almost dead! The revolving door of Mitsubishi presidents is a huge red flag for the company.

    I watched this recently. "Why did Mitsubishi Motors Fail?" The title of the clip alone tells you where things stand for some people.

    https://www.youtube.com/watch?v=VypEjwQq86o

    I really suspect Mitsubishi will become nothing more than a vendor for Nissan or Renault products in the future.

    As far as the Honda Accords with cylinder deactivation, Scotty Kilmer has been ripping on that technology for quite some time. One of his customers recently came up with a way to override the cylinder deactivation on his Accord, & it eliminated the oil burning issue the car was having. I saw that about a week ago & found it interesting.

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    Senior Member Fummins's Avatar
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    Quote Originally Posted by allrock View Post
    ive heard the cylinder deactivation first i think is on the honda accord.
    https://www.hemmings.com/stories/art...dillac-v-8-6-4

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        click to view fuel log View my fuel log 2014 Mirage SE wussie cvt edition. 1.2 automatic: 37.7 mpg (US) ... 16.0 km/L ... 6.2 L/100 km ... 45.3 mpg (Imp)


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    Honda used cylinder deactivation on the 2005-07 Accord. The fact that Honda dropped that technology says something in itself. Honda is the largest engine maker in the world.



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