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Old 07-29-2019, 03:07 AM   #11 (permalink)
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Old news, that video is from 2016. They definitely haven't gotten this to work. I would imagine high power consumption is the main problem.

Multiair is the best system on the market right now. It's basically fully hydraulic valves. The problem is...no other manufacturer has dared to use this. You would think that with the complexity of a hydraulic valve lash adjuster and cylinder deactivation mechanism that someone would've thought putting full hydraulic control would be easier.

If you look at the best new engines (Toyota Dynamic Force and Mazda Skyactiv-X), you'll notice they have very primitive cam phasing VVT, and use high volume cooled EGR to cut pumping losses down. Fancier fuel injection systems allow good fuel-air mixing without the need for different cam profiles. If you want to spend more money, Honda shows us it's not very hard to tack on a second cam profile to squeeze out a little bit more.

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Old 07-29-2019, 08:56 AM   #12 (permalink)
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I would also make the assumption that high engine speed would be a challenge.

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Old 07-29-2019, 02:39 PM   #13 (permalink)
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Its probably not reliable or cost effective. I mean they have been using pneumatic valve springs since the 1980s in racing, but Koenigsegg is still using a new casting Ford small block modular engine.
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Old 08-04-2019, 07:56 PM   #14 (permalink)
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Originally Posted by Ecky View Post
I understand a roller rocker valve system has relatively low parasitic losses, actuating the valves returns most of the energy back to the camshaft as the lob passes and the spring pushes back up. This system would use energy to actuate the valves in both directions.
But it does get valve springs for return. The hydraulic is there more for dampening, and the variable amount of oil does limit the valve lift.

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