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Old 09-21-2017, 09:57 AM   #1 (permalink)
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Volkswagen's New Engine Cycle - The 'Budack' Cycle

Have you guys heard of this?



According to this, the 2017 gets 20/24 and the 2018 will be rated 24/30.

How much of that is from the Budack Cycle?

"the [2.0-liter] engine will provide `1.8-liter power with 1.4- to 1.5-liter efficiency.'


VW's New 2.0L Turbo is More Efficient, More Powerful and Runs on Regular Gas AutoGuide.com News

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Old 09-21-2017, 10:40 AM   #2 (permalink)
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Interesting, they're closing the intake valve early on the intake stroke vs leaving it open longer on the compression stroke. It seems like the Atkinson cycle would still be superior for efficiency purposes as it would reduce pumping losses more than the Budack cycle. However, there isn't air/fuel going back out the intake valve which is a nice thing. Overall I bet the differences between the two are negligible. Therefore it probably comes down to whatever is easier/cheaper to manufacture.
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Old 09-21-2017, 11:09 AM   #3 (permalink)
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Which cycles require licensing? That would affect manufacturing cost, right?
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Old 09-21-2017, 01:42 PM   #4 (permalink)
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Just another trick to emulate the Atkinson effect in an Otto engine, given a different name for marketing reasons. I could guess the intention of naming it as a new cycle might be also an effort to whitewash Volkswagen's reputation in the post-Dieselgate era.
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Old 09-21-2017, 02:08 PM   #5 (permalink)
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Quote:
Originally Posted by Old Tele man View Post
Does NOT sound like a "ground-breaking" design breakthrough, by any means.
Actually, none of the improvements added to the Otto cycle engine throughout its history is worth being deemed "groundbreaking", since the basic operating principle remains exactly the same. Electronic controls, direct injection, forced induction, all did have some benefit to fuel-efficiency and/or performance, and so many valvetrain configurations eventually had their pros and cons, but it's all far from being so "revolutionary" as it's usually pointed out by enthusiasts of each setup. Maybe only the HCCI is going to be an outstanding departure from the original concept of Otto engines.
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Old 09-21-2017, 03:36 PM   #6 (permalink)
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It sounds more like the difference between six and half a dozen.
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Old 09-22-2017, 06:41 AM   #7 (permalink)
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The Fiat MultiAir had early intake valve closing in one of it's modes of operation.
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Old 09-22-2017, 07:27 AM   #8 (permalink)
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Quote:
Originally Posted by Daox View Post
Interesting, they're closing the intake valve early on the intake stroke vs leaving it open longer on the compression stroke. It seems like the Atkinson cycle would still be superior for efficiency purposes as it would reduce pumping losses more than the Budack cycle. However, there isn't air/fuel going back out the intake valve which is a nice thing. Overall I bet the differences between the two are negligible. Therefore it probably comes down to whatever is easier/cheaper to manufacture.
I'm thinking the opposite is true - with the Atkinson cycle, the piston has to do the work of both pulling the air into, and pushing it back out of the cylinder, which to my logic takes more energy.

Also, because you end up with a piston creating lower pressure in the cylinder with the remainder of the downstroke, you're depressurizing the air and may actually be pulling heat out of the cylinder walls, rather than losing it into them, which would be a net thermodynamic gain.
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Old 09-22-2017, 11:28 AM   #9 (permalink)
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Originally Posted by Ecky View Post
because you end up with a piston creating lower pressure in the cylinder with the remainder of the downstroke, you're depressurizing the air and may actually be pulling heat out of the cylinder walls, rather than losing it into them, which would be a net thermodynamic gain
That makes sense.
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Old 09-23-2017, 07:55 AM   #10 (permalink)
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Quote:
Originally Posted by Old Tele man View Post
Pulling a "suction" takes energy just as pushing a "compression" does.
Yes, but in a closed cylinder, the air acts as a spring, with the only significant losses (not related to friction, which would be there anyway) being the heat losses when the compressed air losses energy to the cylinder walls.

This is why cylinder deactivation works better if you close all of the valves, rather than leave them all open. Open, and you're doing the work of pushing air through the valves. Closed, and although you're compressing the air, after TDC that compressed air gives its energy back to the piston.

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