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#4522745 - 09/22/17 12:37 AM VWs new Budack-Cycle engine
wemay Offline


Registered: 04/04/12
Posts: 8865
Loc: Southeast Florida
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#4522783 - 09/22/17 02:48 AM Re: VWs new Budack-Cycle engine [Re: wemay]
skyactiv Offline


Registered: 03/02/13
Posts: 4394
Loc: The Midwest
I noticed the engine use port and direct injection.
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#4522794 - 09/22/17 03:22 AM Re: VWs new Budack-Cycle engine [Re: wemay]
Shannow Offline


Registered: 12/12/02
Posts: 39858
Loc: 'Stralia
AAARRRGGGGHHHH

Quote:
The Budack Cycle—as Jason Fenske from Engineering Explained mentions in his video—uses the same concept, except it closes the intake valve early. Thus, as the piston goes down with the valve closed, the pressure inside the combustion chamber drops, and then rises during the compression stroke. Ultimately—like in a Miller Cycle—this yields a lower effective compression ratio, which makes it easier for the power stroke to turn energy from combustion into downward motion of the piston. Like in the Miller Cycle, the increased efficiency comes at the detriment of power output


I hate these hacks...

The closure of the valve early (or late) traps a smaller volume of air/fuel in the cylinder at the commencement of ACTUAL compression, effectively lowering the swept volume...that's what limits the power.

The effective compression ratio yes, is lowered, but doesn't do what the article explains...lowering the effective compression ratio lowers efficiency.

However, allowing the trapped gasses to expand to a larger volume increases the efficiency, as more work can be gained.

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#4522811 - 09/22/17 04:43 AM Re: VWs new Budack-Cycle engine [Re: wemay]
Floydian Offline


Registered: 09/13/17
Posts: 46
Loc: Outside U.S
Atkinson cycle?

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#4522860 - 09/22/17 06:31 AM Re: VWs new Budack-Cycle engine [Re: Floydian]
rooflessVW Online   content


Registered: 12/24/11
Posts: 4041
Loc: North Carolina
Originally Posted By: Floydian
Atkinson cycle?

Yep its more or less an evolution of the Miller cycle, which was more or less the Atkinson cycle with a supercharger.
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#4523015 - 09/22/17 09:29 AM Re: VWs new Budack-Cycle engine [Re: wemay]
Koz1 Offline


Registered: 03/05/11
Posts: 692
Loc: Ont Canada
Id rather wait for the Mazda Compression gas engines.
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#4523185 - 09/22/17 01:43 PM Re: VWs new Budack-Cycle engine [Re: wemay]
benjy Offline


Registered: 08/23/10
Posts: 865
Loc: pa
those having paid $$$$ for valve cleanings should welcome the dual injection, BUT like anything new issues can arrive before things get sorted out. port injected older engines is all i want + will own for now!!!

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#4523206 - 09/22/17 02:14 PM Re: VWs new Budack-Cycle engine [Re: wemay]
UncleDave Offline


Registered: 06/02/14
Posts: 1636
Loc: Ca.
I see nothing new here, just a repackaging of old ideas.

A compromise in one place barely offsets a compromise somewhere else.



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#4528902 - 09/28/17 10:05 PM Re: VWs new Budack-Cycle engine [Re: wemay]
Cujet Online   content


Registered: 02/15/03
Posts: 7150
Loc: Jupiter, Florida
Closing the intake valve early, is much like a throttle limiting airflow.....
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#4528977 - 09/29/17 01:45 AM Re: VWs new Budack-Cycle engine [Re: wemay]
PandaBear Online   content


Registered: 08/05/02
Posts: 14215
Loc: Silicon Valley
So the "Atkinson" cycle in piston engine closes intake late to avoid too high of a compression, and this Budack cycle closes intake early to avoid too high of a compression. Seems like it is a matter of whether you pump out the excess of what you suck in vs close early so you pull on a loaded spring then release it back.

What is the pros and cons of each method? Which one has less pumping lost?
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#4529041 - 09/29/17 06:02 AM Re: VWs new Budack-Cycle engine [Re: PandaBear]
Cujet Online   content


Registered: 02/15/03
Posts: 7150
Loc: Jupiter, Florida
Originally Posted By: PandaBear
So the "Atkinson" cycle in piston engine closes intake late to avoid too high of a compression, and this Budack cycle closes intake early to avoid too high of a compression. Seems like it is a matter of whether you pump out the excess of what you suck in vs close early so you pull on a loaded spring then release it back.

What is the pros and cons of each method? Which one has less pumping lost?


Here is my best guess:

Closing the intake valve very early really is akin to a partially open throttle. It increases pumping losses. As the cylinder never really fills.

Closing the intake valve very late also slightly increases pumping losses, as the cylinder is allowed to completely fill, then some volume of the gasses are pumped back out into the intake manifold. However, with the Atkinson cycle, the cylinder can be completely filled. The compression stroke starts upon valve close, and the compression ratio is adjusted to match this lower volume of air being compressed.


Edited by Cujet (09/29/17 06:03 AM)
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