OT?: New cars run on partial cylinders?

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Re: OT?: New cars run on partial cylinders?
I pick up the Sun. paper, read a new car "review", sez the machine (I ferget make/model) is designed to run
on partial cylinders (i.e. 4 of 8) when on the hiway and at steady speed for quite a while. "Saves gas."
"How Dey Doooooooo Dat???"
So I'm thinkin', partial cylinders, fuel injection is computer controlled, it just shuts down injection to, say, 4 cyls. But the compression ratio might be something like 7.5/1, and that would make for lots of resistance to effective power train performance with non-firing cyls.
I don't spend much time keeping up with new auto technology. Is it possible/conceivable/not-a-nightmare that the valve train could be controlled by the 'puter (and no longer purely mechanical)? For partial cylinders, could it hold 1/more valves open for designated non-running cyls? Does anybody know?
Better yet, is anyone in a position to evaluate the potential reliability/long-term dependability headaches that might ensue from such "bleeding-edge technology"?
Just curious ... 'scuse my lack on knowledge.
Cheers, Puddin'
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Puddin' Man wrote:

I'm guessing you've never seen a Cadillac V-8-6-4 ?
Well, that came out 25 model years ago... and didn't last very long.
Check this overview:
http://www.greencar.com/index.cfm?content ώatures46
Rob
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That was the mechanical contraption from the medieval ages.
Honda has been running multiple valve trains for several years as part of their VTEC series, with low RPM and high RPM cam lobes engaged via hydraulics.
In the Honda Accord Hybrid, the rear three cylinders are shut off during certain conditions by stopping the valves. Same with all four cylinders of the Honda Civic Hybrid.
Some GM SUVs have similar shutdowns. <http://www.sciam.com/article.cfm?articleID 0F2BEF-ECD0-119B-ACD083414B7F0000> <http://auto.consumerguide.com/Auto/New/reviews/full/index.cfm/id/38687/Act/Showall/
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On Sat, 17 Dec 2005 22:46:15 +0000 (UTC), snipped-for-privacy@XReXXOTXXX.usenet.us.com wrote:

I read a brochure about the Ford Escape Hybrid, plus some pdfs. The intake valves stay open when the engine isn't needed. How it does that, I don't know. I will guess it has dual camshafts. It is a 2.3 :Liter. Don't know if AL or FE. Don't know how many valves, OH, I think I may have read somewhere 3 valves per cyl. Maybe 1 in, 1 out, 1 inlet compression release. Maybe.
It sounds a lot like an earlier engine that fired only when it needed to: Monitor. :) (the technology sounds like it)
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In the trade we used to call it the 3-5-7.... Most (if not all) had the displacement modulation devices disabled at one time or another.
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On Sat, 17 Dec 2005 16:57:26 -0500, trainfan1
Cadillac? Cadillac?? Is that one of them companys mounts a perfectly good V8 transverse and drivin' the front wheels so's you maybe need to pull the motor to replace some steering components and hafta wanna destroy yore hands to work under the hood? :-)

I wonder why? <g>

Thanks. Shows how out-of-touch I am.
Must admit I didn't necessarily understand it all, but I suspect it's just semantics. Article said special equipment caused valves to stay "closed"? I thought a valve was closed when it was fully seated (which would imply that the new motors -are- fighting the compression-stroke-without-firing that I asked about). But that doesn't make any sense (to po' me, at least).
So ya can't even get a German-MoPar Hemi without the MDS stuff?
I asked the wrong question.
Here's a new set of questions:
Is anyone presently making substantial and reliable RWD auto(s) with 1 or more of the following characteristics:
1.) Absence of cylinder deactivation systems.
2.) Iron blocks.
3.) Iron heads.
????
Salut, Puddin'
"Mit der Dummheit kaempfen Goetter selbst vergebens!" (Against stupidity, the gods themselves struggle in vain.) -Friedrich Schiller (1759-1805)
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Puddin' Man wrote:

Well, on the upstroke, there is compression with the valves closed, but you get that energy back on the downstroke - "de-compression" - I guess you would call it.
...or if the valves close on an intake stroke, there is energy used for "sub-compression" - or vacuum to create in the cylinder - but you get that back too on the upstroke.
Either way it's a wash.
Rob
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On Sat, 17 Dec 2005 23:45:09 -0500, trainfan1
...

No offence, but methinks "That Dawg Won't Hunt!!".
Imagine taking any 4-stroke motor (maybe a little Honda OHV mower motor) , disabling the valve actuation mechanism, leaving valves firmly seated by their springs, and turning it over by hand, say by spinning the flywheel. Reasonable to expect it requires zero net effort?
With an V8-4, you don't think it'd unbalance the motor's operation? I won't even ask re, say, a V6-3 (which sounds truly 100% crazy to po' me).
If the valves remain fully seated, it doesn't take a PhD in physics to perceive that unnatural acts are being committed to effective power generation/transmission? Even if 'twere practical to hold valves open, it'd be dragging around twice the weight of the pistons, con-rods, etc that produce power. Not consistent with overall design?
Cheers, Puddin'
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Puddin' Man wrote:

No way it's zero net, but it's better than dragging pistons along doing work (which is what would happen with the valves open). The valves may float VERY briefly to a point where there will be nothing taken in on a downstroke - or 1 atmosphere in the cylinders somewhere around midpoint in the stroke.

Read my link above to see how Honda does it... it actually includes a microphone & the stereo speakers as part of the scheme!

See above.

That would be worse. See above.
Rob
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On Sun, 18 Dec 2005 15:05:28 -0500, trainfan1

Thank you, kind sir.

No comprendere, senor.

After noting that it was, indeed, a V6, I got as far as the microphone.
I did -not- fall on the floor laughing (take these things too seriously, I guess).
The phrase "Engineering Frankenstein" occurred to po' me ...
Strongly suspect that both Rube Goldberg and the Honorable Japanese that invented Godzilla would've been proud. :-)
It ain't that I'm against Technology. They've done all manner of very useful tech things over the decades. It's just that it gets truly out-of-control every once in a while ...
Cheers, Puddin'
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That's on the Accord V-6. The Civic doesn't bother. I can't tell when the valve train is actuated or not.
The microphone/speaker idea is very impressive in a Bose noise cancelling headset in a helicopter.
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snipped-for-privacy@XReXXOTXXX.usenet.us.com wrote:

Odyssey, too...
Rob
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Have you ever started an engine that has a compression release?

I recall watching a huckster pitching an ignition booster module out in front of an old "White Front" store. Old Cadillac V-8, didn't run all that well, to be "improved" with the ignition module. Unplug one spark plug wire. See how rough it runs, just like an old engine missing on one cylinder. Here, let me add the ignition module, and, just to make it harder, I'm going to unplug another spark plug. Gee, look how smooth it runs now!

The pistons, rods, etc, are there for use when needed. More important in open verses closed is all the air that you would be pushing back and forth with open valves. Or the compression and intake load of running with valve train actuated, but fuel cut off, which I think every modern FI car does during deceleration.

I'm sure that Honda, GM, and Chrysler have some designers that thought about it before it was put into production. Maybe even a few with PhDs.
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On Wed, 21 Dec 2005 18:26:31 +0000 (UTC), snipped-for-privacy@XReXXOTXXX.usenet.us.com wrote:

Many many times, every season since '77. On a '73 Yamaha TX650 (only 2 wheels, 2 cyls). Ancient, ancient fire-breather.
Lots easier to turn over with valve partially open. Would be much, much harder were all valves -closed- thru all cycles. Locks rear wheel when push-started in 1st with normal valve actuation and w/o compression release.

Not certain what your point might be, here.

Internal combustion motor has been around a long time now. Original design for pistons, rods, etc was as a means for harnessing power of combustion. Whenever motor is running.

Not certain why that would be an issue.

Sounds plausable. Relevance of deceleration characteristics to stable/constant-speed conditions for cyl. deactivation?

Well, my fear is that, like the "Best And Brightest" in many, many industries nowadaze, "They Often Dance To Their Own Music".
Any with a PhD in Physics and another in Common Sense? :=)
On Wed, 21 Dec 2005 18:18:20 +0000 (UTC), snipped-for-privacy@XReXXOTXXX.usenet.us.com wrote:

Good rings, proper design/maintenance, leakage should be very minimal. Becomes a question of degree.
Any possibility that the mass of the crank, rods, pistons etc would be so great that the negated power stroke would add virtually nothing to power/torque?
At least you don't propose *zero* resistance ... <g>
I'll assume you take very good care of your car. Suppose for a moment the sky fell in, you became financially strapped, and you needed to continue driving your Accord V-6 (or whatever) for many, many years and until you had 2xx k miles on it (doing your own repairs/maintenance). Would you be in a true position to assess the extra diagnostic/repair headaches/costs you might incur due to potentially unnecessary bells/whistles etc in the design of the auto?
Obviously it'd be a different kettle o' beans for someone who trades-in/buys a new car every 3 yrs/36k mi. ...
Cheers, Puddin'
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You only surmise such.

You are working with very little horsepower or forward momentum. Have you ever had a cam chain break? Does the engine turn over easily with no valves moving?

A balanced engine needn't have the number of cylinders that you think it needs.

And cruising at 60mph on level ground, you don't need all the power that was designed in for acceleration from standstill. Did you notice any trouble when cars started chopping fuel delivery on coast? Those pistons and associated equipment aren't delivering much power then. What if it is more efficient to run four cylinders with a 1GPM flow than eight cylinders at a 1GPM flow?

The pistons are still accelerating and decelerating. But we've eliminated pumping losses.

Several, I'm sure. Maybe even a few that think about doing things differently than last year. Maybe solely to be different from last year, and occasionally they think up something that works well.
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On Thu, 22 Dec 2005 00:14:16 +0000 (UTC), snipped-for-privacy@XReXXOTXXX.usenet.us.com wrote:

If you wish to take the position that the compession stroke resistance would be easier to overcome with all valves locked closed relative to when the exhaust valve is partially open (the case with TX650 and compression release), you are "Most Welcome" to do so.

Here's how you unlock rear wheel. Get 2 or more burly guys, kinda like Dick Dee Bruiser or Hulk Hogan, to push like hell while you're standing up on the footpegs, holding the clutch. Then you dive-bomb your young (I was young, then) arse onto the back of the seat at the exact picosecond that ya pop the clutch. Then the damned thang will turn over. In 1st gear. Of course, mot'sicle compression ratios are a bit higher than with the machinery we've been discussing ...

Clearly stated. Thank you.
I'll admit that it may be practical to engineer a V8-6-4 to run in balance for a spell. If it weren't, they'd be shooting themselves in the foot by putting them in the showrooms.
I make no such admission re V6 running 1 live cyl on 1 bank, 2 live on the other bank.
In any event, methinks it'd be a mistake to put 30k or 60k on such an auto and then proclaim "Oh, It Works Great!!". I don't evaluate motorized vehicles in that fashion anymore.

Granted.
It's the deceleration condition. Using compression stroke to brake. Kinda like downshifting. No?

Efficient in what sense(s)? If it saves gas, do you think that there are no attendant costs? Over what life of the vehicle?

See "deceleration condition" above.

Glad you noted that! Also sometimes just to be able to claim a bell/whistle that the competition can't claim ...

Over the decades, more than occasionally. But they still sometimes flounder, sometimes they correct errors, and sometimes they just foist stuff on consumers that are functionally lost in myriad tech. details. And then there are folks that think that, if they done it, and it's been around for a while, and it maybe works OK for 30k or 60k mi., then it must be good ...
Unanswered Q: I'll assume you take very good care of your car. Suppose for a moment the sky fell in, you became financially strapped, and you needed to continue driving your Accord V-6 (or whatever) for many, many years and until you had 2xx k miles on it (doing your own repairs/maintenance). Would you be in a true position to assess the extra diagnostic/repair headaches/costs you might incur due to potentially unnecessary bells/whistles etc in the design of the auto?
You can have the last word if you like. I think it'd be prudent for po' me to bow out of this thread.
Cheers, Puddin'
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I prefer the wheelspinner used at the track to light up high compression 1000cc twins that don't have compression release.
But those engines are getting a new gulp of air on each cycle, and maintaining compression. If the valves are closed, I think the contents of the cylinder either bleed off past the rings in a few cycles to some nominal pressure, or they have a rubbery effect like bouncing a ball.

I think the Accord shuts down the rear bank.

30k? 60k? I have more than that on my Honda already. Honda has millions of miles of experience with VTEC cams. Many Honda motors run 300k. http://world.honda.com/history/challenge/1989vtecengine/text/06.html

This is extending that lack of power during coasting to lack of power when it isn't needed. And reducing the load further by eliminating air pumping losses that are present in the fuel-shut-off models.

Efficient in terms of horsepower delivered for a given amount of fuel. Better airflow and mix in the cylinders that are working. Honda has added Variable Cylinder Management to their large motorcycles, and claim a 30% improvement on the motorcycles, 11% on the automotive V6. http://world.honda.com/news/2003/4030618_1.html

I don't think that this is a bell or a whistle.

I recall when a typical American V8 needed a valve job at 75K. Now they run 2-3 times that, easily.

There are already too many widgets for me to work on. Honda claims to have had zero VTEC failures. Ever.
The cars that I like do go over 200k before I get something different. I don't think I've ever gotten rid of a car just because of engine mileage, although my wife thought my 73 RX2 looked pretty ratty by the time I gave it up at 180,000.

I think so. You seem to dislike cylinder idling because it can't be fixed in your driveway with a dwell meter and a timing light. But cars are way beyond that in many respects. Cylinder idling is less high tech than my transmission. VTEC is just one solenoid controlling oil pressure to a camshaft, and some control circuitry that is probably minuscule in comparison to the fuel injection computer.
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The Chrysler V8 engine runs, at speed with a light engine load, with just four opposing cylinders running rather than all eight. It is my understanding that is accomplished by the microprocessor cutting off spark and fuel to those four cylinders. I have driven several Chryslers V8s. The cutting of cylinders on and off is imperceptible. The EPA rating for that 345 HP low end torque engine is 25 MPG
mike hunt

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The EPA rating for that 345 HP engine may well be 25 MPG but most folks are actually seeing far less than that in real world use...

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I don't know about 'most folks' and I suspect neither do you but what make that opinion different than any other vehicles EPA rating? That's why it says your mileage many vary. My personal experience with EPA figures is that I generally get 2 or 3 miles more than the EPA highway mileage when driving in that circumstance, and 2 to 3 miles less than the EPA rating in overall city driving. My two current vehicles, a 2005 Mustang GT with a 5 speed gets up to 27 MPG with an EPA rating of 24. My 2006 Lincoln Zephyr with a six speed can get 31 MPG with an EPA rating of 28. It all depend on how and where one drives.
mike hunt

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