OT?: New cars run on partial cylinders?

True, and very easily. It wouldn't meet CAFE or EPA requirements but it could easily be done.

So yes they could build one, but no you could not buy one.

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 >tra>> Well, on the upstroke, there is compression with the valves closed, but

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 ...

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'

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.

That assumes that "idiot-proof features/circuitry of any kind" includes CAFE or EPA requirements.

I'm not certain that CAFE/EPA requirements fall into that category.

If some do, I suppose I'd amend the question as follows:

True or False: "Somebody (maybe even Ford) *could* design/build a traditional motor/drive-train (iron block/heads, etc) without idiot- proof features/circuitry not required by CAFE/EPA , which would cost less and provide much improved reliability over what we currently see in the auto market." I seriously, seriously doubt that CAFE/EPA directly requires cyl deactivation or forbids iron motor components.

Prost, Puddin'

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

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...

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)

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'

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

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.

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.

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.

I would also imagine that their rear tires aren't lasting anywhere near the expected life expectancy rated on the sidewall. ;-)

Having said that, Better in a Car with 345 HP than in a SUV with 345HP

Not if one has a wife and five children. LOL

mike hunt

I see where you are going with that. But I still think that if the dad was in the car and the Wife and children were in a SUV parked in the driveway everyone would be happy . Esp DAD ;-)

Take a good, solid 4-stroke, properly maintained, no material ring wear, all cylinders firing. At the end of a compression stroke, combustion occurs. At the point of combustion, there is 2, 3, 4 or more times the pressure that would exist in a deactivated cylinder with valves closed.

And there is either no blowby or only trivial blowby from the firing cylinder. Right?

So why would much lower pressures slip past the rings in a deactivated cylinder?

Peetie

I've seen a car on a hill held only by a manual transmission "in gear", move slowly, lurching as the cylinders lose pressure, and then come up on compression in another cylinder. First gear isn't so bad, but try fourth.

Where is the increased pressure coming from in the firing cylinders? Rapidly expanding gas, that seats rings against the cylinder walls. There is no expanding gas in the deactivated cylinders. There is no new amount of air being replenished during an intake stroke. There is a static amount of air, which either bleeds off or remains static, like the air in a bouncing basketball.

Honda claims a 35% reduction in pumping losses by disabling the valve train.

Turns the motor over at something like 1/4 to 5 rpm?

I suspect the dynamics of air seepage are totally different at 1k + rpm, when the oil pump is active and the crankshaft is splashing oil under the pistons, etc, etc.

It was my impression that the rapidly expanding gas forces the pistons and rings in the precise trajectory defined by the cylinder, that is, towards the crankshaft.

Absent combustion, the rings hug a thin layer of oil separating them from the cylinder walls. With combustion, what would make the rings further and materially expand? I've always assumed the rings were fully seated when properly installed and lubricated.

Hmmmmmm. Entirely aside from the credibility of any auto maker's claims, did they happen to quote what pumping losses amounted to either before or after disabling the valve train?

Best Regards, Peetie

I'm sorry, I always find it difficult to argue with conspiracy theorists. It could very well be that Honda, Ford, GM, Chrysler and others prefer to burden themselves with additional valve components just because it looks good on a sales glossy.

That sounds about right...

Rob

I thought I was the only one in that category.

CJB