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4-6-8 Cylinder Deactivation
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Author:  GregCon [ Mon Sep 28, 2020 6:10 am ]
Post subject:  4-6-8 Cylinder Deactivation
This has nothing to do with anything...but I was remembering how around 1981 my father had 'cylinder deactivation' on his mind...the path to high MPG. Lots of talk due to the recently released Cadillac 4-6-8.....

He had it all worked out - the car really didn't need all 6 cylinders most of the time, and by keeping the valves closed, you'd get most of the energy lost in compression back when the air decompressed. He also reasoned that the Slant 6 (170) in his Dart was the perfect choice, as he could remove four lifters and their pushrods without losing oil pressure.

So, the big day arrived and he did just that. The Dart started up, and was driveable, but it no longer had the smoothness it once had. In fact, it ran quite rough, rough enough that after a few laps around the block, the lifters and pushrods went back in.

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Author:  DadTruck [ Mon Sep 28, 2020 6:51 am ]
Post subject:  Re: 4-6-8 Cylinder Deactivation
Inline six cylinder engines are dynamically ballanced in that
Two pistons are at TDC
Two pistons are at BDC
Two pistons are at the stroke mid-point
as the crankshaft spins.

Possibly if he had de activated 3 cylinders, each matched to a piston traveling in the same positional manner the balance would have been better. The power loss due to internal friction and the extended time between power cycles would have still made for a rough running motor.
Author:  Jase [ Mon Sep 28, 2020 8:12 am ]
Post subject:  Re: 4-6-8 Cylinder Deactivation
Interesting concept to de-activate cylinders to reduce the amount of air and fuel passing through the engine.

I can understand that what is essentially a 3 cylinder engine turning at 2400 rpm will use less fuel than a 6 cylinder engine. Also at that speed the cylinders are moving fast enough to create a pressure drop in the cylinder when the valve does open...

My question would be: Would the slant 3 cylinder engine consume and combust the same volume of air-fuel at 2400, as a slant 6 running at 1200 RPM? IF so, would it not be "easier" for those of us with these engines work to cut engine RPM (and maintain combustion efficiency) for the same result?

Wondering along these lines, I am remembering Smokey Yunick's Hot vapor engine... and did he have some sort of double overdrive to cut RPM, or was it more along the lines of creating a highly efficient combustion process that used ALL of the fuel Thus it could be run at a very lean AFR..?
Author:  GregCon [ Mon Sep 28, 2020 9:13 am ]
Post subject:  Re: 4-6-8 Cylinder Deactivation
Of course, cylinder deactivation has had its day....most 'Hemi' engines built for many years have had it. The improvements in computing abilities are the big reason, as are improvements on the mechanical side. My Ram 5.7L has it and for the most part it works well. But I gotta admit, I've bought 2 Challengers and both times I avoided the automatic in part to not have the cylinder deactivation feature.

On the Slant, I don't recall which cylinders he 'removed' but he didn't do it blindly....he worked out which ones would be the best candidates. At the time, we all kinda laughed because we felt the LAST thing you wanted was less cylinders and less power.
Author:  emsvitil [ Mon Sep 28, 2020 2:37 pm ]
Post subject:  Re: 4-6-8 Cylinder Deactivation
You can get most of the benefits of cylinder de-activation without de-activatiing any cylinders if you cut off the fuel and go to WOT on the cylinders (to minimize pumping losses) that you cutoff the fuel too. For each WOT cylinder, you get back the compressing energy when it expands. The important part is having WOT on those cylinders.


With an inline-6, you treat the front or rear 3 cylinders as separate engines. An inlne-4 would be the middle or outer 2 cylinders.
Author:  GregCon [ Mon Sep 28, 2020 6:44 pm ]
Post subject:  Re: 4-6-8 Cylinder Deactivation
I guess you'd need an individual throttle for each cylinder to do that.

I'm not anti-fuel economy but I get only so interested in it when it results in screwy stuff. Even cars like the Prius...a regular gas engine small car can come very close to the MPG of a Prius without all the negatives. I'd bet a small diesel car could exceed a Prius.
Author:  NEVjr [ Mon Sep 28, 2020 9:35 pm ]
Post subject:  Re: 4-6-8 Cylinder Deactivation
Quote:
You can get most of the benefits of cylinder de-activation without de-activatiing any cylinders if you cut off the fuel and go to WOT on the cylinders (to minimize pumping losses) that you cutoff the fuel too. For each WOT cylinder, you get back the compressing energy when it expands. The important part is having WOT on those cylinders.


With an inline-6, you treat the front or rear 3 cylinders as separate engines. An inlne-4 would be the middle or outer 2 cylinders.
the trick to more efficient cylinder shut off is to hold open the exhaust valve. then you just push and pull the exhaust in and out.

i have driven several durangos with and without the MDS system and it makes a huge difference in fuel economy. roughly 15-20 percent on average with my driving.

also, cylinder deactivation isnt new. 100 year old hit and miss engines turn off the only cylinder unless the rpm drops too low. they do this by having a vacuum operated intake valve and the pushrod of the exhaust valve collapses until it needs to fire.
Author:  NEVjr [ Mon Sep 28, 2020 9:39 pm ]
Post subject:  Re: 4-6-8 Cylinder Deactivation
Quote:
I guess you'd need an individual throttle for each cylinder to do that.

I'm not anti-fuel economy but I get only so interested in it when it results in screwy stuff. Even cars like the Prius...a regular gas engine small car can come very close to the MPG of a Prius without all the negatives. I'd bet a small diesel car could exceed a Prius.
compared to other small econoboxes, there are very few drawbacks to a prius. this is more true now with improved battery technology. F1 cars are all hybrids now, and most new supercars are too. you get all the upsides of an electric drive motor, like instant torque and dynamic braking, with the bonus of fueling anywhere quickly, a motor that can operate at its ideal rpm, and low operating costs
Author:  sixinthehead [ Tue Sep 29, 2020 5:32 am ]
Post subject:  Re: 4-6-8 Cylinder Deactivation
After working on a Prius, I find myself simultaneously impressed and horrified at the engineering involved.
It's the V8-6-4 after a session on Dr. Frankenstein's table :x

GregCon makes the point about a small diesel, which history bears out.
See Peugeot's V.E.R.A., circa 1984. Dennis Simanaitis (writing for Road & Track at the time) participated in a U.S. test of the car which generated some impressive numbers using relatively basic technology.
However, one thing that really stood out to me was the importance of driving habits to achieve the best results.
That applies to anyone who wants to get better mileage out of whatever they drive.
Even that can be taken to extremes (see 'hypermiling'), but the principles are sound.

The real problem seems to be that most people are in too much of a hurry and unwilling to drive more slowly in a small vehicle with a small engine.
Look at how quickly Priuses (Prii?) displaced VW buses as the target of traffic jam angst and humor.
Those who were trying to enjoy their new dashboard power flow and mileage estimator began to ignore the traffic problems they were creating, and the people stuck behind them quickly lost their patience and assumed the opposite position by flooring their vehicles around the offending hybrid.
Despite the prevalence of hybrid technology in new vehicles, people remain unwilling to slow down. The 55 mph speed limit ranked up there with Prohibition on the Unpopular Law scale, and young boys couldn't wait for Dad to put all the pushrods back in :D

(Maybe we should slide this into Social Corner?)
Author:  GregCon [ Tue Sep 29, 2020 6:45 am ]
Post subject:  Re: 4-6-8 Cylinder Deactivation
I have a friend who drives about 45 miles to work each day, then back home. He has a Ram2500, but he also bought a VW diesel Beetle. He gets very good mileage, I think he said around 50MPG.

From what I hear, and believe, it takes more energy to create an electric or hybrid vehicle than you'll ever save by driving one. Plus....the batteries pose some serious environmental issues when you need to dispose them.

As for the Slant, I had a 68 Valiant with a 170, 4 speed OD, and 3.23 gears that I could often crack 30MPG highway ...and always 29MPG. Like a lot of high MPG cars, I got bored with the slowness and eventually geared it back up.
Author:  Tim Keith [ Tue Sep 29, 2020 12:50 pm ]
Post subject:  Re: 4-6-8 Cylinder Deactivation
Quote:
From what I hear, and believe, it takes more energy to create an electric or hybrid vehicle than you'll ever save by driving one. Plus....the batteries pose some serious environmental issues when you need to dispose them.
There hasn't been a lot of EV battery recycling. At the recent Tesla Battery Day Elon Musk said that Tesla will begin recycling batteries in-house. Tesla is switching from cobalt to cheaper and easier to source nickel. He said that eventually most new Tesla batteries will use recycled materials, but I doubt this. If EV batteries become good enough for general energy storage the demand for new batteries will continue to rise. The theoretical solid state batteries would likely use common elements - but these "million mile" batteries may never become reality. The new Tesla batteries are wrapped like a jelly roll to reduce the heat and electrical shorts that have been a problem - these will be made in-house rather than with Panasonic. They will also be welding the battery tray as a structural element into the car body - that reduces weight but makes servicing difficult - not many batteries should fail early with the new design. The new Teslas will have a 16 percent range increase and be lighter, but most notable is the cost of battery production is steadily dropping. But I don't look for 500 mile range EVs priced like a Camry during the next decade. EVs can become a good city car for most people but here in Texas there are many rural areas with zero charging stations. Tesla announced a $25,000 EV.
Author:  slantzilla [ Tue Sep 29, 2020 3:32 pm ]
Post subject:  Re: 4-6-8 Cylinder Deactivation
My '16 Challenger and '17 Ram both had the cylinder deactivation. You could go into the dash menu and turn it off if you wanted to.

We had a customer at the gas station I worked at who bought a new 8-6-4. It got stuck in 4 cyl mode and he brought it to us to fix it. :shock:
Author:  GregCon [ Tue Sep 29, 2020 4:19 pm ]
Post subject:  Re: 4-6-8 Cylinder Deactivation
I guess I'm old-school when it comes to cars, and stereos.....

I had an old radio (later they started calling these receivers in the onset of an ugly trend of pretense). I also had a record player which later became a turntable (another ugly pretense). Anyway, like a lot of old things, they weren't very advanced. If I wanted more Treble, I would go to the radio and turn the dial that was labeled 'Treble' in a clockwise direction to the infinitely adjustable level of Treble I desired.

But by 2020, if I want more Treble, the advancements we've enjoyed are apparent. all I need to do is locate the remote control, point it directly at the receiver, press the Menu button 4 times until I get to Settings, then use the arrow keys to scroll down 11sub-menus until I reach Audio Controls, press the Select button, then use the arrow keys to locate Treble, then press the Select button again. Once I do that, I can scroll up and down through 10 incremental Treble levels, find the two that are above and below the actual Treble setting I want to use, and then simply use the Select button to choose the one I am willing to settle for. All I need to do then is press the Menu button 5 more times to return to the Home screen.

In a similar fashion, each and every time I turn on the Challenger, if I wish to do something like select Sport mode or de-activate the de-activate function, it's a simple issue to scroll through a bunch of menus and buttons to do so. I can tell you, if they had this stuff in 1968, can you imagine the drudgery of flipping a dash mounted switch?

My thermostat at home hasn't broken yet...if I want it colder, I turn it down. I'm looking forward to the day I get a modern thermostat and can spend a few hours programming it!
Author:  Charrlie_S [ Tue Sep 29, 2020 5:01 pm ]
Post subject:  Re: 4-6-8 Cylinder Deactivation
Hell, I'd be happy if my 2011 Ford Fusion would just start, without jumpers, after sitting for a week and a half. My Mopars will start right up after sitting for a month and a half. Damn electronic drain.
Author:  Joshie225 [ Tue Sep 29, 2020 5:47 pm ]
Post subject:  Re: 4-6-8 Cylinder Deactivation
Quote:
Hell, I'd be happy if my 2011 Ford Fusion would just start, without jumpers, after sitting for a week and a half. My Mopars will start right up after sitting for a month and a half. Damn electronic drain.
Shoot Charlie, get a little solar panel to keep the battery charged. Isn't it always sunny there?
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