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      02-21-2014, 05:32 PM   #1
Rupes
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Cylinder Deactivation

GM seems to really understand this technology, but no other manufacturer seems to be using it on a regular basis. Why not? It seems top be a really easy, cost effective way to have a fire breathing V8, and a fuel sipper on the highway at the same time. Does anyone know why this is hard to mimic, does it have something to do with the push-rod engine?

I would have loved to have seen the new M3 use an updated version of the S65 with this technology.
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      02-21-2014, 06:35 PM   #2
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Wind resistance is a factor. Vettes are slick in the wind. It doesn't take 420 hp to make it go
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      02-21-2014, 06:41 PM   #3
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Quote:
Originally Posted by 4corners
Wind resistance is a factor. Vettes are slick in the wind. It doesn't take 420 hp to make it go
Come on...you have to admit running 4 cylinders on the highway vs a V8 is a much bigger factor in fuel efficiently than the aerodynamics vs. an M3.
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      02-21-2014, 06:49 PM   #4
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whats funny is that people hate that Cylinder Deactivation. reason: when you have a exhuast, your car will sound like a 4 banger at times. (tunes can turn this off)

BUT if Cylinder Deactivation is something necessary to keep V8s then so be it!
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      02-21-2014, 07:25 PM   #5
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My Pontiac G8 GT had this and it never was an issue, though I rally didn't get great gas mileage on the highway.
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      02-21-2014, 07:30 PM   #6
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i have found in my truck that on cruise its usually in V8 mode anyways.....
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      02-21-2014, 07:33 PM   #7
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Apparently it was very difficult for GM to get the transitions between cylinder modes to occur smoothly, especially with a manual transmission involved, so I wouldn't call it an easy way to get a benefit. I imagine there's also the added weight, space, and complexity factors. Most automakers seem to be content simply abandoning NA and dropping cylinders instead.

Also keep in mind that in much of Europe, fees are assessed by engine displacement, not MPG directly or the presence of features like that, so that market responds more to getting power from less displacement rather than making higher displacement engines more efficient. In fact I believe the displacement tax is an ANNUAL charge like our registration fees, not like our gas guzzler tax that the first owner pays once at delivery.
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      02-21-2014, 07:41 PM   #8
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Quote:
Originally Posted by jphughan View Post
In fact I believe the displacement tax is an ANNUAL charge like our registration fees, not like our gas guzzler tax that the first owner pays once at delivery.
really?
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      02-21-2014, 07:44 PM   #9
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Quote:
Originally Posted by Ezio
Quote:
Originally Posted by jphughan View Post
In fact I believe the displacement tax is an ANNUAL charge like our registration fees, not like our gas guzzler tax that the first owner pays once at delivery.
really?
Not 100% certain, though I seem to remember registration fees scaling with displacement. I'm sure someone in Europe will chime in on this thread before long though.
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      02-21-2014, 07:56 PM   #10
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Quote:
Originally Posted by jphughan View Post
Not 100% certain, though I seem to remember registration fees scaling with displacement. I'm sure someone in Europe will chime in on this thread before long though.
It's like that in Singapore; annual tax based on displacement. And since Singapore mimics a lot of British laws, this wouldn't surprise me.
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      02-21-2014, 09:07 PM   #11
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Quote:
Originally Posted by Rupes View Post
GM seems to really understand this technology, but no other manufacturer seems to be using it on a regular basis. Why not? It seems top be a really easy, cost effective way to have a fire breathing V8, and a fuel sipper on the highway at the same time. Does anyone know why this is hard to mimic, does it have something to do with the push-rod engine?
These systems are still being used on vehicles today. These are some of the late model systems:
Chrysler = Multi-Displacement System (MDS)
Dodge = Displacement On Demand (DOD)
GM = Active Fuel Management (AFM)
Honda = Variable Cylinder Management (VCM)
Daimler AG = Active Cylinder Control (ACC)

GM
Introduced 2005 T- truck, Envoy, Trailblazer 5.3L V8 RPO LH6, 2005 grand Prix 5.3L
More engines added in 2006, (Monte Carlo, Impalla) 2007 SUVís added, 150,000 produced in 2005, Over 2 million by 2008

Chrysler
Introduced in 2004 on the 5.7L Hemi
2005 on 300C, Magnum, Grand Cherokee
2006 Durango, Ram, Commander
2007 Aspen
2009 Challenger

The engine management system monitors the following on GM vehicles to allow activation:
Transmission in 3rd,4th,5th or 6th gear
Engine oil pressure between 25-75 PSI
Engine Speed 900-3000 RPM
Engine oil temp between 20-150c (68-302f)
Engine load steady
Battery voltage 11-18 volts

The GM and Chrysler versions deactivate the exhaust valves using a special valve lifter on specific cylinders.
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      02-21-2014, 09:13 PM   #12
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Quote:
Originally Posted by Rupes View Post
Come on...you have to admit running 4 cylinders on the highway vs a V8 is a much bigger factor in fuel efficiently than the aerodynamics vs. an M3.
Yes it is. I'm not comparing it to anything.
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      02-21-2014, 10:02 PM   #13
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I'm probably totally off but doesn't the 4 cylinders have to move 8 cylinders worth of engine still ?
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      02-21-2014, 10:12 PM   #14
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Quote:
Originally Posted by 4corners View Post
Wind resistance is a factor. Vettes are slick in the wind. It doesn't take 420 hp to make it go
My 2013 GMC truck has it, that isnt aerodynamic at all.
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      02-21-2014, 10:30 PM   #15
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Quote:
Originally Posted by dreamspeed View Post
I'm probably totally off but doesn't the 4 cylinders have to move 8 cylinders worth of engine still ?
It has to move the weight of an 8 cylinder engine (ie. the total weight of the car). But cruising on the highway, that's more than enough power, especially when you consider the new Vette has 460 HP.
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      02-21-2014, 10:30 PM   #16
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Works great in the Odyssey but its not like you get great mileage because of it. It helps but it's not a huge improvement.
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      02-21-2014, 10:45 PM   #17
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AMG uses cylinder deactivation on the current SLK55. The M152 engine is exclusive to that model and it's part of the AMG2015 "Road to Sustainability" campaign. Naturally aspirated 415 hp/398 lb ft torque. 19/28 fuel economy - which is obviously good for an 8-cylinder. It's basically the current engine used in the AMG 63s without turbochargers.


Quote:
Originally Posted by Ezio View Post
whats funny is that people hate that Cylinder Deactivation. reason: when you have a exhuast, your car will sound like a 4 banger at times. (tunes can turn this off)
The SLK55 does have a drone in 4-cylinder mode, but cylinder deactivation can be turned off with start/stop.

Quote:
Originally Posted by jphughan View Post
Apparently it was very difficult for GM to get the transitions between cylinder modes to occur smoothly, especially with a manual transmission involved, so I wouldn't call it an easy way to get a benefit.
Obviously MB doesn't offer automatics but they had to use the 7-speed AMG SPEEDSHIFT (which is not the current tranny in most AMGs) to provide smooth shifting between modes rather than a DCT like in the latest AMGs.

Quote:
Originally Posted by dreamspeed View Post
I'm probably totally off but doesn't the 4 cylinders have to move 8 cylinders worth of engine still ?
The SLK55 still makes 170 lb ft of torque in 4-cylinder mode in a car only weight 3500 lbs. It switches between modes in 30 milliseconds if it senses greater load and it feels seamless. The only way you'd really notice is the sound of the engine and the mode indicator on the dash.

Long-story short, I agree with OP...I'm surprised this technology isn't more prevalent and although it requires some compromises it still is a viable option even in a performance car.
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      02-22-2014, 12:28 AM   #18
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My tahoe use to deactivate some cylinders. I hated it! It would lag on quick acceleration (felt like 1-2 seconds to switch back to full v8) and the exhaust note (I have a tame borla cat back) was horrid.

I removed it with a handheld programmer and the can tune got me 1.5 MPG MORE even with cylinder deactivation off.

Its crap in my book.
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      02-22-2014, 04:55 PM   #19
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I think the Veyron has this technology down cold. It only takes a couple of hundred HP to maintain 200mph once you're there. I guess that's what millions will buy you.
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      02-22-2014, 06:20 PM   #20
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I am very interested in this topic actually. How does the other companies' system work?

- Do the valves still open/close when the cylinder is deactivated? I remember to have read that the intake/exhaust valves stay close on the deactivated cylinders to minimize pumping lost but how is it implemented in an overhead cam design?

- Is it always the same cylinder that get deactivated? Seems to be but wouldn't this cause uneven wear on the engine in the long run?

Our cars (and most modern cars) already sorta have a cylinder management system in that if you lift off the gas while cruising, the ecm will cut all fuel injection until the engine is near idle. How hard is it or if it's possible to elaborate on this a little bit and have the computer just 'skip' a beat when not all the power is needed? I would imagine this would be a smoother transition between on and off and also no uneven wear on the engine either and should help gas consumption. Other posters have mention something about pumping lost negating the benefit though.
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      02-22-2014, 06:54 PM   #21
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Quote:
Originally Posted by e92zero View Post
I am very interested in this topic actually. How does the other companies' system work?

- Do the valves still open/close when the cylinder is deactivated? I remember to have read that the intake/exhaust valves stay close on the deactivated cylinders to minimize pumping lost but how is it implemented in an overhead cam design?

- Is it always the same cylinder that get deactivated? Seems to be but wouldn't this cause uneven wear on the engine in the long run?
The GM and Chrysler systems deactivate specific cylinders by using a special valve lifter. The ECU controls oil flow solenoids for the unique lifter to prevent the exhaust valve from opening. The injectors on those cylinders are also shut-off.

E92zero:
PM me with your email and I can send you a PDF file with more information and color photos. I just attended a great webinar on Active Fuel Management systems. I teach automotive technology and there are always plenty of new changes.
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      02-22-2014, 07:54 PM   #22
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^pm sent. Thanks in advance!
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