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Discussion Starter · #1 ·
Clearly I'm no mechanical enginner but I am baffled why the Colorado does not spend more time in V4 mode. It would seem they would get much better MPG if it switched to V4 while in park, at stop lights or cruising down the freeway or flat surfaces. It seems the only time mine switches is when I'm coasting downhill. Can any explain why it switches so infrequently? TIA. 2021 Colorado Z71
 

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Variable Cylinder Management, or whatever Chevy calls their system is a pretty complicated system that uses a reasonably sophisticated algorithm to determine when to deactivate cylinders. Various manufacturers have tried it over the years, does anyone remember the Cadillac 4-6-8 engines? They were complete nightmares and everyone just bypassed that system to run as V8 all the time.

We have learned some valuable lessons along the way, like sitting in your driveway in P with no load on the engine is a great way to coke up your cylinders and foul the valves with cylinders de-activated. I think the Chevy system is largely a joke to get the CAFE credits. The V6 is a good engine for our trucks with an appropriate amount of power, and cutting back to 4-cyl mode is just not adequate in all but a few perfect scenarios. There are other hidden issues to consider, switching back and fourth puts additional stress on the fuel management and delivery system, the motor mounts and a bunch of other parts, so it's really in the trucks best interest to run all 6 cyl's all the time. The increase in fuel economy is a joke.
 

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Discussion Starter · #4 ·
Yes, I agree its a joke because it never kicks in. One would think that at a stop, idle, or red light would be the optimum time for it to kick in but I guess Chevy engineers disagree.
 

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2021 Colorado 2.8L Diesel Z71
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I don't see any reason that cylinder deactivation would 'stress' most engine systems like fuel or ignition. The dead cylinders valves are just turned off and the cylinder becomes an air spring.

I imagine the main reason that GM doesn't activate it much on the 3.5L V6 is that the engine probably has bad NVH in very low load running on four cylinders. That's the main reason I can think of for not using it at idle, for example.
 

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GM gets a CAFE credit for having this feature whether or not it improves mileage or not.
In order to get that credit it has to save fuel and raise the MPG, and with the amount of money it costs to design, test and implement something like DoD it has to work pretty well in the fuel savings department or that money wouldn't at all be worth what they are getting "credit" for. If it only saves a tenth or two then hundred of millions spent isn't worth it with say DoD, but a lower plastic valence? Yeah, that cost benefit is there. It is pretty standard to know that when conditions are met that DoD can save anywhere from 8-10% or more over normal full cylinder running mode, so the cost savings and credits all add up to be worth it to many manufacturers.

Tyler
 

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The feature is a carry over from the cars this engine is used in. Those vehicles weigh less and are more aerodynamic so they use the only 4 cylinders mode more often.

No engine with multi displacement tech uses it at idle. The vibration would be awful.
 

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We have covered this before in several threads here.

The AFM in this truck is a Off Cycle Credit with the EPA. Since there is no way to consistently test this system the EPA awards an Off Cycle credit that goes not just to MPG but Emissions too.

Off Cycle credits can be applied to a number of things that can not be consistently tested. Some automakers have received it for paint that is reflective to run the AC in a car less as is some glass some automakers are trying. Altenators that are low drag and other odd ball trick they are using all can count as off cycle credit.

While it may not kick in a lot and add much if any detectable MPG these credits applied let the automakers still offer a larger and more powerful engine than they could other wise.

As for durability yes the early version of this had issues but GM has engineered this system in the new V8 and the new V6 so it is generally undetectable and also so far not showing any of the issues the past models had. To be honest GM would be better off not to even say anything about this and few people would ever know they had it.

To be honest things to day are not always what you think they are. While some look at this as a gas saving feature the automaker see it as a way to offer you a V6 and not just only a 4 cylinder in your truck. That credit is what helps them sell you what you want.

This is also like the EV models coming. GM is going to move to EV products like a number of other MFG are now doing. They are not out to save trees or the planet. They see they will be able to offer EV vehicles in 15 years that will be easier to built at lower cost that will be more profitable. They also expect charging times to be Lower and ranges to where they need to be. The development cost of ICE engines will continue to get more and more difficult and expensive because they have to add system like this. You can only cut so many cylinders too. No there will still be some things that will need to change but in the big picture it will be the easier and more affordable way out.

Many never consider the development cost that just keep increasing with ICE and how EV will have lowering cost as they go forward. For a long while they never though the tech would be here and now they can see where they will be in 20 years and feel it can be accomplished.

We are going to see some very historic things happen in the next 20 years. You don't need to be a crusty old auto enthusiast to see that.
 

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Youll see it a ton more if you use manual shift mode and stay in a gear that keeps the rpms around 2k. Also it turns off after a very low throttle precentage. Mine is on a lot with in town driving.


GM has all these new trannies programmed to upshift asap even at low speeds. This eco crap kills the purpose of a pickup.

V4 wont come on lets say when youre going 40mph and the tranny already in 6 or 7th gear. It gets the rpms so low, v4 would be under powered.
 

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I had one of the first Hemi Challengers with cylinder deactivation. It went from 8 to 4 but only while cruising gently at city or hwy speeds. Of course you never really wanted 4 cylinders in a car like that but it made sense on long trips. I could get an amazing 30 mpg imperial while using that mode.
 

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2019 Chevy Colorado ZR2 3.6 v6 Midnight Edition with sports bar
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This is also like the EV models coming. GM is going to move to EV products like a number of other MFG are now doing. They are not out to save trees or the planet. They see they will be able to offer EV vehicles in 15 years that will be easier to built at lower cost that will be more profitable.

We are going to see some very historic things happen in the next 20 years. You don't need to be a crusty old auto enthusiast to see that.
I generally avoid talking politics. Though this kind of is, it is more on the idea of the subject, and not slamming either side of the debate...

This reminds me of a recent proposed mandate by "Joe" that by 2035 all vehicles sold in the US will be EV. Currently, only 2% of vehicles sold in the US are EV. To me, this shows how much people actually want it. Having to regulate something into reality isn't the way they should go about it.


Regarding previous 4/6/8 engines, my mom had a Northstar engine in her Caddie and while for the time it was a fairly quick car, it became a string of issues as time went on. She nearly gave the car away even though the body and interior was nearly perfect. The person put a different drivetrain in it and drove it for many more years. It sucks to be an early adopter on certain tech.
 
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This reminds me of a recent proposed mandate by "Joe" that by 2035 all vehicles sold in the US will be EV. Currently, only 2% of vehicles sold in the US are EV. To me, this shows how much people actually want it. Having to regulate something into reality isn't the way they should go about it.
I have not actually heard politicians suggest that EV's should be mandated, nor that ICE should be banned. At least not any center left politician like Biden. I think the concept is, build the infrastructure like widespread rapid charging, and the technology will take off because it is so much cheaper to operate and maintain. Now, that's fine if you disagree as to the economics or speed of adaptation, but that's what I mostly hear.

It is worth noting how much of what we take for granted has not come about organically or through the 'magic' of the free market. One reason we all love driving around in cars for example is that we as a society decided to exercise government will to build roads all over the place. Imagine if every road was privately owned, and could only be built through private acquisition of property and not eminent domain. I'm not sure what our society would look like with that different history, but it sure would be different.

A lot of industries have a huge public funded background.....oil, automobiles, etc. I imagine the future of transport will depend a lot on whether or not we support charging networks the same way we supported oil exploration, pipelines, etc. etc.
 

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I generally avoid talking politics. Though this kind of is, it is more on the idea of the subject, and not slamming either side of the debate...

This reminds me of a recent proposed mandate by "Joe" that by 2035 all vehicles sold in the US will be EV. Currently, only 2% of vehicles sold in the US are EV. To me, this shows how much people actually want it. Having to regulate something into reality isn't the way they should go about it.


Regarding previous 4/6/8 engines, my mom had a Northstar engine in her Caddie and while for the time it was a fairly quick car, it became a string of issues as time went on. She nearly gave the car away even though the body and interior was nearly perfect. The person put a different drivetrain in it and drove it for many more years. It sucks to be an early adopter on certain tech.
The problem is the politics are becoming less of an issue as the mfgs are now planning the move to EV because of economics For them.

The only politics anymore are the political folks grand standing by setting dates already set by most major mfgs.

The EV models will in time keep prices down but profits up. Also they will require EV in hi a and the automakers need China for market growth.

As for tech we are going to get it no matter what. If we stay with ice we will get more crap on them to make them clean. It will get only more expensive to buy and difficult to fix.

Now I am not endorsing EV but as they get return on investment prices will continue to decline and much less will be needed to be spent.

the automakers are working 15 years or more out now and they feel the goals needed can be met. With the amount of time the transition takes I expect they will meet most all of them. With less spending the last ten years too this from impossible to do able.

There is just a lot of false info out there as well as people only looking at today not where they will be in 10-20 years. The money being spent can accomplish much.

I would rather not make the change but this is far and away beyond a one stopping it now.

If this was political a vote could have stopped it but now the mfgs have their own reasons And little will stop this Now. Just look at the names and dates of the mfgs already announcing the change.

Even now the NHRA is working to bring EV racing in due to anticipation of grass roots racer with EV cars.
 

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I have not actually heard politicians suggest that EV's should be mandated, nor that ICE should be banned. At least not any center left politician like Biden.

I really don't mean to pull it a political direction. I'll completely refrain from picking a side. My comment is based more off the idea that in a capitalist society, that many/most things are consumer driven. Right now, only 2% of consumers wanted EV enough to buy it. I'll certainly agree that our government "gently" guides states, consumers, and businesses by dangling the carrot of incentives and money. I wish it weren't, but as you say, that is the way it is. I have a lot of family in Iowa making a living farming corn. I commented once that at least they wouldn't go hungry. They just laughed and said this corn isn't fit for eating. We grow it because they pay us subsidies (because it is used for Ethanol) which result in more to income than to grow food corn. So, uncle Sam is paying the farmers to grow an ethanol specialty corn. Then, paying subsidies to convert the corn into ethanol. Then, giving a tax break for those states and businesses that offer it. And, finally, it is sold for a lower cost. I realize there is a finite amount of dinosaur gas. However, it seems like a less than ideal sustainable idea financially. Then again, with the national debt growing exponentially, we'll be bought out eventually anyway.
OK. I am stepping off my soapbox. I don't mean any disrespect to the two posters' that I quoted. They just got me thinking (which is a bad idea). Hopefully my cynical @$$ will be long gone by then. :confused:
 

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I have not actually heard politicians suggest that EV's should be mandated, nor that ICE should be banned. At least not any center left politician like Biden. I think the concept is, build the infrastructure like widespread rapid charging, and the technology will take off because it is so much cheaper to operate and maintain. Now, that's fine if you disagree as to the economics or speed of adaptation, but that's what I mostly hear.

It is worth noting how much of what we take for granted has not come about organically or through the 'magic' of the free market. One reason we all love driving around in cars for example is that we as a society decided to exercise government will to build roads all over the place. Imagine if every road was privately owned, and could only be built through private acquisition of property and not eminent domain. I'm not sure what our society would look like with that different history, but it sure would be different.

A lot of industries have a huge public funded background.....oil, automobiles, etc. I imagine the future of transport will depend a lot on whether or not we support charging networks the same way we supported oil exploration, pipelines, etc. etc.
Actually the government is not saying they want all EV directly,. But they want Zero Carbon Emission which is just another way of eliminating gasoline use. It is like banning bullets but not the gun.

As for the transition. It was being forced by the Zero Carbon mandate. The initial trouble was that automakers needed suppliers to make parts but there was no market. Few would invest. Then cars like the Volt while not perfect came to make a market for suppliers though companies like GM made little to nothing on the cars. Now that investment has come up GM is going to grow the EV models over the next 20 years to where the people with chargers will come along as there will be cars to service.

The market has had to balance investment with market needs. It has been a back and fourth deal. We are now to a point where the market can start to grow on its own vs the need to be seeded.

There are some things gov does well but then there is cases where if they were run as a company they would fail short term due to waste.

The one area they did seed the market well was with the space program. Much of what was developed really moved our tech industry. That was even just a side effect as this was more about missiles and war items.

But when it comes to just spending money on things that we need and then the things that go to graft there is too little oversight. We would not be bankrupt as a country if we ran a tighter ship fiscally.

This money hand out over the last six months is going to bite us hard in the end. Things were not that bad and when handing out the money they should have targeted it much better. Most of us were not out of work and hurting.

But that is an argument for another day.
 
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