Bought my first new car yesterday :)

[GuitarDaddy]

Originally posted by: desy
The cylinders also deactivate at lights , where you don't have a load

Nope, it stays in 8cyl mode when idleing so full torque is available on take off. The only time it drops to 4cyl is when you are traveling 40mph+ and let off the gas.


I've driven the Impala with DOD for a little over 3yrs and I can tell you for day to day stop and go driving it saves very little gas probably 2-3mpg. Now freeway trips are a different story, it saves significant gas on long trips. I get almost 30mpg on long trips, which is remarkable for a V8 with 300+HP.

 

[GuitarDaddy]

Originally posted by: RGUN

Originally posted by: LTC8K6
"Cylinder deactivation is such a gimmick... someone please attempt to give me a logical explanation how it saves fuel.... "


Why would you need that explained? It's pretty simple. While it doesn't save a whole lot of fuel, it certainly works well these days.

To maintain a certain speed you need a specific amount of energy. Regardless of whether you have 3, 4, 6, or 8 cylinders, you will need to burn a specific amount of fuel to maintain that particular speed, neglecting friction of course. For my own information please convince me that cylinder deactivation is beneficial.

Your simplified view of physics fails, your assumption that fuel usage scales perfectly with weight and speed regardless of engine type or other factors is just so wrong it hurts. It's all about energy efficiency, a large engine that if basically idleing to maintain a speed is very inefficient and burns more fuel than a small engine that has to work much harder to maintain the same speed for the same vehicle weight.

 

[rh71]

My first new miles were horrible... like 10mpg... and it leveled out around 13mpg after a couple hundred more miles. After 1k miles now, it does 16mpg and highway is a lot more like 18mpg. I heard it will really settle out after 10k... but maybe less the way it looks now.

To illustrate what a difference highway driving makes... the range indicated 102miles left for the tank before I left for a 40mile journey. After I got there, it stated 89miles left.

 

[RGUN]

Originally posted by: GuitarDaddy

Originally posted by: RGUN

Originally posted by: LTC8K6
"Cylinder deactivation is such a gimmick... someone please attempt to give me a logical explanation how it saves fuel.... "


Why would you need that explained? It's pretty simple. While it doesn't save a whole lot of fuel, it certainly works well these days.

To maintain a certain speed you need a specific amount of energy. Regardless of whether you have 3, 4, 6, or 8 cylinders, you will need to burn a specific amount of fuel to maintain that particular speed, neglecting friction of course. For my own information please convince me that cylinder deactivation is beneficial.

Your simplified view of physics fails, your assumption that fuel usage scales perfectly with weight and speed regardless of engine type or other factors is just so wrong it hurts. It's all about energy efficiency, a large engine that if basically idleing to maintain a speed is very inefficient and burns more fuel than a small engine that has to work much harder to maintain the same speed for the same vehicle weight.

huh? If you could phrase your answer in the form of english I might be able to understand it. I still see no logical argument. I made my argument simple because we are talking about an identical engine operating on 4 or 8 cylinders... so before your head hurts, please read my statement and understand what I am arguing.

 

[RGUN]

Originally posted by: GuitarDaddy

Originally posted by: desy
The cylinders also deactivate at lights , where you don't have a load

Nope, it stays in 8cyl mode when idleing so full torque is available on take off. The only time it drops to 4cyl is when you are traveling 40mph+ and let off the gas.


I've driven the Impala with DOD for a little over 3yrs and I can tell you for day to day stop and go driving it saves very little gas probably 2-3mpg. Now freeway trips are a different story, it saves significant gas on long trips. I get almost 30mpg on long trips, which is remarkable for a V8 with 300+HP.

Our Corvette gets better highway gas mileage than any of the 4cyl or 6cyl in the house. It will get 40mpg on a trip to the cottage, and it will make 400HP

 

[Dman877]

The reason your corvette gets such good mileage on the highway is because it's light, aerodynamic, and it has very tall gearing.

As to your other argument, it's really pretty simple. You're ignoring friction. The more cylinders you have, the less efficient the engine is simply because there is more metal-on-metal rubbing. While you may only need 15 hp to cost on the highway, and you're right that that doesn't change based on engine size, a 4 cyl engine will make that 15 hp more efficiently than a 6 cyl engine (which has 50% more friction).

EDIT: It probably also has something to do with the fact that 3 out of the 4 strokes in a 4 stroke engine don't make power, but sap it instead. IE, the compression and exhaust strokes both sap power so the less cylinders you have doing that, the more efficiently the motor will run.

 

[RGUN]

Originally posted by: Dman877
The reason your corvette gets such good mileage on the highway is because it's light, aerodynamic, and it has very tall gearing.

As to your other argument, it's really pretty simple. You're ignoring friction. The more cylinders you have, the less efficient the engine is simply because there is more metal-on-metal rubbing. While you may only need 15 hp to cost on the highway, and you're right that that doesn't change based on engine size, a 4 cyl engine will make that 15 hp more efficiently than a 6 cyl engine (which has 50% more friction).

EDIT: It probably also has something to do with the fact that 3 out of the 4 strokes in a 4 stroke engine don't make power, but sap it instead. IE, the compression and exhaust strokes both sap power so the less cylinders you have doing that, the more efficiently the motor will run.

I am not forgetting about friction... its the same engine! it will develope the same friction regardless of how many cylinders it runs on.

 

[Dman877]

see my edit. I'm not really sure how the cyl deactivation schemes work, I guess they can't exactly stop the pistons so they probably just open the valves. But friction explains why a 6 cyl engine running on 4 cyl will never be as efficient as a normal 4 cyl motor.

 

[BUTCH1]

They just shut off fuel to the "dead" cylinders, the cylinders then use the compressed air to "boomerang" off on another...

 

[boomerang]

Originally posted by: RGUN
To maintain a certain speed you need a specific amount of energy. Regardless of whether you have 3, 4, 6, or 8 cylinders, you will need to burn a specific amount of fuel to maintain that particular speed, neglecting friction of course.

So, by your logic, if you are driving 70 MPH uphill, it takes the same amount of energy to drive 70 MPH downhill. Correct?

 

[RGUN]

Originally posted by: boomerang

Originally posted by: RGUN
To maintain a certain speed you need a specific amount of energy. Regardless of whether you have 3, 4, 6, or 8 cylinders, you will need to burn a specific amount of fuel to maintain that particular speed, neglecting friction of course.

So, by your logic, if you are driving 70 MPH uphill, it takes the same amount of energy to drive 70 MPH downhill. Correct?

Correct

 

[RGUN]

Originally posted by: Dman877
see my edit. I'm not really sure how the cyl deactivation schemes work, I guess they can't exactly stop the pistons so they probably just open the valves. But friction explains why a 6 cyl engine running on 4 cyl will never be as efficient as a normal 4 cyl motor.

The argument is not about 6 cylinder engines versus 4 cylinder.... its about the same engine running on less cylinders... so the friction is exactly the same.

 

[RGUN]

Originally posted by: BUTCH1
They just shut off fuel to the "dead" cylinders, the cylinders then use the compressed air to "boomerang" off on another...

Please elaborate

 

[GuitarDaddy]

Originally posted by: RGUN

To maintain a certain speed you need a specific amount of energy. CorrectRegardless of whether you have 3, 4, 6, or 8 cylinders, you will need to burn a specific amount of fuel to maintain that particular speed Incorrect

You assume that all engines under all conditions will create the same forward energy per gal of fuel, that is incorrect.

 

[boomerang]

Originally posted by: RGUN

Originally posted by: boomerang

Originally posted by: RGUN
To maintain a certain speed you need a specific amount of energy. Regardless of whether you have 3, 4, 6, or 8 cylinders, you will need to burn a specific amount of fuel to maintain that particular speed, neglecting friction of course.

So, by your logic, if you are driving 70 MPH uphill, it takes the same amount of energy to drive 70 MPH downhill. Correct?

Correct

So let's assume the same car, on a level road and 70 MPH.

Scenario #1: 35 MPH headwind. The wind is blowing at 35 MPH directly at the front of the car.

Scenario #2: No head wind. A perfectly calm day.

Under which scenario is the throttle opened further on the car? I'll give you the answer. Scenario #1. When the throttle is opened further, more fuel is being used. Surely you will agree on this. If not, read no further.


Something new to think about:

Same car, same level road and once again, 70 MPH.
Your car makes 185 lb/ft of torque at 1800 RPM. 1800 RPM is the speed the motor is turning at 70 MPH.
Based upon the mass of the car, the wind resistance, rolling resistance and what have you, it can be calculated that it takes 125 lb/ft of torque to move your car down this road at 70MPH. Your motor is creating 60 lb/ft of torque that is not needed. It's using more fuel than is required. If you cut off fuel to several cylinders, it is now producing 125 lb/ft of torque and using less fuel in the process. You're still going 70 MPH.

These are random figures and may or may not have any bearing in the real world, but you have just read an analogy of why cutting off cylinders saves gas.

Edit: An apology to Gobadgrs for taking over his thread. Great choice on the Malibu. I hope it serves you well.

 

[RGUN]

Originally posted by: GuitarDaddy

Originally posted by: RGUN

To maintain a certain speed you need a specific amount of energy. CorrectRegardless of whether you have 3, 4, 6, or 8 cylinders, you will need to burn a specific amount of fuel to maintain that particular speed Incorrect

You assume that all engines under all conditions will create the same forward energy per gal of fuel, that is incorrect.

I would also assume you read my question, but I would be incorrect.... one final time... It is the same engine, under the same conditions, save for cylinder deactivation.

 

[RGUN]

Originally posted by: boomerang

Originally posted by: RGUN

Originally posted by: boomerang

Originally posted by: RGUN
To maintain a certain speed you need a specific amount of energy. Regardless of whether you have 3, 4, 6, or 8 cylinders, you will need to burn a specific amount of fuel to maintain that particular speed, neglecting friction of course.

So, by your logic, if you are driving 70 MPH uphill, it takes the same amount of energy to drive 70 MPH downhill. Correct?

Correct

So let's assume the same car, on a level road and 70 MPH.

Scenario #1: 35 MPH headwind. The wind is blowing at 35 MPH directly at the front of the car.

Sceanario #2: No head wind. A perfectly calm day.

Under which scenario is the throttle opened further on the car? I'll give you the answer. Scenario #1. When the throttle is opened further, more fuel is being used. Surely you will agree on this. If not, read no further.


Something new to think about:

Same car, same level road and once again, 70 MPH.
Your car makes 185 lb/ft of torque at 1800 RPM. 1800 RPM is the speed the motor is turning at 70 MPH.
Based upon the mass of the car, the wind resistance, rolling resistance and what have you, it can be calculated that it takes 125 lb/ft of torque to move your car down this road at 70MPH. Your motor is creating 60 lb/ft of torque that is not needed. It's using more fuel than is required. If you cut off fuel to several cylinders, it is now producing 125 lb/ft of torque and using less fuel in the process. You're still going 70 MPH.

These are random figures and may or may not have any bearing in the real world, but you have just read an analogy of why cutting off cylinders saves gas.

Edit: An apology to Gobadgrs for taking over his thread. Great choice on the Malibu. I hope it serves you well.

Ill try to break it down for easy understanding... You have introduced drag into the equation, and therefore of course it is different.

Secondly, a car does not create extra torque that is not needed... you can make 185 lbft of torque at 1800 rpm, you can also make 125 lbft at 1800 rpm... it depends on how much fuel is injected into the engine. The fuel injectors change their pulse width the accomodate the current requirement for fuel. It will still require the same amount of fuel regardless of how many cylinders have been shut down....

Please go revise your analogy, as it is incorrect and poorly founded.

 

[boomerang]

Originally posted by: RGUN

Originally posted by: boomerang

Originally posted by: RGUN

Originally posted by: boomerang

Originally posted by: RGUN
To maintain a certain speed you need a specific amount of energy. Regardless of whether you have 3, 4, 6, or 8 cylinders, you will need to burn a specific amount of fuel to maintain that particular speed, neglecting friction of course.

So, by your logic, if you are driving 70 MPH uphill, it takes the same amount of energy to drive 70 MPH downhill. Correct?

Correct

So let's assume the same car, on a level road and 70 MPH.

Scenario #1: 35 MPH headwind. The wind is blowing at 35 MPH directly at the front of the car.

Sceanario #2: No head wind. A perfectly calm day.

Under which scenario is the throttle opened further on the car? I'll give you the answer. Scenario #1. When the throttle is opened further, more fuel is being used. Surely you will agree on this. If not, read no further.


Something new to think about:

Same car, same level road and once again, 70 MPH.
Your car makes 185 lb/ft of torque at 1800 RPM. 1800 RPM is the speed the motor is turning at 70 MPH.
Based upon the mass of the car, the wind resistance, rolling resistance and what have you, it can be calculated that it takes 125 lb/ft of torque to move your car down this road at 70MPH. Your motor is creating 60 lb/ft of torque that is not needed. It's using more fuel than is required. If you cut off fuel to several cylinders, it is now producing 125 lb/ft of torque and using less fuel in the process. You're still going 70 MPH.

These are random figures and may or may not have any bearing in the real world, but you have just read an analogy of why cutting off cylinders saves gas.

Edit: An apology to Gobadgrs for taking over his thread. Great choice on the Malibu. I hope it serves you well.

Ill try to break it down for easy understanding... You have introduced drag into the equation, and therefore of course it is different.

Secondly, a car does not create extra torque that is not needed... you can make 185 lbft of torque at 1800 rpm, you can also make 125 lbft at 1800 rpm... it depends on how much fuel is injected into the engine. The fuel injectors change their pulse width the accomodate the current requirement for fuel. It will still require the same amount of fuel regardless of how many cylinders have been shut down....

Please go revise your analogy, as it is incorrect and poorly founded.

You're so wrong as to be laughable, but you've got your heels dug in and will not budge. That is obvious.

You really should offer up your services as a consultant to many of the major automobile manufacturers on the planet. They're spending tons of cash on the engineering and manufacture of cylinder cut off systems that are not needed. You could provide a great service to them. Call them now, they need your divine genius. Me, I'm through with you.

 

[Dman877]

I think it's more about the efficiency or inefficiency of an engine. Internal combustion engines are about 35% efficient. That means they convert just 35% of the energy that exists in fuel molecules into mechanical motion at the flywheel. Now, that other 65% of the energy is lost several ways. Friction is one. The other is in the 3 non-power strokes of the 4 stroke engine.

Compressing the fuel-air mixture down to one ninth or one tenth of it's original volume takes work. Pushing waste gas out through the exhaust system does as well. Drawing the fuel-air mixture in probably saps very little power. Still, that's two power-sapping strokes out of four. Now obviously the power stroke more than makes up for these losses.

So here's a scenario for you. You have an 8 cyl engine that can deactivate half of its cylinders. Now, say your driving somewhere and you only need 16 horsepower to do it. With 8 cylinders running, you need 2 horsepower from each cylinder. However, in addition to that 8 hp, you need, say one additional hp to overcome the losses from the non-power strokes. Therefore, you need 3 hp from each cylinder, or 24 hp worth of energy from gasoline. Now, if you deactivate 4 cylinders, each cylinder will need to make 4 hp + 1 to overcome non-powerstroke losses, or a total of just 20 hp worth of energy from gasoline.

In 4 cylinder mode, the engine would have to run richer than in 8 cylinder mode but rpm would remain the same and it wouldn't have to make as much power (gross if you will) as it would with all 8 cylinders active.

I might not be correct here but given the way cylinder deactivation works, and given the fact that it does increase fuel economy, it has to be something like this.

 

[GuitarDaddy]

Originally posted by: RGUN

Originally posted by: GuitarDaddy

Originally posted by: RGUN

To maintain a certain speed you need a specific amount of energy. CorrectRegardless of whether you have 3, 4, 6, or 8 cylinders, you will need to burn a specific amount of fuel to maintain that particular speed Incorrect

You assume that all engines under all conditions will create the same forward energy per gal of fuel, that is incorrect.

I would also assume you read my question, but I would be incorrect.... one final time... It is the same engine, under the same conditions, save for cylinder deactivation.

Your insults are cute, first I can't speak english, now I can't read🙂

But that doesn't change the fact that your absolutely wrong, the same engine does use less fuel at the same speed in 4cyl mode.

But I'm sure that you won't except that because it's contrary to your baseless misguided argument. Do you really beleive multiple automakers would spend millions of dollars on R&D and thousands of hours developing the technology and putting it in production if the science wasn't provable.

Cars are made by the man, it's all a farse man, it's bogus technology invented to steal our money man. If I don't understand it, it's not posible.

Grow up and quit spreading FUD

 

[RGUN]

Originally posted by: boomerang

Originally posted by: RGUN

Originally posted by: boomerang

Originally posted by: RGUN

Originally posted by: boomerang

Originally posted by: RGUN
To maintain a certain speed you need a specific amount of energy. Regardless of whether you have 3, 4, 6, or 8 cylinders, you will need to burn a specific amount of fuel to maintain that particular speed, neglecting friction of course.

So, by your logic, if you are driving 70 MPH uphill, it takes the same amount of energy to drive 70 MPH downhill. Correct?

Correct

So let's assume the same car, on a level road and 70 MPH.

Scenario #1: 35 MPH headwind. The wind is blowing at 35 MPH directly at the front of the car.

Sceanario #2: No head wind. A perfectly calm day.

Under which scenario is the throttle opened further on the car? I'll give you the answer. Scenario #1. When the throttle is opened further, more fuel is being used. Surely you will agree on this. If not, read no further.


Something new to think about:

Same car, same level road and once again, 70 MPH.
Your car makes 185 lb/ft of torque at 1800 RPM. 1800 RPM is the speed the motor is turning at 70 MPH.
Based upon the mass of the car, the wind resistance, rolling resistance and what have you, it can be calculated that it takes 125 lb/ft of torque to move your car down this road at 70MPH. Your motor is creating 60 lb/ft of torque that is not needed. It's using more fuel than is required. If you cut off fuel to several cylinders, it is now producing 125 lb/ft of torque and using less fuel in the process. You're still going 70 MPH.

These are random figures and may or may not have any bearing in the real world, but you have just read an analogy of why cutting off cylinders saves gas.

Edit: An apology to Gobadgrs for taking over his thread. Great choice on the Malibu. I hope it serves you well.

Ill try to break it down for easy understanding... You have introduced drag into the equation, and therefore of course it is different.

Secondly, a car does not create extra torque that is not needed... you can make 185 lbft of torque at 1800 rpm, you can also make 125 lbft at 1800 rpm... it depends on how much fuel is injected into the engine. The fuel injectors change their pulse width the accomodate the current requirement for fuel. It will still require the same amount of fuel regardless of how many cylinders have been shut down....

Please go revise your analogy, as it is incorrect and poorly founded.

You're so wrong as to be laughable, but you've got your heels dug in and will not budge. That is obvious.

You really should offer up your services as a consultant to many of the major automobile manufacturers on the planet. They're spending tons of cash on the engineering and manufacture of cylinder cut off systems that are not needed. You could provide a great service to them. Call them now, they need your divine genius. Me, I'm through with you.

I applaud you for coming up with the courage to call me wrong yet not provide any proof.

 

[RGUN]

Originally posted by: Dman877
I think it's more about the efficiency or inefficiency of an engine. Internal combustion engines are about 35% efficient. That means they convert just 35% of the energy that exists in fuel molecules into mechanical motion at the flywheel. Now, that other 65% of the energy is lost several ways. Friction is one. The other is in the 3 non-power strokes of the 4 stroke engine.

Compressing the fuel-air mixture down to one ninth or one tenth of it's original volume takes work. Pushing waste gas out through the exhaust system does as well. Drawing the fuel-air mixture in probably saps very little power. Still, that's two power-sapping strokes out of four. Now obviously the power stroke more than makes up for these losses.

So here's a scenario for you. You have an 8 cyl engine that can deactivate half of its cylinders. Now, say your driving somewhere and you only need 16 horsepower to do it. With 8 cylinders running, you need 2 horsepower from each cylinder. However, in addition to that 8 hp, you need, say one additional hp to overcome the losses from the non-power strokes. Therefore, you need 3 hp from each cylinder, or 24 hp worth of energy from gasoline. Now, if you deactivate 4 cylinders, each cylinder will need to make 4 hp + 1 to overcome non-powerstroke losses, or a total of just 20 hp worth of energy from gasoline.

In 4 cylinder mode, the engine would have to run richer than in 8 cylinder mode but rpm would remain the same and it wouldn't have to make as much power (gross if you will) as it would with all 8 cylinders active.

I might not be correct here but given the way cylinder deactivation works, and given the fact that it does increase fuel economy, it has to be something like this.

There we go now we are getting closer to a reasonable answer. Except I would argue that neither the intake nor the exhaust stroke will be change, only the compression stroke. So I would indeed agree that you will save a marginal amount of energy by not having to compress the mixture.

 

[RGUN]

Originally posted by: GuitarDaddy

Originally posted by: RGUN

Originally posted by: GuitarDaddy

Originally posted by: RGUN

To maintain a certain speed you need a specific amount of energy. CorrectRegardless of whether you have 3, 4, 6, or 8 cylinders, you will need to burn a specific amount of fuel to maintain that particular speed Incorrect

You assume that all engines under all conditions will create the same forward energy per gal of fuel, that is incorrect.

I would also assume you read my question, but I would be incorrect.... one final time... It is the same engine, under the same conditions, save for cylinder deactivation.

Your insults are cute, first I can't speak english, now I can't read🙂

But that doesn't change the fact that your absolutely wrong, the same engine does use less fuel at the same speed in 4cyl mode.

But I'm sure that you won't except that because it's contrary to your baseless misguided argument. Do you really beleive multiple automakers would spend millions of dollars on R&D and thousands of hours developing the technology and putting it in production if the science wasn't provable.

Cars are made by the man, it's all a farse man, it's bogus technology invented to steal our money man. If I don't understand it, it's not posible.

Grow up and quit spreading FUD

Unlike most people I tend to question things to increase my level of understanding.... Hell the pharmaceutical companies spend millions on getting you fat loss pills... those MUST work right? Or they know that people will automatically assume that since its called fat loss, or cylinder deactivation, then it must do exactly that right?!

I simply asked for an explanation, and rather than attempt to present one you just call my theories into question. My theories are 100% correct, please prove me wrong.

 

[Chunkee]

bunch a cornholers in this thread

jeebers

 

[GoingUp]

Wow did this thread get derailed. Can we stop the pissing contest please? 🙂