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VW engine will be the first 4-cylinder in the industry to use cylinder deactivation tech

With more stringent fuel economy standards looming in the U.S. and elsewhere, auto manufacturers are looking to pull out all the stops to improve economy as much as possible. Carmakers are turning to technology like direct injection and automatic start/stop. Several automakers are also using cylinder deactivation on their larger engines.

Cylinder deactivation is something that some carmakers in the U.S. and abroad have used for years. Chrysler has used the technology in its Hemi engines, Honda uses it on some of its V6 models, and Audi will use cylinder deactivation in its new line of “S” performance models.

VW is set to make a first in the automotive market by offering cylinder deactivation on its 4-cylinder models.

The VW tech will turn off two engine cylinders under certain conditions. The engine is called the 1.4L TSI and VW promises that it will offer a fuel savings of 0.4-liters/100km and when combined with start/stop technology the vehicle would save 0.6-liters of fuel. For those more familiar with U.S. mpg ratings, that works out to an improvement of in the range of 
3 to 4.5 mpg on average. 

The engine would turn off two of the cylinders under low to medium loads, and VW says that the tech will meet the future European EU6 emissions standards. The cylinders will be deactivated when the engine is operating between 1,400 and 4,000 rpm and the engine torque is in the range of 25 to 75Nm.

VW claims that operating range applies to about 70 percent of the driving distance in the EU fuel economy driving cycle. VW also points out that as soon as the driver presses the pedal the cylinders will reactivate without the driver being able to tell it happened. The cylinders also would not turn off if the vehicle were being driven in a sporty manner apparently. 

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RE: the reason you have not seen this
By Argon18 on 9/6/2011 3:08:26 PM , Rating: 3
IMO this all goes back to a fundamental shortcoming of the gasoline engine; that for a given amount of air in the cylinders, a certain percentage of fuel MUST be injected. Gasoline engines cannot run much leaner than 16:1 without overheating.

Diesel engines on the other hand can run as lean as 80:1 air to fuel ratio, which is part of the reason they are far more fuel efficient than gasoline engines. It's also the reason that a modern diesel engine uses almost no fuel at all while idling - as the computer knows to lean the mixture out to the maximum leanness. Also, while gasoline engines run hotter the leaner the mixture is, diesel engines run *cooler* the leaner the mixture is. So when they're sitting there idling, not only are the conserving fuel, they're also virtually immune to overheating.

By Spuke on 9/6/2011 5:09:22 PM , Rating: 3
Gasoline engines cannot run much leaner than 16:1 without overheating.
Nope. Direct injected engines can run as lean as 40:1 and even 65:1 or more.

RE: the reason you have not seen this
By lagomorpha on 9/6/2011 6:16:22 PM , Rating: 2
You're comparing constant pressure engines to constant volume engines.

In a diesel engine, the air intake is left fully open and the throttle controls how much fuel is injected into the cylinder. Press on the gas pedal = more fuel.

In a gasoline engine, the gas pedal controls a butterfly valve in the intake which lets more air in then either a carb or fuel injection will do its best to keep to the designed air-fuel ratio. (14.7:1 stoichiometric though modern EFI will run leaner under certain conditions for emissions reasons and old British motorcycles ran rich to aid with cooling and no one cared that they got bad gas mileage).

It isn't a matter of the computer leaning out the diesel when it's idling, the throttle position directly means less fuel is being injected.

RE: the reason you have not seen this
By haplo602 on 9/7/2011 2:41:59 AM , Rating: 2
modern cars have without exception electronic gas pedals. means the computer ALWAYS controls how much fuel is injected.

By mindless1 on 9/8/2011 11:49:52 PM , Rating: 2
They don't have to be so modern either, nor have electronic gas pedals. When the first, maybe 2nd generation of fuel injected vehicles arrived over 20 years ago, you still had a throttle cable from the gas pedal but it went to a throttle plate which just opened more to let more air in, then the mass airflow and temperature sensors fed the ECM (computer) this data upon which it determined fuel injection time = rate/volume.

By Calin on 9/7/2011 3:26:44 AM , Rating: 2
The FSI technology (fuel stratified injection) for gasoline engines allows to use only a part of the cylinder volume for burning fuel (the rest of the cylinder space is air). This helps reduce the fuel needed at idle (and increases the apparent fuel-to-air ratio for the entire cylinder volume)

By tastyratz on 9/7/2011 12:12:42 PM , Rating: 2
direct injection has alleviated much of the lean burn issues at light throttle but yes, you still need a certain amount. That's why I was thinking egr. if you need 1 cc of fuel for example with no egr system at all, the egr could fill 50% of the chamber and you would only need 0.5cc of fuel to achieve the same exact ratio as before. This of course is all in theory and I don't know what other issues one might run into trying to implement a system like this

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