CAR report quantifies automotive’s position as a leading high-tech industry
Ford MyEnergi Lifestyle adds home energy storage

Volkswagen to intro Passat BlueMotion Concept at Detroit show; 4-cylinder with cylinder deactivation; 42 mpg highway

Passat BlueMotion Concept. Click to enlarge.

Volkswagen of America will introduce the Passat BlueMotion Concept at the 2014 North American International Auto Show in Detroit next week. Based on the current Passat that was developed specifically for North America, the BlueMotion label defines the version that has the best efficiency in the model lineup. In this case, the Passat BlueMotion Concept has a manufacturer-estimated highway fuel economy of 42 mpg (5.6 l/100 km), best-in-class among non-hybrid, gasoline-engined mid-size sedans.

The Passat BlueMotion Concept features an all-new version of the Volkswagen 1.4-liter EA211 TSI engine with direct injection and turbocharging. (Earlier post.) Additionally, this Passat also offers Active Cylinder Management (ACT) technology, previously seen on the European Volkswagen Polo and Golf models.

ACT deactivates the valvetrain on cylinders two and three for situations when the driver only applies light throttle pressure to maintain specific city speeds. This is the first inline four-cylinder engine with cylinder deactivation.

Another Volkswagen innovation that helps save fuel is the coasting function, used also on the Jetta Hybrid. As soon as the driver releases the accelerator pedal, the DSG transmission decouples the engine, allowing the Passat to roll with the lowest possible mechanical drag from the other moving components.

Additional fuel savings come from the stop/start system, which shuts off the engine when the car comes to a temporary stop. As soon as the driver lifts his or her foot off the brake, the 1.4-liter four-cylinder engine starts again. All these measures result in the manufacturer-estimated highway fuel economy rating of 42 mpg. The Passat BlueMotion Concept also delivers 150 hp (112 kW) and 184 lb-ft (249 N·m) of torque.

The Concept’s Reef Blue Metallic color will be introduced on other Passat models as well. The interior of the Concept also offers two-tone seats that carry blue dividing lines between the darker and lighter leather seating surfaces. The stitching indicates this is a member of the BlueMotion family, which has been rolled out globally since 2006 on many highly fuel-efficient Volkswagen models.



Seems like a very good alternative to a hybrid Camry or Fusion, if you drive mostly on the highway.


The VW 1.4-litre TSI ACT (cylinder deactivation system) was voted at the Engine Expo International as the “Best New Engine” of 2013.

Quote from the Internet (test drive of the small VW POLO 1.4 TSI ACT):
“Temporary shutoff of the second and third cylinders – in conjunction with an economical style of driving – reduces fuel consumption by over 0.5 liters per 100 kilometers.
Even with two cylinders the excellently balanced 1.4 TSI runs just as quietly and with low vibration as with four active combustion chambers.”

The consumption reduction comes from the fact that the two active cylinders of VW operate at substantially heavier load when the two others are deactivated.
At light loads the efficiency of the spark ignition engine drops a lot.
The bad thing with VW’s solution is that the deactivated cylinders still have pistons and piston rings reciprocating inside them consuming energy as friction.

When the VW ACT engine operates at partial loads, it pays its vibration-free quality / smoothness / quietness with the friction (mechanical energy loss) of moving a pair of “useless” pistons / sets of piston rings.

If the two deactivated pistons could be removed, the reduction of the fuel consumption would double (?), as well as the vibrations and the noise.

Unless I am wrong, the two middle cylinders of VW ACT engine are the only ones that are deactivated. What is the long-term effect on the engine after, say, 100.000 miles? Is it clever to operate at heavy load the two “worn” cylinders and leave the actually “unused” pair of cylinders idle? Does it reduce the TBO?

By the way, the “cylinder deactivation” in Diesels is not so good because the friction of the idle cylinders is bigger and because the thermal efficiency of the Diesels at partial loads is not bad.

What the VW Passat TSI ACT proves is that a single combustion per crankshaft rotation is acceptable / adequate for small and medium size cars (a four-stroke with two active cylinders has one combustion per each rotation of the crankshaft).

The same is proved by the four-stroke two-cylinder TwinAir engine of FIAT / Chrysler used in several small / medium size cars like the New Alfa Romeo Mito TwinAir. In this case (true twin cylinder engine) the absence of another pair of “driven / inactive / power consuming” cylinders reduces the friction and increases the mileage (as well as the inertia vibrations and the noise).

A well balanced internal combustion engine having one combustion (i.e. one power pulse) per crankshaft rotation seems as the future for “green” small-medium size cars.

With the cylinder-liner rid of intake and exhaust ports, the single-cylinder two-stroke PatPortLess engine at combines among others:
true "four-stroke" lubrication,
true "four-stroke" specific lube consumption,
true "four-stroke" scuffing resistance,
true “four-stroke” emissions,
and one combustion per crankshaft rotation, i.e. as much as the VW Passat 1.4 TSI ACT (at partial loads) and as much as the Alfa Romeo Mito TwinAir.

As for the smoothness / “vibration-free” quality of the single-cylinder PatPortLess, it is comparable to that of the four-in-line of VW Passat 1.4 TSI ACT and it is substantially better than that of the two-cylinder TwinAir of FIAT / Alfa Romeo (last GIF animation in the abovementioned web page).

So, would you consider buying a small - medium size car having a single cylinder engine?

Manolis Pattakos

The comments to this entry are closed.