Volkswagen’s various platforms, including the new MQB architecture, can enlist many different engines, but those engines will start to look a lot more similar. As it stands now, VW engines worldwide vary quite a bit. U.S. four-cylinders are fairly similar to the diesel variants—their intake valves are fore of the exhaust valves and the engine is canted forward. But in Europe, the EA111-series engines breathe the other way around and are canted backward.
To complement the MQB platform’s modularity and keep things more consistent, VW is developing the EA211 gasoline engine series, which will replace the EA111 series. The new engine group has a displacement range from 1.0 liter (a port-injected engine) up to 1.6. It’s the 1.4-liter turbo engine, however, that really sparks our interest. (For reference, VW’s ubiquitous 2.0-liter direct-injection turbocharged four-banger—dubbed EA888—that powers the GTI, A4, A5, et al., is actually managed by Audi.)
With 16 valves, direct injection, and a turbocharger, the basics are comparable to what we’ve seen from VW four-cylinders before. But the differences are vast and, aside from sharing an 82-mm bore spacing, little carries over. The 1.4 is the only EA211 variant we expect to get in the U.S. It will arrive first in the Jetta hybrid (more on that later), and there’s a good chance the 1.4 could replace the naturally aspirated 2.5-liter five-cylinder as the base engine for U.S.-bound Golfs. The 1.4 turbo has a slightly lower power rating than the 2.5 (140 hp versus 170) but a little more torque (184 lb-ft compared to the five’s 177), which peaks at 1400 rpm. The decision to use it more widely here hinges in part on the little bit of turbo lag the engine exhibits; Volkswagen planners fear it could be off-putting to American buyers.
Saving Weight, Wonders of the Headifold
Instead of being cast entirely from iron, the 1.4-liter block is made of aluminum with iron liners, which saves 42 pounds. Each connecting rod is about a third of a pound lighter. By lightening this reciprocating mass, the crankshaft’s mass, with better-optimized counterweights, drops from 25 pounds to 20. All told, the engine is 49 pounds lighter and delivers up to 20-percent-better fuel economy, according to VW.
The fuel-economy improvement comes from a combination of many innovations. For one, the exhaust manifold is integrated into the head. This setup reduces the distance exhaust gases have to travel before entering the turbocharger, helping fire the catalyst faster—it’s located right next to the turbo, adjacent to the cylinder head. The headifold (we just made that up, let’s see if it sticks) features its own cooling circuit. Valves in the coolant paths control this circuit’s flow. By isolating and collecting the heat in the head, this engine comes up to temperature quicker, reducing the fuel-rich environment of a cold engine and heating the cabin quicker. Conversely, when the engine is up to temp, this circuit can cool the exhaust gas about 212 degrees Fahrenheit under full load, which is a boon for emissions.
Cam Belts and Suspenders
In complete defiance of the norm, the EA211’s camshafts are driven by a belt. Yes, a belt. The advantage is less friction loss than with a chain system. The kicker: VW says the EA211’s belts are good for the lifetime of the engine. No mileage was quoted, but we expect “lifetime” to mean at least 100,000 miles. Cam phasers inside the belt-driven cogs produce variable valve timing on both the intake and exhaust for more high-end torque and improved response at low revs.
Gone is the air-to-air intercooler. In its place is an air-to-water heat exchanger that has been integrated into the intake manifold. This tightens up the packaging and, like the headifold (we’re not giving up on that name!), reduces the distance air travels between the turbo’s compressor wheel and the cylinders.
The really cool part: In some applications, the 1.4-liter EA211 will feature cylinder deactivation (called ACT in VW jargon, which translates to active cylinder management) that reduces the firing cylinders by half. This is a feature normally reserved for larger-displacement engines. This system is very similar to what is found on the new 4.0-liter V-8 powering Bentley Continentals and the Audi S8, among others. The camshafts are not honed from a solid piece of steel; instead, a splined shaft is fitted with cam profiles. The profiles for cylinders one and four are fixed with a pin, while the other two actually slide and feature two distinct shapes: one for normal operation, and a second with no profile. When the engine computer deems the middle cylinders superfluous, a tiny actuator atop the head drops a pin into a guide path, which swaps it to the blank profile. The whole process takes no more than 36 milliseconds (it’s a little quicker when engine rpm is higher).
The 1.4 can operate on two cylinders between 1400 and 4000 rpm. Engineers opted not to have the four go twin at idle because the vibrations would not be well received by passengers. If you’ve ever seen a Harley shake at a stoplight, you’ll understand what they’re avoiding—and why.
Playing EA211 Polo
We briefly drove a Polo with ACT and found the system impressive. All four cylinders pitch in for meaningful acceleration, but once you’re up to speed, two shut down. We did detect a change in the exhaust note during the switchover, but were told this car wasn’t finally calibrated. Other than that, there was no detectable change in the powertrain downsizing.
Besides the rpm stipulation, two-cylinder mode is active when the engine is asked to make no more than about 74 lb-ft of torque. Surprisingly, this amount of torque is sufficient to make moderate speed changes. Slight grades are even maintained without kicking the other combustion tubes back on.
When switching back to four-cylinder mode, there is a clear hesitation before the middle cams are realigned. The sensation does not feel like turbo lag, but more like a hybrid system restarting its gas engine. You can feel the step in power development because all of a sudden the engine is using twice as many cylinders. This is not a bad thing and it will never cause a heart palpitation when trying to thread the needle in an intersection; remember, all four cylinders are firing at idle. Again, this was an early car, so the reactivation could get massaged one final time, but in our opinion the system worked well.
Interesting too is the shift strategy that’ll be employed along with ACT. In some cases, running on two cylinders at a higher rpm in a lower gear will be more efficient than four cylinders at a lower rpm in a higher gear. Dual-clutch automatics will choose the most efficient option automatically, but manual-transmission drivers will have to pay attention to a gauge display that indicates the most efficient gear.
The Jetta Hybrid’s 1.4 Turbo
We also got some seat time in the upcoming Jetta hybrid. There, a 150-hp, 1.4-liter TSI is married to a 27-hp electric motor that is fed an AC diet from a 1.1-kWh lithium-ion battery pack, built by Sanyo. This TSI engine variant does not feature ACT cylinder deactivation, but it does have a few efficiency tricks of its own.
As is the case with other VW Group hybrids, there’s a clutch between the engine and the electric motor. This allows the engine to be completely shut down and not creating any drag while coasting or while the car is in electric-only mode.
Like the ACT-equipped Polo, the Jetta we drove was still under the protection of the prototype heading. That said, the operation impressed with its seamless switches between hybrid, gas, and electric-only drive. The seven-speed dual-clutch automatic makes no bones about shuffling through the gears as quickly as possible. Regenerative braking always has its quirks, and in this Jetta an initial regen bite felt comparable to grabby brakes. It took some getting used to and we have no doubt that final brake programing will smooth it out some.
Chances are the EA211 will be available, if not standard, on the next-generation Golf. That car rolls out in Europe later this summer and should be here around this time next year.
1 comment:
this is so creative article.
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