Automotive

Volkswagen turns to the Miller Cycle for improved efficiency

VW is promising impressive efficiency improvements from its new engine
VW is promising impressive efficiency improvements from its new engine
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A breakdown of the tech in VW's new engine
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A breakdown of the tech in VW's new engine
VW is promising impressive efficiency improvements from its new engine
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VW is promising impressive efficiency improvements from its new engine

Manufacturers are leaving no stone unturned in the quest to improve the efficiency of their internal combustion engines. Just this week, we've seen a fastidiously engineered diesel engine from Ford and a camless engine from Qoros. Now Volkswagen, no stranger to doing whatever it takes to lower consumption (figures), has joined the party by releasing a 1.5-liter Miller Cycle engine tasked with improving fuel consumption and increasing low-down torque.

Volkswagen's engineers say there are a number of improvements that come courtesy of the improved thermodynamic efficiency associated with Miller Cycle engines. An increase in the geometric compression ratio has, according to VW, allowed for improved efficiency in the load range most customers will actually use, while the final compression temperature has been lowered through early closing of the intake valve and the expansion cooling that brings.

A breakdown of the tech in VW's new engine
A breakdown of the tech in VW's new engine

Thanks to these improvements, VW claims its new engine offers up peak torque from just 1,300 rpm, while also improving fuel economy by 1 l/100 km (8 US MPG) compared to the current 1.5-liter TSI engine.

Working tandem with these big changes to the combustion cycle are a number of small changes that, when combined, contribute to the longevity and efficiency of the engine. On the 110 kW (148 hp) version of the engine, the cylinder liners are coated with an atmospheric plasma spray to cut down on friction, improve heat dissipation and improve corrosion resistance.

The engine's cooling system has also come under the microscope, and now will make sure the water in the crankcase and engine remains stationary while the car is warming up. As well as cutting the amount of time spent without the engine operating at ideal temperature, VW says the system helps warm the cabin more quickly on cold mornings.

Although it's usually used on high end, big displacement engines, VW has even fitted cylinder deactivation to the new engine, allowing it to run as a two-cylinder under light loads.

An increasing injection pressure 350 bar has improved the mixture formation in the engine, which should also lead to lower particulate emissions.

Interestingly, the release makes it very clear the efficiency and emissions improvements are unlikely to show up under test cycle conditions, but argues that they're likely to have a "distinct impact on the customer's everyday driving."

The new four-cylinder engine will find its way into showrooms later this year in 96 kW (129 hp) and 110 kW (148 hp) guises. It's currently on show at the Vienna Motor Symposium.

Source: VW

14 comments
Mel Tisdale
Put a fly-by-wire throttle on it and it would probably be possible to increase the expansion ratio - and thus efficiency - even further, especially if the intake valve closes late instead of early. Also, whilst of no particular benefit in terms of efficiency, it might be possible to control the operation cycle such that it can run on either petrol (gasoline) or diesel, or a mixture of the two, if only to get home with it instead of being stranded, This would save a lot of strong language, not to mention expenditure, if one has filled up the tank with the wrong fuel. It would be of particular benefit to those who drive a company vehicle during the day which uses one fuel type, but commute etc. in a vehicle that runs on the other type. This is a situation that I experienced for a few years and refueling was always stressful compared to when one can operate on 'autopilot'. That said, it really is about time the car industry and the fuel suppliers go their act together and developed a way of ensuring that the correct pump was being used in the first place.
Grelly
A 235 US MPG improvement! I think not. P.S. Petrol or Diesel?
Shaggyrock
An improvement of 1l/100km is not equivalent to a 235mpg improvement. Assuming the base efficiency of the car is 5.9l/100km (2016 Jetta) an improvement of 1l/100km would equate to about 4.4 mpg. This highlights one of the issues of using mpg as an efficiency measurement, and the recent push to move to the more easily applied gallons/100 miles. 235mpg doesn't even make sense - even the Tesla has an 'equivalent' fuel economy of only 90-100mpg...
Randy Moe
"distinct impact on the customer's everyday driving." Is code for German Tech is superior to USA EPA desires. Which is possibly true.
telocity
The VW XL-1 had a 1 liter engine and achieved 240mpg U.S., so maybe a 1.5 improved engine can do that kind of MPG? Would be great if it did.
Jay Finke
Trust us ! it will get 230 mpg and is clean burning . lol
justme70
Shaggy, It's true that gallons per mile (or liters per km) is somewhat more easily applied if the objective is to gauge vehicle efficiency. However, in daily life the inverse is a better measure of how far I'm going to go on the fuel remaining in the tank. Personally, I prefer the measure that is most useful while driving, rather than the measure that is useful for internet kibitzing.
Martin Hone
Mel, not sure how using a fly-by-wire throttle would possibly have any effect other than removing hard cable or rod linkage. More importantly, where is the explanation of what the Miller Cycle actually is and why it might offer any improvement ????
William H Lanteigne
Put Miller Cycle together with camless timing and some other recent advances and maybe we could have 50 mpg (4.7L/100km) [gasoline/petrol] sedans and 40 mpg (5.9 L/100km) pickup trucks and SUVs.
Martin Leitner
A total waste of money to still invest into combustion engines!