ANN ARBOR, MI – In the powertrain world, Miller, Atkinson and Otto are well-known names of thermodynamic cycles that slightly alter the efficiency, function and power output of 4-stroke internal-combustion engines.
Volkswagen has a new name for that esteemed list: Budack.
Ralf Budack is a VW Group advance development engineer who started working in 2006 on a new combustion process that builds on the Miller combustion cycle, which was embraced years ago by Mazda.
His patented technology appears for the first time in a Volkswagen vehicle when the all-new ’18 Tiguan CUV arrives in the U.S. at the end of July with a 2.0L TSI turbocharged and direct-injected 4-cyl.
VW’s heralded EA888 4-cyl. gasoline engine family now is in its third generation, and this latest 2.0L TSI is known internally as Gen 3B, with the “B” paying tribute to Budack.
While the traditional Miller cycle closes the intake valves just before the end of the intake stroke, Budack proposed closing the intake valves much earlier. The result is longer effective combustion and faster air flow for the incoming gases, which improves the mixing of fuel with air.
A key enabler of the new technology is the variable valve timing system on the intake camshaft.
During idle and light load, the valve opening is shorter. But a heavy foot activates a camshaft lobe that keeps the intake valves open longer and lets the driver experience the engine’s full power and torque. The camshaft moves laterally within the head – like Honda’s proven VTEC valve-control system – to switch lobes.
The automaker claims an 8% improvement in efficiency and fuel economy over third-generation TSI engines without “B-cycle.”
The high-efficiency combustion technology requires significant changes, such as a redesigned head, turbocharger, balance-shaft chain, valves, valve springs, controller, exhaust manifold and main bearing. The engineers also swapped the camshaft positions and reversed airflow through the engine for better control on the intake side and to optimize the B-cycle.
The crankshaft carries over, and the block continues to be made of cast iron but required modest changes.
New aluminum-alloy pistons have a crown to increase pressure within the reconfigured combustion chambers, contributing to a higher compression ratio of 11.7:1 vs. 9.6:1 for third-generation TSI engines without B-cycle.
Fuel enters the combustion chambers faster by way of new fuel injectors capable of 2,626 psi (250 bar) of pressure and up to three injections per intake stroke depending on conditions. The injectors also were moved closer to the combustion chambers.
The B-cycle TSI engine with chain-driven dual overhead camshafts will run on regular unleaded fuel, while the outgoing ’17 Tiguan recommended premium fuel for its second-generation EA888 2.0L turbo-4.
After the ’18 Tiguan launches with the B-cycle 2.0L turbo mated to an 8-speed automatic transmission, other models, including the Passat, will get it as well.
VW presented the technical details of the new engine to journalists here and allowed test drives in pre-production versions of both the Tiguan and Passat with the B-cycle engine.
In the Tiguan, the engine churns out 221 lb.-ft. (300 Nm) of torque at 1,600 to 3,940 rpm, up from 207 lb.-ft. (281 Nm) at 1,700 rpm.
What it gains in torque it loses in power: The Tiguan’s new engine makes 184 hp at 4,400 rpm, down from 200 hp at 5,100 rpm from the previous Tiguan’s 2.0L turbo. The B-cycle engine is tuned for improved fuel efficiency, so the variable-valve system holds the power in check until the driver really wants it.
Automakers for years have extolled the virtues of “downsized” engines with fewer cylinders, optimized fuel economy and adequate power, but VW says the B-cycle 2.0L turbo in the Tiguan is part of its “rightsizing” powertrain strategy.
During this week’s media event, Passats were driven on the highway while Tiguans were taken only on off-road trails an hour west of here at the Bundy Hill Offroad Park in Jerome, MI.
On the highway, the Passat engine was confident, unobtrusive and eager to spin up when pressed. A 51-mile (82-km) trip on the freeway ended with a fuel-economy rating of 34.6 mpg (6.8 L/100 km) – impressive for a generously proportioned sedan.
On steep, off-camber trails, the Tiguan with 4Motion all-wheel drive soldiered on without a hint of protest, scampering through mud, over rocks and up sandy terrain. Fuel economy was less impressive when creeping in off-road mode, much of it in first gear.
In normal driving mode, the engine turns the front wheels until slip is detected, at which point up to 100% of available torque can be directed to whichever wheel has traction. Without slippage, the AWD system splits torque equally between each axle. The same system is arriving now on the new Atlas 7-passenger utility vehicle.
Actuated electro-hydraulically, the fifth-generation AWD system is optional with 5- and 7-passenger versions of the Tiguan. Front-wheel-drive models come standard with three rows, allowing all versions of the Tiguan to be classified by the EPA as trucks.
As VW continues suffering the effects of its diesel-engine cheating scandal, its rollout of the Atlas and Tiguan CUVs into hot segments represents a product offensive that is critical to the brand’s future.
The Atlas arrives in WardsAuto’s Large CUV segment, while the new Tiguan, assembled in Puebla, Mexico, moves from the Small CUV class to WardsAuto’s Middle CUV sector because it is 10.7 ins. (272 mm) longer than its predecessor. Both the Atlas and Tiguan spring from VW’s flexible MQB (Modular Transverse Matrix) architecture.
That opens the door for VW to introduce a new small ute sometime in early 2019, a company insider says. Until that vehicle arrives, VW will continue selling the previous Tiguan, which will be marketed as the Tiguan Limited.