Simanaitis Says
On cars, old, new and future; science & technology; vintage airplanes, computer flight simulation of them; Sherlockiana; our English language; travel; and other stuff
YOU WANT CYLINDERS? WE GOT ‘EM!
THE VOLKSWAGEN W16 is a brilliant example of modular engineering. In this world of high mpg/low carbon footprint, this 8.0-liter 987-hp engine may smack of overkill. But, like a Buckshot Betty’s Yukon Burger, it’s still a delight to consider.
The VW W engine concept; here, its W12 configuration is shown, with its twin narrow banks of three cylinders each. This and other images from Self-Study Programme 248: The W Engine Concept, Design and Function.
I gleaned scads of information from Self-Study Programme 248 borrowed from a friend whose technical knowledge I highly regard. Here are a few tidbits gleaned from this and other sources.
VW has been developing its W concept for almost two decades; its point, to achieve compact layouts for its powerplants. For example, a V configuration is roughly half the length of an inline engine with the same cylinder count and displacement. And VW’s VR idea sets these two banks of the V at a narrow 15-degree angle. The R stands for Reihen, literally string or in a line; VR standing for vee-inline.
Optimal compactness of cylinder layouts is evident.
The VR bank angle is in contrast to the conventional 60- or 90-degrees typical of V-6 or V-8 designs, these angles selected to optimize dynamic balance. These days, though, counterbalance shafts and other tricks offer more choices of bank angle.
The 15-degree layout reduces the width of an engine, compared with one of the same cylinder count but wider bank angle. Also, with alternating cylinders nestling between each other, it’s possible to design a common cylinder head with the same camshafts for each bank.
The VW VR6’s nestled cylinders share a cylinder head and double overhead camshafts. Image by Toffguy from nl.
By combining a pair of VR layouts sharing a common crankshaft, the result is a VV or W layout. Note, this is different from the three-banked or broad-arrow configuration of the classic Napier Lion engine that powered John Cobb’s classic Napier-Railton.
The 24.0-liter Napier-Railton has three banks of four cylinders in a broad-arrow design.
In the late 1990s when VW assumed Bugatti ownership, the Bugatti EB 118 concept car had a broad-arrow engine of 18 cylinders; this, in marked contrast to VW’s later W configurations. In fact, this engine shared conceptual kinship with the Isotta Fraschini Asso aero engine powering the Savoia-Marchetti S.55 seaplanes of Italo Balbo in the 1930s.
VW’s W16 evolved from the company’s earlier W engines, the latter based on pairs of narrow-angle VRs. Its first W16 powered the Bentley Hunaudière concept car. The design’s later appearance in another concept car, the Audi Rosemeyer, preceded its use in the limited-production Bugatti Veyron.
The Bugatti Veyron is powered by a Volkswagen-designed W16 engine. Image by Florian Linder (User: SuperFloh).
In true modular fashion, many components of VW’s VR and W series are identical, for example, much of the valve gear. W engine designs have appeared in a variety of VW Group cars, including the VW Passat W8; W12s in the Audi A8, Bentley Continental, VW Phaeton and VW Touareg; and the Bugatti Veyron W16.
The four overhead camshafts of a VW W engine are driven by chain. Much of this hardware is common to W8, W12 and W16 engines.
VW chose an angle of 72 degrees separating the two VR banks in its W8 and W12 designs; the W16’s separation angle is 90 degrees.
As the car’s nomenclature suggests, the Bugatti Veyron 16.4 has VW’s 7993-cc W16 teamed with four turbochargers. Its four valves per cylinder lurk in the engine’s 8.0 WR16 64v4T designation, 4 times 16 equaling 64. And if the Veyron’s 987 hp is deemed inadequate, there’s also the Veyron Super Sport with 1183 hp.
As a concluding note, VW’s 63-page Self-Study Programme 248 ends with a 14-question quiz. Answers are provided. ds
© Dennis Simanaitis, SimanaitisSays.com, 2016
Simanaitis Says 
Wouldn’t it be fun to see Bob Lutz of Cadillac Sixteen fame, in this modular playpen?