Fuel economy is a top concern these days as automakers, suppliers and consumers alike strive to stretch every drop of petroleum as far as possible. Cylinder deactivation is a key way of bolstering the large-print numbers on a vehicle’s window sticker.
Today this technology is primarily used on large-displacement engines. GM’s LS V8 family as well as Chrysler’s Hemi lineup are two notable powertrain architectures that feature it, but there are many more. Still, one supplier company is working on bringing cylinder shut-off capability to much smaller engines.
Schaeffler has adapted this technology to tiny three-cylinder powerplants in a bid to decrease consumption and emissions. The German firm’s system uses specially modified roller finger followers. Normally these parts transfer the motion of a camshaft lobe to the valve it actuates.
But when a cylinder is deactivated the rocker can partially collapse so the valves remain unaffected by the camshaft; it’s pretty clever. If you’re familiar with the way Honda’s VTEC system works this is sort of the inverse of that; rather than increasing valve lift and changing timing at higher engine speeds it prevents a cam’s lobe from activating the valves at all.
When adapted to an inline-three, Schaeffler’s system shuts one of the cylinders down. But this makes us question NVH, that is, noise, vibration and harshness. A three-pot engine running on just 2/3 of its cylinders doesn’t sound like it’d be very smooth or refined. Additionally we wonder if cylinder deactivation is worth the added cost and complexity on such small powerplants. The gains can’t be all that great, though the company claims it can increase efficiency by at least 3 percent.
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[Source: Ward’s Auto]