For regular folk such as us – the sort of people who don't have slots penciled in on waiting lists, or colors named after them – the most exciting part of any new supercar is the cutting-edge technology that will trickle down into regular sedans within the next few years.

Such is the case with the 2.5 liter four-cylinder engine found in the Nissan Altima. Using technology originally developed for the Nissan GT-R, the Altima's engine foregoes traditional cylinder bore liners in lieu of what Nissan calls a mirror bore process.

This process involves spraying a thin, lightweight coating of molten iron onto the cylinder bores. This is accomplished by using gas to blow atomized, charged metal wire into the bare cylinders. Then, a diamond carbide tool is used to hone and polish each coated cylinder bore into a sparkling, reflective mirror shine that reduces friction.

That reduction in friction results in less wear, more efficiency, and, hopefully, improved longevity. The 2.5 liter four-cylinder in the new Altima is good for 182 horsepower, and is rated at 37 miles per gallon on the highway.

For what it's worth, the Altima also comes with a five-year, 60,000 mile powertrain warranty. It'll be a few years before we find out how this coating holds up in this application.

Those numbers are not nearly as impressive as the Altima's GT-R stablemate, but they're more than good enough for your average Altima customer – many of whom will buy, own, and drive their cars for years without realizing the technological triumph that lurks beneath the hood, just in front of them.

What is impressive is that the Nissan powertrain plant that builds these engines, located in Decherd, Tennessee, produces over 1.4 million engines per year, at a rate of up to one every 19 seconds. Even with the added complication of the mirror bore process, the plant is expected to keep up its current pace. How's that for technological progress?

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DECHERD, Tennessee – A special manufacturing technique usually reserved for supercars has found its way into the all-new 2019 Nissan Altima 2.5-liter engine.

Inside the four cylinders of the engine block is where Nissan's state-of-the-art mirror bore process is used to reduce friction and improve efficiency. The treatment, first used in the Nissan GT-R and applied to other specialty models like the Sentra NISMO, helps engines run smoothly by eliminating the need for bulky cylinder liners.

The Decherd assembly line added mirror bore equipment for the launch of the Altima – making it the highest volume application of the technology within Nissan. The team in Decherd assembles an engine every 19 seconds and is capable of building about 1.4 million engines a year.

"Advanced technology like the mirror bore process only makes sense for Nissan if we can offer it to as many customers as possible," said Jay Boyte, director of engineering at Decherd Powertrain Plant, Nissan North America. "The end result is an innovative and efficient engine made with manufacturing technology usually not available at this volume or price point," added Boyte.

The process involves spraying and polishing the cylindrical space inside the engine in which the piston moves. During the spraying phase, sparks fly as charged metal wire is blown using gas to atomize the material and coat the inside of the cylinders. The thickness of the coating only needs to be about 200 microns (0.2 millimeters) – or about twice the thickness of a human hair (100 microns) or three times thicker than a grain of salt (60 microns).

In the second stage, a special drill bit is used containing tiny bits of diamonds that were unfit for jewelry. The bit is spun at high speed inside the cylinder to polish the metal until shiny and smooth – giving the process its "mirror bore' name and the cylinder walls a reflective surface. The water applied during this stage is intended to keep the machinery and metals at optimum temperatures and reduce friction.

The Nissan Decherd Powertrain Assembly Plant is the highest-volume engine plant in the U.S., assembling more than 1 million engines annually; and nearly 13 million since opening in 1997. The 1.1 million square-foot facility is located about 90 miles southeast of Nashville and employs 1,700 people.

Nissan Decherd currently assembles engines for Nissan Altima, Maxima, Rogue, Pathfinder, Frontier, TITAN and INFINITI QX60, as well as motors for the all-electric Nissan LEAF.

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