Whenever a customer buys a vehicle from the General powered by the 5.3 liter Ecotec3 V8, they might have a bit of a difficult time spotting every polished part on the engine.
That’s because in this Ecotec3, General Motors uses a precisely polished crankshaft to keep the tolerances to within “the width of a human red blood cell,” according to a press release. That allows for a range of variation within 8 microns, an unfathomably small span.
Not all polish is for appearance’s sake, of course. As gearheads, we all know this, being already familiar with the concept of porting and polishing cylinder heads to optimize air flow and fuel atomization within an internal combustion engine. But General Motors’ process of polishing the crankshaft doesn’t have performance and efficiency necessarily within its cross-hairs. Instead, it’s all about durability.
As Tonawanda Engine Manufacturing Engineer Anthony Lewandowski explains: “When a truck’s tachometer says that its engine is comfortably cruising at 3,600 RPM, that means a crankshaft is revolving 60 times each second inside its bearings on a thin coating of oil. Micropolishing the crank’s journals improves this oil film’s consistency to reduce friction and improve the EcoTec3’s reliability and durability over the life of the truck.”
To accomplish this level of life-extending precision, the polishing process is automated; even after the shaft looks smooth and shiny to the naked eye, 80 micron microfinishing tape is taken to the part, while it’s automatically rotated back-and-forth until an electronic sensor verifies that the crank is within this tight tolerance range. Even a small temperature change of a couple of degrees Fahrenheit within the manufacturing plant is accounted for, and the sensors recalibrated as needed.
The Tonawanda Engine Plant in New York puts out about 900 of these finely-polished Ecotec3 crankshafts per day.