Federal-Mogul’s new crankshaft seal design

Federal-Mogul Corporation has developed an innovative new seal design called MicroTorq that reduces friction by up to 70 percent versus conventional lip-type seals. The new seal can provide an improvement in vehicle fuel economy of up to 0.49 percent and a reduction in CO2 emissions of 1-2 g/km compared to traditional seal designs.

The seals are also easier to install, more accommodating of shaft misalignment or eccentricity, and require less package space. The many benefits can be achieved even on existing engines as the new seal can be utilised without changing the design of adjacent components.

The friction contribution from a pair of conventional crankshaft oil seals can account for up to 3.5 g/km of a vehicle’s CO2 output, depending on the sealing technology, even at modest engine speeds of around 2000rpm.

“By adopting a fundamentally new design approach, we have developed a family of low friction seals that offer vehicle manufacturers a simple, cost-effective and easily implemented route to reduced emissions and improved fuel economy,” said Larry Brouwer, director, Sealing Technology and Innovation, Federal-Mogul Powertrain Sealing and Bearings. “There are very few technologies that offer such an affordable route to CO2 reduction, making this an extremely attractive solution for all vehicle manufacturers.” Friction occurs because conventional lip seals are preloaded against the crankshaft to maintain sealing when the crankshaft moves within the bearing clearance under varying load conditions.

As well as consuming energy, friction at the seal’s lip creates heat that degrades the oil, causing a build-up of carbon that destroys the hydrodynamic function of the seal lip, leading to oil leakage. The MicroTorq seal overcomes these problems by virtue of its innovative ‘dual-hinge’ lip design that allows the main sealing element to maintain uniform contact with the shaft under conditions of varying geometry while maintaining a light contact load at both the main lip and the dirt excluder lip. Unique hydrodynamic features moulded into the seal are shaped to efficiently pump oil back into the engine while the crankshaft is turning, and provide static sealing when it is not. The MicroTorq seal is also equipped with a piloting foot that allows error-free installation every time, without the use of special tools, simultaneously simplifying the assembly process and improving installation robustness. Additionally, while conventional seals require 7-10mm of axial space on the crankshaft, the MicroTorq seal can be packaged in under 5mm, contributing to the design of compact lightweight engines.

Federal-Mogul has carried out extensive validation and durability testing on the new seal technology. Dynamic tests at various speeds showed MicroTorq to generate approximately one-third to half the friction torque of conventional seal designs on average, while pressure/vacuum testing and air sealability tests demonstrated substantial benefits for the MicroTorq design. When conventional crankshaft seals were replaced with MicroTorq seals, calculated fuel consumption yielded improvements between 0.25 percent for a compact car equipped with a two-litre engine and a six-speed automatic transmission and 0.49 percent for a V8 pick-up truck.