The detailed information gleaned from running more than 100 tests annually on a unique engine enables Federal-Mogul engineers to design low-friction powertrain components.
Engineers at Federal-Mogul use the specially designed Floating Liner Engine (FLE) for piston and ring friction measurements that are virtually impossible to obtain with a conventional internal-combustion engine.
With cylinder pressures and engine loads akin to a naturally aspirated gasoline engine, the FLE architecture emphasizes a cylinder liner "floating" atop load cells calibrated to read the precise piston and ring friction force.
"With a carefully designed cylinder pressure sealing arrangement, the liner can react to friction forces, translate this to the load cells for measurement, and remain out of contact with the cylinder head to prevent any interference of cylinder pressure from affecting the friction results," Ross Gladwin, Instrumentation Team Leader for Federal-Mogul Powertrain Energy in Plymouth, MI, explained to AEI.
The ability to test piston and ring friction in a fired engine is highly relevant because without normal in-cylinder combustion, the pressure loading and thermal operating conditions would not mimic what occurs to engine components during actual usage.
According to Keri Westbrooke, Director of Engineering and Technology for Federal-Mogul Powertrain Energy, "Piston and ring friction results obtained from a non-firing environment have a high possibility of lacking correlation with those seen in a standard running engine configuration."
Recent FLE-tested products include a range of advanced piston rings, piston ring coatings, and piston coatings such as EcoTough. Introduced to the marketplace in 2010, the EcoTough-coated piston is comprised of solid lubricants, including graphite, molybdenum disulfide, and carbon fiber.
According to Dr. Frank T. H. Doernenburg, Director of Technology for Pistons and Pins at Federal-Mogul, "by using the FLE, we were able to determine that EcoTough-coated pistons show an 18% piston friction reduction compared to conventional coated pistons, and up to a 3% improvement in overall engine parasitic loss in comparison to standard coated pistons."
Federal-Mogul technical specialists typically test piston and ring variants in similar groupings for the purpose of comparing designs and component features. A test group usually spotlights one type of component so engineers can fundamentally understand that particular part's contribution to overall friction.
A typical test for an individual component spans 48 h.
Noted Westbrooke, "That time frame includes component pre-test and post-test metrology, engine assembly/disassembly, running the engine for component break-in, which entails a test schedule of varying operating points, hot test for friction measurement, cold test for NVH performance, and steady-state oil consumption measurement."
After individual component features and designs have been examined, a verification test is conducted to validate overall system performance.
Originally manufactured by Musashi Institute of Technology in Japan, the FLE provides Federal-Mogul engineers with specific information about piston and ring friction as well as NVH behaviors.
"Since piston friction and NVH performance can be in conflict, engineers and designers use the data collected from the FLE to find the 'sweet spot' between the two variables," Westbrooke said. FLE test information is also used to balance dissimilar design and performance parameters relative to ring tension, profiles, coatings, and engine lube-oil consumption.
"By measuring and analyzing the trade-offs between design and operating variables, our engineers can arrive at the best possible component designs," Westbrooke said.