| AVS 61st International Symposium & Exhibition | |
| Tribology Focus Topic | Friday Sessions |
| Session TR-FrM |
| Session: | Applications of Novel Materials in Tribology |
| Presenter: | Peter Lee, Southwest Research Institute |
| Correspondent: | Click to Email |
Fuel economy is one of the most important issues facing the automotive industry due to rising fuel costs, the need to conserve fossil fuel and government legislation. Although most of the energy losses are controlled through engine design, there is increasing interest in the role of lubricants in improving fuel economy. Crankshaft bearings can account for up to 40% of total engine friction due to the shear losses in the hydrodynamic lubrication regime and it is for this reason that average lubricant viscosities are reducing. However, this reduction in lubricant viscosity increases the frictional losses in boundary contacts in other engine components. In order to reduce this negative impact on fuel economy, engine manufacturers and lubricant and additive suppliers invest heavily in developing novel coatings, base oils and additives to reduce the frictional losses in these contacts.
ASTM have a test method for measuring fuel economy using a 2009 3.6L V6 General Motors gasoline engine. The fired engine test (ASTM D7589) runs for 100 hours using external lubricant heating/cooling systems and a ‘flying flush’ system for changing lubricants without engine shutdown. It compares a baseline lubricant with the test lubricant and measures the fuel economy improvement. However, such engine testing is expensive and hence all companies screen lubricants and coatings prior to running full engine tests.
Lubricants and coatings are screened in commercially available tribometers that are developed to replicate the contact geometries present in the engine. Reciprocating tribometers are used to replicate piston assembly and liner interactions and rotating tribometers are used to replicate camshafts and bearings. Test components may be standard test parts or manufactured from the real engine parts, and lubricant supply may be changed during the tests. In addition to this, engine specific test rigs are often designed and developed. These utilize real engine components operated in the same manner and in the same environment that they experience in the engine without using the full fired engine. Examples of test rigs, test parts and test results showing what can be achieved with these tribometers and test rigs will be presented.
An additional step in tribological testing is the use of single cylinder fired research engines. A specially developed test engine, capable of measuring the friction in the inlet and exhaust overhead valvetrains as well as the piston assembly will be presented along with example data.