Kenyu Akiyama

Cylinder Wear Mechanism in an EGR-Equipped Diesel Engine and Wear Protection by the Engine Oil

Piston ring moving zone in the cylinder is one of the most critical lubrication regimes in diesel engines. This area is susceptible to combustion substances. In particular, abnormal wear is occasionally detected due to Exhaust Gas Recirculation (EGR) system equipment. In Japan, NO/sub x/ emission requirements for passenger car diesels have become more stringent effective October 1, 1986. OEMs tend to apply EGR systems to reduce NO/sub x/ in exhaust gas. In order to identify the phenomenon of abnormal cylinder wear of EGR equipped engine, engine bench tests were conducted under varied conditions in EGR equipment, cooling water temperature and fuel sulfur content. The test results suggest that wear caused at low temperature is mainly corrosive wear attributable to sulfuric acid formed by reaction with fuel sulfur and condensed water. Engine oil additives behavior against sulfuric acid was studied for control of corrosive wear and excellent CD 10W-30 engine oil was developed by selection of additives from the viewpoint of capability to neutralize sulfuric acid. The developed product demonstrated very good wear protection performance in the bench tests using EGR equipped engines.

A study of engine oil aeration

Abstract The foaming and aeration properties of crankcase oils were investigated through the observation of foam behavior in the crankcase. Entrained air bubbles in the crankcase oil, that is oil aeration, increased as engine speed and oil temperature increased. This also depended on oil formulation. However, surface foam disappeared in high-speed conditions. It was found that the aeration performance of oils had an effect mainly on the connecting-rod bearing wear under high speed-high temperature engine operating conditions.

Effects of lubricant composition on fuel efficiency in modern engines

A bench engine test for evaluating the fuel efficiency of automotive crankcase oils using modern engines was developed. The fuel consumption was primarily proportional to the viscosity of the oils down to 5 mm**2/S at operating temperatures, indicating that the use of low-viscosity oil was effective in improving fuel efficiency. This may be because the oil film would be formed easily, since sliding parts, such as valve train systems, in modern engines are finely finished. Organo molybdenum dithiocarbamates were effective in improving fuel efficiency at high temperature. A 2.7% improvement in fuel efficiency relative to conventional SAE 10W-30 oils was achieved by the combination of low viscosity SAE 5W-20 oils and organo molybdenum dithiocarbamates under constant operating conditions with engine speed 1,500 rpm and torque 37.2 N.m

A mechanism for the needle crystal formation from magnesium detergents in engine oils

Abstract Engine oils are always formulated with overbased metallic detergents to neutralize acid and to prevent the deposition of degraded products. Among the detergents, overbased magnesium detergents sometimes form needle crystals. From research on the mechanism of needle crystal formation, we found a significant effect of water content and carbonic acid gas content in oil, and the type of magnesium detergents.