There are various ways to regulate the output of a variable-flow pump:
mechanical, hydraulic and electrohydraulic. In the case of the latter, a solenoid valve is used instead of the spring-loaded type. This is where PPT was able to revert to the extensive experience accumulated by affiliate Pierburg GmbH.
PPT is working on both car and truck engine projects; its oil pumps are currently installed in gasoline engines of up to 4 liters displacement and diesel engines of between 1.3 and 16.0 liters.
On commercial vehicles, the variable oil pump will deliver fuel savings of about one percent in typical truck operations. This electrohydraulically controlled oil pump ensures constant oil pressure and automatically adjusted oil flow across all engine speeds and operating conditions. As a first-tier supplier, PPT is in a position to deliver the entire assembly comprising both pump and solenoid valve.
The variable pump can also be used on systems with discontinuous or increased oil needs. The latter may occur as a result of piston cooling. In order to maintain oil flow even at low engine speeds, non-variable oil pumps would have to have a very high output. Then, at the higher speeds, much of the oil flow would have to be diverted by an overflow valve.
For its commercial vehicle applications, the company has come up with further material innovations: instead of heavy gray castings for the housing and cover and steel for the hydraulic components, these pumps have aluminum diecastings and sintered steel. This lightweight approach permits weight and, above all, cost savings.
There are a number of additional spin-offs derived from the use of variableflow pumps. On-demand lube oil supply minimizes the problem of crankcase oil foaming and the occurrence of peak pressures. As a result, the oil undergoes less punishment and oil-change intervals are lengthened. Another advantage: less noise when driving. The drawbacks normally associated with pulsation and cavitation are also abated.
In all, variable oil pumps permit improvement potentials achievable with a good cost/benefit ratio. Hence they will increasingly find a place in new generations of engines and become standard one day.
At present, PPT manufactures worldwide some five million oil pumps and is one of the few companies which, thanks to a standardized flexible assembly strategy for delivering the utmost manufacturing quality, produces these units in France, Italy, Brazil, Mexico, India, and China.