This content is not included in
your SAE MOBILUS subscription, or you are not logged in.
Variable Valve Timing-A Possibility to Control Engine load without Throttle
Annotation ability available
Sector:
Language:
English
Abstract
1
A spark ignition engine's pumping loss increases over-proportionally when the engine load is reduced. Without throttling, control of the charge of the S. I. engine can be realized by variation of the intake valve opening period. Therefore, the variable valve timing has great potential for reducing pumping losses. A mechanically operating variable valve timing system has been implemented on a Porsche 924 TOP. Under both full load and part load, improvement is obtained with optimization of intake valve closing at any load and speed condition. Under low speed wide open throttle conditions, intake valve closing at the correct time causes an increase in volumetric efficiency and therefore a torque increase of up to 8%. Under lower part load conditions, fuel consumption can be improved by as much as 4%, and at idle by 10%. These improvements are the result of a 20%-50% reduction of pumping losses and of an improved combustion process due to less residual gas fraction.
Recommended Content
Authors
Topic
Citation
Lenz, H., Wichart, K., and Gruden, D., "Variable Valve Timing-A Possibility to Control Engine load without Throttle," SAE Technical Paper 880388, 1988, https://doi.org/10.4271/880388.Also In
References
- Ramiro, Gonzales-Soenz 23 5 1984 120 121
- Stojek, D Stwiorok, A. Valve Timing with Variable Overlap Control SAE Technical Paper Series 84026 1984
- Schunichi, Aoyama 16 10 1980
- Torazza, G. A Variable Lift and Event Control Device for Piston Engine Valve Operation XIV 1972
- Scott, David Yamaguchi, Jack Eccentric cam drive varies valve timing Automotive Engineering October 1980 120 124
- Alberts, Pedro Microprozessor - Based Control of Engine Valve Timing IEEF Transactions on industrial Electronics IE30 May 1983
- Walzer, Peter Adamis, Panagiotis Heinrich, Hartmut Schumacher, Volker 1986 1 15 20
- Nuccio, P. Variable Valve Timing as a Means to Control Engine Load SAE Technical Paper Series 82071 1982
- Geringer, Bernhard Technical University Vienna 1986
- Wichart, Klaus Technical University Vienna 1987
- Hara, Seinosuke Nakajima, Yasuo Nagumo, Shinichi Effects of Intake Valve Closing Timing on Spark-Ignition Engine Combustion SAE Technical Paper Series 850074 1985