Benefits of the Electromechanical Valve Train in Vehicle Operation

2000-01-1223

03/06/2000

Event
SAE 2000 World Congress
Authors Abstract
Content
One of the most promising methods to reduce fuel consumption is to use unthrottled engine operation, where load control occurs by means of variable valve timing with an electromechanical valve train (EMV) system. This method allows for a reduction in fuel consumption while operating under a stoichiometric air-fuel-ratio and preserves the ability to use conventional exhaust gas aftertreatment technology with a 3-way-catalyst.
Compared with an engine with a camshaft-driven valve train, the variable valve timing concept makes possible an additional optimization of cold start, warm-up and transient operation. In contrast with the conventionally throttled engine, optimized control of load and in-cylinder gas movement is made possible from the start of the first cycle. A load control strategy using a “Late Intake Valve Open” (LIO) provides a reduction in start-up HC emissions of approximately 60%. Due to reduced wall-wetting, the LIO control strategy improves the transition from start to idle. A very low standard deviation of indicated mean effective pressure and very good lean-mixture driveability at low operating temperatures can be achieved with LIO during the early phase of the compression stroke. In concert with this intake approach, “Late Exhaust Valve Open” (LEO) timing during the exhaust stroke leads to exhaust gas afterburning and, thereby, results in high exhaust gas temperatures and low HC emissions. Vehicle investigations have demonstrated an improved accuracy of the air-fuel-ratio during transient operation.
Results in the New European Driving Cycle have confirmed a reduction in fuel consumption of more than 15% while meeting EURO IV emission limits.
Meta TagsDetails
DOI
https://doi.org/10.4271/2000-01-1223
Pages
13
Citation
Pischinger, M., Salber, W., van der Staay, F., Baumgarten, H. et al., "Benefits of the Electromechanical Valve Train in Vehicle Operation," SAE Technical Paper 2000-01-1223, 2000, https://doi.org/10.4271/2000-01-1223.
Additional Details
Publisher
Published
Mar 6, 2000
Product Code
2000-01-1223
Content Type
Technical Paper
Language
English