Knock Control on Small Four-Two-Wheeler Engines Robert Bosch GmbH

Format:

Conference/Event

Author/Creator:

Jahn, Jahn, author.

Contributor:

Kempf, Stefan

Schuerg, Frank

Conference Name:

2012 Small Engine Technology Conference & Exhibition (2012-10-16 : Madison, Wisconsin, United States)

Language:

English

Physical Description:

1 online resource

Place of Publication:

Warrendale, PA SAE International 2012

Summary:

Today, knock control is part of standard automotive enginemanagement systems. The structure-borne noise of the knock sensorsignal is evaluated in the electronic control unit (ECU). In caseof knocking combustions the ignition angle is first retarded andthen subsequently advanced again.The small-sized combustion chamber of small two-wheeler engines,uncritical compression ratios and strong enrichment decrease theknock tendency. Nevertheless, knock control can effectuate higherperformance, lower fuel consumption, compliance with lower legallydemanded emission limits, and the possibility of using differentfuel qualities.The Knock-Intensity-Detector 2 (KID2) and the Bosch knockcontrol tool chain, based on many years of experience gained onautomotive engines, provides an efficient calibration method thatcan also be used for two-wheeler engines. The raw signal of thestructure-borne noise is used for signal analysis and simulation ofdifferent filter settings.A feasibility quick test was executed on a water-cooled 125ccsmall engine of a mass-produced two-wheeler. Although the knocksensor position was not optimized, a satisfactory knock detectionquality was achieved across the entire engine speed range up to10,000 rpm. Without knock control an ignition safety margin of 6°CAto the knock limit is necessary due to tolerances of thecompression ratio and different fuel qualities.With active knock control, the following benefits could beachieved at the engine's standard load point of 7,500 rpm: - Atmoderate ambient temperature (25°C intake-air), a torque increaseof 3% with original enrichment or equal torque with 10% lessspecific fuel consumption at lambda 1. - At high ambienttemperature (60°C intake air), the specific fuel consumption couldbe reduced by 16% - at lambda equals unity and original torque.The benefits that are achieved by merely including knock controlto an already existing engine are only given at full loadoperation. The objective for the near future is to increase thecompression ratio of the engine to attain higher performance andreduce the fuel consumption especially at part load, by finding acompromise between performance and fuel economy

Notes:

Vendor supplied data

Publisher Number:

2012-32-0052

Access Restriction:

Restricted for use by site license