Analysis of the fuel economy potential of a direct injection spark ignition engine and a CVT in an HEV and a conventional vehicle based on in-situ measurements

A Toyota OPA was selected as a test vehicle as it has the components of interest: a Direct Injection Spark Ignition (DISI) engine and a Continuously Variable Transmission (CVT). In order to estimate the benefit of the DISI engine and CVT, a 2001MY Toyota OPA was tested to collect the engine and CVT maps using in-situ measurement techniques. Two torque sensors were installed into the powertrain in the vehicle for that purpose; one is between the engine and transmission and the other one is installed on the driveshaft. The overall efficiency of the engine and transmission was estimated using the measured torques and speeds during Phase 3 of the FTP cycle. The overall efficiencies of the engine at different operating modes including the lean and stoichiometric combustion modes were compared to each other. The overall efficiencies of the CVT are analyzed similarly. Finally, the measured steady state efficiency maps and emissions maps were used to predict the fuel economy and emissions of an HEV with the DISI engine and CVT.; The FTP test for the test vehicle shows that Toyota has made a remarkable improvement of tailpipe HC and NOx emissions with their second generation DISI engine. The reduction of HC emissions is attributed to the improvement in the combustion system using a slit nozzle injector. The dominant factor for NOx reduction turns out to be the catalyst efficiency. Due to the increase in the catalyst capacity, the average catalyst efficiency for NOx is improved from 67.5% to 89.9%.; The steady state characteristics of the DISI engine and CVT were collected successfully using the in-situ mapping technique. The operating range of the lean combustion was revealed. The maximum engine load for lean operation was 6 bar BMEP and the maximum engine speed was 2750 rpm. The improvement in steady state fuel consumption is about 20% at low speed and around 3 bar BMEP. The engine-out HC emissions are 2∼3 times more and the engine-out NOx emissions are one-half to one-sixth of that in stoichiometric combustion mode.; The energy losses were calculated from the measured power flows. The engine, the largest energy sink, consumes 62.3% of total energy loss during power mode and additionally consumes 11.8% more during idling and braking. (Abstract shortened by UMI.)...