ANALYTICAL EVALUATION OF ENGINE AND VEHICLE HARDWARE EFFECTS ON VEHICLE RESPONSE. Drew Raftopoulos

Transcription

1 ANALYTICAL EVALUATION OF ENGINE AND VEHICLE HARDWARE EFFECTS ON VEHICLE RESPONSE Drew Raftopoulos

2 WHY IS TRANSIENT RESPONSE IMPORTANT? The focus on vehicle transient response has become important with the shift towards downsized boosted engines for improved vehicle fuel economy A downsized turbocharged engine requires time to build turbo boost pressure and generate torque Prior to building boost pressure, a downsized turbocharged engine behaves like a small naturally aspirated engine trying to move a large vehicle!

3 METHODS TO EVALUATE VEHICLE TRANSIENT RESPONSE Vehicle Testing Good assessment of hardware impacts Costly to complete Occurs too late to have meaningful impact 0-D Vehicle Model Reduced Cost Occurs early in program development Does not comprehend transient engine events Constant Engine Speed Load Step Occurs early in program development Analytically or Dyno Testing Engine only evaluation of torque build Does not represent a real vehicle condition Next evolution of predicting vehicle transient response System Level Vehicle Model Allows for higher fidelity evaluations Early in program development Timing Program Concept Can impact hardware decisions Too late to impact hardware decisions Production Coarse Fidelity 0D Vehicle Model System Level Vehicle Analysis Constant Engine Speed Load Step Vehicle Testing Constant Engine Speed Load Step 0D Vehicle Model System Level Vehicle Analysis Fine Vehicle Testing

4 SYSTEM LEVEL VEHICLE ANALYSIS METHODOLOGY SYSTEM LEVEL VEHICLE MODEL Uses GT-Suite to couple : A transient GT-Power engine model Load mode Crank angle resolved calculations Simplified Controls Transient GT-Power Engine Model GT-Drive Vehicle Model A GT-Drive Vehicle Model Subset of necessary vehicle parameters Road loads, mass, inertias, N/V Ratio Simplified Controls Evaluation of a wide open throttle tip in from constant speed with fixed N/V ratio GT-Suite

5 SYSTEM LEVEL VEHICLE ANALYSIS METHODOLOGY SYSTEM LEVEL VEHICLE TRANSIENT RESPONSE EVALUATION Vehicle acceleration and rate of change of acceleration (Jerk) over time Correspond to impulses that the customer will feel from the driver s seat As the magnitude of acceleration and rate of change of acceleration increase, the vehicle will have a better vehicle transient response If there is not enough acceleration, or rate of change of acceleration, then the vehicle will feel sluggish Acceleration Time

6 COMPARISON OF METHODOLOGIES The ability of the different methods to discern engine and vehicle hardware effects on vehicle transient response was evaluated with different hardware combinations Small Turbocharger Large Turbocharger Alternative Set of Cam Profiles Alternative Set of Vehicle Hardware Final Drive Ratio and Torque Converter Change Evaluations performed at various N/V Ratios High N/V = Low Gear (~0-100 KPH) Medium N/V = Mid Gear (Mid gear gradability) Low N/V = Top Gear (Top Gear gradability) Constant Speed Load Step versus System Level Vehicle Model 0-D Vehicle Model versus System Level Vehicle Model

7 CONSTANT ENGINE SPEED LOAD STEP Small Turbo Alternative Cam Target Load Slowest response is the baseline engine hardware Large turbocharger and Baseline cam profiles Small turbocharger improves response Alterative cam profiles also improves response Not as much as the small turbocharger Baseline Hardware Large Turbo Base Cam These results would suggest : Small turbocharger and the alternative cam profiles both improve vehicle transient response Small turbocharger will have a larger improvement

8 SYSTEM LEVEL VEHICLE ANALYSIS ENGINE HARDWARE COMPARISON : HIGH N/V RATIO (LOW GEAR) Alternative Cam Baseline Hardware Large Turbo Base Cams Small turbocharger Does not improve the acceleration of the vehicle Lower acceleration Longer time to peak acceleration Alterative cam profiles Improves acceleration Improves time to peak acceleration Small Turbo For this maneuver : Alternative cam profiles work best for vehicle transient response Small turbocharger is the worst Contrary to the results seen in the constant engine speed load step

9 SYSTEM LEVEL VEHICLE ANALYSIS ENGINE HARDWARE COMPARISON : MID N/V RATIO (MID GEAR) Alternative Cam Small turbocharger Same initial acceleration Builds acceleration faster Reaches peak acceleration quicker After peak acceleration, the magnitude of acceleration starts to decay earlier Overall customer experience is degraded Baseline Hardware Large Turbo Base Cams Small Turbo Alternative cam profiles Improves initial acceleration Improves the time to peak acceleration Does not degrade acceleration after peak For this maneuver : The alternative cam profiles are the best hardware set for vehicle transient response

10 SYSTEM LEVEL VEHICLE ANALYSIS ENGINE HARDWARE COMPARISON : LOW N/V RATIO (HIGH GEAR) The closest a vehicle will operate to the constant engine speed load step Results in the lowest overall vehicle acceleration magnitude Alternative Cam No significant changes in vehicle acceleration observed for the different hardware sets Baseline Hardware Large Turbo Base Cams Small Turbo

11 SYSTEM LEVEL VEHICLE ANALYSIS VEHICLE HARDWARE COMPARISON : HIGH N/V RATIO (LOW GEAR) Baseline Hardware Alternative Hardware FDR Torque Converter Double Hump Response Engine hardware held constant Constant engine speed load step is the same Suggests that a given engine hardware set will produce similar vehicle response If the engine and vehicle hardware is not integrated well then vehicle transient response can suffer Double hump response When the acceleration gradient is less than or equal to zero Degrades customer experience since it applies two separate impulses on the customer ( Turbo Lag feel)

12 0-D VEHICLE MODEL VERSUS SYSTEM LEVEL VEHICLE ANALYSIS A 0-D vehicle model can also be used to evaluate the effect of engine and vehicle hardware, but Predicted 0-D Vehicle Model Measured Vehicle Data Predicted System Level Vehicle Analysis Predicted 0-D Vehicle Model Predicted System Level Vehicle Analysis Measured Vehicle Data Not able to comprehend detailed vehicle transient Due to not comprehending transient engine events Has potential to over predict engine load and initial acceleration System level vehicle analysis also over predicts vehicle acceleration Due to modeling and control simplifications System level vehicle analysis captures the engine load response and acceleration trace better

13 HARDWARE DIAGNOSTIC WITH A SYSTEM LEVEL VEHICLE ANALYSIS Engine Maximum Torque Power to Weight Ratio and N/V Ratio Influences all aspects of vehicle acceleration Most notable prior to torque converter stall Acceleration Power to Weight Ratio N/V Ratio Double Hump Response Engine Capability Maximum torque capability Influences maximum acceleration Response capability Influences acceleration from torque converter stall to maximum acceleration Double hump response Occurs when the torque converter stall point and engine response capability are not integrated well Torque Converter Stall Time

14 SUMMARY / CONCLUSIONS Compared different transient response methods in the context of fidelity and program timing Showed system level analysis allows a higher fidelity evaluation of vehicle transient response early in product development System level vehicle analysis allows understanding of hardware effects on vehicle acceleration and rate of change of vehicle acceleration, and thus customer experience This allows early optimization of vehicle level response, performance and fuel economy

15 QUESTIONS?