Benchmarking and Hardware-in-the-Loop Operation of a 2014 MAZDA SkyActiv 2.0L 13:1 Compression Ratio Engine

Abstract

As part of its technology assessment for the upcoming midterm evaluation (MTE) of the 2022-2025 Light-Duty Vehicle Greenhouse Gas (LD GHG) emissions standards, EPA has been benchmarking engines and transmissions to generate inputs for use in its Advanced Light-Duty Powertrain and Hybrid Analysis (ALPHA) model, a physics-based, forward-looking, full vehicle computer simulation tool. One of the most efficient engines today, a 2.0L Mazda SkyActiv engine, is of particular interest due to its high geometric compression ratio and use of an Atkinson cycle. EPA benchmarked the 2.0L SkyActiv at its National Vehicle and Fuel Emissions laboratory. EPA then incorporated ALPHA into an engine dynamometer control system so that vehicle chassis testing could be simulated with a hardware-in-the-loop (HIL) approach. In order to model the behavior of current and future vehicles, an algorithm was developed to dynamically generate transmission shift logic from a set of user-defined parameters, a cost function (e.g., engine fuel consumption) and vehicle performance during simulation. This paper first presents the results of EPA's benchmarking of a Mazda 2.0L 13:1 CR SkyActiv engine. It then details the implementation of the SkyActiv 2.0L engine in an HIL test bed to represent chassis testing of an advanced vehicle configuration, which includes assumptions for a future high-efficiency transmission and reduced vehicle road loads. The engine was operated over simulated EPA city and highway test cycles to assess the greenhouse gas (GHG) emissions performance in the context of EPA's LD GHG standards through year 2025.

Air Flow Optimization and Calibration in High-Compression-Ratio Naturally Aspirated SI Engines with Cooled-EGR

“…Initial engine and intake airflow model development based upon the U.S. version of the 2.0L SkyActiv-G was conducted under an engineering services contract with FEV North America, Inc. The 2.0L Mazda SkyActiv-G GDI gasoline engine was thoroughly dynamometer tested as part of a preliminary EPA benchmarking study [2]. The resulting measured engine map was converted into a GT-Power model to study the potential application of future technologies.…”

“…The best BSFC of the Ricardo EGRB engine package was approximately 225 g/kW-hr, corresponding to a peak brake thermal efficiency (BTE) of approximately 37%. A recent benchmarking analysis by EPA of a 2015 Mazda SkyActiv-G naturally aspirated (NA) gasoline direct injection (GDI) engine showed a best BTE of approximately 36-37% [2], relatively high for SI engines. This was in part due to an ability to use lateintake-valveclosing (LIVC) Atkinson-cycle operation to decouple the knock-limited effective compression ratio (CR) from the expansion ratio available from a very high 13:1 geometric CR.…”

Potential Fuel Economy Improvements from the Implementation of cEGR and CDA on an Atkinson Cycle Engine

“…Table 1 summarizes the engine specifications. The engine was similar to a previously benchmarked engine [16] except it was optimized for the higher octane gasoline available in Europe. It utilized a 14:1 geometric compression ratio, which was an increase from the 13:1 of the North American versions of this engine.…”

“…Figure 1. Additional details of this test setup, including instrumentation, were consistent with previous EPA benchmarking programs [16]. The engine was instrumented to measure temperatures and pressures of the intake manifold, exhaust manifold, and engine oil.…”

“…To focus calibration development where it would have the most significant CO 2 reduction impacts, the engine operating range over the FTP and HwFET GHG regulatory cycles was used as a guide. A previous paper [16] investigated potential two-cycle GHG emissions for a future vehicle with the 13:1 2.0L version of this engine. This vehicle was a 2008 Mazda6 with 10% weight reduction, 20% rolling resistance and aerodynamic drag reductions along with a future 8 speed transmission.…”