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Cooled LPL EGR is a proven means of improving the efficiency of a Gasoline Turbocharged Direct-Injection engine. One of the most significant hurdles to overcome in implementing a LPL EGR system is dealing with condensation of water near the entrance of the turbocharger's compressor wheel. A gasoline engine, and to a greater extent a spark ignition engine running on Natural Gas, will encounter enough water condensation at some steady-state conditions to damage the compressor wheel due to the high-speed collision between the compressor blades and the water droplets. As an alternative to not utilizing beneficial EGR at the condensing conditions, the team at BorgWarner have developed a LPL EGR mixer that is effective at condensing and collecting the water droplets and routing the water around the compressor wheel. The new Condensing EGR mixer was developed from the known concept of utilizing a mild venturi section to enhance EGR delivery and mixing.

This paper gives a thorough review of the HC/CO emissions challenge and discusses the effects of different diesel oxidation catalyst designs in a pre turbine and post turbine position on steady state and transient turbo charger performance as well as on HC and CO tailpipe emissions, fuel economy and performance of modern Diesel engines. Results from engine dynamometer testing are presented. Both classical diffusive and advanced premixed Diesel combustion modes are investigated to understand the various effects of possible future engine calibration strategies.

In our introductory paper on the VEMB system (SAE 2010-01-1222) we discussed the concept of a divided exhaust period turbocharging system controlled by a concentric cam system, and we presented several fixed speed/load point sets of results that demonstrated the expected BSFC benefits. The BSFC reductions (2.5% to 4%) correlated to reduction in pumping work and to improvement in combustion phasing at knock-limited points from substantial reductions in Residual Gas Fraction compared to the conventionally-boosted baseline engine. In this paper we present additional results from engine tests in the areas of full-load performance and emissions with and without Scavenge-sourced EGR. To demonstrate the WOT performance potential of a VEMB engine, we show the effect of turbocharger matching steps, with results that exceed the baseline engine output across the engine speed range.

Diesel engines nowadays are faced with enhanced emission standards, which limit further improvements in fuel economy. In order to meet future emission regulations in a cost effective way, high levels of EGR are needed. One way of increasing the level of EGR with current technology boosting systems is to utilize low pressure loop EGR. This paper discusses the benefits of low pressure loop EGR as well as some of the challenges. A new component is presented which overcomes some of these challenges. Also, modifications to current technology compressor wheels are presented which enable the compressor wheel to survive ingestion of exhaust gas.

Control strategies for engines with multiple sources of EGR (Hybrid EGR), such as high and low pressure, have been developed and are in or near production. Next generation engines require these basic approaches be extended to take advantage of the capabilities these advanced air systems offer. This paper presents a number of the practical challenges encountered when attempting to do this control system optimization as well as proposed solutions. Engine test results showing the net improvements to emissions and transient response when using these techniques are discussed.

Prior work with the concept of dividing the exhaust process into an early and late phase has shown the potential of applying only the early stage (blow-down) of the exhaust period directly to a turbocharger or turbocharger system, and the later stage (scavenge) arranged to bypass the turbine. In this manner, the exhaust backpressure required to extract high turbine work from the engine can be isolated from the displacement phase of the exhaust stroke and thereby greatly reduce the exhaust pumping work and Residual Gas Fraction. In previously-published efforts, the challenges of valve-event control and high turbine inlet temperature have been revealed. The BorgWarner Engine Systems Group, in conjunction with Presta, has applied a cam-phaser controlled concentric camshaft system to the exhaust side of a divided exhaust port 4-valve per cylinder DOHC GDI engine, to enable variable phasing between the Blow-down and Scavenge cam profiles.

The paper presents the structure of an air system controller and its application to a modern boosted dual loop EGR Diesel engine. Results over a U.S. FTP cycle which show improvements in emissions and fuel consumption with future opportunities for increased performance are discussed. A recent application of the controller is also shown where standard engine sensors are eliminated to reduce cost and their function is replaced with in-cylinder pressure measurement combined with signal processing techniques.

As CO2 legislation tightens, the next generation of turbocharged gasoline engines must meet stricter emissions targets combined with increased fuel efficiency standards. Recent studies have shown that the following technologies offer significant improvements to the efficiency of turbocharged GDI engines: Miller Cycle via late intake valve closing (LIVC), low pressure loop cooled EGR (LPL EGR), port water injection (PWI), and cylinder deactivation (CDA). While these efficiency-improving technologies are individually well-understood, in this study we directly compare these technologies to each other on the same engine at a range of operating conditions and over a range of compression ratios (CR). The technologies tested are applied to a boosted and direct injected (DI) gasoline engine and evaluated both individually and combined.

As CO2 legislation tightens, the next generation of turbocharged gasoline engines must meet stricter emissions targets combined with increased fuel efficiency standards. Promising technologies under consideration are: Miller Cycle via late intake valve closing (LIVC), low pressure loop cooled exhaust gas recirculation (LPL EGR), port water injection (PWI), and cylinder deactivation (CDA). While these efficiency improving options are well-understood individually, in this study we directly compare them to each other on the same engine at a range of operating conditions and over a range of compression ratios (CR). For this purpose we undertake a comprehensive simulation of the above technology options using a GT-Power model of the engine with a kinetics based knock combustion sub-model to optimize the fuel efficiency, taking into account the total in-cylinder dilution effects, due to internal and external EGR, on the combustion.