Browse Publications Technical Papers 2007-24-0062
2007-09-16

Fun to Drive and Fuel Economy: the New 1,4 16v Turbo Gasoline Engine from FIAT Powertrain Technologies 2007-24-0062

The present work describes the characteristics and the main development issues of a new 1.4 dm3 gasoline turbocharged engine. The main driver for target definition is “high effectiveness in terms of overall performances and cost” which, in other words, is: high output at low engine speed as well as at rated speed; fast transient response; wide lambda=1 operation; “smart simplicity” for the architecture; no major impact on the machining lines. This engine had to be suitable for sport vehicles as well as for downsizing applications, so to replace a 1.8 dm3 engine, with much lower CO2 emissions levels, mass and cost.
The main performance are: max. BMEP 22 bar at 3000 rpm, with about 20 bar at 1750 rpm; specific power 83.3 kW/dm3 at 5500 rpm. These results are obtained with a MPFI injection system, fixed cam timing and single scroll turbine, with RON 95 gasoline. The limit for turbine inlet gas temperature is 950 °C.
In order to reach the performance and efficiency targets with such a standard equipment, a big effort was spent during the development phase, in order to optimize the combustion behaviour and knock resistance, which are the focal points for boosted engines. In fact knock tendency forces to retard spark advance with respect to best setting, hence limiting combustion efficiency and raising exhaust gas temperature; since this latter must be limited at safe levels for exhaust valves and turbine reliability, then air-to-fuel ratio must be set quite rich, thus combustion efficiency results further lowered.
A comprehensive development activity was carried out, concerning combustion system, intake and exhaust manifold, cam profile and phasing, intake system, engine coolant circulation and, of course, turbocharger.
Deep investigations were done simulating the whole thermodynamic cycle and injection phase with 3-D CFD techniques, as well as the engine cooling circuit.
Thermo-mechanical analysis was performed in order to assess the stress levels of cylinder head, cylinder block and piston, Intake ports and intake manifold optimization at flow-bench and at engine test bed was done, in order to reach the best possible compromise between volumetric efficiency and in-cylinder charge motion, considering also its behaviour along crank angle position. Finally mixture preparation quality and knock tendency were also studied using a single cylinder engine with optical access.
The very good results in terms of combustion behaviour allowed to adopt a very small turbocharger which, together with optimized induction system, exhaust manifold and cam timing, resulted in very good transient response. Also a wide lambda = 1 operation range was obtained allowing high efficiency and low emissions also in off-cycle operation.
The engine described here was developed and industrialized in 18 months only, and put into production in April '07, to be installed in several B and C Segment cars by FIAT Auto.

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