Aumento de potência com baixo custo através de indução forçada com turbocompressor centrífugo em motor da década de 90

Abstract

The average age of the Brazilian vehicle fleet has been steadily increasing, which sustains a significant market for modifying vehicles from the 1990s and 2000s for recreational use. Engines from this period, designed as naturally aspirated units, have their power output limited by the intake air mass flow rate, a constraint that can only be overcome by increasing intake air density. This work presents the design, fabrication, installation and calibration of a forced induction system based on a centrifugal turbocharger applied to a BMW M50B25TU engine, converted to hydrous ethanol and managed by a Speeduino open-source programmable engine control unit, aiming to double the original power output and sized for an intake gauge pressure of up to 100 kPa. The use of components available on the Brazilian used- parts market was adopted as a cross-cutting design constraint, in order to ensure low cost and replicability. The sizing procedure covered the fuel system, the compressor, the turbine housing, the wastegate valve, the exhaust manifold, the pressurised piping and the intercooler, with analytical verification of each component. Tests were carried out on an inertial roller dynamometer developed during the project, across four successive configurations: baseline, ethanol and programmable engine management conversion, boosted operation at 25 kPa, and boosted operation under electronic boost control. A progressive performance improvement was observed, rising from 201.3 hp and 261.2 N·m in the baseline configuration to 409.2 hp and 489.7 N·m in the final configuration. Ignition timing was maintained at maximum brake torque under all wide-open-throttle conditions, with no knock limitation, confirming the margin provided by hydrous ethanol in an engine with a 10:1 compression ratio. The first failure observed was clutch slippage, a non-destructive failure mode anticipated during the design phase. The metrological limitations of the dynamometer are discussed, whose evidence of overestimation restricts the validity of the results to relative comparison between configurations.