Comparing the Performance and Limitations of a Downsized Formula SAE Engine in Normally Aspirated, Supercharged and Turbocharged Modes

Abstract

This paper compares the performance of a small two cylinder, 430 cm 3 engine which has been tested in a variety of normally aspirated (NA) and forced induction modes on 98-RON pump gasoline. These modes are defined by variations in the induction system and associated compression ratio (CR) alterations needed to avoid knock and maximize volumetric efficiency (η VOL). These modes included: (A) NA with carburetion (B) NA with port fuel injection (PFI) (C) Mildly Supercharged (SC) with PFI (D) Highly Turbocharged (TC) with PFI The results have significant relevance in defining the limitations for small downsized spark ignition (SI) engines, with power increases needed via intake boosting to compensate for the reduced swept volume. Performance is compared in the varying modes with comparisons of brake mean effective pressure (BMEP), brake power, η VOL , brake specific fuel consumption (BSFC) and brake thermal efficiency (η TH). The test engine used in experiments was specifically designed and configured for Formula SAE, SAE's student Formula race-car competition. A downsized twin cylinder in-line arrangement was chosen, which featured double overhead camshafts and four valves per cylinder. Most of the engine components were specially cast or machined from billets. Experimental results showed BSFC or η TH values in the order of 240 g/kWh or 34% could be achieved. TC BMEP values in the region of 25 bar were also achieved, the highest recorded for small engines on pump gasoline [1]. The engine was installed into successive Melbourne University Racing (MUR) vehicles in 2003 and 2004, where it was very competitive, finishing first in the fuel economy event at the 2004 Australasian competition.

Contribución a la Mejora del Margen de Bombeo en Compresores Centrífugos de Sobrealimentación

“…Esto no ha pasado desapercibido para los fabricantes de automóviles que han ido implementando estos sistemas debido al extraordinario rendimiento final que se obtiene del motor diesel. Respecto a los motores de gasolina sobrealimentados, aun quedan problemas por resolver, como son: la alta temperatura de los gases de escape, el bajo rendimiento y lograr un aceptable comportamiento desde el punto de vista de la conducción [9]. Pero también en este campo hay nuevas soluciones técnicas que hacen que ciertos expertos se aventuren a predecir que de aquí a 10 o 20 años, los motores sobrealimentados dominarán el mercado [50, …”

“…Esto a su vez ocasiona un incremento en el costo de fabricación, que repercute de forma directa sobre el consumidor final. Y además también, se acrecienta cada vez más la complejidad de los sistemas de control del motor, con las asociadas desventajas que esto ocasiona [9].…”

Highly Turbocharging a Flow Restricted Two Cylinder Small Engine - Turbocharger Development

“…From the process used to accomplish the project objectives, a variety of interesting findings have been discovered [1,2,3,4,12]. This paper focuses on turbocharger implementation, in particular the development needed to control oil consumption in throttled compressors, featuring piston ring type oil seals.…”

“…Brake power could also be increased, as the maximum mass flow was limited by the mandatory 20 mm diameter intake restriction. If the restriction could be choked, delivered power would increase due to the reduction in frictional losses associated with the smaller capacity [1,2,3,4,5].…”

Desenvolvimento de um motor de combustão interna para Fórmula SAE

“…A Figura 7.5 mostra o resultado computacional do torque ao longo do ciclo motor aplicado ao virabrequim para o motor Formula SAE operando em plena carga, a 6000 rpm, sobrealimentado, com IMEP de 24 bar e torque no eixo de saída de 70 N.m. Tal condição de operação é considerada extrema para o carregamento sobre os componentes mecânicos do motor e para o controle de detonação da mistura ar/combustível, conforme apontado por Attard et al (2006), e será tomada como referência para o dimensionamento do novo motor Formula SAE.…”