Abstract
Lotus recent experience of a research project into a high specific output pressure charged engine is discussed. The study focused on achieving more than 75kW (100bhp) per litre from a mechanically-supercharged engine without fitting an intercooler. To achieve this, introduction of fuel before the compressor was employed, but only at high BMEPs so that part load driveability and emissions were unaffected.
This paper discusses the history of pre-compressor fuelling (principally from aero engines) and the theoretical considerations which lead to a reduction of charge temperature and compressor power consumption. For the research engine project, the paper details thermodynamic and packaging considerations leading to the supercharger choice (from centrifugal, Lysholm screw-type or Roots), and dynamometer and vehicle performance results, principally in comparison with a naturally aspirated engine of the same swept volume and approximately the same power output.
The benefit of pre-compressor fuelling is quantified in terms of density improvement in the plenum and increased knock limit, and some discussion of future development directions is carried out.