INDEX

THE METHOD OF CHARACTERITICS: description of the general aspects of the method of the characteristics and its importance in the model introduced software. Basic hypothesis and complete mathematical formulation.

BOUNDARY CONDITIONS: indication of the conditions to the contour for the cases: Communication with a known pressure environment (coming flow); Communication with a known pressure environment (outgoing flow); Closed pipe extremity; Joint type: N-part coming 1 outgoing; Pipe and pipe joint; Joint type: N-part coming 1 outgoing

THE FLOW COEFFICIENT: The complex fluido-dynamic status in the gap valve can be shown using this factor;

EXPERIMENTAL APPARATUS: description of the Soft-Engine's braked dynamometer BRAKER 150; by this dynamometer all test were made, to measure the motorcycles horsepower and torque; presentation of the new version of the Soft-Engine 4TBASE 2.0 software, by this the consequential theoretical comparisons have been effected by the simulation. In 4TBASE 2.0 all mathematical models (showed in this article) were transformed into informatical algorytms.

ENGINE TESTS: test on the APRILIA SL1000 and of a YAMAHA YZF R6 SS engines. Comparison among the Horse-power and torque measured by dynamometer and the corresponding curves produced by 4TBASE 2.0 software; discussions on these comparisons; after having noticed the extreme reliability of the software model vs the dynamometer results, the curves of flow coefficient (inlet and exhaust) computed by software were shown. Besides, the diagrams of pressures displayed during the simulation were shown also, at three notable regimes for both the engines. 

CONCLUSIONS.

This paper introduces the last evolution of 4TBASE 4 stroke engine simulation software for multi-cylinders engine, offering the possibility of ample choice for ducts and cylinders geometry. Besides, special attention has been set on the definition of the flow coefficients, considering especially the formulations, to focus the aspects of the friction losses in the gap valve; moreover it is possible to input  the flow coefficients as three-dimensional map with a friendly data input. Then, the software simulation has been validated using twin and four cylinders engine data; the bench data tests are also available for the discussion of the results.