.The object with this paper is to give performance data for an ISG (Integrated Starter/Generator) which is mounted around the flywheel. With regard to weight, the ISG concept shall be competitive compared to a system with conventional components. The comparison will be based on a 48 V DC-system, and performed for a vehicle which is heavily equipped with electrical loads.The paper focuses on the electrical machine in the ISG (which is of induction type). The convertor is only covered in brief.For design of the start system, a computer program for simulation of a start sequence is used. Models implemented in the program will be discussed. A simplified equation for the load torque during cranking will be explained.For design of the generator system, two different drive cycles will be discussed. One is more related to the traditional load-balance situation during city driving, and the other related to the new load-balance obtained with the characteristic of an induction machine.The results will indicate dimensions of a flywheel-mounted ISG which is competitive with conventional technique.