Cold starting in spark ignition engines has many undesirable effects that can be often suppressed preheating the engine. Among different possible solutions, the best system seems to be to preheat the intake manifold by hot water. A thermochemical type storage system based on the reaction cycle of Ca (OH)2/CaO was chosen to provide the energy necessary to heat the water. Several cycles of dehydration/hydration were carried out in the laboratory both in a static reactor based on different volume bakers and in a prototype designed by the authors.Results showed that heat release characteristics remained unchanged after many cycles of operation and that the chemical product did not suffer important changes in its chemical composition. Heat exchanger behavior was adequate and might be further developed to improve its performance, and to test it during normal running in the vehicle.Although this energy storage system is still under study, the technology is easy to develop and the substance has many favorable properties.