This data is very hard to find. Please note that normally is confidential and companies are normally not willing to share it.Of course it all depends on the the information you want.
If you are lookig for basic , trivial information, internet and other dissemination publications can be usefull: max vehicle spped, max noise level, power, subjective assessments...
If you need detailed engineering data, then finding it is quite difficult. Journal papers can then be more useful. Collaboration with industrial companies and research institutes in sponsored projects can also be a good approach to have access to more advanced data.