I am happy to see this question because I find it very interesting myself. It is somewhat astounding that the mathematical engineer/scientist can reach a new, observable result purely on the basis of mathematics. We can call this the "mathematical method", a kind of specialized form of the scientific method, or perhaps an entirely different method altogether.
First of all, you say that there are no experiments in the mathematical method. I don't entirely agree. For example, say you plug some numbers into a formula, providing some concrete relations between observable (or notional) quantities. This is tantamount to doing an experiment, because if you had done an actual experiment, you would wind up (in the end) with a set of numbers or relations between quantities -- say, between temperature and pressue. So plugging numbers into an equation seems a bit like doing an experiment.
Furthermore, you can program the equations of scientific processes into computers and then run simulations which show the results of the theory under certain circumstances. Again, this is exactly tantamount to performing an experiment, only in this case, the concept of "plugging in a few numbers" is massively extended. In fact, with a bit more programming, you can produce graphical results on the computer screen which may duplicate very realistically the kind of visual results you would see in a laboratory. So I do not agree that mathematics is entirely devoid of experimentation -- however, the experiments it allows are not founded on the laws of reality; instead, they are founded on the specific, perhaps peculiar mathematical basis which the experimenter controls from the beginning.
Anyways, the mathematical method really provides results through the logic extension. Starting with realistic postulates and representative deductions, an equation may be established, say, for the vibration of a series of connected masses. Then these equations may be operated on LOGICALLY -- i.e. preserving the truth and integrity of the original representation -- to provide a previously "unseen" observation. The key point, in my mind, is that the mathematical research method relies on the logic structure to start with some representations -- verify the truth of these representations -- and then extend or manipulate these representations mathematically to provide previously unseen information. I could go on a lot longer but I feel this is too extensive already.