PCI Ring Fueling
Cosworth started experimenting with providing fuel at the turbo compressor inlet in the early 90s. They called the system Pre-Compressor Injection or PCI and they introduced it into competition on the XB. I think this is one of the factors contributing to Mansell's success.
The PCI system is basically a ring of four side feed injectors arrayed around the inlet to the turbocharger compressor. When then engine goes under load, these injectors provide a good bit of methanol (over 20% of the engine's requirements and I have heard numbers as high as 40%) which is atomized by the spinning compressor wheel and the heat generated by compressing the incoming air. It basically acts like an intercooler with the added benefit of better fuel atomization.
The system works remarkably well. When I first started looking at engine data, I really thought the inlet air temperature sensor was broken. It just sat on 68 DegF which just could not be so given that there was a turbocharger and ambient temperatures were up around 90 DegF. I then expanded the data session to look at all the data from the session including firing up in the hot pits. As you can see below, inlet air temperatures start off at about 130 DegF then rapidly fall when the PCI ring fires. With heat soak, I've seen these temperatures up in the 190s and yet they fall like a rock when you stand on the gas. Neat trick Cosworth!