Some extra info on AWI from the SA227-BC ( Metro III) AFM.
Engine: Garrett TPE331-12UA
ENGINE OPERATION WITH CONTINUOUS ALCOHOL-WATER INJECTION (CAWI)
The CAWI system may not be operated if the AWI fluid has been exposed to ambient temperatures below -24'C within the preceding one hour.
Minimum OAT for AWI operation......-6'C
Mixture Composition % of volume:
Methanol 40%, Water 60%
The approximate freezing point of the AWI fluid is -31'C (-24'F).