I haven't been able to track that down well enough to see it confirmed independently by a 2nd source. Have seen it estimated at 0.63 - 0.82
GM-X series = IHI RHC6
It's a fairly old design. There are comp maps & other data on IHI's website, but the newer designs in the same wheel diameters/framesize, that the newer info on the updated models isn't really good data for the old RHC6.
I'll PM you a link to one of the better forum discussions I've found on it.