Water injection in exhaust to reduce backpressure

[robbilau]

I wanted to throw this out there because I know it's done in the marine/boating world. By injecting into the exhaust the effective exhaust length is tuned.

I'm wondering if it might help spoolup by reducing backpressure after the turbo. The injection pattern would be the reverse of usual, say only at WOT or high throttle and tapering off with rpm. Not sure if this could be done in the downpipe since it would travel through the catalytic converter or if you'd have to inject after the cat.

Has anyone heard of this being done on cars?