Originally Posted by theotherguy
Are the pinouts on a hydra 2.1 the same as the pin outs for a hydra 2.5? I have both and I'd like to remove the hydra 2.1 for a sohc engine in a 2001 RS and reuse the adapter harness on a hydra 2.5 for a wrx engine and re-install it into the 2001 RS. The sohc engine is broke and I have a complete wrx motor ready to go.
Yes the wiring used for the 99-01 RS 2.1 Hydra is the same as the 2.5 Hydra for 99-01 RS.
WRX Hydra will work in the RS as long as you are running the WRX engine, not an RS engine. RS engines require different cam/trigger signal conditioning, therefore the EMS is physically different.