I have a 92 GSR with a B18c.out of a 94 in it. Went from B17 to B16 to now B18c. I am currently running a p28 in it with No problems and vtec engages at 5600 rms. I'm wanting to switch to a virgin p72 ecu bc of this and it's made for the setup. Today I put in a p72 and the vtec will not engage. We took the p72 and put it in a prelude and the vtec engages at 4500 rpm without a problem.... Put the p28 in and it works fine.
Both ECUs are obd1.
My knock sensor is there and hooked up. What could be causing this???