Question: what is the difference between a jdm engine and an usdm?
Answer: ALL USDM motors have a suffix number after the engine code. EX: a USDM GSR is a B18C1 and a USDM ITR is a B18C5. JDM motors don't use the number suffix so both the GSR and ITR are a B18C. It's still obvious to be able to tell the JDM GSR and ITR apart if you know the motors.