I am pretty sure that both have tach's. How ever I know on CRX's 88-91 wiring is different, there as they made changes after 89 so new "stuff" in 90-91. On the Si's, i believe there is a little green arrow to tell you when to shift during economy driving, and theres a little blue plug slot in the center of the guage cluster, located on the rear for the tachometer.