That's odd, my Si engine is a D15A3. j/k On the 1g 84-87 CRXs, the Si usually came with a sunroof, 14x5 alloy wheels, MPFI, a better geared transmission, and most importantly, a shiny badge that says "Si". If you are running in a stock class in auto-x, the Si's do pretty well and can often embarrass much *faster* cars.