The number designation represents the engine used(ex: n20) not the type of engine(ex: Inline 4 turbo) (in respect to the model year of course) The newest 228, 328, 428, and 528 use the N20 motor. The 235, 335, 435, and 535 use the n55 motor. The 340 uses the new B58 motor, and is NOT the 335. the B48 engine is in the…