The “i” badging indicates that the car has a fuel injection engine (Petrol) which first appeared in the E21 & E30 models.
With the introduction of the xi models in 2001, BMW brought back AWD which hadn’t been an option in the 3-series since 1991 when the E30 325iX was discontinued. BMW produced the 325xi and 330xi in the US between 2001-2005, but only in Sedan (4-door) trim.
The AWD models were well received by reviewers for giving customers in severe winter climates the option of an AWD 3-series. At the same time, the xi was criticized for its added weight, slower acceleration, decreased gas mileage, softer suspension, and poor original equipment tires.
The transfer case used in all BMW E46 xi models is manufactured by New Venture Gear, Inc., which is owned by Magna Powertrain. The NV 124 transfer case used in the E46 xi models is a full-time four-wheel-drive gear driven transfer case.
The xi models have a permanent front/rear 38:62 torque split which differs from the E46′s successor, the E9X, which incorporated BMW’s new xDrive platform. Both the front and rear differentials in the E46 xi are open differentials which are aided by DSC (Dynamic Stability Control) to control wheel spin and oversteer/understeer.
The “d” indicates that the car is a sedan with a diesel powered engine.
The “Ci” indicates that the car is a coupe with a petrol powered engine.
The “Cd” indicates that the car is a coupe with a diesel powered engine.
The “Cic” indicates that the car is a 2 door convertible with a petrol powered engine
The “T” in the “iT” badge stands for “Touring”, the BMW nomenclature for a 4 door wagon. It has a petrol powered engine.