@Orion ZyGarian
Hi, iīm tobiīs brother!

The batterys of the "older" BMW 4 cylinders (M40/42/43/44; E46īs N4x) are located in front.
They are sitting just in front of the firewall, on the passenger side.

Newer 4-bangers (E8X/E9X) have the battery in the back, E9X has it on the passenger side of the trunk, E8X in the middle under the floor-mat.

@tobi
acual diesel engines still do have glow plugs, otherwise a diesel wonīt start.
The difference to the older ones is, that thereīs a ECU which will engage the plugs as soon the car is unlocked by the driver.
Thatīs the reason you wonīt see the "glowing wire" on the instrument cluster in modern Diesels.

Only if itīs extremely cold outside, it might be that the engine needs more time to pre-glow and youīll see the light go on for a short time.