I couldn't find any decent LED license plate bulbs for the Z4 (and had read on the board that other OEM solutions were too white or dim) I thought I'd make some of my own.
The problem with all of the white LED 501/W5W bulbs I could find is the LEDs weren't oriented in the right way. They either had LEDs facing forward or in all directions so would be pretty dim.
I wanted a white bulb without loosing any output.
The parts required are:
12 x 5050 SMD Power LED
2 x 4x21 Hole Vero-Board
2 x Rectifier Diode
6 x 180 Ohm Resistor
The diodes are there to protect the bulb from blowing if it is connected the wrong way round. The resistors were calculated to limit the LED current to 23mA - this should give a decent output whilst giving a decent life. I could have upped the current to make the bulbs brighter but the LEDs wouldn't have lasted as long. Some pictures for people wanting to DIY (please ask if not clear):
Here they are all soldered up, tested and ready to go:
The bulbs slot straight into the stock holders and fit nicely into the housings. Some pictures on the car (camera's exposure fixed to give accurate comparison):
Before:
After:
All in all pretty chuffed with the result, a bit brighter and really smartens up the back at night IMO.