Original post
8 years ago

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Low Cost Shift Light for BMW E30

johna posted 8 years ago

A shift light is one or more lights that warn you that you are approaching, or have reached the maximum engine speed.

I wanted to fit one to my car and decided to build my own using an electronics kit from Jaycar Electronics (Australia). There are shift lights available off the shelf but I wanted to choose how and where it was installed, and I thought I could build one myself for much less.

First I purchased Jaycar kit KC5265 which is called Rev Limiter / Gear Shift Indicator Kit for Cars. It has three lights, two green and one red, and all the components can be mounted in one box (not included in the kit) if you like. Its front panel contains a power switch, the three lights, and four potentiometers for adjusting when the lights come on.

I chose to fit the lights in a small custom made display mounted at the top of the instrument cluster. The rest of the components are mounted in a box installed out of sight above the engine computer.

The kit can also connect to an optional rev limiter kit but that is not needed on a 318is because the engine computer already does that, of course.

The kit requires power (12V DC), ground and an engine speed signal.

I connected power to the cigar lighter, and for engine speed, I connected to the tachometer input of the instrument cluster. Unfortunately when it was connected the tachometer stopped working so some components in the kit had to be changed to make both work.

Parts Required:

• Jaycar Kit, part number KC5265.
• Box, if required, for mounting circuit board, switch, etc (use Jaycar HB-5970).
• 5.6K 1/4 watt resistor.
• You may also want an additional box and wire for fitting the lights remotely, as I have done.

Instructions:

• Construct the kit according to the instructions and assemble for the low voltage input option, but do not install the 1k resistor on the low voltage input or the 10k resistor closest to the ignition coil/points/hall effect input.
• Fit a 5.6k resistor in place of the above mentioned 1k resistor.
• Connect the 12V and ground (0V) where you like (the cigar lighter is a fairly simple choice).
• Connect the engine speed input to pin 7 of C1, the connector on the back of the instrument cluster closest to the tachometer.
• Calibrate it according to the instructions and your personal taste, for example, first light on at 5750, second on at 6000, third at 6250.

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