27 July 2012

First things first: Why install a turbo timer...

A "Turbo Timer assists in cooling down the turbocharger to prevent oil coking in the centre bearing cartridge assembly. Oil 'coking' occurs when a turbocharger is not properly cooled down and the oil that normally lubricates the centre cartridge heats up and forms solidified oil deposits. A turbo timer allows an engine to idle for a preset amount of time after the ignition key has been turned to the off position and removed. By allowing a turbocharged engine to idle, oil continues to pass through the turbo until it has cooled down to the point where oil 'coking' will not occur." - taken from HKS website.

The turbo timer I chose to install is an Apexi, which can use the O2 sensor voltage to automatically determine the amount of time needed for the turbo to cool before shutting off. However, as my truck is a manual, it doesn't have an O2 sensor, so this function doesn't work for me.

The timer comes with a relay box, and a control unit.

I mounted the control unit at the top right-hand corner of the windscreen using double sided tape, and ran the wire from it behind the plastic trim on the A-pillar, to the relay box under the dash. The trim on the pillar comes off by simply pulling it away from the pillar.

Timer control unit:

There are six wires coming out of the timer relay box (excluding the one leading to the control unit). One of these (white) goes to the O2 sensor, so I just taped it up.

The rest of the wiring can best be explained by a diagram (found online somewhere):

Here is the pin-out of the ignition switch of the Navara, looking into the connector from the ignition side:

Following from the two above images:
Red goes to pin1 (constant 12V), Blue to pin2 (Acc +12V), and Green to pin3 (Ignition +12V).
Black wire goes to ground, which I just connected to a bare piece of metal under the dash (if using O2 sensor, this should be connected to ECU ground).

Here's a photo of where I tapped into the wires at the back of the ignition (I made a short harness so that I can disconnect the turbo timer at any time, and I used a black wire with red stripe instead of green):

The grey wire needs to be connected to the handbrake for safety and security, so that the engine will switch off immediately when the handbrake is down (or cut out if someone tries to drive off while the truck is still running). I ran the wire from the relay box to the centre of the dash and back under the centre console. The supplied wire was just about long enough to reach.

To access the handbrake switch, the cup holders in the centre console just have to be pulled straight up. The single wire connected to the handbrake switch has a clip on the connector to stop it slipping off (visible in the photo below). It's a very fiddley job to get this off because of the restricted space, but it is possible to lift the clip with a finger nail. There is a little plastic tab on the top of the connector, which when folded back exposes a little bit of metal of the connector. That was enough for me to solder the wire from the turbo timer to it.

The turbo timer will work as it should at this stage. However, with the engine running, the remote locking will not work, so you either have to lock the truck by putting the key in the door lock, or stand watching the truck until the engine switches off, which defeats the purpose of the timer.

After studying the service manual, I found that the Body Control Module controls the remote central locking. The BCM disables the remote locking when it gets a signal to say that the key is at positions Acc, On or Start. These signals are input to the BCM at pins 3 (On or Start) and 4 (Acc or On). To get the truck to lock remotely while the turbo timer is counting down, I had to break these signals to the BCM because, although the key has been removed, the turbo timer keeps those signals on. There is a key switch inside the ignition cylinder, which tells the BCM if the key is in the ignition or not (pin 5 into BCM). I used this switch to control a relay which will open, breaking the wires to pins 3 and 4 on the BCM, when the key is removed from the ignition.

Here is a photo of the wires to pins 3 and 4 after I've cut and stripped them to attach the relay:

Here's the little board with the double pole single throw relay (at the back of the board) and all the wires attached. Yellow and blue wires are the two opened/broken by the relay. Red is from pin 5 of the BCM, the key switch, which I use to switch the relay on and off, and the black wire is ground, which I connected to the ground connection on the transfer control unit, beside the BCM. (Second photo below).

Here's the box I enclosed the board in for protection:

When I was working on the BCM, I managed to activate the immobiliser more than once. Each time I solved it by disconnecting the battery for 10 minutes or more, but if you permanently activate your immobiliser, don't blame me! I would recommend disconnecting the battery before starting any of the work I've described above. I needed the battery connected while I was working, as I needed to verify that signals were what I thought they were. Hopefully, with this how-to, that won't be necessary for anyone else.

I hope this helps anyone planning to install a turbo timer. If anyone has any questions or wants any help, feel free to ask.
If you like the blog and would like to be notified when I post new content, you can subscribe to my mailing list.

Flag Counter