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Old 03-05-2012, 11:12 PM   #1
Scooby Newbie
Member#: 276395
Join Date: Mar 2011
Location: Bacolod City, Philippines
2011 GVF

Default DIY Turbo Timer Installation (Apex-i unit with HKS harness)

A turbo timer is a nice DIY mod project that helps cool down your turbo by allowing the engine to remain idling for a user-defined duration even if you turn off the ignition switch, exit, and lock the car. Theoretically, it helps prolong turbo life by allowing the oil to circulate in the turbo and give it enough lubrication, as well as allowing the coolant to circulate before shutting it off. Proponents say that shutting off the engine immediately after a hard or sustained run with lots of turbo spool prevents the turbo from properly cooling off, allows the oil to "cake", and would lead to problems later on. Installing a turbo timer in a subaru engine is very controversial, with lots of debate and discussion about it since it is already for both an oil and water-cooled unit. Let's leave the discussion to another time and topic but for now, I'd like to describe the steps on installing one in the GVF if ever you decide to go the route of installing a TT.

There are several TT units available in the market. I chose the Apex-i version because I had good experience with this in my Nissan Patrol diesel SUV and it was offered at a very good price that made it very tempting. What is good about the STI is that there are several aftermarket companies that have offered a plug and play solution to installing a turbo timer. One of this is HKS, whose wiring harness allows you to merely plug it in with no splicing whatsoever. Also, the HKS harness is also compatible with other TT brands like Blitz.

Unboxed Apex-i TT unit:

The unit comes with instructions (which need good English 101 corrections) for connecting to the optional harness or if you need to splice the wires directly. If ever you decide to go the harness route, you would still need to connect 2 wires manually: black wire which you hook up to any grounded bolt, and the gray wire to the handbrake wire. I believe it is essential that the gray wire be hooked up with the handbrake wire switch since it acts as a safety measure that prevents TT activation/countdown when the handbrake is not engaged.

Picture of the HKS harness:

This project was done in conjunction with my alcantara shift and handbrake boot install so I had the consoles out already making installation easier.

The drivers side underconsole should be removed to facilitate routing the wires:

Once done, I attempted to look for the ignition harness and connectors under the dashboard only to find out that the connectors are in the steering column itself, specifically on the left side just in front of the turn signal indiator levers. My bad!

Installing it was as simple as removing the main harness connector and inserting the HKS harness in between and plug it back. The free end then goes to the control unit of the TT. Before you do this, please make sure you disconnect the battery ground.

I mounted the TT control unit on the left dashboard steel frame using 3M mounting tape. The included wires have more than adequate length for grounding and tapping into the parking brake. The gray parking brake wire was then snaked through under the dash and just above the steering column and secured with zip ties. The wire then snaked through under the center console to the left side of the ECU and tapped into the parking brake switch wire:

Tap connector (supplied with kit) to tap gray wire into parking brake switch wire:

Ground was tapped into a body bolt near the TT control unit mounting location.

Put all the trim back together. I mounted the TT unit just below the left front aircon vents. The nice thing about the Apex-i unit is that its small form factor allows it to be mounted in just bout any location. This is how it looks:

The TT can be manually turned on and off. If the engine is turned off with the parking brake un-engaged, it does not deploy. If turned off with the handbrake engaged, it engages and keeps the engine idling for the specified duration selected. Once the countdown timer has engaged, you can turn off the engine anytime but disengaging the handbrake or by holding the joystick button towards the left.

Of course, make sure the you leave your gearshift in neutral unless you are an A/T.

Thanks for looking!
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Old 03-06-2012, 01:08 AM   #2
Scooby Guru
Member#: 22035
Join Date: Jul 2002
Chapter/Region: SCIC
Location: San Diego, CA
2003 Brocoma DCab
71 FJ40, 13 DRZ400SM


ahh, such things are not needed on the wrx. a quick search would have shown that. its more of a kiddy thing. but nice write up
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Old 03-06-2012, 01:13 AM   #3
Scooby Guru
Member#: 157348
Join Date: Aug 2007
Chapter/Region: NWIC
Location: Benghazi
1996 JNCO Jorts
Stonewashed Denim


Yep. Nice writeup, but a TT is 1000% unnecessary.
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Old 03-06-2012, 01:17 AM   #4
Scooby Guru
Member#: 22035
Join Date: Jul 2002
Chapter/Region: SCIC
Location: San Diego, CA
2003 Brocoma DCab
71 FJ40, 13 DRZ400SM


Originally Posted by XanRules View Post
Yep. Nice writeup, but a TT is 1000% unnecessary.
i wouldnt say 1000% unnecessary, as everybody knows walking away from your car wile is still running "cooling off the turbo" makes the chicks wet
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Old 03-06-2012, 11:20 AM   #5
Scooby Specialist
Member#: 170439
Join Date: Jan 2008
Location: Sioux Falls, SD
I <3 Lamp


Turbo timers are only necessary on air cooled turbos, it won't hurt on a water cooled turbo at all though.
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Old 03-06-2012, 09:13 PM   #6
Scooby Newbie
Member#: 235359
Join Date: Jan 2010
Chapter/Region: International
Location: SoCal / Philippines
2004 Impreza


Nice write up doc.
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Old 02-11-2013, 10:43 PM   #7
Scooby Newbie
Member#: 201073
Join Date: Jan 2009
Chapter/Region: Tri-State
2012 WRX STI


did you have issues fitting the steering column cover after the harness was installed?
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