R53 Turbo Build – Part Three (Wiring, Wiring and More Wiring)

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One of the major benefits of using a standalone ECU (aside from actually being able to tune the car properly and decent throttle response!) is that the standalone ECUs usually support additional inputs/outputs above and beyond those offered in the stock configuration.

The ViPEC ECU uses an extension loom that provides the additional connections, meaning the stock wiring loom can be left well alone which, is a definite bonus.

There are a number of additional things I wanted to connect to the ECU:

Boost Switch – I wanted to be able to have two boost levels available one for use on the road and one for the track. The idea is to run about 250hp in road configuration and all of the available power in track configuration.

Traction Control Switch – Normally when I’m driving on track I disable the DSC and traction control (mainly because I don’t like the way the DSC intervenes if you ride over curbs or even get the car light over a crest). With an ECU that provides a proper motorsport implementation of traction control I’d like to be able to have switchable levels of TC depending on track/road conditions.

Oil Pressure – A critical engine parameter to monitor, the idiot light available via the standard oil pressure switch comes on at such a low pressure (less than 10psi) that engine damage will probably have resulted by the time it comes on.

Oil Temperature – Much more critical to monitor than water temperature, if the oil gets too hot it breaks down and doesn’t lubricate the engine properly.

Wideband O2 – Replacing the standard O2 sensors with a proper wideband O2 one allows some more advanced tuning features in the ECU to be used.

Boost Control Solenoid – Using a boost control solenoid will allow much more fine grained control of the boost pressure rather than just relying on the spring in the waste gate. It also means a lower pressure spring can be used so that a number of tuning techniques can be used e.g. boost per gear.

I wanted to make sure that all of the external connections were made via suitable waterproof automotive connections so nothing was hardwired to the ECU making removal relatively easy. A number of the connections are inside the car there is an additional connector so the looms can be split if required.

Although this doesn’t seem like a large number of things to wire this was bespoke to my car and I had to make the majority of the looms from scratch, it took the best part of a day to get most things in place. As part of making the additional connections required I also routed the programming lead from the ECU into the cabin (terminating in the passenger side cubby so it’s easily accessible).

The majority of the wiring was completed during the previous build session but there were a few connections that still needed to be terminated (oil pressure and oil temperature). The first job was to drop the sump and replace it with one that had additional holes tapped for the turbo oil return and the oil temperature sender. Having access to a lift has definitely made a number of the jobs much easier, dropping the sump definitely fell into this category. A number of the bolts wouldn’t be very accessible if using a set of jack stands. With the old sump removed the modified sump was fitted with a brand new gasket (or course!). The next job was to wire up the AEM 100psi oil pressure sender, an expensive but necessary choice. Trying to fit oil pressure switch, turbo oil feed and the pressure sender all on a single t-piece while still having sufficient clearance around the oil filter housing would have been very difficult with the traditional style oil pressure senders.

With the engine wiring completed only the wires for the boost control solenoid need to be finished, the power for the solenoid (the ECU proving a low-side drive) coming from the heater circuit for the stock O2 sensor.

This has been the single longest task I’ve undertaken during the build so far for a number of reasons. Firstly, I didn’t have anything to reuse from the Time Attack car and secondly it just took a long time to work out how/where to run the wires.

All that’s needed to complete the setup is configure the various external connections using the ECU software.