Sylva J15 Build Blog: September 2012

The wiring and dashboard design

The wiring loom needs to be installed at this stage as the inner panels need to be fitted immediately after this.

The wiring has consumed more time and effort than any other part of this project so far. This was a direct result of deciding to reuse the Puma ECU.The ECU controls among other things the progressively variable valve timing (VVT) which I definitely wanted to keep. It has the other advantage of saving you pots of cash on an after market ECU like an Omex and buying a engine wiring loom to go with it. The disadvantage of an after market ECU is that it is unlikely to control the valve timing progressively like the Ford ECU. The theory is I can get an up graded Ford ECU mapping to cope with the tuning I had done earlier in the year at Sitec Racing.

If you want to retain the PAT's (Passive Anti Theft) system then the Ford ECU from the original car must be retained. That ECU matches the keys and steering colum so be warned.

Dashboard fuse box

The original wiring from the Puma had a Central junction box that took care of all the non Starting and ECU functions. This was an overkill in terms of size and complexity that is not desirable in a light weight kit car.

I substituted my own design to replace the Central Junction box having three relay locations (only two used) and 9 fuses.

Layout drawing

The design process was as follows:
1) Produce a circuit diagram integrating the useful parts of the Battery fuse box and necessary ECU connections + the Dashboard fuse box functions.
2) Produce a wire routing table and importantly the wire size for each function
3) Make a crude loom template and start running the wires terminating in the Battery fuse box. Don't add the terminations at this point this can be done later. Tape the loom temporarily every 150mm or so with loom tape. Mark all the wire functions with labels ( I used masking tape and ball point pen).
4) Install the loom in the chassis with duct tape.
5) Design a dashboard and switch mounting plate.
6) Terminate all the wires in actual devices and test the loom. Pots's were used to simulate sensor feedback from the engine.
7) Correct the documentation so that faults can be diagnosed at a later date when we get the engine running.
8) Remove the loom and tape it up.
9) Return it to the chassis and clip it out.

The above took weeks of work and that is with a stripped down version of the Puma engine wiring loom did earlier in the year.

In the unlikely event anybody wants to follow my path I am quite willing to share all the design files.