March 2003: Emerald ECU Part 1

The Emerald ECU is probably one of the most complex modifications under taken on the Tiger so far and so I split this down into various sections.

Preparation

The reason for fitting an electronic ECU is primarily to improve the low speed engine running and possibly the fuel comsumption. Not that the fuel consumption is an issue (19mpg is just affordable) however when you only have a 5 gallon tank long trips to Lincolnshire are taken with a large petrol can strapped to the passenger seat! There are several different programmable ECU's on the market all having various advantages and disadvantages although a couple of points steered me towards Emerald:-

A very good book published by Dave Walker (owner of Emerald)
Various other Tiger owners have fitted these successfully
- Neil Wain
- Richard Appleby
- Ian Martin (although his is an Escort Mk1)
- and others I have forgotten
You can actually talk to the people behind the company
And finally Emerald are moving from Brixton to Watton (60 miles from me!)

Once I had decided on this the unit was ordered and the real work could begin. First I had to obtain a new dizzy which does not have a mechanical advance function. The standard Sierra distributor has a set of advance weights which alter the timing as the engine speed increases. However if you used this with the ECU then the ignition timing would be all over the place as the ecu and distributor would both be trying to do the same job.

The new dizzy cost me a fiver from a local engine builder a bargain.

The next job was to obtain a suitable enclosure for the unit (if you look back at the section Heater removal you will see the work needed to prepare the space for the ECU enclosure). The enclosure is an IP65 junction box with a hole at one end for a cable gland. Because of clearance in the case the programming lead has to be permanently attached to the ecu and coiled up inside the enclosure.

Fitting

The fitting of the ECU is fairly simple as all it needs is a suitable speed signal (in my case supplied by the replacement distributor) and a throttle position sensor. The bracket is constructed from a single piece of aluminium bent into shape and bolted to the carburettor with the position sensor held on using two machine screws and a pair of rivnuts.

The replacement distributor was literally a drop in item - having made sure that the engine was locked at TDC before removing the old unit so I had a reference to work from.

Once the wiring had been made I connected up the office laptop to the ecu installed the software and set about getting it started. The first stage was to calibrate the throttle pot against full throttle which was easy, I then programmed the basic settings (distributor trigger, 4 cylinders etc) and looked ready to start the engine.

The first couple of attempts at starting produced no reaction from the car at all, until I noticed that every time the car started the Laptop said the ECU had disconnected itself. Further investigation found that the "accessory" terminal on a Ford ignition switch is disconnected when the engine starts. Not the best idea for an ECU! After rewiring the system did stay live when starting but the car still wouldn't read the engine speed.

Now at this point I had a problem - obviously something was wrong with the pickup in the dizzy, however what was wrong it could be either the power supply to the sensor or the sensor. The easiest option was to get a replacement dizzy from a scrapyard which I did - however this had seemed to have the same problem. I had a sudden flash of inspiration and phoned a friend (Neil W), he turned out to have come across the same problem. It appeared that the sensor was not obtaining enough power to operate, the solution was to run a new 12V power line to the sensor, with this done the ECU picked up the engine rotation and fitting the distributor cap resulted in the engine starting.

The next stage was to calibrate the ecu to the engine by locking the advance at a known value and moving the dizzy to match the marks on the timing wheels. So at this point the engine runs but the engine bay looks a complete mess, the cables are being tidied using a length of split flexible conduit. This is wonderful stuff all the cables are fully enclosed but the casing can be opened up to insert or remove cables as required. Once all the tiding up has been done the next stage will be to take the car over to Emerald to be rolling road tuned.

Pictures of installation