Since the early nineties when the 355 was designed, electronics have moved on somewhat. The now relatively simple but still costly CAT ECU unit would not cost anything like it did back then to manufacture now using modern techniques. With the unit still being made the same way, Ferrari have no real reason to reduce the cost of a replacement unit and certainly have no real incentive to redesign it to make it cheaper.
This is where the aftermarket comes in. The CAT ECU is "a black box" unit (quite literally as well!) - you don't need to know how it works inside in order to replicate its behaviour as long as you know the inputs and the intended outputs. It turns out this information is readily available and is in part at least officially documented and certainly documented enough for someone with a modicum of intelligence to be able to work out the remaining details.
If you open a unit up, which is quite a challenge due to all of the potting surrounding it, you'll find a rectangular metal shield with the two plugs sticking out at the ends. Inside the shield is a circuit board containing a whole bunch of surface mounted components, a couple of pots, and a couple of ICs which I think are probably op-amps. The CAT ECU is basically a voltage amplifier - the signal that comes from a thermocouple is a very small voltage and this is no good for the main ECU to measure, so the CAT ECU is put in between the thermocouple and the Motronic.
Having had problems with the slow down light on my own car and not being too keen to buy another CAT ECU (since I bought one replacement already a few years ago and it failed) I decided to see what could be done to engineer a replacement unit.
I am aware that a manufacturer of aircraft components has built a very high quality replacement solution which includes a screen that can show temperatures. This is nearly $700 US, so is not necessarily suitable for everyone, but I am advised it is a much more reliable solution than the original Ferrari one. It does present a problem though as to where to mount the screen. Those that like originality wouldn't like it (I count myself as one of those people). This unit can be found at Aerospace Logic
The articles in this section are intended to blog the progress of production of my own ECU to replace the standard one at a lower cost. Let the fun begin!