So, getting this thread back on track
As I think I have mentioned, I am having a serious issue with some of the so called professionally converted looms out there, and one of the issues I will now address as it means I can lose a few wires.
The ECU controls everything, and by that I really do mean everything. The blower motor in the cabin is controlled by an ECU wire and there are several inputs and outputs that are also connected to the Air Conditioning system too. Now I know what you are thinking, a blower motor can just use a 12v supply and the air con is going to be lost anyway - but hang on a minute.
The ECU carefully monitors all of the temperatures and settings to ensure the most efficient means of running, and it even controls the outputs to the radiator fans. Its an over complex system, and to be honest a simple thermostatic switch would work just as well.
So, why am I having problems with the looms then?
The Subaru, like many modern cars, has two cooling fans. They name them as a Main fan and a Sub fan, even though they are identical in size. The theory is that one fan will come on at a certain temperature, and under other certain conditions, then sub one will then kick in for extra cooling. Sounds straight forward so far and most of these converted looms have ecu wiring and relays included to power both fans independently.
Except, that the secondary sub fan only comes into play when the Air Conditioning is running at full tilt to give extra cooling to the secondary radiator that is part of the air con system, it has little to do with the normal temperature of the water system. But if we have removed the air con system wiring from the ECU, then that sub fan system is never going to function at all - unless the ecu is tricked into thinking that the air con is indeed fitted and running the twin fans.
And this is the problem. If you trick the ECU into thinking that the air con is installed and running by grounding the signal on B136/Pin30 in order to make that second fan work, what people do not realize is that it also remaps the ecu characteristics to take into account of the extra engine loads involved by running the air con compressors. You have spent all that effort in getting the best performance out of a Subaru engine, only to restrict it by limiting the software and ignition parameters. So many conversions seem to have gone down this route and it is just wrong.
Far better to have no air con fitted, ditch the secondary fan output, run two great big cooling fans on the single output (or a separate thermostatically switched circuit) - and that will leave you to run the ECU at its optimum performance settings. As a bonus, you can also lose another bunch of wires.
On that note, my ecu diagram has now had an update.
Topic: Alternative Engine Conversions - A Closer Look at the Subaru (Read 9368 times)
