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However, in the meantime I had stumbled upon a very interesting
little feature that James (one of the main guys behind the
Extra code variant I am using) had incorporated into the
code. This was a shift
light function, something I quite fancied in the se7en,
and this one wouldn’t cost me much to implement. The
change to the code made use of two spare pins on the CPU
(10 and 11) and you could set it to operate in one of two
modes. The simplest is a single light that comes on at a
certain rpm. The other, and the more interesting, was a
sequential shift. In the tuning software you could set an
upper and lower limit, effectively where you want the first
light to come on, and when the last one should illuminate.
If the values are different the ECU grounds the first pin
at the lower limit and grounds the second pin at half way
between the limits and then grounds both at the upper limit.
With a simple little diode logic circuit you can turn this
into three LED’s that come on at the first limit, half
way and the upper limit. To do this I soldered a couple
of leads onto the back of the CPU pins and fed them to two
spare pins on the main connector (pins 27 & 29). These
were then taken out to a separate box with the diode logic
board and some transistors which all fed a shift light array
which I made which mounted behind the steering wheel with
a coiled cable (See here).
In addition to this there are a number of extra output options
which I decided to make use of. The first couple I am simply
using to drive some more LED’s. These can be set to
activate based on many of the inputs and I am using the
coolant temp, which is illuminated until it reaches 70 degrees
– which is when I can remove a self-imposed lower mental
rev limit. The second is based on the TPS and comes on when
I have maximum throttle applied – no use at all, but
fun. These two LED’s are also fed by a couple of transistors
in the shift light box.
The last extra function is to use the output usually used
for idle control, which most modern cars have and which
involves a solenoid actuated valve to increase the engine
idle speed when it is cold or under heavy load (like air-con,
radio, lights, etc). I don’t have this – individual
throttle bodies make it a bit tricky – so this output
is wasted. The option which I decided would be interesting
was to use it instead to control the radiator fan. The idle
control valve function (Fidle) was the EDIS route for the
ignition SAW signal. By using
the relay board I was placing a relay in the way of the
signal, so I was already swapping cables around to avoid
this problem. I could therefore use a spare output pin (X11)
to feed the Fidle relay circuit on the relay board which
could then feed a high power relay to power the fan. I didn’t
figure out the need for a second relay until I tested it
all though – after the fan cut out a few times. I scratched
my head for a while before I remembered that the relay board
has some thermal cutouts– the Fidle one was cutting
out due to the load being put on it – then it was cooling
off and it would work briefly again. The addition of a separate
relay fed directly from the car fixed this.
To be able to test the above modifications I replicated
the connections on the Stim and added a number of LED’s
to indicate each of the functions.
The next part was make the shift light display housing.
I had the three stages of the shift light and two additional
warning lights. After a couple of experiments I decided
to use two LED’s per shift level to give a good shift
indication, without being too bright. This gave me 6 shift
LED’s and 2 for the warning/indications. I decided
to mount the display behind the wheel with a 15 way coil
cable to allow for the wheel movement. I couldn’t afford
for the display to stick up too far above the wheel rim
as it would interfere with the speedo and rev counter. I
used some 3mm Ali and copied the radius of the top of the
wheel. I then offset this by 15mm and this would be where
the top of the wheel would sit. I allowed for the plate
to come down as far as the top two bolt holes through the
wheel so that it could be clamped between the wheel and
the boss using some slightly longer bolts. Unfortunately
I didn’t have a large enough piece of Ali to cover
the third hold in the wheel, so I had to make a small part
that would simply act as a spacing washer in this lower
position.
Once the outline was cut out and filed to the right shape
I marked on the position of the LED’s, offsetting the
warning lamps slightly further apart to differentiate them
from the shift lights.
Once this was done all that remained was to run the coiled
cable from the shift light circuit board and fit the LED’s.
I initially painted the bracket but after a short period
it started to chip off, so I stripped it all off and polished
the bracket.
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