Starting a new thread following on from Apache's one here
, to detail what I've managed to do so far to create full manual control of the auto gearbox in a 1993 KZN130. If you're going to attempt this, I'd recommend reading that whole thread to get more of an idea of what's going on. I'd really appreciate any feedback or comments, as I'm neither an expert at electronics or Surfs... (managed to melt 2 chips and blow 1 fuse while getting this far...)
I've just been for a test drive and have a fully working manually controllable auto gearbox. It's still sitting out in a messy breadboard, but working well.
ECU pinouts are available courtesy of Apache and MattF in this thread
. I've tapped into "+B" (pin number A12) for power when the ignition is 'ON', used one of the screws mounting the ECU as earth, and cut and re-directed S1 (C2), S2 (C15) and SL (C1) through my new hackery. These are the three solenoids in the gearbox. S1 and S2 control the gear selection, SL engages lockup (the drop in engine speed at approx 55mph). Lockup removes the torque converter from the loop, potentially increasing efficiency by 5-10% (similar to a manual).
The gear signals are, with 1 meaning on (12V) and 0 off (earth):
1 / 0 / 1
1 / 1 / 2
0 / 1 / 3
0 / 0 / 4 (OD)
Here are the steps I've taken so far.
First, remove the ECU cover in the passenger's footwell:
Then make 100% sure you're working with the correct ECU signals by linking them up to LEDs and driving around watching them for a while:
A hard on-off switch to change between the ECU lockup signal and a plain 12V signal shows that over-riding lockup is feasible and works in all gears:
Next was to design a small circuit to give more sensible, safe control of lockup, only allowing it in 3rd and 4th gear. Thanks to Apache, on page 2 of the thread linked above, for the circuit diagram that got this whole thing going. The button hanging off the bottom right is an LED-lit push-to-make, which lights up when lockup override mode is active. The red LED on the board lights when lockup isn't allowed (1st or 2nd gear), the green LED lights when lockup is actually selected, including when simply doing over 55mph:
This was then modified to include a 7 segment display to show the current gear, using the decimal point to mean that the gearbox is in lockup. The green and red LEDs were then removed:
This is the stereo control paddle from behind the steering wheel on an old Laguna, which I'm using for controlling the gear changes:
Finally, with the addition of some more logic chips and many, many hours of cutting jumper leads, here's a picture of the current breadboard circuit in the Surf. Note the mechanical 'on/off' switch to change between auto and manual mode, and the red led-lit push button for entering lockup on mode (works in manual or auto). The top strip of breadboard is unchanged from the simple lockup over-ride system:
A brief description of the system logic as it stands. A counting chip (CMOS 4069) is used to keep track of the current gear. I'm using offset binary, so it starts at 1 not zero: output 00 means first, 01=second, 10=third and 11=4. If for any reason it reaches number 4 or above (shouldn't ever happen), it instantly resets, and synchs to the auto box.
The chip can be preset to a set number by feeding it the correct inputs and putting the 'preset' pin to 12V. This is done continually when the main switch is set to 'OFF' (auto mode), meaning the counter follows the auto box. A relay connects the S1 and S2 inputs and outputs, so all the circuit is doing is following (and displaying) the current gear.
When the switch is moved to 'ON' (manual), the preset pin is grounded, so you stay in whatever gear it was in (can do this at any speed). The output of the counter is then translated to S1 and S2 signals, which are passed to relays to pass 12V to the output signals appropriately.
Counting above 4 or below 1 is blocked, as is counting up and down simultaneously. Most of the logic chips are working to translate between pure binary counting (the 7 segment display), offset binary counting (the counter chip) and S1/S2 modes.
One awkward thing about the counter chip is instead of having a 'count up' and a 'count down' pin, it has an 'up/down' pin and a 'count' pin. So if 'up/down' is high, it counts up, and vice versa. So if the pin is constantly pulled down, then to count up it must be pulled up before the count signal is sent.
Also, the circuit must be protected against all the solenoids and relays by diodes. All 3 solenoid outputs must be protected.
I'll draw up a full logic flow diagram and circuit diagram and post them here too when I have time.