Auto gearbox modification

[Apache]

Have you thought about putting an standalone tranny computer as I'm doing? It's cheap and you can configure almost everything...

David

No. If I couldn't do it myself, I wouldn't bother to be honest. I'm basically only doing it for interest's sake, because I like messing with the electronic side of things.

One thing I have noticed though, even with the just the basic manual lockup switch connected, is that I do get a noticeable improvement in fuel economy on long runs.

Normally when I fill the tank to the 'clunk' on the pump, I get around 50 miles before the fuel gauge needle gets to the last mark on the scale, using the lockup in 3rd and OD down to about 1500rpm (use the OD button to shift between the gears) I managed 65 miles to the same point! I haven't been able to do a definitive comparison as yet as I dont do too many miles, but on my next trip up 100 or so miles of the A49 and back, I'll check it again.

[KERRSURF]

sounds promising Andy, let us know how you get on.

[joedude]

Any new developments on this?

I'm thinking of installing a simple lockup switch in my surf cause I'll be doing an 800km trip where I'll be pulling a trailer with all my stuff in it. (not sure on the weight, but It'll be plenty) I don't have the electrical knowledge to build that circutry with the bells and whistles mentioned previously - As long as I remember to flick the switch off when I stop!

Any suggestions on this? I figure the lockup switch would stop my trans from switching in and out of lockup which should avoid an overheat potential right? Also won't have to do the trip with OD OFF, therefore increasing my MPG?

Thanks!

[Apache]

TBH, no.

I kind of got sidetracked, and my winter 'fiddling' time evaporated! It's another of those "will get round to it one day" projects.

However, the simple lockup switch is dead easy. Matt F's site has data on the ECU (exact wiring depends on which one you have) and it really is just a simple matter of applying 12v to the lockup solenoid / disconnecting the ECU output.

Mine is still wired in and still used on long A-road trips when the traffic speed is up and down between 40 - 60mph. The 3.0 is completely happy in top / lockup down to 40ish on the flat, and it does seem to help mpg a little. Kickdown still works, and feels like a manual box as the downshifts / upshifts are harder because the TC is locked up.

[adpsimpson]

Andy, here's what I've managed while trying to mimic your setup.



I've made a slightly different circuit, using just a triple NOR gate and copying your setup with the switch, debouncer and flip flop. I've stuck some LEDs on to tell me what's happening, including one in the switch (LED1 in the diagram), one for each of solenoid 1 and 2 (LED2 and 3), one for when the vehicle decides to go into lockup normally (LED4) and one for when lockup is active (LED5). I've not go the brake signal in there yet, but it will go to pin 4 of the NOR gate.

When I short the lockup input and output signal together and don't provide the 12V input for the solenoid, the LEDs all do what they're meant to. Activating the override lights LED5 in 3rd and 4th gear. But when I set it up as in the diagram, I can drive away normally, engage the override, and it works. But I can't then disengage it. The button still seems to be working, but the solenoid 1 LED lights dimly no matter what state it's in, and the relay stays activated.

I suspect I should be limiting the current through the lockup solenoid as its resistance is only about 12 Ohms. I think the problems are because I am basically shorting 12V to earth while it's active. Did you have a resistor between the 12V supply and the solenoid? Any other ideas what could be happening?

[BUSHWHACKER]

Blimey!
Wouldn't it be easier to buy a manual gearbox?

[adpsimpson]

Aiming for a manual override on the automatic gearbox - best of both worlds

Should in theory be pretty simple. Off to speak to an electronics guru at work now to see what he says...

[adpsimpson]

To keep the thread updated, he suggested putting a diode between the solenoid output (lockup out) and earth, as the solenoid may be causing inductive spikes which could keep the mosfet open, causing the NOR gate to behave badly.

Makes sense, I'll try it this evening and post back.

Apache, did you ever build your circuit, or just install a simple flick switch? I've got that in just now and it works, but isn't exactly nice at low speed.

[BUSHWHACKER]

Aiming for a manual override on the automatic gearbox - best of both worlds

Should in theory be pretty simple. Off to speak to an electronics guru at work now to see what he says...

My Celica is semi-automatic (Tiptronic) Fully auto or select 'D' then across into 'manual mode' and change up and down gears with buttons on the steering wheel.
When driving in maual mode and I approach a junction, the transmission automatically downhifts back to first which is a nice feature.
I'll see if there's a wiring diagram for it on my workshop CD, might be of some use to you whiz kids.

[Apache]

To keep the thread updated, he suggested putting a diode between the solenoid output (lockup out) and earth, as the solenoid may be causing inductive spikes which could keep the mosfet open, causing the NOR gate to behave badly.

Makes sense, I'll try it this evening and post back.

Apache, did you ever build your circuit, or just install a simple flick switch? I've got that in just now and it works, but isn't exactly nice at low speed.

Didn't get around to building it. Too much else on my plate really.

However, I expect your mate is on the right track in that the loads are causing odd responses from the gates. Can you get your hands on a scope and have a look at the gate inputs while the system is operating?

I was giving it some thought today in work, and thought about maybe buffering the inputs with schmitts, and possibly the outputs with darlingtons. That would at least give the logic stable, less noisy loads to work with.

Why not start with manual control of the solenoids via a debounced 'counter' of some sort, so you can only get the gears in sequence via a couple of pushbuttons (up / down) and include lockup when 3rd is selected. You would then drop out of lockup on the way down the gears again. The foolproof features can be added later.

[Apache]

I'll see if there's a wiring diagram for it on my workshop CD, might be of some use to you whiz kids.

It'll amost certainly be programmable logic, or software in an ECU somewhere Vince, and pretty difficult to replicate in off the shelf parts. It would be good to know the logic flow though, if thats included.

[adpsimpson]

Right, got it working last night and went for a drive this morning. It did just need a diode to buffer the lockup solenoid, nothing else, and it pretty much does what it's meant to.

I'd already done a very simple manual override (on/off switch), and now have a 7 segment display to say what gear it's in. Thought that would be a good launch point to start the manual control, so picked up a nice simple volume control paddle from an old Laguna today. It's got + and - buttons, with an extra one on the top and one on the bottom - ideal for system manual/auto, lockup on/off and change gear. Also got a roller on the back which I'm sure I'll find a use for...!

Was thinking a 7 segment display using the point to mean lockup, with a separate LED to mean auto/manual mode, all mounted in the space in front of the 4WD selector stick, with the buttons on the paddle doing all the control.

I've not yet included the brake signal, which is pretty important - slowing through the 20-30mph zone is pretty unpleasant (and not to good for the truck) while in lockup. Accelerating through it is fine if ECT is on. Anyone know offhand if there's a wire live when braking anywhere near the ECU? Couldn't see one in the ECU pin-out, Andy you suggested the brake lights wire, any hints where that's located to stop me digging around?

Vince, did you get anything useful?

[Apache]

There is a brake signal to the ECU. I checked that when I started out with the design work. I'm bu99ered if I can find the diagrams now, I think they're on my old laptop.

[adpsimpson]

I now have a breadboard with 8 ICs, one relay and about 50 resistors on it. It can reliably lock and unlock the torque converter, display what gear you're in on a 7 segment display, and generate the signals required to override the automatic gear selection.

All that's left is 2 more relays to send the gear-changing signals to the gearbox instead of the ECU signals, and one more relay and a Big, Solid Switch to turn the whole thing on and off.

Then it'll need tested in the Surf, of course. Assuming it works as planned I'll draw up circuit diagrams to get a PCB made, and post everything here. I'd also be happy to put together kits if anyone else fancies having a shot at it.

Since I've not touched any electronics since the Edinburgh Science Festival when I was about 8, it's been a steep learning curve - I've also had to spend 3 or 4 times the value of the components on stocking up, prototyping boards, etc. I reckon the total value of components is about £20 (much of that is the 4 relays), although it could be brought down by more careful buying.

The gear changing counter (CMOS 4029) has a presetable output, so when in auto mode I'm continually feeding it with the current gear number and continually resetting it. That means that whenever you change to manual, it stays in the same gear as it was in. When in manual the preset number is still being fed with the ECU's favourite gear, so a simple push button could 'synchronise' the gear to a sensible selection. Not sure if that would be useful yet though.

It would also be pretty simple to automatically synchronise the manual selection every time the auto box wants to change to 1st gear (ie when you stop), which might be more useful - kind of a simplified version of what Vince was suggesting. Think I'll put this function in with a jumper on the board to turn it on and off, so I can play and see which way I like it.

[Apache]

Sync between auto and manual is something (of pretty high importance!) I hadn't considered. Nice one for spotting it