Auto ECU without engine ECU

[mrshin]

On my MX83 (still with that nasty ol' 7M in it!) the auto ECU is connected to the engine ECU via 3 wires: L1, L2, L3. I am presuming if when I fit a Motec I (heaving forbid) turf the airflow meter (or better yet, please, the entire 7M EFI system!) the auto ECU won't be happy? Has anyone ever done anything like this before? Maybe I should try measuring/scoping L1 etc. and make the Motec output something similiar? Someone has to know something about this!

[CrUZida]

Mos would be the man to know.
We've had discussions about it before, search his posts.

I can't remember if we came to a definitive answer though.

[ViPeR_NiPPleX]

id guess you could leave the engine ecu hooked up to talk to the auto ecu and just wire up the motec as per normal, just have the engine ecu recieve the minimum possible inputs. Hopefully it doesn't need to keep the AFM

[mrshin]

I figured Mos might have an idea... At this stage I'm not really convinced it'll work properly without the AFM, or an imitation of it at least. Basically, I'd like to be able to get rid of the 7M ECU and engine loom - naturally, I intend to get rid of the 7M itself eventually too, but I have reasons for doing things in my own crazy order...

[CrUZida]

It should work fine without the AFM.

AFM controls fuel, TPS/RPM controls shift positions

[mrshin]

I've tried a similiar trick with Nissan before, and while it still worked, the transmission was clearly grumpy about not having the MAF meter there.

[CrUZida]

I know of plenty of people who have gone aftermarket ecu on 1uz's, but left the factory ecu there to shift (and thus ditched the AFM).

I don't recall any of them complaining about poor shifting.

[Mos]

The solenoids are S1 S2 S3. S1 and S2 are basically a binary gear selection, with S3 being the converter lockup. (L1,2,3 is a binary representation of the throttle position).
S2 also runs to the cruise control computer so it can switch that solenoid on without relying on the transmission computer to select 3rd gear when required.

You could in theory hook up three switches and switch them in turn ;p (good luck! ) or just two switches.

As I haven't wired up a transmission without the engine part I can't directly comment but I would expect the ECU would need at least the SP2 signal, which depending on the version of MX83 comes either directly from the extension housing or from the ABS computer. The SPD or SP1 signal is not critical if the SP2 is present.

The AFM might be used for some sort of load sensing but who knows what it will expect.

I just reread your post - oops - as L1,2,3 are the TPS, that's what you would need to feed into it the transmission computer to keep it happy (in theory). I don't know what the capabilities of the motec are, but it could be possible it could generate that signal, otherwise leave the MX83 engine ecu in there just for the A/D conversion...
I didn't realise any MX83s had a separate transmission computer? What year is it?

Mos.

[mrshin]

Ahh, well I might have just gone ahead and made a grade A fool of self... To be honest, I've never even looked to see if there is a seperate ECT box there or not - I merely presumed there was one there based on MA70's having one! Intention is to have 7M running with Motec and as little other 7M related stuff as possible, yet still shifting its own gears properly. Intention is then to use 7M as a trusty partner during extended fishing trips, and replace with supercharged UZ, still able to shift its own gears.

[CrUZida]

Honestly, I don't know.

Some 7M's definitely have seperate boxes, some have integrated ones.

I'm not sure if its a year/model/Toyota being idiots that causes the change.

[cambelt]

mx 83 is auto and efi all together
Dave

[mrshin]

Plan has changed slightly now - 7M is now leaving the house, to be replaced by 1UZ running with Motec, however control of the auto is still desired. It SEEMS as though it SHOULD be possible to run it by leaving the 7M ECU in place, and connecting it to the crank sensor, throttle, temp sensor and speed sensor, although something that takes up less room than the 7M ECU would be nice - something more like the old school 'ECT' boxes. Does anyone have a reasonable idea of what one of them might need to be connected to?

I intend to put a box of diodes etc. there so I can still shift gears manually when I press the 'power' button.

[CrUZida]

Does anyone have a reasonable idea of what one of them might need to be connected to?

If you can dig up the MA70 wiring diagrams, the ECT box is listed there.

FWIW it has the exact same plug and pin outs as the MX73 ECT box.
Whether or not the internals of the ECT box are different or not I don't know.
(MX73 is A43DE and MX83/MA70 is A340E)

I've wired up an MX73 with an MA70 7MGTE and ECT, but used the MX73 ECT plug, and from memory I didn't change/add any pins.

The Cygnus Supra page is down at the moment though (that has the MA70 wiring diagrams) but I remember someone posting a temp link only a few weeks back

[mrshin]

A little further interwebbing has suggested that L1, L2, L3 are only switched on/off relating to throttle position, which should = pretty easy.

[CrUZida]

ECT wiring diagram

Doesn't seem to have TPS input, so you could well be correct.