using an auto ecu in a 5 speed car - performance loss?

[Deanfun]

Theoretically, let's say i've got an 85 SDR that used to have an auto. After much humming and hawing, it now has a 5 speed out of an 84. Now, i'm still using the 85 auto ecu and the car seems to run just fine. I had to jerry rig the neutral start switch to get the car to start, but other than that it's peachy keen. The car runs and drives fine from what I've seen - the only immediate problem is the O/D light going on the fritz every once in a while.

So I have a few questions:

1. am I losing much in the way of performance by using the 85 auto ecu? better yet, am i doing any damage by using the 85 auto ecu?

2. can i directly swap the 84 manual ecu in the 85 auto's place? will the unused connectors be able to dangle freely in my glovebox? (there are three plugs for the auto tranny directly)

also - NEVER EVER AGAIN will i consider converting an automatic supra. Never again will i assume that the oil drain plug is tight, and NEVER again will I go through 11L of ATF to drive 75km.

[Emohawk]

Theoretically, let's say i've got an 85 SDR that used to have an auto. After much humming and hawing, it now has a 5 speed out of an 84. Now, i'm still using the 85 auto ecu and the car seems to run just fine. I had to jerry rig the neutral start switch to get the car to start, but other than that it's peachy keen. The car runs and drives fine from what I've seen - the only immediate problem is the O/D light going on the fritz every once in a while.
by '85 auto ecu' do you mean the ECU from the 85? Because auto transmissions have a seperate computer (NOT the ECU). Not sure if manuals have their own computer too, but if they do you could just swap that.
If you have to jerry rig the neurtral start, it sounds like your auto tranny computer is still in there.
I can't find the thread, but somebody else was having problems with a flashing o/d light and there was a more coherent/comprehensive solution there.

[3000cc MK2]

this topic has been discussed before...

and 85 AUTO swapped w/ a W58 5SPD but still utilizing an AUTO ecu would not affect performance at all...

I have done this and even used 3 other computers from a 85 5SPD, 84 5SPD, and 84 AUTO and it did not make any difference at all.

CHEAPPOWER82 can back me up with that since he has been ussing the auto ecu after the swap of W58 tranny recently

I have my MK2 running with the W58 w/ auto ECU for 3 years already and no problems at all

[Deanfun]

emohawk - i was referring to just the ecu, not the separate control unit.

3000cc - great!

thanks guys, I won't worry about fiddling around with a swap then.

[DannyG]

I had to jerry rig the neutral start switch to get the car to start.

Oh my goodness, maybe this is why my starter just clicks. I have swapped an 84 w/5 speed into an 82 w/a 85 auto ecu. Hey SliP :!: can you tell me how you did it>, what is a jerry rig? Just sticking the wire in the ECU?

I know some neutral safety switches are located at the clutch pedal, maybe i'll have to put one there to signal to the ECU? I'm searchin some more :confused: maybe just getting an 84 manual ecu will be a better route. Not using the 3rd inlet on the 85 auto ecu worries me too :roll: But if theres anything you know I'm missing, please tell me, and I'll give it a shot :wink:
EDIT/ I think I just found out to jerry rig the 85auto ecu w/manual harness you just stick one wire into 2 ecu plugs :D Time to test :roll:

[Deanfun]

I had to jerry rig the neutral start switch to get the car to start.

Oh my goodness, maybe this is why my starter just clicks. I have swapped an 84 w/5 speed into an 82 w/a 85 auto ecu. Hey SliP :!: can you tell me how you did it>, what is a jerry rig? Just sticking the wire in the ECU?

I know some neutral safety switches are located at the clutch pedal, maybe i'll have to put one there to signal to the ECU? I'm searchin some more :confused: maybe just getting an 84 manual ecu will be a better route. Not using the 3rd inlet on the 85 auto ecu worries me too :roll: But if theres anything you know I'm missing, please tell me, and I'll give it a shot :wink:
EDIT/ I think I just found out to jerry rig the 85auto ecu w/manual harness you just stick one wire into 2 ecu plugs :D Time to test :roll:that should work...

but what we did is pulled the switch assembly off the side of the auto-tranny. the one that the shift lever connects to from inside the car. we plugged the wirse coming out of that switch assembly into their respective plugs (near the firewall, intake side) and just let the switch sit in and around the cruise control... box. you can stick a screw driver in and rotate the "gear" to "park" so that the car will start.

but shorting the pins is much easier.

[DannyG]

Thanks a million SliP, just reading your thread solved a problem I've been trying to solve for months :idea: :lol: Great info you just posted on another method of doing it :wink: Time to see what happens.

EDIT/I was just looking at the TSRM and saw 1 N/C plug, what other plug do I stick the 2nd wire connection too? The STA or the IG S/W?

[ITSUKI Drifter]

that should work...

but what we did is pulled the switch assembly off the side of the auto-tranny. the one that the shift lever connects to from inside the car. we plugged the wirse coming out of that switch assembly into their respective plugs (near the firewall, intake side) and just let the switch sit in and around the cruise control... box. you can stick a screw driver in and rotate the "gear" to "park" so that the car will start.

but shorting the pins is much easier.

Actually Slip there is far more out easier way to get the nuetral switch work out even with out the nuetral safety switch from the automatic.

You just have to get the old harness from the automatic tranny... there is 3 plugs plugged to the automatic transmission for you 85... the one you need is the plug that has a 3wires in it (2 big wires and a small one) you have to splice and connet the two big wires so that you would have connection for you ignition and the only feedback on this set-up is that you would not have to step on the clutch to strat the car.... and if you want the clutch switch to be installed you just have to wire up the clutch switch inbetween the two big gauge wires and presto you have a clutch switch in the ignition system.

[DannyG]

Actually Slip there is far more out easier way to get the nuetral switch work out even with out the nuetral safety switch from the automatic.

You just have to get the old harness from the automatic tranny... there is 3 plugs plugged to the automatic transmission for you 85... the one you need is the plug that has a 3wires in it (2 big wires and a small one) you have to splice and connet the two big wires so that you would have connection for you ignition and the only feedback on this set-up is that you would not have to step on the clutch to strat the car.... and if you want the clutch switch to be installed you just have to wire up the clutch switch inbetween the two big gauge wires and presto you have a clutch switch in the ignition system.

I would like to ask what are those 2 big wires called?> Coming from the ECU plugs? Temporarilly without the auto harness piece, I'd like to short the 2 pins but not sure what else besides the 1 N/C (nuetral start/clutch pin from ECU), sounds like the IG S/W (ignition switch).
This seems to be the best method. Since I don't have the the little auto harness plug piece w/2 big wires, shorting the pins seem really hard with the ECU pins so close to each other :roll: And using just a wire.

[DannyG]

I found the place to look to get started at least> http://www.cygnusx1.net/supra/library/TSRM_MKII/at/AT_006.html

Still trying to figure out what 2 specific ECU pins to connect.

[SupraFiend]

that should work...

but what we did is pulled the switch assembly off the side of the auto-tranny. the one that the shift lever connects to from inside the car. we plugged the wirse coming out of that switch assembly into their respective plugs (near the firewall, intake side) and just let the switch sit in and around the cruise control... box. you can stick a screw driver in and rotate the "gear" to "park" so that the car will start.

but shorting the pins is much easier.

Actually Slip there is far more out easier way to get the nuetral switch work out even with out the nuetral safety switch from the automatic.

You just have to get the old harness from the automatic tranny... there is 3 plugs plugged to the automatic transmission for you 85... the one you need is the plug that has a 3wires in it (2 big wires and a small one) you have to splice and connet the two big wires so that you would have connection for you ignition and the only feedback on this set-up is that you would not have to step on the clutch to strat the car.... and if you want the clutch switch to be installed you just have to wire up the clutch switch inbetween the two big gauge wires and presto you have a clutch switch in the ignition system.

That would be shorting the pins, look up :wink: The neutral switch is coming off soon, that was just a hack so we could transport the car.

And come now slip, converting this car to manual wasen't that hard, changing auto trannies now (brggghhh)

[3000cc MK2]

I have to take a picture of the wiring harness for it is not in the ECU pin outs it is just the harness to the autotranny

[DannyG]

I have to take a picture of the wiring harness for it is not in the ECU pin outs it is just the harness to the autotranny

That would be really helpful, a pic of the piece where I can keep it at park, and hopefully I get it to work :roll: I was a little confused till now. Just time to find that piece, or a manual ecu, whichever I can get first.

[3000cc MK2]

I have to take a picture of the wiring harness for it is not in the ECU pin outs it is just the harness to the autotranny

That would be really helpful, a pic of the piece where I can keep it at park, and hopefully I get it to work :roll: I was a little confused till now. Just time to find that piece, or a manual ecu, whichever I can get first.

A manual ECU would not make a difference at all for the nuetral safety switch... it is in a different wiring than the ECU wiring

[DannyG]

My wiring is a 84 manual wire harness w/a 85 auto ecu. In that case, I have no nuetral start switch. I thought the 85 auto ecu was acting as the nuetral safety switch and not letting me work the starter.

I think my first theory is right, the clicking is from a bad starter solenoid. Time to get it checked and replaced. Oh well, got excited for nothing :lol:

[NORCALDREW]

I recently swapped out my auto transmission in favor of a w58 on my 83 l type. In order start the car, I installed a engine start button where the A/C button used to be. Then I took the wires that originally went to the auto trans mission and found which ones will start the car. I found that when the thick orange wire and thin black one are touched together, the starter is engaged. For 2 months now, I have had these two wires connected to a momentary engine start button made by ignited. To start the car you simply turn the key to the on position and push the button. This is working perfectly fine without any electrical problems. (the rest of the wires in the harness were cut and capped.)