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Discussion Starter · #21 ·
Also, I did end up gettingy hands on a proper 7mgte igniter recently. Possibly when I add this (swap ignition over to gte coils setup) I will do a clean write up / more of a step by step.
 

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There are a few items to address (buy$) if you go this route

1. Ecu. I paid $55 for a 7mgte ecu
2. Afm signals
A) you could use an actual 7mgte meter, this would give you the signal wire and intake temp signal. I don't know what these cost as I thought there is a much better way (than an used, prob somewhat inaccurate OEM karmen afm meter + housing ...)
B) use a piggy back to generate the correct afm signal. I went this route and used a maft-pro. With this method the maft pro has a map sensor and IAT that only feed it. It (maft) then calculate the afm hz signal. The cars ecu is given a fake iat signal (simulating 72°)

I have $150 in my used maft pro and (new) map/IAT sensors

**There are other ways to generate this afm signal (I believe). Hks alphabet soup, or map ecu. Maft has gen 2 (still available) that would allow a GM 3" afm by converting it's signal to what the 7mgte ecu needs (gen2 does not do speed density but does everything else pro does)

3. The correct 7mgte o2 sensor. It's a heated sensor vs the 7mge 1 wire basic o2)

My setup already has a Innova wideband. So I programmed an analog output to simulate a narrow band signal (free)

Added a pair of LED light load resistors so the cars ecu would not throw an o2 code. $12

4. Ignition. If you use your 7mge igniter / coil this is free (and requires no wiring change)


5. Altitude compensation sensor. $2 resistor to feed the cars ecu a value (sea level). If you use an actual Supra afm you need a real hac sensor ! If you using a maft pro you have that device read barometric pressure at key on and it compensates for you

6 fuel pump relay rewire. The non turbo uses a simple switch in the afm to turn the relay on. The 7mgte ecu has the fc pin that grounds out (when the ecu sees air flow) and turns it on. I ran a new relay /wiring to the pump but you could re-use the cars stock wiring / relay.
Thanks for the reply. Maybe I need to do a lot more research on this car (just got it a few months ago) because all that talk sounds foreign to me right now. ? Did you happen to make any how to videos similar to the videos you had in your OP?
 

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Discussion Starter · #24 ·
244757


time for an ignition upgrade....


finally converted the car over to a proper multiplex 7mgte ignition (aka no more running the GE ignition on the turbo ecu)

found an igniter for $20 on FB, matched it with some used denso 90919-02216 coils ($10 ea)
added new wires and boots... and installed:



a few hiccups on the way

1. had shitty boots on the coils. failed to note a wire set does not include coil boots. makes sense (not), why change the boots when the wires are toast lol. anyway old cracked oil soaked boots will make it break up really bad under boost, trust me. advance has a cheep is300 $4 boot that will save you from spending $30 ea on ngk (retail)

2. after I put new boots on...still had mild breakup at 5500 rpm ~14 psi boost. found out I made a mistake and wired one coil with opposite polarity. this gave that particular coil a very weak spark.

3. dash conversion. "its just 4 resistors i need to swap out" as I tell the wife it should take an hour. ah, no. 30 screws later and the dash is out and apart in several pieces. swapped in the resistors pictured below and the original na tach now works with the turbo multiplex igniter.
244758



244759


244760





(some notes on the wiring / etc I used)

244761
 

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So what do we have going for us here, what is similar between GE and GTE --specifically 87/88 era

1. CPS sensor and Distributor are electrically equivalent. Same pickup coils, teeth count, resistance (in early 86.5-88) dizzy
2. Fuel injection drivers (3), injector wiring and resistance is the same
3. IGT signal is the same on both. GTE ecu just has 2 more multiplex specific outputs for the matching GTE igniter. IGF is also same between ge and gte
4. Many sensors are the same / most of the wiring harness is the same
So would this not work for a 1989 Supra? I really hope there is a way to make it work because I really want to do this!
 

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So would this not work for a 1989 Supra? I really hope there is a way to make it work because I really want to do this!
After spending some time comparing the electrical systems it seems to me nothing major changed in terms of the way in which things work electronically between the 86.5-88 to 89-92.

1986.5-1988:
260295


1989-1992:
260296


The AFM voltage is different as well as the injector voltage (9-14v for 87, 10-14v for 89+), but given that the AFM can be simulated by the MAF-T and that the reason behind the difference in voltage for the injectors is lack of resistor pack which should be fixable by high impedance injectors?

1986.5-1988:
260297


1989-1992:
260298
 
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