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Discussion Starter · #1 · (Edited)
I recently installed a MAFT Pro speed density setup in my NA-T supra.
• 1986.5 Supra NA 5 speed.
• 7mge rebuilt w GTE pistons
• ARP studs and felpro gasket
• 440 injectors / stock ct26 turbo
• 3” DDP / exhaust / 2.5” intercooler
• Xtd stage 3 sprung 6 puck clutch / stock w58 / 4.3 LSD rear

I did this using the cars original 7mge electronics, removing the flapper style air flow meter and running speed density(with gm map / IAT sensors). Turbo + Piggybacking the GE electronics is not ideal – I was originally intending to use MAFT pro timing control…. But the more I learned about how timing control worked, IGT and IGF signals, GE vs GTE igniters etc.. the more I started to realize the GTE engine computer may play nice with some GE wiring/components.

OK so what, this is nothing new right, everyone swaps the GTE electronics in with the engine. BUT, I am specifically talking about:

• Running GTE ECU
• Running this turbo ECU on the original (slightly modified) 7MGE wire harness
• Having the GTE ecu drive a 7MGE ignition system ( igniter and distributor )

***I could be wrong here, in 30 years am I really the first person to try this ? ***

WHY not just swap over a wire harness and igniter + coils (you may be thinking) ? simple, I ate a lot of glue growing up. Really, we are balling on a budget, only looking to make 300 hp now, maybe 400 down the road with a turbo upgrade. The current price of GTE engine Harness+igniter+coils = ~$500. If my lowly GE electronics (igniter / coil / dizzy) can cover the ignition demands of 400hp I am set.

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

Enough talk, time for action. Last week I bought a 87 GTE ecu of ebay for $55. It arrived so I prepared the car, cut some wires in the existing ge wire harness, added a pin to it (image below), reconfigured my maft pro to generate the gte AFM signal….and no shit, car started right up. First thing I did was checked timing angle to see if it was the same as the GE ecu…and It is exactly the same with the diag jumper in. unreal. I am starting to think this will work...and be much safer than boosting on piggybacked GE electronics.




Before I do further testing I still have a few things to sort out

1. Strategy to turn fuel pump on (likely maft pro can do this—was actually doing it with GE setup, just have not looked into how to approach it with GTE config)
2. The diode trick to get MAFT pro on before engine ECU
3. THA and HAC maft pro tricks (its different than ge wiring, just have to change)
4. Oxygen sensor--simulate load on HE (heater) pin on ecu with a resistor (LED light dummy load resistor for example). My wideband (LC1) is feeding the ecu a simulated narrow band o2
5. Add 2nd knock sensor and wiring. I have the sensor, but am not 100% sure where I will mount #2 ( I may just wire it in and run with only 1 attached to block so I don’t get codes)

Curious if anyone on here is reading this thinking “what about XYZ” (or, conversely, thinking “your nuts bc of x/y/z”) . Otherwise I will update as progress is made.
 

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90T
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A couple of comments:

1) The GTE FP output can be used to control the fuel pump. It will drive the COR directly.

2) The missing knock sensor will set a code. The ECU listens for normal combustion rattle to verify the sensor is good. If the sensor is connected but not attached to the block you will get a code.
 

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Discussion Starter · #3 · (Edited)
A couple of comments:

1) The GTE FP output can be used to control the fuel pump. It will drive the COR directly.

2) The missing knock sensor will set a code. The ECU listens for normal combustion rattle to verify the sensor is good. If the sensor is connected but not attached to the block you will get a code.
thank you for the input.
1.I assume this to be the "FC" pin, "circuit opening relay" (per tsrm) ? this would make sense, the maft pro diagram for 7mgte makes no mention of dealing with the fuel pump control... which now makes sense because you don't need to touch it (when installing maft) on the turbo.
so differences between ge/gte would be:
a) GE ecu does not control fuel pump relay, rather mechanical switch in flapper afm turns it on
b) gte ecu does control fuel pump (via FC).

2. knock sensors. this is interesting. I had assumed a knock sensor was a threshold type sensor, no "data" until the devices is hit hard with vibration (knock). now Im not going to take my motor out to tap the block for it, at least for now....so Im tempted to throw it on the head / engine lift hook. but this somewhat concerns me as there has to be upper valve train noise up there (as compared to stock location).
 

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90T
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Sorry, you are correct FC pin. The FP is for the pump speed, don't use that.

The knock sensors feed a dedicated digital signal processing CPU. That CPU is quite sophisticated for mid 80's gear. It listens at specific sectors of crank angle and outputs a 2 bit knock severity, plus a bunch of diagnostic signals. It cannot be fooled easily. Can you tap the block where the GTE sensors go? That would be best. Another option might be to join the two ECU sensor inputs to the single sensor. No idea how that would work but it would be easy to try.
 

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Discussion Starter · #5 ·
3p - your thread over at sm was part of what made me give this a try / the desire to run the turbo ecu with a maft pro. I actually just stumbled into it within the last few months - for those who are interested there is an awesome 10 year long thread about tccs hardware/software/operation/modification/code etc.

http://www.supramania.com/forum/threads/3ps-tccs-disassembly-analysis.73379/

I hope to have some time this afternoon to mess with the car a bit and will try splitting the one knock sensors output first since that is the easiest (and it may work well enough since im running around 10psi)
 

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I love this figure-it-out grassroots style stuff! I'm interested to see how this will play out... :beer:
 

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Discussion Starter · #7 · (Edited)
Ok, spent some good time with the car today. Things are progressing well here with the project.
Updates :
-gte FC pin tied into existing NA AFM harness . GTE controlling fuel pump perfect.
-did the dual circuit relay / diode trick to get maft pro powering up before car ecu, eliminating afm / hac codes as maft pro sending 3.6 volts to HAC as it handles alt compensation with its own map sensor
** you have to remember to pause at acc key position (when turning key) to make this work so the maft boots up and outputs voltage/signal before car ecu. I have to get used to that….
-THA (air temp) to ground resistor in, locking GTE ecu into always thinking its 70 f. – maft pro has a gm fast acting IAt sensor plumbed in right after intercooler and handles intake temp correction
- o2 sensor heater circuit tricked with large LED “waring light eliminator” resistors.
***at first I ran only one 6 ohm resistor as TSRM says the o2 heater circuit is 3ohm. Well that little bastard ran so dam hot (+250 degrees!) I ended up putting another resistor inline so its 12 ohms (12v ---to 12ohm resistors, -->ecu HT pin).
They still run hot but not so bad. I have no idea if the ECU needs to see current on o2 heater pin or how much but its not tripping a code (yet)

- Knock sensors. Tied the one sensor I have into both ECU channels as 3p suggested. After looking at that knock wire and its clear jacket I decided not to touch it. Instead I did this by opening ECU up and soldering a small bridge in between both inputs so the one physical sensor feeds both gte knock channels
- Bonus item. Swapped in a GTE fuel pressure regulator I had. Figured it made sense since the gte ecu is expecting its pressures.

After warm up I drove it around for 40 miles or so watching AFR and the tccs trim voltage. Just nice light cruising. Wanted to give the cars new gte ecu a chance to build its fuel trims up, and it was a great day for cruising with the top off too. Car drove fantastic. Fuel trim stayed around 2v most of the time, AFR was always stoich on cruise. Idle was spot on, smooth. Below is a data log of the first pulls I did. I still had 97 octane in the tank so I gave her a pull to get some data. Car is running like a scalded dog and I am pleased how this 55$$ gte ecu + $99 maft pro ( + ge igniter and distributor) is waking it up …and giving it room for more once I add that walbro pump…and injectors, and turbo….down the line 

i hope to spend some time tuning over the weekend. car is only throwing 2 codes so far, HAC and 51 which i suspect is the AC circuit not being tied in. other code is from turning the key to on right away a couple of times on accident


7mgte_maftpro_basetune.jpg



 

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Discussion Starter · #9 · (Edited)
update ** and a few questions ***

car has been running great, put maybe 100 miles on the setup so far. did a few pulls while I captured data. below is the graph of rpm/boost/af ratio (wideband) / calculated grams air / temp

a few questions / thoughts

1. my boost seems wild up and down.

a) i am running a $10 3-bar map. just ordered a delphi name brand one to swap this out as maybe its playing a part in it

b)I am tapped into large vac port on turbo intake (by isc). 1/4 line direct to map sensor. is this maybe a bad setup. for instance would a smaller line be better ? i have seen people run a (lawn mower style) fuel filter right before the map to give it a smoother signal. this is mostly megasquirt guys that I have seen the map + filter setup.

c) possibly there are settings to smooth out intake signals in maft pro

d) maybe this is just what a stock ct26 + DD 3" downpipe + 3 exhaust looks like and i need to up the wastegate pressure with some washers (or install my MAC valve and use maft pro to control boost)

2. a/f ratio seems to track the boost ...up and down a bit, more erratic than i like.

car feels like its pulling well, I cant really feel the surging that the logs seem to record. but I am not comfortable upping boost until its stable

my plan is to now wait for the new MAP, drop in my walbro 255 pump and then have at it again next weekend. curious if any stand alone users can chime in on how they interpret that (seemingly) erratic map signal,and if they did any (mechanical) things to smooth out the vac signal.

tune1.jpg



 

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Discussion Starter · #11 · (Edited)
This is a typical stock closed loop operation. O2 should be transitioning rapidly and with very stable period.
View attachment 231890
3p - I am not sure what you mean (is my cruse o2 looking problematic ?). looking at another log I appear to cross stoich 15-20 times in a 10 second interval while at cruse 2250 rpm light load. LC1 wideband is running its simulated narrow band output to 7mgte ecu. I am not concerned about the o2 signal bouncing at cruse as I understand that is what closed loop mode does...my concern was more at WOT where I expect af ration to be more stable/linear as its running w/o o2 correction at wot.



****more updates******


last night I was feeling motivated so I dropped the tank and put the new walbro pump in. also made a change to the MAP sensor vac line (both the line and source).

had time to take one quick pull this am... things are looking much more stable as far as VAC / MAP signal / AF ratio stability. at full boost now I am only seeing a pound of up/down (vs 4 before). as expected new pump is fattening things up in boost. logs are looking better / more stable.



map_sensor_take2.jpg



tune123.JPG
 

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90T
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Your O2 looked a little unstable, but maybe I just don't know what I am looking at. 10-20 transitions in 10 seconds is good.

The plot I attached shows going open loop near the beginning which is the part where the knock sensor shows some timing being pulled (green line). There the O2 sensor just goes rich as its narrowband, but you can see the engine load increases very smoothly with time.
 

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Discussion Starter · #13 · (Edited)
**update**

car is running fantastic on its maft pro + GTE ecu + ge distributor/igniter combo. logged dozens of trips / hundreds of miles and am getting comfortable with the tune / getting vf learned trims where I want them (spending half the time betwen 3 and 4.x volts) .

starting to push the 440cc + walbro combo and hit fuel cut the other day

I was under the assumption fuel cut was 1500 hz across the entire rpm range. with that in mind I was boosting harder early and letting off too stock boost at 5100 rpm or so.

while experementing, here I am hitting fuel cut around 1160hz @ 3300 rpm



so I ended up delaying the electric boost control kick in to around 3500 (and stilll backing off to wastegate only after 5100 to prevent fuel cut..)






any thoughts on how to push this harder I am all ears. possibly getting more aggressive with the low map (pulling more fuel) and getting the ecu to do vf fuel trim 4-5 v is the key ?
 

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Discussion Starter · #14 ·
clip finally uploaded, here is the video of the above data capture (just the quick 3rd gear pull). please ignore my "custom" gauge setup haha

I really love how the maft pro boost controller is working. I am running a mercedes slk mac valve around 45% duty cycle. pn 0025401497

 

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90T
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Fuel cut is based on load, which is calculated from AFM frequency, plus temperature and altitude. So it moves around a little, its not just a set frequency.
 

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this is pretty badass:D
I'm quite possibly going this same route on my resurrection project just to get it going, but hardwiring a GCC/VPC combo instead of the MAF-t you're using.
stock ct26, divorced dp, recirc w/g for now
ideally i'd like to meld my GE harness with the haltech e6k I have with my twin scroll and FFIM manifolds and make some big numbers but for now i have till the end of FEB to move the car :crossjerk
anyways, I can kinda figure the schematic in the OP, but im having trouble visualising any wiring changes in the engine bay that might have beem done.
and since i have the harness and engine out of the car already this'll be pretty straight forward drop n go once this damn clutch gets here.
any 2019 update on this current setup?
 

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Discussion Starter · #17 · (Edited)
this is pretty badass:D
I'm quite possibly going this same route on my resurrection project just to get it going, but hardwiring a GCC/VPC combo instead of the MAF-t you're using.
stock ct26, divorced dp, recirc w/g for now
ideally i'd like to meld my GE harness with the haltech e6k I have with my twin scroll and FFIM manifolds and make some big numbers but for now i have till the end of FEB to move the car :crossjerk
anyways, I can kinda figure the schematic in the OP, but im having trouble visualising any wiring changes in the engine bay that might have beem done.
and since i have the harness and engine out of the car already this'll be pretty straight forward drop n go once this damn clutch gets here.
any 2019 update on this current setup?
car ran great all 2018 -- ran a 13.6 at 106 mph.

https://www.supraforums.com/forum/s...rs-raising-fuel-cut-boost-limit&highlight=440

I did end up rewiring my fuel pump (walbro 255), on its own custom harness / big wiring. the GTE ecu has the FC pin which will ground out the relay to turn the pump on. this keeps it safe....aka pump is only on when car is cranking/running. also added a fuel regulator and cranked base pressure way up to 50 psi

now I did most of my engine wiring harness mods right at the ecu plug since I was also integrating in the MAFT pro piggy back. I added in custom (additional wiring) harnesses for Map / intake temp / wideband / boost mac valve etc etc

the cars GE harness is not modified too much at all under the hood. injector wiring / original ignitor / sensors etc etc all the same and untouched, just mods made at plug under the dash by ECU to arrange wiring so that its correct for the GTE ecu ( a few key things are different)

car has held its tune well- always starts and is very good off boost and in light throttle. just like a stock ecu + piggy back BPU car should be. this winter I am rebuilding my turbo with a larger compressor and will keep pushing it.
 

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Man this is awesome and inspiring. Makes me want to go this route instead of doing a full swap. I’m curious as to how much this costs...do you have a price breakdown or a step by step guide to help someone like me achieve these results?
 

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Discussion Starter · #20 ·
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.
 
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