VEMS on Supra MKIII 7MGTE?

[PeepPaadam]

Hi guys,

I'm going to install VEMS on 7MGTE engined Supra that has automatic gearbox. Car has cruise control and air conditioner too.

I have severel pinouts regarding this ECU.

I'll be using mostly factory loom but I'm going to install crank sensor as I understand there's CAS wheel on camshaft? I'd rather not use it.

If anyone has experience/suggestions/hints on this one, please chime in.

TIA, Raceboy

[BenFenner]

Why not use the CAS wheel on the camshaft? The only problem if I remember is that it causes a poor idle, and that holds true with the stock ECU as well. Meaning, you should be able to have idle just as good as stock with it using VEMS.

[PeepPaadam]

So I found  a sensor datasheet for 7M-GTE (available here: http://www.autoshop101.com/forms/h23.pdf ) and it has G1, G2 (both reference sensors) and Ne (rpm sensor) on camshaft.

Question is do I have to use all three of them or can I get away with just one reference (G1 or G2) and rpm sensor (Ne)?

I don't see any reason why straight-6 couldn't idle smoothly, I'll change out the idle valve if I need to....

[BenFenner]

I don't see why you shouldn't be able to just use the signals you're interested in. If you just want to use the crank (rpm) signal, that should work just fine.

The reason for the poor idle (which your car has from the factory) is because you have a belt, or chain driving the camshaft. This introduces slop between the crank and the CAS disc. This means the ECU doesn't get the correct timing at idle, and can't do a terrific job of controlling rpms at that engine speed. I have the same thing on my Nissan SR20DE. It is not a big deal, as it is almost indistinguishable if everything else is working correctly. You could try watching your car idle, and pay close attention to it, then get in something like a BMW (same straight six engine configuration but with a crank wheel) and watch how rock solid the idle is.

[PeepPaadam]

It's my friends car, not mine

Because of the cam slop I'd like to fabricate crank trigger but if I could use stock trigger arrangement easily, I'd go that route.

[rob@vems.co.uk]

We've got a Supra 1JZGTE running, and I've tested the 24 tooth Ge trigger and single tooth G1 and G2, looks to work fine and we have the settings.

We've also got the connectors on order   But they're 12weeks away

The 1JZGTE engine has a 12 tooth crank trigger, its a shame that this one doesnt.

[PeepPaadam]

Today I connected Ne (24teeth rpm) signal and all others (TPS, IAT, CLT) to EC36 and all of them worked ok, though rpm reading was slightly on the high side when cranking (500-600 rpm). I'll probably use just one secondary sensor, just ave to wait until second LM1815 arrives.

BTW, there's a good way to bypass the original igniter by unplugging the connector and connecting it to coilpacks connector. Just have to connect +12v supply to it.

Rob, do you happen to have any info on the tachometer operation on this engine? Where does it take it's impulse (igniter perhaps? It's not from ECU as far as I know).

[rob@vems.co.uk]

Yes, I should have been more clear, use the 24 tooth for primary and only one G1 or G2 for secondary cam sync.
I dont know the details on the tacho - I know that the other earlier ones take a feed from the ignitor pack, so I expect to see the same on this one.

[irishtwincam]

7mgte gets its tacho signal from an RPM output on the igniter.
If you just use vems to drive the coils youll need to setup an RPM output on VEMS.
Or rob can do you a diode thingy on the coil negative wires.
Or you can power up the igniter rmo 12v, earth it by bolting it to the body and T-off the coil - wires and feed them back into the igniter. It will act as an RPM signal generator


Do the 7M-GTE use a 24tooth NE? Are the signal wires shielded?
Bob tried doing a PnP loom on my AE86 but I dont thin the signal wires from stock CAS are shielded in my loom. Would be cool if yours were

7M-GTE igniter wiring
CODE - COLOUR = description
IGt (LG)      = Calculated signal from ECU to drive selected coil
IGf (LG-B)   = Confirmation signal from Igniter to ECU that coil fired)
IGda (L-B)  = binary selector (coil 1 = a0,b0 / coil 2 = a0,b1 / coil3 = a1,b0)
IGdb (L-W)  = binary selector ^^
Ecu chooses which coil to fire by earthing/bringing live either/both of these terminals.
IG1 (L-R)    = coil 1 earth
IG2 (L-Y)    = coil 2 earth
IG3 (Y)       = coil 3 earth
+B (B-O)    = +B (Coil Common 12v feed)
IG- (B)       = TAC (Tachometer & Diagnosis Connector)

Toyota wire colouring, page 5 of this PDF
http://www.autoshop101.com/forms/h09e.pdf

[PeepPaadam]

Thank you, I was looking for the ingiter pinout!
I'll just take the tach wire and connect it to VEMS, using 1k pullup or inductive pullup, whatever it needs.

7MGTE uses 24tooth Ne. Wires coming from CAS housing are NOT shielded, though I've seen VR looms without shielding and still working fine with VEMS. We'll see about this one at the end of this week I hope.

[irishtwincam]

That tach signal is for driving a tachometer, its not fed into the ECU at all?
I think you understand this already, Ne should be used for CAS, tacho should just be for a gauge.
VEMS will drive a tacho gauge based on its interpretation of the Ne signal.
Bob will tell you how to set that up.

[PeepPaadam]

Yes, I understand all this very well, after all, it's my 19th VEMS install

Tachometer is not connected to ECU in original application. I won't use stock igniter at all, I bypassed it and driving coils directly from VEMS.

[PeepPaadam]

Ok, got the correct rpm reading from engine using original triggers and 1.1.12 firmware. That resulted spark from all three coils

But, I can't seem to get the fuel pump working? I connected the fuel pump relay wire (GND) to VEMS and activated it but nothing. P259 outputs are just fine because I connected EFI MAIN RELAY also through that and it functions just fine. Tried to connect fuel pump straight to GND but heard no buzzing.

What do i have to do to get the fuel pump working? Is it related to 2speed relay and additional fuel pump wire from the OEM ECU?

[rob@vems.co.uk]

What happens if you ground the EFI pump relay pin?

[irishtwincam]

On 7mgtes theres a dual speed fuel pump relay I believe.
There might be some fanciness to get it working.

7MGTE MA70 owners have issues with a dual voltage relay feeding the pump.
Low voltage for lowrpm/cruising, higher voltage at high rpms/load.
During transitions the pump voltage drops and risks leaning the fuel mixture.

Its a recommended mod to bypass stock wiring and feed the pump the 12v from
the max fuelpump rated fuse.

Best to run this suggestion past some hardcore MA70 dudes first.
There may be another wire on the MA70 ECU that when earthed triggered the fuel pump relay to turn on.
Toyota had something similar on early AE86s.
The Fc wire switched on the power TO the injectors.
Perhaps the MA70 stock is killing power TO the pump because an undocumented wire needs earthing to switch a magic relay?
The Fc wire is not on later AE86 looms, maybe the same is true for MA70 looms?
There could be variations?

HTH