Removing boost cut on gen1 3S-GTE

[Wildsupra]

I want to wind up the boost in my SW11 MR2 but i need to cure the boost cut problem first. Its currently is set to 10psi and will cut if i get it up to around 12psi.

What i need to know is, which wire should i intercept to "fool" the computer, i have the bits to solder up an adjustable boost cut defender, but unlike all the other gens of the 3S mine does not run a turbo pressure sensor. Which is where you would normally intercept a signal.

I assume its going to be one of the wires from the AFM but im not sure which one.
Does anyone know specifically which wire on the ECU it is?

Just to clarify, this motor is a 1st gen 3S-GTE out of a ST165 gt four celica.

Cheers
Matty

[-==L=a=N=c=E==-]

just pull and plug the vacuum line running to the map sensor on the back of the firewall. Boost cut will be removed completely (and your stock gauge will stop working as well - if you have one still)

Other option is to wire a zener diode between the signal wire of the map sensor to ground in backwards, so when 4.7V is seen at the signal, it bleed current to ground.

[Wildsupra]

My series motor doesnt run a map sensor, its the only 3S that doesnt use one. Thats what i meant by turbo pressure sensor.
Thats why im stuck, because it would be easy if it has the MAP sensor aswell.

Matty

[Roundy]

www.gtfours.co.uk

u can see how to install an FCD there

What boost are u looking to run??

[JustCallMeOrlando]

Have you established whether or not it's running rich yet? It has a vane AFM right? Give it a couple of notches on the AFM. Should bring the cut up a few psi like it did for mine. Hasn't leaned off my mixtures much at all unfrotunately though.

[Wildsupra]

Roundy.... been there mate, but it doesnt show you where to connect on the 3S that doesnt use the MAP sensor aswell. Apparantly there was only 1 version of this 3S delivered to some random country (maybe australia) that doesnt use the MAP sensor.

Every other one ive seen does use it

Nathan, yeah man already notched it up a tad, but i dont want it leaning out all through the range, preferebly on in top end which is why i wanna use the defender idea.

It was cutting at 11ish, now cutting at 12ish after notching it up a bit.

I need someone who has the same motor as me!! Without the MAP to tell me which wire to intercept.

Cheers
Matty

[Jorrs]

haha i have the same engine dood, and couldnt figure it out either... i just run 10psi now,
i think DV figured out a way of getting past it.
also i dont believe it is any wire.. as i tried all the wires at AFM and at the ECU when i tried to install an EBC ages ago, all it did was let it boost right up to boost cut and cut out.

[JustCallMeOrlando]

Basically the fuel cut is at a set condition of variables, predominantly the AFM output. Get a multimeter and work out which wire (voltage) changes with respect to the flaps movement. I *think* mine was yellow and green...

[Jorrs]

which motor was that on ?

[JustCallMeOrlando]

1GGTE, but I'd take a punt and say most Toyota ECU's of a similar vintage will be alike. Perhaps not in exact wire colour, but definetly in function.

[Jorrs]

yeh for sure 1Gs and 3s of late 80s prob very similiar, id like to see if there is a soloution to this also, even though i am selling it maybe i can pass it onto the next owner,
and yeh i think DV had sum kind of solution from memory, when hes on later he should have something.

[Squid]

I'm pretty sure all gen 1 and gen 2 3s-GTE's were afm, and the first map appeared on the gen 3.

[Toobs]

Gen 1 and 2 control fuel via the AFM BUT the boost cut is based on a pressure sensor that looks like a MAP sensor (because it essentially is) that Toyota call a "Turbo Pressure Sensor".
Disconnect the hose to this sensor and plug er up and boost cut is gone.

[Jorrs]

hey Toobs u wouldnt no where the sensor is located ?

[Wildsupra]

Gen 1 and 2 control fuel via the AFM BUT the boost cut is based on a pressure sensor that looks like a MAP sensor (because it essentially is) that Toyota call a "Turbo Pressure Sensor".
Disconnect the hose to this sensor and plug er up and boost cut is gone.

I agree but disagree, other gen 1 and 2 motors use this sensor, called the turbo pressure sensor, which yes does look like a MAP sensor.....HOWEVER there was 1 specific version of the gen 1 3S which does not use the additional sensor. This just so happens to be the 1 i have, and possibly appears to be the 1 jorrs also has.
Well this is what i have been told by someone who "apparantly" knew there 3S's
Having said that, i will now go and disconnect everything that has a hose running to it and see if my boost cut goes away.

Hope its that easy

Will post my findings or non findings later

Matty

[Jorrs]

hey dood, our 3s are JDM mine was from a halfcut.. as would been yours, we dont have that sensor, i no what toobs is talking about now.. dont bother disconnecting anything mate u me piggy and DV seem to have the problem..

[Wildsupra]

Hmm there HAS to be something that initiates the cut though, a voltage somewhere, all we have to do is find it If there is defianantly no extra sensor of any kind anywhere then it is going to most certainly be involed with the AFM. If i get motivated enough i'l start checking output voltages etc on the AFm and try to narrow it down.

This sucks balls!!! i want 15psi

Matty

[JustCallMeOrlando]

It has to be down to AFM voltage then Matty.

[Wildsupra]

Yep totally agree man, one of those 5 or 7 wires is going to be the key, it may even be as simple as 1 wire, it may be triggered by a on off kind of switch when the AFM hits full flow it hits the boost cut switch as such.

[jonra23]

Asuming pinout is the same for most toyate AFM (3s &2vz camry manual shown)

Looks like the VS wire would be the one to put interceptor in if fuel cut is calculated off airflow.

This will mess with the way the ECU calculates fuel and ignition requirements, it will lean off mixture and advance spark if you tell the ECU that less air is entering for same sensed rpm, this may be good or bad depending on how car is currently running.

regards
jon