[bosons]

i have a 92 turbo that hits fuel cut at about 11PSI ( it used to be at around 14.5-15). I currently have a truboost controller. I have verified this with another boost guage. I have also checked the turbo pressure sensor and it checks ok according to the manual. If i unplug the sensor it hits the fuel cut the same. So i think it is acting as if the boost signal is not getting through to whatever component controls the fuel cut. Does anyone know excatly how the computer gets the boost signal, if it does? according to the official toyota wiring manual the boost sensor does not feed to the computer.

 

[88yoda]

fuel cut is determined by the afm not a boost signal. if it gets to much air and not so much fuel you will hit fuel cut. mods? if your stock fuel cut is anywhere from 9-14 psi.

to properly tune you should have 550's, lex afm, afpr, and a wideband.

you can do with out the 550s and lex and just get a afpr and wide band and there a spot where it looks like there shold be a screw on the body and lightly drill into (with a drill not by hand) about 1/8-1/4 in in and pop out the plug buy taking the drill bit and going to the side. adj the screw in some and see if it gets any better.

any time you start turning up the boost you should ahve a wideband to see your air/fuel ratio.

 

[bosons]

turbo overpressure/fuel cut problem

Are you saying that the computer inputs air temp, volume and calculates the pressure? I see that the 93+ supras have an input on the ECU specifically for the pressure sensor. According to the manual for my car there is no pressure input.

my car has been running fine under these conditions for about 3 years. it normally hits fuelcut at around 14-15. something has changed in my system. my AFM meter says its running rich (0.9-1V) under full load (floored). That is normal. what is odd is that under idle or at cruise the meter swings frequently from 0.1 - 0.8V. The air flow sensor tests fine according to toyotas manual.

 

[suprra_girl]

Small boost leak I should imagine.

Check all pipes for small leaks, what's your vacuum at idle?
fyi the turbo pressure sensor is just that. A "turbo pressure" sensor i.e a boost gauge.
You will notice that when you unplug it your stock boost gauge will go to 0 or above due to it not reading boost. Pull the line or the plug from your boost gauge, same effect.

All air calculations are made through the air flow meter in the intake pipe to the turbo.
Have you changed anything else? Exhaust, intercooler etc?

 

[mk2racer]

I agree on the boost leak, probably just a little one. I racked my brain trying to find a leak on my car once, and it turned out to be a fitting on the boost controller itself. No one bothered to put teflon tape on, and it decided to start leaking one day, but it only affected about 2 psi difference in FC, so had I not KNOWN what it was previous, I never would have noticed it.

Also, when you say your AFM reads "rich" at 0.9v - 1.0v, what exactly are you measuring?? Assuming you are using a stock turbo KV meter, you will be getting a 5vdc square wave with increasing _frequency_ as intake volume increases. The voltage on the KS line (which is the only one measuring flow) should remain constant at 5 volts.


Also, insofar as I know the ECU only receives it's airflow signal from this AFM (KS), a frequency, and uses that, the temperature, and throttle position to determine FC. That is why there is no "easy" way to beat the fuel cut, since it is programmed into the ECU directly.

 

[suprra_girl]

There are other tools available for fc
Which I'm using, and works blardy great but I
a) Don't recommend them in the wrong hands
b) By the time you need this device... don't pussy foot around, just save up the $$ and buy an aftermarket ecu

Also I believe he is more than likely reading from VF