4AGE Tuning

[sergei]

I can say, yes. I had SAFC on mine and only thing it did is make it worse.
I also noticed by monitoring VF it happily reverted itself to factory after a while, if Oxygen sensor is functioning. Or if you do change certain things over certain threshold it would run in semi-limp mode (VF=0V), which equals too rich and no advance. The oxygen sensor affects the full throttle operation, even if it is open loop mode, in long term. When ECU is reset it will start rapidly learning from O2 sensor what fuel trim it supposed to run, and it set long term fuel trim. Also it constantly adjust long term fuel trim to compensate for sensor calibration. Thus adjusting the spring on AFM (or intercepting the signal) will only affect the transients on long term while base line will stay more or less the same.

So your oxy sensor was faulty and the correct fix would have been to replace it?

Steve

Why do you think it was faulty?
The first thing what happens to VF when Ox. is faulty is that it stays 0 all the time. If it is at 2.5V,then everything is fine. If it is any other voltage (at 2000rpm) then there is something wrong (eg: AFM bypass).
It is easy to tell if it is faulty or not, warmup the car and measure Ox. output in the diagnostics tab, it should fluctuate between 0v and ~0.9V (voltage is not that important as long as it is higher than 0.5V or whatever is threshold in ECU). The frequency of fluctuations would should be about 8 times in 10 seconds. Each fluctuation is when ECU adjust the mixture. The Ox. sensor has got really steep hysteresis so it no use to measure voltage directly (it basically has no linear region) so what ECU does is guesses the fine tune (can't remember exactly but it will be just a small amount of injector duty cycle adjustments) so what it does is trying to keep the mixture at exact Ox. sensor switch over point (just like balancing a pole). If anyone done AI at uni, that algorithm should fall into fuzzy logic section.

[MAGN1T]

There's "faulty" and there's "dead"

They go faulty before they go dead. As to how they theoretically work, it's a bit irrelevent.

A good sensor will read about .9 at 12 to 1 AFR (as you said, and cycles up & down in closed loop mode)
I've got a faulty one here that reads .97 at 12 to 1 (a temporary freebie)and another faulty one that never reads over .8 regardless as to how rich it really is. That one makes the car run rich and makes the fuel trims change. Sure it's on a Mitsi but all factory computers go about doing things in a similar way.

As far as "fuzzy logic" goes.... to me that's just fancy sales talk for any electrical circuit that uses feedback to continually update an non volatile ram chip. If the feedback signal is wrong, then everything will be wrong.

Steve

[sergei]

There's "faulty" and there's "dead"

They go faulty before they go dead. As to how they theoretically work, it's a bit irrelevent.

A good sensor will read about .9 at 12 to 1 AFR (as you said, and cycles up & down in closed loop mode)
I've got a faulty one here that reads .97 at 12 to 1 (a temporary freebie)and another faulty one that never reads over .8 regardless as to how rich it really is. That one makes the car run rich and makes the fuel trims change. Sure it's on a Mitsi but all factory computers go about doing things in a similar way.

As far as "fuzzy logic" goes.... to me that's just fancy sales talk for any electrical circuit that uses feedback to continually update an non volatile ram chip. If the feedback signal is wrong, then everything will be wrong.

Steve

There is difference between fuzzy logic, and feedback system.
http://en.wikipedia.org/wiki/Fuzzy_logic
As in faulty oxygen sensor. The value does not matter as long as it is above certain voltage and it changes with the right "curve". ECU does not read voltage directly, it is probably a simple Schmidt trigger on the end of that goes 5V on anything above say 0.45V (don't know exact number). ECU will read it as "Oh shit, too much". So your theory on not going above 0.8v goes out of the window. As it will still fluctuate even on something that outputs 0.7v.
BTW it is really easy to bring back to life most "dead" oxygen sensors with butane torch, most cause is carboning up (most of the time something else going wrong, and causing ECU to go into limp mode and causing carbon build up in first place). I have brought to live numerous oxygen sensor that still function fine with butane torch treatment.

[sergei]

If the feedback signal is wrong, then everything will be wrong.

Steve

That all depends how good is your programming.
ECU is not a "dumb" feed back system.

[MAGN1T]

Sergei, your logic defies logic.

3 sensors between 2 cars, swap them around and the state of tune (and fuel trim) follows the sensor....... fact. Therefore the theory is wrong.

Steve

[sergei]

Sergei, your logic defies logic.

3 sensors between 2 cars, swap them around and the state of tune (and fuel trim) follows the sensor....... fact. Therefore the theory is wrong.

Steve

It has been proven here on Toyspeed that YOUR logic is problematic.
It is not a theory.
http://www.autoshop101.com/forms/h37.pdf
Here.
it is clearly demonstrated in the article that the Ox. sensor is not measured directly.
Also it has been said the following:

Small changes in the air/fuel ratio from stoichiometric point radically changes the voltage signal. This type of oxygen sensor is sometimes referred as a narrow range sensor because it cannot detect the small changes in the exhaust stream content produced by changes in the air/fuel mixture. The ECM will continuously add and subtract fuel producing a rich/lean cycle.[cut]
Think of the oxygen sensor as a switch. Each time the air/fuel ratio is at stoichiometry (14.7: 1) the oxygen sensor switches either high or low.

As three different sensor question you put, maybe one of the sensor is actually "jammed" at 0.8v (or whatever you stated), hence different effects due to oxygen sensor never goes below certain reading.

[Vita]

so to pull what you have stated there - adding a wideband controller such as LC1 is usefull?
some like the "Aux Box" would be ideal
http://www.innovatemotorsports.com/products/lm1.php
I'll be happy with the "RPM KIT"

edit: well including the LC1 controller

[sergei]

if you want to know any value large enough to care about above or below stoich, the narrow band sensor will be useless. (jesus what a sentence, could some one translate this for me?)

[Vita]

no need no need, i get that, just trying to keep this on topic a little and to the point for future searches.

Ill explain my reasoning a little
I have a 6a13tt - and you can replace the o2 sensor with a LC-1 and use the programmable analogue output to the ecu as a NB signal. (you can put one in each header and use the average as well) but at WOT the ecu ignores the o2 signal and goes to its own fuel MAP.

My logic is going that you can replace the ST 4AGE o2 sensor with an LC1 and controller and output the NB signal to the ecu.
What does the ST 4age do at WOT in regards to the ox signal though?


pulled this from another thread here viewtopic.php?t=70442&highlight=lc1

Air/fuel Mixture and Characteristics
AFR Comments
6:0 Rich burn limit (fully warm engine)
9:0 Black smoke/low power
11.5 Approximate rich best torque at wide-open-throttle
12.2 Safe best power at wide-open-throttle
13.3 Approximate lean best torque
14.6 Stoichiometric AFR(chemically ideal)
15.5 Lean Cruise
16.5 Usual best economy
18.0 Carbureted lean burn limit
22+ EEC/EFI Lean Burn Limit.

[sergei]

What does the ST 4age do at WOT in regards to the ox signal though?

It ignores oxygen sensor. it uses preprogrammed map and fuel trim and ignition learned map corrections (and BTW corrections are actually small, any corrections different more than certain value are not stored in long fuel trim).
Any car would ignore the narrow band sensor at WOT as at those circumstances the reading will be close to 0v and thus useless (due to 10:1 ~ 13:1 ratio).

[Vita]

Ok, I would have thought that it's not that much of an issue if they are not stored in long fuel trim?


I thank you for your input on this sergei

[1hypo3]

if you want to know any value large enough to care about above or below stoich, the narrow band sensor will be useless. (jesus what a sentence, could some one translate this for me?)

Exactly!!
I agree with sergi. The only problem with oxygen/lambda sensors is that they get contaminated quite quickly and they need to be calibrated to read acurate lambda and lifespan is shortened by high EGTs as well.
NB sensors are useless go the linear sensor (lc1) and calibrate frequently

[Vita]

learnding is such a good feeling
I'm still in the negotiation stage at the moment with this fxgt, but still this info is good, relevant even if i keep the bitsa

What I'm leading to here is with a LC1, or LM(2?) will something like the SAFCII/NEO be good? ideally the link would be better, but budgets cant quite go that far and ill be keeping this N/A

[MAGN1T]

http://www.autoshop101.com/forms/h37.pdf
Here.

Did you read the bottom of page 8.

Google is always a bit of fun. It's not so much what it tells you, more what it misses out.

Interestingly enough it doesn't tell you what the sensor after the cat should be reading..... which in closed loop should be close to zero all the time.
That's because to generate a voltage there needs to be a chemical reaction which involves the sensor converting o2 and CO to CO2. If the cat is working properly then there will be very little CO in the exhaust in closed loop and therefore no or very little voltage generated by the NB sensor after the cat.
Once you know that then you'll understand why , when you go on a dyno and stick the wideband up the exhaust, the wideband gives a wrong reading (lean) at low rpms.

So obviously a dyno, cat and wideband up the exhaust is far from perfect.

Any car would ignore the narrow band sensor at WOT as at those circumstances the reading will be close to 0v and thus useless (due to 10:1 ~ 13:1 ratio).

The reading will be somewhere between .8 and .97 ish depending on whether the sensor is working properly and depending on AFR.

The level of uselessness is dependant on who's doing the job.


If you want to tweak the closed loop AFR then the only way to do it is to modify the signal that the NB sensor sends to the ECU. You could possibly get a bit better economy from making it run closer to 16 to 1 but then the cat wouldn't work too well, not that anyone worries about that.
Like you say , using a WB you could bias the NB signal slightly to do it, also you could bias the signal from a NB sensor..... it would take a bit of time to get working properly and there's probably no point really.

Ill explain my reasoning a little
I have a 6a13tt - and you can replace the o2 sensor with a LC-1 and use the programmable analogue output to the ecu as a NB signal. (you can put one in each header and use the average as well) but at WOT the ecu ignores the o2 signal and goes to its own fuel MAP.

My logic is going that you can replace the ST 4AGE o2 sensor with an LC1 and controller and output the NB signal to the ecu.
What does the ST 4age do at WOT in regards to the ox signal though?

That makes a lot of sense.

The 6A13TT has a lot in common with a 6G72TT.
They both run lowish boost stock but can happily run at higher boost.

When you turn up the boost, the AFR is significantly richer (far too rich ),getting richer as RPMs rise. You could look at it as being a fault condition because they're not supposed to run higher boost. The richer mapping is a sort of failsafe to try to prevent detonation and at the same time make it run as best as it can. Using an AFC you can lean it out at the top end only and gain more power whist being careful not to get detonation. So long as you don't make any AFR changes in the lower RPMs where it will go into closed loop, then fuel trims won't change.

Steve

[ROBODISCO_20v]

i was also told that there only good on 16v 4age engines but the blacktop is too smart for its own good.

interesting to hear about results with blacktops using piggybacks.
i was told that the blacktop ecu is fuzzy logic and over time would revert the settings done by the safc2 and neo to normal factory settings.

The proper name is a closed loop ecu & black tops dont have them. They run an open loop ecu so they will never over ride an AFC. My Altezza on the other hand has a closed loop, so I have to run a power fc

[frost]

i was also told that there only good on 16v 4age engines but the blacktop is too smart for its own good.

interesting to hear about results with blacktops using piggybacks.
i was told that the blacktop ecu is fuzzy logic and over time would revert the settings done by the safc2 and neo to normal factory settings.

The proper name is a closed loop ecu & black tops dont have them. They run an open loop ecu so they will never over ride an AFC. My Altezza on the other hand has a closed loop, so I have to run a power fc

i thought closed loop was at WOT and open was at cruising.?!$

spataaaaa. I'm getting mixed reports,
the guy i got my blitz ecu from said the Apexi neo will work really well to fine tune it. so did the guy i got the Apexi neo from
robo says the same.

a guy on club4ag (who i trust and have been getting good info from for years) says hes been there done that and had dynamo plots to prove it went back to stock. I'm still trying to find that thread.
sergei says the same.

time to book some dyno time and see what happens i think.

[sergei]

I've made a mistake I meant it would run close to 0.9v on rich.
On other hand that reading is useless. It is non linear region, every sensor will be very different in that region.
Also you are forgetting that that voltage depends on temperature on sensor greatly in that region than on actual air fuel ratio.
There is no exhaust temp sensor.
there is no control of rate of sample oxygen from cold side of the sensor either.
Trying to use NB sensor beyond stoich is a wild goose chase (worse actually).
There is no Oxygen sensor after cat on 4AGE. The ECU guesses every time it makes adjustment.
The stuff about the wideband sensor does not apply to 4AGE and most of toyotas.
You claim to know electronics, so here is example, it is like trying use saturated transistor to amplify linearly the signal.

As for reading page 8, I am aware badly contaminated sensor will affect the accuracy of "guessing" of what actual AFR is. That is why I stated output of healthy Oxygen sensor will switch 8 time or more in 10 second during normal operation.

Basically on 4AGE (and most toyotas) the ECU operates in closed loop under light to medium load, and open loop on high load.

You cannot stick a simple voltage source or a biased voltage follower on the sensor out put and use that to tune the car.
As the ECU does not look at the voltage but more of voltage change.
here how it does it:

while(1){
if (sensor > 0.45) {
fuel--;
}else {
fuel++;
}


On other hand, if it is a 16v 4AGE, you could get a NZ/AU-new ECU that has a variable resistor input instead of oxygen sensor, that resistor alters whole fuel map.