Ox or Vf signal to tap for simulating 02?

[IwantMKIII]

I'm in the process of rewiring my ZT2 WB. My stock 02 sensor connector was melted so I figured I'd just use this function, plus it allows me to change the ECU optimal AFR ratio to above 14.7 to save some gas. The issue is I'm not sure whether to cut into the Vf signal or Ox signal to simulate.

Any clarification would be appreciated. Keep in mind, this is not just a tap in, its cutting the existing harness supplying an all new feed source, at least from what I understand of it

 

[Crypton2006]

I'm in the process of rewiring my ZT2 WB. My stock 02 sensor connector was melted so I figured I'd just use this function, plus it allows me to change the ECU optimal AFR ratio to above 14.7 to save some gas. The issue is I'm not sure whether to cut into the Vf signal or Ox signal to simulate.

Any clarification would be appreciated. Keep in mind, this is not just a tap in, its cutting the existing harness supplying an all new feed source, at least from what I understand of it

I used the thick brown wire. But im not sure that it was the right wire.

 

[CRE]

You can't feed a signal to Vf. At least not that I know of.

OX is the ECU's input from the stock O2 sensor. That's the one you need to supply a signal to. I've been thinking of doing the same thing actually.

 

[IwantMKIII]

^ ok, i looked at the wiring diagram, just wasn't sure what the current flow was,

It either goes Vf to check connector to Ox input

or

Ox to check connector to Vf input

after I do this i will be setting my target cruising AFR to 16.0 about, and this should save me a bunch of gas w/o causing idle issues

 

[CRE]

I don't see what ever it is that you're looking at that's causing confusion.

http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=48

The OX line Y's out from the ECU to the O2 sensor and to the diag box. That's it.


EDIT: Do keep in mind that the ECU tries to maintain stoich even under some pretty heavy loading. You may want to watch your exhaust temps while determining a good AFR to run in open loop. Something a little richer may be well advised.

 

[IwantMKIII]

^The ECU will see 14.7 but in actuality it will be about 16.0. This is a special function of Zeitronix. under load from the turbo i will be around 11.4-11.8

That diagram is a bit different from what i remember looking at. I'm confused mostly because i know i tap the Vf signal to read the voltage outputs of the Oxygen sensor for my ZT2

 

[jetjock]

No, you didn't. Not unless you hooked it up contrary to their instructions and ran the car in diag mod all the time...

 

[IwantMKIII]

No, you didn't. Not unless you hooked it up contrary to their instructions and ran the car in diag mod all the time...

i followed instructions from isnms on istallation of ZT2. it specifically says to tap VF signal for aux. input, it was my understanding this is the voltage indirectly from the Oxygen signal. It is the signal to increase or decrease fuel, is it not?

 

[jetjock]

A look at their install instructions shows a general purpose user input. In that case yeah, I suppose you could have hooked Vf up to that. However since Vf outputs an emulation of the narrowband signal only when in diag mode with the engine off idle I don't see how it'd be useful for anything other than troubleshooting.

 

[IwantMKIII]

A look at their install instructions shows a general purpose user input. In that case yeah, I suppose you could have hooked Vf up to that. However since Vf outputs an emulation of the narrowband signal only when in diag mode with the engine off idle I don't see how it'd be useful for anything other than troubleshooting.

ooo ok, so in closed loop mode, the Ox signal would act the same way, i mean, outputing the same voltages, in other words this is the wire i want to tap my ZT2 into for sure (for emulation purposes that is)?

edit: i thought maybe the Ox signal was sent and then altered some how into what the Vf sends to the ECU (what i read from the ZT2)...hence my confusion

 

[CRE]

haven't we already covered this?

me>slaps head.

 

[jetjock]

Yeah but he seems more confused by the post.

Lets back up. Since Vf is unique to Toyotas why would the ZT2 have a specific input for it? Why would it need to monitor Vf to perform any of its functions? I see no mention of a Toyota specific model of the instrument on their website. All I see in a user input that can be used to monitor 0-5 vdc. Connecting Vf to that would give you a way to monitor long term fuel correction during normal operation but that's about it. You'd have to drive around in diag mode to get any narrowband O2 information and again, that's not much use except for doing diag work.

 

[IwantMKIII]

ok, ill try to explain a bit better:

My impression on FIRST installation (before the fire in the other car). When i tapped the Vf line, i thought this WAS the oxygen sensor signal interpretted for the ECU. As in the Ox sent a signal and it was slightly corrected somehow? I don't know. Basically I was under the impression this ultimately was the signal the ECU saw from the Oxygen sensor to make fuel corrections.

Now, ZT2 offers a SIMULATED narrowband signal for ECU. Since i no longer have an 02 sensor available to me I figured I'd use the WB I have. So based on the earlier impession I thought that cutting the Vf wiring TO the ECU and rewiring the ECU to the ZT2 simulation, this would allow me to not have one.

Based off what you're telling me, Vf is only for diag modes and the real signal is from Ox wire. So I should cut that, and wire the ZT2 to the ECU via Ox wire to simulate.

ZT2 offers the option to trick the ECU into thinking its getting 14.7 AFR while in reality you can adjust it however you want with the simulation. In my case I was to get closer to 16.0 for fuel savings and see how the car idles/runs. Obviously under full throttle and boost these conditions would not be conserved.

 

[CRE]

ok, ill try to explain a bit better:

My impression on FIRST installation (before the fire in the other car). When i tapped the Vf line, i thought this WAS the oxygen sensor signal interpreted for the ECU. As in the Ox sent a signal and it was slightly corrected somehow? I don't know. Basically I was under the impression this ultimately was the signal the ECU saw from the Oxygen sensor to make fuel corrections.

Gotcha.

Now, ZT2 offers a SIMULATED narrowband signal for ECU. Since i no longer have an 02 sensor available to me I figured I'd use the WB I have. So based on the earlier impession I thought that cutting the Vf wiring TO the ECU and rewiring the ECU to the ZT2 simulation, this would allow me to not have one.

Based off what you're telling me, Vf is only for diag modes and the real signal is from Ox wire. So I should cut that, and wire the ZT2 to the ECU via Ox wire to simulate.

Correct, as stated, you need to supply the signal to OX.

ZT2 offers the option to trick the ECU into thinking its getting 14.7 AFR while in reality you can adjust it however you want with the simulation. In my case I was to get closer to 16.0 for fuel savings and see how the car idles/runs. Obviously under full throttle and boost these conditions would not be conserved.

I've already mentioned my only concern with this plan of action... I'm not saying it's a bad idea, I'm suggesting you pay attention to how hot things get as a result and trying to point out the the ECU aims under heavier loads then many suspect.

 

[IwantMKIII]

I've already mentioned my only concern with this plan of action... I'm not saying it's a bad idea, I'm suggesting you pay attention to how hot things get as a result and trying to point out the the ECU aims under heavier loads then many suspect.

not understanding you here

 

[jetjock]

It's simple: Lean running should only be done with care, in steady state cruise at part throttle, say on flat stretches of highway. Normal fuel control must be returned to the ECU before making demands for power.

 

[IwantMKIII]

It's simple: Lean running should only be done with care, in steady state cruise at part throttle, say on flat stretches of highway. Normal fuel control must be returned to the ECU before making demands for power.

yea, i get that np. 16 is a decent target for CRUISING, but under more throttle my AF's drop quick. My tune right now is right in the 11.4-11.8 range.

And once throttle hits around 70ish (iirc), it no longer reads from 02 input anyway. From what i understand of it anyway
.

 

[jetjock]

That's true but consider other conditions. For example if you climb a grade with partial throttle and boost it may not go to 70% and open loop. Instead it may go boom...

 

[isnms]

Seems like you got this point now, but just in case:

i followed instructions from isnms on istallation of ZT2. it specifically says to tap VF signal for aux. input, it was my understanding this is the voltage indirectly from the Oxygen signal. It is the signal to increase or decrease fuel, is it not?

No

...All I see in a user input that can be used to monitor 0-5 vdc. Connecting Vf to that would give you a way to monitor long term fuel correction during normal operation but that's about it...

Yes

Monitoring is all that connection is for. So you don't have to break out the DVOM every time you want to check VF.



Additionally; From the wisdom of jj and autoshop101 I learned that VF is the result of many inputs including o2 but not just:

Input sensors used in basic injection and spark calculation:
AFM & air temp (Ks & THA),
RPM (Ne and G1),
water temp sensor (THW),
throttle (VTA and IDL),
O2 (OX),
igniter (IGf)

http://www.cygnusx1.net/Supra/Library/ToyotaTech/h24.pdf

 

[jetjock]

I wish everyone would read every article from Autoshop 101. It'd make my life here a lot easier.

Yes, Vf with the diag block not jumped is an early type of adaptive strategy indicator. It's Toyota's predecessor of the fuel trim values found in OBD II systems. However Vf with the block jump and IDL open *is* an emulation of the O2 sensor so that may be where confusion occurs. Since both forms of the signal are valuable for troubleshooting I can certainly understand it as a good candidate for an instrument's aux analog input.