heater circuit to power wideband?

[bwest]

I was installing my LC-1 and intend on using one of the analog outputs to feed the tccs the NB signal. Innovative reccomends using a circuit fused with a min of 5 amps. Does anyone know the amperage draw on the factory O2 heater? B and B1 on the ecu is fused at 15amps (efi fuse) - so I didn't want to over-stress that circuit for power and cause other issues.

Can anyone clarify if there is enough overhead for this?

 

[jetjock]

Stock current changes with resistance. Goes down as the heater gets hot. Worst case on the stock sensor is around 4 amps IIRC. Newer sensors people often use are less because the heater is smaller and more efficient. 5 or a bit more amps for the fuse ought to be just about right.

edit: OK @14 volts the stocker starts out at 3.3 amps, dropping to 1.6 amps after 15 seconds, and stabilizing at 1.5 amps after 60 seconds. Bugger gets toasty fast. As the Doc says no worries. That said it's bad form to power something off the ECU main bus. I'm not a fan of using an emulated WB signal to provide a/f feedback either but it's your call.

 

[drjonez]

eh, no worries about powering the LC-1 from the ECU....

 

[bwest]

Thanks for the response guys.

JJ: I'm running the MPro for tuning w/ plans on using the p/t tracking for general cruising once everything is tuned correctly. When I re-wrapped the harness I wanted to try and simplify things (run 1 sensor) but incase that didn't work as planned, I didn't completely remove all the wires from the harness, so going back to the factory set-up could be done in an afternoon. I will keep your concerns in mind.

Doc: If this thread didn't get a response, I was going to PM you directly about this. I had just recalled a post recently w/ JJ mentioning that B1/B staying hot from the time key on, but I wasn't sure how the amperage was regulated.

Thanks again for the help.

 

[jetjock]

Yeah, B/B1 are hot whenever the main relay is closed, which happens when the key is on. The wiring will be fine as long as it's fused. I'm just anal. Years of working with aircraft and industrial automation taught me to be careful where I pick power from when adding things. Good design practice is to keep aux stuff off of critical feeds. Not like it matters much in a car though.

 

[Supraman]

[...] JJ: I'm running the MPro for tuning w/ plans on using the p/t tracking for general cruising once everything is tuned correctly. [...]

I'm already doing this, but I have yet to properly wire up the power to my wideband. As the + supply to my cig lighter can't handle the wideband (the ground path is fine, as I have tested an alternate + supply returning through the cig lighter ground), I have been running the wideband off of 28A-Hr batteries (I have a few, so I can exchange and recharge them easily).

Right now, I have cut the sensor wire on my narrowband to force the ECU into open-loop. The heater circuit is still connected so the ECU doesn't throw a code. How about using the heater circuit wires to power my LM-1, which should have similar draw as compared to the LC-1? I didn't see a real conclusion to this thread.

One problem with using the heater circuit is the round-about path the wiring would take, going out through the harness and all the way back into the car again. However, it would put the power to good use, instead of heating the narrowband for no purpose.

 

[jetjock]

Batteries huh? As a friend of mine likes to say: "Crude, but effective".

Powering the WB heater from the stock circuit may work as long as the stock heater is disconnected and the WB heater doesn't draw more than the stock one did. In that case the ECU will be happy and you'll remain code free.

I don't see why the lighter circuit didn't work but I don't know the current required for the WB heater. Seems like it'd be less than the lighter but without checking I dunno.

I'm confused about the ECU being in open loop. You're running the emulated WB signal to it right? If not you should've already had one of the other O2 codes set.

 

[Supraman]

Batteries huh? As a friend of mine likes to say: "Crude, but effective".

Powering the WB heater from the stock circuit may work as long as the stock heater is disconnected and the WB heater doesn't draw more than the stock one did. In that case the ECU will be happy and you'll remain code free.

I don't see why the lighter circuit didn't work but I don't know the current required for the WB heater. Seems like it'd be less than the lighter but without checking I dunno.

I'm confused about the ECU being in open loop. You're running the emulated WB signal to it right? If not you should've already had one of the other O2 codes set.

Yes--exceedingly crude, indeed, but it has been effective enough to allow me to get by without worrying about the wideband wiring for quite some time now. The batteries last at least a dozen hours of drive time, and I have an automotive battery charger that can recharge them pretty conveniently.

Assuming that newer O2 sensor heaters are more efficient...I think the power will be OK. Mostly, for using that as the solution, I'm worried about having such a strange setup...with wires coming from the harness, across the turbo area, and through the firewall, all the way to the wideband unit in the cab. But coming from hauling batteries, I can't say that isn't an improvement, haha.

The cig lighter, if in perfect condition, should power the WB just fine. However, something is wrong with it, and it has a low maximum output current. For instance, it will charge my cell phone--but not start my power inverter, even when it has no load. It has a 2 ohm path to ground, which is a bit high, but I verified that the WB will warm up properly if it gets a + supply from somewhere other than the cig lighter, and uses the cig lighter's - terminal for the return. If I indeed direct-wire the WB, I don't really have much use for the cig lighter, other than my cell phone--though perhaps the inverter would be nice on occasion. I've yet to figure out what the problem could be on the + side of the cig lighter, and threads I have created about it in the past have been very unpopular.

I run the ECU in open loop, because my MAFT-Pro is operating in "Partial Throttle AFR tracking" mode. In this mode, the Pro tunes the AFM signal using a feedback loop with the wideband to reach a frequency where the ECU's open-loop calculation is perfect. It's pretty awesome, and a heck of a lot faster and more accurate than the stock narrowband feedback! Also, it is more flexible, in that the MAFT-Pro can regulate different AFRs for idle, general operation, as well as leaning out during cruise if desired. WOT AFR tracking is always available, because the ECU runs in open loop there too.

Since you're the TCCS expert around here, I'm sure you didn't need that much of a description--but maybe someone else will read it and discover the wonder of PT AFR tracking

 

[jetjock]

Understand about the cig socket. There's a limiter in there or maybe a CB of some kind. I forget. I know little about the Maft Pro so thanks for the explanation. Based on what I read it's quite the gadget. Are you saying you have the stock sensor input on the TCCS floating? If so you should be setting a code. Not a heater code but one of the others.

 

[Supraman]

Understand about the cig socket. There's a limiter in there or maybe a CB of some kind. I forget. I know little about the Maft Pro so thanks for the explanation. Based on what I read it's quite the gadget. Are you saying you have the stock sensor input on the TCCS floating? If so you should be setting a code. Not a heater code but one of the others.

Yes, the stock narrowband sensor wire is floating. I researched it before deciding to force open loop in this manner, and apparently, no code is thrown if the sensor wire dies but the heater circuit is still operating. And indeed, I see no codes. The ECU is definitely operating in open-loop without complaints, which definitely surprised me too.

 

[jetjock]

Huh. I've never seen that happen. The ECU is programmed to set a code whenever the sensor stops cross counting for a certain period of time or faults to open or shorted. Codes 25 and 26. It doesn't set right away though. Needs to be there twice for a certain time with an ignition key cycle in between. It'll light the MIL only on USA, Canada, or OZ cars but the code should still be set in memory. Mine does it without fail (no pun intended). Monitoring O2 sensor activity is one of the key EPA mandated requirements for OBD which was designed not for helping repair cars as much as for emissions purposes. From that standpoint what you're seeing makes no sense. Very interesting.

 

[Supraman]

Wow--yeah, I see what you're saying. I couldn't believe it at first either, when I read about it. But, I assure you, my car is not turning on the CEL, which I know is operational. The only warning light on my dash is the darned brake-light out warning, which came on when the center mounted taillight burnt out after a rain...but continues to reappear even after I replaced that bulb and the others work.

The ultimate irony is that this is a California-original car, where emissions laws are at their most strict. I'm just as interested as you are to hear that most Supras will not do this.

 

[jetjock]

Ok, after a bit of research I have a suspicion about what's going on but I'll have to run a few tests to verify it. What year is the car? Are there any connections to Vf?

 

[Supraman]

Ok, after a bit of research I have a suspicion about what's going on but I'll have to run a few tests to verify it. What year is the car? Are there any connections to Vf?

The car is a 1988 Turbo, 5 speed. The MAFT-Pro monitors Vf, but I'm pretty sure it doesn't assert any signals onto the line. Predictably, Vf remains constant at or very near 0V, signaling open-loop in this case.

 

[Supraman]

Well, I just got finished with the wiring. It was particularly unpleasant, mostly because of the maddening fact that I could not find a consistent 12V between any two wires in the O2 sensor harness. Nor could I find the ground wire--the lowest resistance to ground was about 1KOhm, IIRC. However, I found the 12V-hot wire, which was easily able to power the LM-1 if I used a ground from somewhere else on the car (initial test was just a clip onto the thermostat housing).

So, that is definitely peculiar. My final installation is disappointingly unusual--power is sourced from the O2 harness, which now has all wires cut off from the actual sensor, two of them not connected to anything; and the return is routed through...the unused TEMS connector ground!

The LM-1 warms up just great, but I have yet to see if I will get a code when driving the car. I have no idea what sort of circuit structure detects if the heater circuit is complete...