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Discussion Starter #41
iircc, a pfc can fake o2 sensors because its a full standalone unit and not a piggy back.
 

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What Levi said in post #10 is the best and closest to factory spec there is that works. Put in both O2 sensors, on the runners or collector, so both heater wires work independently, meaning do not cut them. Take the blue wire from one O2 sensor, cut it, and splice it into the other uncut wire. Take the white wire from the same O2 sensor, cut it and splice it to the other also uncut wire.

Alternatively you can leave the 2 sensors as is in the engine bay and cut at the engine harness. At the ECU, C12 E4 is the O2 Sensor Lead for Bank 1 Sensor 1 and C21 E4 is the O2 Sensor Lead for Bank 2 Sensor 1. Cut one lead, tape off or put a wire nut on the end at the harness and with the lead at the ECU splice into the other intact signal wire. This is what has worked for more than a decade on the Power Enterprise kit bc they placed their O2 sensors inline and the signal did not make the ECU happy causing misfires.

This is a diagram PPE sent me many years ago via e-mail. And for anyone not running a cat, just run a bung extender or those L shaped extenders, whatever it takes to move the O2 sensor far away from exhaust flow.

So in this setup is sensor one just zip tied in the engine bay somewhere?
 

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Just wondering would this mod need to be done on a car running a PFC? Will i be able to tune that using just the bung setup out of the box or would I have to weld in new bungs like for the OEM ecu to properly map the fuel?
I have only one wideband lambda after collector. Narrowband signal is divided two and goes directly to ecu. All original lambda wires are completely unused. PFC seems to work just fine with that setup.
 

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Hello, I have been "blessed" with P0175 after installing OBX header, downpipe and oil pan (which has nothing to do with P0175, I know). I have new O2 sensor sockets welded into header, cyl no 1 and 2. Now long term fuel trim is between -23 at idle to -5 at full throttle, as reported by OBD. Are these values acceptable for both daily drive and track days?
 

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P0175 System too Rich (Bank 2)

NO..

You Likely have a fuel injector problem..

I'd yank them and have them cleaned.. or put in a known good set..

Cap
 

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Hello all. I recently acquired a used ppe header and catless midpipe. It has 2 o2 sensor bungs at the opening of the midpipe right after the 4-1 collector joint.
My question is, why is it better to have a sensor each in pipe 1 and 2, rather than using the 2 bungs already provided?
Would it not be better to have the sensors be reading a blended mixture of all cylinders rather than eliminate the readings from cylinder 3 and 4? Would the ECU not be able to build fuel trim maps with this method as well?
I guess i just don't understand why some people opted to use only 1 sensor and split the signal or splice wires when the bungs are already present in the pipe. It would seem the solution is either lengthen the wires, or use a post cat o2 for the extra length..
I'm asking to understand, and i appreciate all responses

Thanks
Brad
 

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Brad..

For the ECU to Build the Fuel Trims Properly, it needs to snif each of the banks separately..

This set up will not provide this with any reliability.. as the gas stream will be combined somewhere before the two O2 Sensors, but the Mixture is not COMPLETELY combined and mixed. It's likely the Left O2 Sensor in this picture will read a different Gas Pulse than the Right one.. and it's uncertain which bank will read more accurately on which bung in the picture.. you can try it and see how it works out..

I'd Install two o2 sensors.. with one only being used as a heater load, and the Other one used to split the actual O2 Sensor Sig..

Cap
 

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When you put sensors only in runners 1 and 2, runners 3 and 4 are completely unmonitored. They could be doing anything. ECU will never know. For example you could completely wash the rings on cylinder 4 because of a faulty injector, and fuel trims will not change and rich CEL will not trigger.

The mid-pipe was not always available with 2 bungs. Previously it was available with only 1 bung. The split-wire solution was prevalent when only one bung was available.

Monitoring the combined stream with two separate circuits can lead to interesting problems. For example one bank can be running rich and the other lean and they combine to the right ratio. The computer will not correct this. There is even the possibility of a divergence where one bank runs richer and richer while the other runs leaner and leaner with the combined result being the correct ratio. In practice I don't think this ever happens. But it's a fun thought experiment. In reality it would not be far-fetched to consider that there could be problems in stability of the fuel trims and lack of convergence i.e. drift or oscillation of fuel trims over time. But this could be overshadowed by other factors...

The best solution is to chuck the stock ECU and get an aftermarket standalone that monitors all four cylinders combined on a single AFR sensor. Or possibly you could run with a Celica GT-S 2zz ECU that uses just one O2 sensor. It should be entirely possible to run a 1zz engine on a 2zz ecu. If you use a 2zz-sized MAF and 2zz injectors everything should be fine. In absence of lift rev limit will be 7000.

PS. Ole!
 

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Hey thanks for the replies. I have decided to stick with the dual o2 setup in pipes 1 and 2.
The question i have now is about the depth of the sensor in the pipes. The photos in the first post indicate keeping the sensor out of the direct exhaust stream is best to not interrupt the flow.
Traditionally a sensor extender or removing the sensor out of the exhaust stream is used to make the ECU see a leaner mixture. OP indicated that about a 1" or 30mm bung would keep the sensor out of the direct stream, but prior experience states this will cause the ecu to see a leaner mixture and attempt to richer things up.. No?

Brad
 

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No..

The 'Fooling' of the O2 Sensor in the Cat Exhaust Stream is done so the O2 Sensor will not see the Mixture Swings of Lean/Rich that the ECU does during Normal Air/Fuel Gulping..

This is usually also done with a SMALL sensor hole in the End of the Bung..

For your application we just want the End of the Sensor flush with the Pipe..

Cap
 

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Alright, so I was able to get a pair of o2 bungs welded into the header. Inn ready to install it but i want to make sure i know what I'm doing before throwing everything together. My car has a stock muffler that i intend to keep. I purchased new hardware and gaskets for the install.

I know i can use the article hardware to attach the midpipe to the stock muffler. But what or how are the supplied bolts w/ springs on them supposed to be used? Do the attach the mid pipe to the header?
I saw no mention of them in the install instructions?
I can easily get the nuts tightened on the bolts wothout the spring. If i try to put the spring on first, it seems the bolt is too short. Maybe a photo would help if anyone has one of the header-midpipe junction, i would greatly appreciate that!

Brad
 
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