I don't even think the FSM is worded properly... sensor 1 is wideband and doesn't have 'switching characteristics' like sensor 2. Wideband outputs a steady current. Probably leftover verbiage from previous model years that had all narrowbands.

The way it reads to me is in line with what Neimad mentioned, about sensor 2 being important in bringing A/F to stoich (14.7) especially in modified cars with TP, HFC, forced induction, ect.. (which are now sending data outside of 'normal' conditions to the ECU).

Sort of, stoich means everything is burned, simply that. Power comes from containing the expansion of gases inside and directing in where you can make it do work. ICE has so many variables that you don't always want everything burned, run rich to keep combustion temps in check to prevent pre-det. Now with DGI we can run leaner like diesel, it's all about getting the most bang for your buck. I thinks it's like 70% of energy produced gets reinvested to keep everything moving, the rest spins the tires, plus heat waste.

I love rotary's because they are so simple, but the good ole piston engine is one of the greatest group projects of all time, so many peoples ideas over humanities history contributed to this, a bunch of self-contained cannons with ball thats that can't escape to move us around?!

Riddle me this, why do we put the weak spot in the combustion chamber (headgasket), at the point of combustion? I really don't know, I would at least extend the head over the block a bit, but I can't understand why the Miller-Offy unit construction (No head, 15:1 comp ratio) never caught on

AF switches too, more like MAF though, keeps constant amperage and sees how much power was needed to calc.

i was almost ready to self tune until i read this thread, i dont understand enough to optimize what i have

I wonder, so even if we have 14.7 dialed in on the ECU (which is the maximum you can BTW) the ECU may purposely go leaner/richer in order to reach stoich? And the rear o2's are responsible for this...

SO.... the top sensors adjust to 14.7, then the rear sensors take over at some point (steady cruise for example) to dial in stoich for best emissions. But let's say the rears are in extender tubes and not seeing reality... A/F starts going overly rich. rear o2's still seeing lean... lean codes time.

my wideband has had my stoich at 15.0 if i remember right, that was before the test pipes. currently, untuned, my wot a/f ratios get up into the 16s

That is very, very dangerous. I wouldn't go WOT anymore until you get it tuned.

Stoich isn't a specific A/F but it's 'generally' around 14.7 for pump unleaded.

yea, i know, but the good news is that i should be able to pick up some good power out of my tune though, right?

I'm thinking you should try and trick the computer into staying in open loop all the time, maybe by relocating the coolant temp sensor to read somewhere the ECU thinks it isn't warmed up. This should default to a rich state, more codes will be generated but...

No matter what you do with this system if it goes closed loop it will keep adjusting AF everytime it reads the front, when it sees the rear sensor reading wrong it assumes cat is dying and defaults to some other mapping to do what it can to prevent fire in cat, most likey lean because if cat cant store oxygen it can't burn it off and ECU don't like fires.

Hmm, so is there anyway this can be tuned out at all?

That's why I asked how much power you guys were making. I really see no point removing the cats, plenty of power to be had elsewhere (turbo, SC), this is a headache for tuners unless you do standalone. The factory tuning adjusts to keep optimum performance as the engine internals wear out. I'm really interested in the supposed reflash you can get from Nissan Motorsports for Spec Z. Might put into open loop and max power, find out soon!

Well the cats are the most restrictive part of the stock exhaust, so easy power to be made, right across the board, it's always been that way with cats.

However, not sure how this potential problem is with the secondary sensors when held in anti foulers, however, any of the tuners out there can turn off the rear sensors, but what would that do to the stock tune? it really depends on what's possible in, say, the Uprev tuning.

If the tuner can simulate a rear 02 signal, almost steady with minor fluctuaions around the .5 volt range, it's possible. That seems rather simple, but it's the warm up process that might need more thought. Even though it's ignoring the signal till it's fully warm, it's checking to see if the sensor warms up within spec too.

Interesting.

Now what we need is a tuner in here, to see if a) they know about this, and b) if they can/do anything about this?

I think the thread is derailing a bit and people are overthinking this. My main point was that even with the cats deleted you can get proper closed loop as long as the o2 is in the exhaust stream. The primary issue is with test pipes with the 'extension' on the rear sensor. At least for some model/years this can cause issues... If you have issues just hack the extension off, weld on a bung and you're fine. None of this forcing open loop (ect) needed. I'm F/I at >400WHP with no issues.

So, your tune has disabled the rear o2's?

i am unwilling to give up test pipes. i am a fully built NA car and will have a 150 shot of nitrous as soon as i get tuned. probably same hp range as djamps, even more torque

no, he keeps the function of the rear O2s, he has just deleted the catalytic converter codes in the computer. the rear O2s are still functional, the coumputer just will not trip those codes

Nothing has been derailed, and you guys still seem to miss what I'm trying to get at. You are trying to trick an emissions oriented system by giving the sensors what they want to see. It will never stop trying and your state may one day go with the Cali madness. You can achieve what you want while still operating under the emissions controls, leave the cats and see what you get. Otherwise go full standalone and get optimum performance. I can honestly say that excessive HC and CO emissions are bad for health, I have been testing cars for 8 years now and I hack up particulate matter everyday. I'm not telling you to comply. It's more an observation on performance, you're not in my state anyway, I would rather run 3 dual downdraft Weber/Solex carbs with throttle cable setup than this stuff.

i think i understand what you are saying. i guess i still dont fully understand how the rears will operate without cats though, idk.

but since the rears just adjust to stoich, as long as i can achieve stoich whenever i want in my tune, i should be ok, right?