** Title should read: 3rd Gen Oxy Sensor Disconnect & Tuning **

Does anyone know 100% whether disconnecting the oxy sensor on a TJ AWD will put an engine check light on (and limp mode)? Reason I ask? Imagine I wanted to tune leaner than 14.7:1 for specific applications because I thought the headwork would let me. My concerns are that changing ecu fuel values for cruise speeds with an interceptor the ecu will continue to adjust trying to get 14.7:1 while the interceptor will be constantly adding/subtracting fuel from the ecu's adjusted signal and so on and so on each time the ecu tries to compensate and get to stoicometric operation. Why not just go into open loop and ignore the 14.7:1 - tune 16:1 for example, at low throttle loads and low boost. Better economy.

Thoughts?

Everything I looked into regarding that just suggests the ECU defaults o2 emmisions to the open throttle setting when the o2 sensor is not functional or disconnected. Can't say that with 100% certainty though as I've never had anything to prove it with, though I can say running my car without the o2 connected didn't bring up any warning lights and certainly didn't throw it into limp home mode, can't imagine it being any different in a AWD model.

yeah, i disconnected mine to check its functionality, and it didnt throw up an engine warning light.
you plan kinda sounds risky, especially if your running boost, a 02 sensor is there to give the ECU, some feedback on the A/F ratio, disconnecting this, could it be possible to get a leanout, say while under load? and with boost, say goodbye to your engine.
i say, just get your fuel mapping done to exactly the way you want it. as if you are running Raptors prosequential ecu, it will just change the factory ecu injector pulse signal. it can be mapped regarding, rpm and load conditions in any compination you like.
im sure it could be mapped to run close to stoic, when under light load conditcions. you will need to be richer for under highload conditions. tell your tuner what you want, im sure they can do it for you.
as for tuning to 16:1 that seams a little to lean, even for light load conditions.

have a read of this thread, he basically added a interceptor to the 02 sensor, to adjust the signal, for when the car was cruising (ie closed loop mode) http://www.aussiemagna.com/forums/showthread.php?t=62542&highlight=air+fuel+ratio

I have the Prosequential from Moristech (the 1st Magna installed one actually) and helped tune it on my car last year when it was atm pre-engine meltdown. The Prosequential modifies the injector duty cycle BETWEEN the ECU and the INJECTOR, rather than fiddle with the air flow meter as is traditionally done by interceptors.

I would be tuning it with the AFR stick up it's bum and monitoring it VERY closely along with a knock sensor kit I'm assembling from Ishrub. I will be installing water to air water temp sensor to monitor it's health too. Lots to consider but was looking to know what experiences other tuners had had.

Glad to see the O2 sensor disconnect didn't raise any concern from the ECU fault system that was of a terminal nature. Will verify myself time permitting I suppose.

Does anyone know 100% whether disconnecting the oxy sensor on a TJ AWD will put an engine check light on (and limp mode)? Reason I ask? Imagine I wanted to tune leaner than 14.7:1 for specific applications because I thought the headwork would let me. My concerns are that changing ecu fuel values for cruise speeds with an interceptor the ecu will continue to adjust trying to get 14.7:1 while the interceptor will be constantly adding/subtracting fuel from the ecu's adjusted signal and so on and so on each time the ecu tries to compensate and get to stoicometric operation. Why not just go into open loop and ignore the 14.7:1 - tune 16:1 for example, at low throttle loads and low boost. Better economy.

Thoughts?

I don't know specifically about the Magna regarding the check light coming on and limp mode taking control. Others may know what has happened when they have disconnected the Lambda sensor and be able to pass on their experience or you could test yourself. Different manufacturers have different methods of the ECU dealing with sensor faults(?).

At cruise most 4 valve engines with proper spark advance, proper cam advance and no EGR will be fine down to very lean, 17:1-18:1, before issues with misfire and surging. That has to be avoided with most blowers(more risk of backfire) but centrifugal type are usually OK in this regard. 16:1 should not cause any concern as valves and seats, piston crown and top rings are not being hammered at cruise and so shouldn't need extra fuel to cool them.

Closed loop, about 14.7:1 with ordinary unleaded, is there purely for emissions. CATs work at stoicio, but best economy is much leaner just as best power is much richer, and safe power richer again.

Cheers,
Alan