Can a NB O2 support slight fuel enrichment - Miata Turbo Forum - Boost cars, acquire cats.

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Old 02-27-2013, 08:12 PM   #1
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Default Can a NB O2 support slight fuel enrichment

I'm NA and looking for alittle fuel enrichment when the ECM is in closed loop. I know that a NB O2 sensor is only accurate near 14.7 but I haven't seen much about where its accuracy falls off in terms of voltage or AFR. I thought that if I used either the analog voltage input/output or the intake input/output channels I could get some fuel enrichment and some of the added torque for a race tune. Note I have to keep the MAF and NB O2 for scca STS so I don't currently believe that I need the intake channels for anything and I can't just use a wideband O2 at least when racing. Let me know if you think this would work or if it's just a waste of time.

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Old 02-27-2013, 09:26 PM   #2
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What ECM do you speak of?
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Old 02-27-2013, 09:59 PM   #3
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It is very inaccurate for anything other than 14.7
Not only is it not linear, but because its 0-1v, the resolution is very poor.

So no, it will only be of any use getting to 14.7, nowhere else.
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Old 02-28-2013, 09:16 PM   #4
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This was refering to an 96 which is the OBDII. But thats not really relavant since this is really just about the NB O2 sensor.

That image realy clarifies what the NB sensor's outputs are and confirms that a NB sensor really is only good for a 14.7 AFR. To top it off the analog channels only offer a .1 volt increment which would be way to far out of range for the sensor to be accurate at all.

I guess the best option is to get a dyno tune with an WB and use the analog channel to send a 1v signal to the stock ECU to stabilze the fuel map and keep the check engine light off. And since I don't want to worry about my CAT it will be a race only tune for me, but that should work well enough.

One last question what conditions throw the stock ECU into open loop? Specifically does it go into open loop only at WOT or is it above a certain throttle position or percentage?
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Old 03-03-2013, 04:11 PM   #5
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What type of engine management do you have?

Presuming emanage then you could
1) resize the injector scaling to run richer in open loop
2) use an narrow band 02 clamp/autotune circuit to change the target AFR

I use the second option with EMB to target 12 AFRs in boost and it works well. I am not sure how it would work to target 13.5 AFR but I guess it would be ok as adjustments are based on error correction.
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Old 03-04-2013, 02:04 PM   #6
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I have an EMU and since I'm NA I don't have boost which I believe is what activates the O2 Clamps from what i remember. So I think that the best option is adjusting the fuel map in open loop base on WB readings initially probably via autotune. I can copy the part of the O2 clamp that keeps the ECU from sending a CEL with the analog channels by just setting the signal the ECU sees to 1v for the O2 signal. But doesn't the fuel map occilate between slightly rich and slightly lean to support the O2 function. I think I might be better off maintaining open loop by clamping O2 sign at 0v to get a stable fuel map since I will not have a WB to chase the osicilating fuel curve constantly since they are illegal for me.
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Old 03-04-2013, 05:30 PM   #7
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Quote:
I have an EMU and since I'm NA I don't have boost which I believe is what activates the O2 Clamps from what i remember.
[IMG][/IMG]
A DPDT relay type o2 clamp can be activated by a switch or an EMB/EMU output as opposed to the boost pressure type. (I use the EMB vtec output.)

Quote:
But doesn't the fuel map occilate between slightly rich and slightly lean to support the O2 function
I think this oscillation only happens at idle as usually WB and NB signals are steady in cruise. With an o2/autotune clamp you could send a stoich lambda to the ecu and route the NB signal to the EMU to use in a target AFR table.
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Old 08-14-2015, 02:29 PM   #8
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Well I don't think I saw this till now. The double pole relay with the v-tec signal used for control is a great idea. After looking for stock AFR number at WOT I don't know if there is a lot to gain and if I only tune the fuel map at WOT the ECU should still be in open loop so the O2 signal wwon't matter. I would like to tune the AFR when the ECU is in open loop but don't know how th tell when it goes into open loop operation. I recall reading that the ECU goes into open loop base on the calculated load but haven't read what load triggers the transition. Does anyone know when this happens or if I'm on the right track?
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