Need a little O2 correction help

[SloS13]

I'm going to be turbocharging my miata soon and the miata ECU is in closed loop part throttle.   Part throttle + boost + lean = bad.

What would be the best method on overcoming this problem.  I was thinking at first that a MAP load o2 correction with a voltage would be best but in the software, it looks like you need to specify voltages in each cell, not only those you really care about (positive manifold pressure)

The percent mode seems to be a bit better choice in the aspect that you can choose only to enter values in the areas of the map with positive pressure and leave non-boost sections unaffected for good out-of-boost closed loop driveability.

To be perfectly honest, I don't understand the explanation for the FIXED method in the manual.   Perhaps I'm over-complicating this? 

Any help would be greatly appreciated.   All of the other maps make sense and I've got my gameplan for those but i'm very confused on how to handle the o2 situation.

[BrianJ4G]

I would also like to know about the O2 maps...

Maybe a small explaination or instructions on general items like shifting the whole map by .5 AFR, etc.

[SloS13]

bump for help

[SloS13]

bump again.

Another question - in Voltage mode with a value of 0, does the ECU still receive the signal from the o2 sensor, or does the FIC somehow force a 0 voltage to go to the ECU?

[BrianJ4G]

If you're in voltage mode and there's a "0" value, it will output 0 volts.

[JDMC]

bump??

[larryinkc]

I had the same problem with the ECU staying in closed loop at low boost and pulling the extra fuel I was adding. I use the O2 correction in the MAP load percent mode and set it up to lower the O2 input voltage when there is boost. I started with a minus 25% correction and played with it until the fuel trim stays close to 0%.  If the -% correction got too high the ECU would add fuel, not good either.

[SB]

How the FIC works with stock ECUs and O2 sensors:

Most of the time, the stock ECU is running in closed loop mode. This means it is sending a certain amount of fuel into the engine, then checking the O2 sensor to see if that made the car run lean or rich. If the O2 sensor indicates the engine was too lean, it will add some fuel  using the short- or long-term fuel trims. If it indicates too rich, it will decrease the fuel.  You can monitor the fuel trims, in real-time, with a good OBD scan tool.

The stock ECU is usually trying to maintain an air/fuel ratio of 14.7  for emissions and fuel economy purposes. It will monitor the O2 sensor and change the fuel trims until it is happy with the sensor readings. If you've modified your engine for increased airflow, the stock ECU might be adding 10% fuel to maintain its desired air/fuel ratios. If you've increased the fuel pressure, the stock ECU might be subtracting fuel to maintain its desired air/fuel ratios. To summarize, the stock ECU is pretty smart but you might not agree with its desired air/fuel ratios. Then again, the stock ECU is  assuming you haven't installed an aftermarket turbocharger, and that 14.7 will work just fine.

Since you can't (or might not want to) reprogram the stock ECU, and it will get very upset if you just disconnect the O2 sensor, what we need to do is trick the ECU. The FIC's O2 table is how you do this. The FIC can modify the signal from the O2 sensor: it can tell the stock ECU that the O2 sensor reading is 14.7, even when it is actually something different. If you adjust your O2 table correctly, the stock ECU can actually add fuel until it gets to A/F ratios of 12.0 or 11.0 or whatever air/fuel ratio you choose to run.


Here is how we suggest you modify the values in the O2 table:
1. Install a wideband O2 sensor.
2. With the car idling, adjust the O2 table volts parameter and monitor the A/F Ratios on the wideband.
3. Get a piece of paper and create a simple table:   1.0V  =   ____ AFR,  2.0V = ____ AFR, 3.0V = ____ AFR,  etc...   
3a. If you have an OBD scan tool, try to write down the fuel trims that the ECU is using: for instance, 1.0V = 11.9 AFR = +20% fuel. (note: I pulled 20% out of thin air, it might be adding more or less fuel than that)
4. Use your paper to fill in the O2 table. For instance, if you want to run 11.9 AFR when the car is boosting, and 1.0V resulted in 11.9 AFR, you will enter 1.0  in those parts of the table.
5. If you want more fuel than the stock ECU was using, you should add some fuel using the fuel map.
5a. When adding fuel to the fuel map, you might want to use the fuel trim percentages you found in part 5a.
6. Drive the car and monitor the wideband to verify that the AFR's are near where you wanted them to be.
6a. The FIC Version 2.01 software allows you to datalog the output from an AEM wideband (UEGO) sensor. Just connect the white wire from the UEGO to pin 18 (Aux input) of the 22-pin connector on the FIC.



As an aside, the stock ECU doesn't always monitor the O2 sensor. It might not be monitoring the O2 sensor at high RPMs and wide open throttle. A good OBD scanner will tell you if the car is in closed loop (monitoring the O2 sensor) or open loop (not monitoring the O2 sensor) mode. We have an AutoXray EZ-Scan 6000 here at AEM, it allows you to monitor channels such as open/closed loop status, coolant temp, intake air temp, short & long-term fuel trims, fuel injector duty cycle, ignition timing, engine RPM, engine load, MAF voltage, MAP voltage, and a few other parameters that aren't as useful as the ones I've mentioned.

Hope this helps,
SB
 
 

[BrianJ4G]

Here is how we suggest you modify the values in the O2 table:
1. Install a wideband O2 sensor.
2. With the car idling, adjust the O2 table volts parameter and monitor the A/F Ratios on the wideband.
3. Get a piece of paper and create a simple table:   1.0V  =   ____ AFR,  2.0V = ____ AFR, 3.0V = ____ AFR,  etc...   
3a. If you have an OBD scan tool, try to write down the fuel trims that the ECU is using: for instance, 1.0V = 11.9 AFR = +20% fuel. (note: I pulled 20% out of thin air, it might be adding more or less fuel than that)
4. Use your paper to fill in the O2 table. For instance, if you want to run 11.9 AFR when the car is boosting, and 1.0V resulted in 11.9 AFR, you will enter 1.0  in those parts of the table.
5. If you want more fuel than the stock ECU was using, you should add some fuel using the fuel map.
5a. When adding fuel to the fuel map, you might want to use the fuel trim percentages you found in part 3a.
6. Drive the car and monitor the wideband to verify that the AFR's are near where you wanted them to be.
6a. The FIC Version 2.01 software allows you to datalog the output from an AEM wideband (UEGO) sensor. Just connect the white wire from the UEGO to pin 18 (Aux input) of the 22-pin connector on the FIC.



Hope this helps,
SB
 
 

I'm a little confused here...your first step is to add a wideband sensor, which I understand...but then you suggest to use to wideband voltages (0-5v) to adjust your map...the problem is that you can't have a value above 1v with the stock narrow band sensor...

Did I miss something here??? If not, could you outline how to "move" the A/F ratio on a normal narrow band system, without getting the ECU to revert all your changes back to stock baseline...

Please clarify....thank you!

Brian

[SB]

When referring to Voltage, I intended for people to adjust the values in the FIC's O2 table.


That particular example was referring to newer cars which are using different types of sensors, so you can send them 2 or 3 Volts. You can perform the exact same process with a 0-1V narrowband sensor. You will set the O2 Volts output in the FIC table to 0V, 0.1, 0.2, 0.3, 0.4V, etc...  and monitor the AFR results in on your wideband. If you notice a clear pattern, then you can use that to create your O2 table.


Some OEM ECUs are simply looking for the narrowband sensor's voltage to switch back and forth between ~1V and ~0V, and will actually get upset if the O2 voltage stays constant for too long. For these ECUs, you might have more success working in percentage mode. Instead of manually setting the voltage, you can simply add a certain percentage to the signal. Again, add 0%, 5%, 10%, etc... and monitor how the wideband responds to this. Try negative percentages also.


Hope this helps,
SB

[raydawg]

5a. When adding fuel to the fuel map, you might want to use the fuel trim percentages you found in part 5a.

not questiong anything, just learning....but why wouldn't you just adjust the fuel maps instead of even messing with the 02 maps?  are there advantages/disadvantages between using one or the other?  or are they just different ways to do the same exact thing?

[Raj]

If you just added fuel during closed loop through the fuel table, the ecu would try to subtract any fuel added because it would see itself as running to rich.  If you feed the ecu a bogus o2 reading that is lean, it will naturally try to richen itself to an extent.  Alot of how you tune this really depends on how your oem ecu reacts to your changes.  You really need to experiment with the FIC and see if your oem ecu does what you need it to do in return.

[SloS13]

I've got a 96 miata and I recently had the o2 table working great but I fat-fingered the laptop and ended up over-writing it.  I'll work on it some this weekend and see if I can't come up with a decent o2 map.  I know it's possible.   Unfortunately I forgot how I did it

More than any ECU I've ever worked with, the Miata's seems the most stubborn about closed loop.  Currently I've got it set to OFFSET and im subtracting about 0.2 during boost yet it still goes to ~16:1 A/F  for some odd reason.  My open loop table is pig rich in that area (mid 10:1's) so it's definitely a closed-loop problem.

One thing I noticed while trying to get values at idle last night is: when using offset, you have to make extreme changes to see any change in your A/F and when you do see a change, it's extreme.

Also, after setting vales back to 0, it takes quite a while to recover to a stoich idle which would make it *seem* like there's a delay (5 seconds or so) between making a tuning change and that change being written to the F/IC.  Is that the case?  Or is that the Miata ECU being...weird.

[SloS13]

Ain't GREAT but it'll do the job.  My setup is 96 miata, 460's, 14b

A bit overkill but it's a hell of a lot better than going lean 

[MrMeaty]

OK, I have a question...if the 02 table is tricking the ecu to reading stoich, and my wideband is reading 10.0afr, then makeing changes to the 02 table will not help that cause i don't need to trick the ecu anymore, as it's alrady thinking it's reading stoich, right?
So, now that my ecu is thinking everything is stoich, I can leave the 02 table alone, right?  What table to I need to make changes to in order for my ACTUALL afrs to be leaner then 10 when boosting?