Here's your basic auto tune using stock narrow band 02 sensors. (there are more advance auto tuning with broad band 02 sensors).

Auto tune runs only when you are doing an auto tune session. Once you are done auto tuning auto tune is no longer needed, you save those results and make them the base for your permanent tune.

Here's how auto tune works.
Note: The auto tune sets the afr to 14.6 not 14.7 and it sets this across the board so every fuel cell is at 14.6 during an auto tune session.

Once you are done auto tuning you save those auto tune results and you use them to build your tune.
The purpose of auto tune is to get your VEs dialed in, once this is done auto tune has served its purpose and is no longer needed.
You will then use those newly created auto tune VE numbers for the tune that you are going to run with the bike.

How the ECU uses the VEs in open loop.
In order to hit the desired afr in an open loop cell the ECU looks at the VE number for that cell and then calculates the amount of injector on time to achieve the amount of fuel needed.

So if you want 13.8afr at 3000rmp and 70kpa you assign that 13.8 number in the fuel cell for that area.
What the ECU is going to do is get the VE number for that cell from the VE table (which was created with the auto tune) and then using that number calculate the amount of fuel to inject in order to achieve the 13.8afr amount that's being requested.

How the ECU uses VEs in Closed loop.
Closed loop (afr 14.2-15.0) uses the 02 sensors for feedback, in other words the ECU looks at the 02 sensor readings for confirmation that the desired afr has been reached.
The VEs play a part by being used for the initial targeting of the desired afr.
The VEs also come into play when the engine is cold or when an 02 sensor fails.
If an 02 sensor fails the ECU will look at the VEs and calculate the proper fuel/air mixture for those cells, just like open loop.

Keep in mind that the Volumetric Efficiency of the engine is based on the mechanical attributes of that engine.
Until there is a mechanical change to the engine your VEs will always say the same.
This is why it's important that you run 3-4 auto tune sessions hitting as many cells as possible, this is how you get accurate VE numbers for any given cell in the map.
Once your VEs are set they stay that way until a mechanical change is made to the engine (new cams or pipes, or intake, head work, displacement etc...)
If you make a mechanical change to the engine you will have to run some new auto tune sessions to get your new VEs, then you just copy them to your tune using your PC.

I hope this clears some things up.

 

Well I found all these posts very interesting and informative I checked out all of the links thanks. That being said I'm going to try and auto tune (target tune) this weekend and let you know how it works out. I would really be interested in how your tunes went

 

To add another note. The narrow band sensors have a limited range. Most of the newer bikes use lambda instead of afr. To my knowledge the nb sensors lose accuracy lower than .977 lambda or 14.43 afr. I have seen calibrations with .974 but not to many. When you use say a 14.2 or .966 lambda the nb sensors do not work in this range so there is no correct info being sent to the ECM, thus open loop. Wide band sensors work in this area and all the other areas. There are other wb systems out there, but I believe target tune is the only wb system that really communicates with the ECM on a constant basis. Been using tt for a month or so, really happy so far. There is nothing wrong with nb sensors, the bike just runs leaner where their range is useful.

 

I like to see how that works out. From what I can tell it would be better than sticking the bike on a dyno because you are measuring real life riding and not simulated.
Yep that's the EPA stuff, the want to keep the fuel where the cats are happy so having narrow band sensors on a stock bike makes sense.
The ECU firmware can only read in the narrow band which is why Target Tune has an interface.

 

Thanks again. But my questions have still not been answered.

If there is not data at 14.43AFR, and hence open loop (probably) what does the Auto Tune then sense to get/set that value ? (and my other questions).

Or yet another way, how can it fill the cells if it has no data 'cos the o2's have gone out to lunch ?

 

The auto tune (basic) doesn't operate at 14.3, the auto tune function sets the afr at 14.6 (not 14.7 as I erroneously noted before) across the entire fuel map, this is where the 02 sensors are most accurate. The auto tune then uses the feedback from the 02 sensors to determine how much air is flowing through your engine.

 

But the ECU can and does that. So why the Auto Tune ? But the stage 1 maps call for say 14.3, how is that measured to enable the cells to be filled in ? (if the 02 sensors have stopped working at that ARF)

 

The ECU only does what the map tells it to do, one is hardware the other software.

You have 3 major parts to a map/tune; VE, fuel and spark. What ever number you assign to a cell is what the ECU is going to execute.

As far as "filling cells" when you auto tune that's the only time you "fill cells" after you are done you save the results, throw the auto tune away and apply those results to your map, because you are done auto tuning.

 

So how does that work if the o2 senors are out to lunch, where does the Auto Tune get its data from ?

 

If the O2 sensors are "out to lunch" they'll need to be replaced.