Commanding other then stoich in CL.

[pauly24]

If I change B3671 at the 0% ethanol point to say 15.2, then when the car is running my log says the commanded AFR in CL mode is 15.2.

I don't have my wideband hooked up yet to verify, but didn't people say this was impossible?

[odd boy]

log the STFT to verify. Then use this chart....

http://www.vortexbuicks-etc.com/nbsensor.jpg

[pauly24]

Figured it out, we'll I read some posts that explained it.

But in case anyone else stumbles across this, ill post what happens.

Simplified version leaving out some steps, but this is what happens.
The ECU looks up the amount of air entering the cylinder through the VE table, it then uses this value in table B3671 to figure out the amount of fuel to be injected.
So if I change it to 15.2 it will think it only needs to inject 1 part of fuel to every 15.2 parts of air to get a correct 1 lambda reading.

Then what happens now is after it injects the fuel the O2 sensor says hey we are lean not enough fuel, so then the fuel trims go up and inject more fuel to compensate.

So no matter what happens in CL, the O2 sensor will switch around 1 lambda and force more or less fuel to meet this irregardless of what your settings are.

So if you put in E10 fuel, and your ecu still thinks stoich for your fuel is still 14.7, but in reality your fuels stoich point is roughly 10% off from this, your fuel trims will start to show this 10%.

[WeathermanShawn]

I 'think' you got it.

See from my perspective I do not think Closed-Loop is the 'enemy' that some have made it out to be. If an EQ of 1.00 is your goal, closed-loop not only works, but has the ability to maintain it and faster than any human being can program in.

If your application requires something other than an EQ of 1.00, then you need to go COS or be very innovative in your thinking.

If you work with how closed-loop is designed tuning can be relatively painless. You just have to understand what your set-up and application needs.

Good research. It can be complicated, but I think you stated it correctly..:)

[pauly24]

Is there a COS for the E38? If there is can you point me in the direction. (I haven't really started looking into COS yet)

Yes, well the other two options I see about getting around this is. Either force the car to stay into open loop, can do this by changing B1502 to a value that is never reached, say 140 degrees. This way the coolant must get to this temp before it goes into CL mode. (ie. never)

Or play with the PE mode to give the values you want.

[WeathermanShawn]

Is there a COS for the E38? If there is can you point me in the direction. (I haven't really started looking into COS yet)

Yes, well the other two options I see about getting around this is. Either force the car to stay into open loop, can do this by changing B1502 to a value that is never reached, say 140 degrees. This way the coolant must get to this temp before it goes into CL mode. (ie. never)

Or play with the PE mode to give the values you want.

I am not sure about the E38.

You can do Open-Loop. I am just pointing out that for every problem you avoid in one tune will be replaced by another. There are several active threads of tuners attempting open-loop and are in their 2nd or 3rd month of trying. You have to address how IAT affects fueling, start-up etc.

I take it you are relatively new to tuning? A lot of times you have to evaluate the basics. Am I using this car for street, track, both, etc. What are my modifications. How much time do I want to spend 'fiddling' with my tune.

With E38, I do not want to get in over my head commenting. Was just trying to help you out. Joecar had a thread that regardless of your OS, I though was pretty enlightening. Here is the link: http://forum.efilive.com/showthread.php?13288-Calc-VE-Setup&p=119640#post119640

Good luck..

[pauly24]

New to tuning? sure am, I connected my newly brought flashscan to my car only couple of days ago, started playing with the demo version several days before. (been reading for a long long time though)

Thanks for the help.

[joecar]

Changing the stoich AFR effects the calculated fuelmass, but it doesn't effect trimming to the actual stoich of the fuel being used.If you set the stoich AFR to some value, then the initial fuelmass calculation will be from this, but then the NBO2 CL feeback trimming will trim to unity lambda which is the actual stoich of the fuel being used.