Re: [alfa] Re: alfa-digest V9 #1175

[Eric Storhok <alfa@xxxxxxxxx>]

> With a batch fired system, there's no perceptable difference in AFR from 
> one bank to the other.   The only exception to that would be an injector 
> or driver failure which would only take out 1 cylinder.    I'm limiting 
> this statement to batch fired systems of Jetronic/Motronic-1.3 
> vintage.   Modern batch and sequential systems aren't that simple.
That is not the problem that would need addressed.  Even with sequential 
fired cylinders, you can easily have cylinder to cylinder a/f variations 
based on the intake manifold design.  The original V12 in the DB7 had a .6 
a/f variation from high to low, which is a lot, when you take into account 
trying to run closed loop for emissions



> Depends what problem you're trying to solve.  On a stock daily driver I'd 
> tend to agree.   The poster indicated modifications to his car and looking 
> for performance.   Every tuner I've read or talked to works with WB02 for 
> performance engines, including every dyno shop in my area.
Well, if he is still using the stock computer, then that set up is not 
capable of using the O2 sensor for anything but stoich.  If one does use 
some other system, such as the MS, which is set up to use it, then perhaps 
it might be worth while.  But just adding headers doesn't mean that a new 
computer will be installed.



>Read the Tech Edge data sheets or better yet look at the MS target AFR 
code.   There's no way target AFR would work with a NB02.   It >requires 
WB02 for it's speed and accuracy for sub-second correct based on Lambda 
feedback.


> O2 crossover tuning is an educated guess at best, and I've witnessed that 
> trying to tune the Verde on a NB02.   Everyone in the MS community 
> suggests tuning with WB02.   I can't wait to get my Precision Wideband 
> Controller that B&G just released to get my tuning right once and for all.
>
> The 1000's of running MegaSquirts out there say volumes to me about 
> real-world experience.   Probably more relevant is Per Andersens 
> MegaSquirtAVR (who developed the targetAFR code) and MegaSquirt TomTek who 
> does a lot of work with WB02, ignition and ion sensing.
>
> -Peter
Let see, there are about 60,000 PZEV Focuses on the market right now, none 
of them have a WBO2.  Crossover tuning is far from an educated guess, and 
it happens to coincide with what the catalyst wants to see for optimum 
emissions capability.   WBO2 control is starting to make some headway, but 
considering how low of emissions are still capable with a NB sensor, I 
don't see the real cost benefit of using a WB sensor.   With decent 
sensors, exactly what target a/f is so important that you need a sensor- 
there is very little difference between 12:1 and 12.5:1 WRT power adding, 
and 12.5:1 is only about 5% better than stoich if both can run at MBT 
spark.  I've seen the data, it is true.   I have a car with a basic TECII, 
and it reliably hits 11:1 under boost with no exhaust feedback at all- just 
me reading a very high quality a/f meter.  We will try to run some basic 
feedback with a real WB sensor on Bonnie, but the basic system is very 
repeatable and reliable.

Right now, at work, with parts that are aged to 150,000 miles, we are 
producing emissions so low that you can't fathom it.  No WB required.

I know the popular perception is that steady a/f control will produce the 
lowest emissions- that is NOT true, you have to oscillate the system to 
make it work the best.

Should we take this off the digest?
Eric Storhok

>
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