GM '89 Bosch MAF - was RE: MAF & base fuel tables

[Ward]

Generaly your understanding is correct, except the repeatabity is a lot
better that your assumption. How do I know. I have measured the process
several times using my eight channel Horiba Lambda test bench. I have always
found the OEM sensor adiquate for most applictions.

What you realy care about is how well your engine proforms, knowing the AFR
to two decimal places will add very little to the process. 

In practice, you don't know what AFR is going to provide the most go power
anyway. I would be a lot more worried about how I would establish which
value provided the best out come.
Ward


On Sun, 27 Jun 1999 09:55:51 -0400, Mike Pitts wrote:

> The big question is, how do you know 850mv is really 13:1? 
> 
> Standard O2 sensors behave more like a digital switch than 
> an analog feedback sensor.  If you ever look at the response 
> curve, you will see it's *extremely* steep around approx 14.5:1 
> to 14.9:1.  This is the desired behaviour of a standard O2 
> since the ECM switches between lean and rich such that it 
> averages out to approx 14.7:1.  Outside of that range, there is 
> no guarantee any two O2 sensors will return the same voltage 
> for a particular A/F ratio. 
> 
> Basically all you are guaranteed of at 850mv is that the mixture 
> is richer than 14.7:1.   Could be 13:1 or 14:1 or 11:1. 
> 
> A UEGO is much different.  It has an oxygen pump that is driven 
> by the ECM.  The reading portion of the sensor is the same as a 
> standard O2 sensor in that is switches around 14:7:1.  The big 
> difference is that the ECM can add O2 to the reference side of 
> the sensor to move the switch point up and down.  The amount 
> of current that the ECM has to supply to maintain the switch 
> point determines the actual A/F ratio.  At least, that's the way I 
> understand it to work.
> 
> -Mike
> 
> -----Original Message-----
> >I don't understand the UEGO statment though, the standard o2 sensor woke
> >very well for you application, generaly most of these engine reach amax
HP
> >arround 13:1 AFR or about 850 mvdc.
> 
> 





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