O2 sensor voltage output

[Frank F Parker]

On Wed, 11 Feb 1998, bruce plecan wrote:

> Kinda suprized no one caught it but your numbers "might" be 
> right for the Bosch, but are useless for the purpose that you
> responded to.  When discussing performance tuning ar WOT......
> You say at 650d C what engine runs a 1200d F EGT  in the
> SBC, BBC, SBF, BBF, that was the object of my posting?.

I just picked the 650 deg curve. The Bosch data sheet for the sensor
also shows curves for 750 deg cC and 900 deg C. They all pass thru the
same region  from 0.1 to 0.7 volts but diverge above 700 mv for the 3
curves I have: 650, 750 and 900 deg C. 
For example at 830 mv, which is just a # I picked, not necessarily what
the GN guys use, the approx a/f are:

	830 mv   13.94 (650)   13.23  (750)   12.02  (900 deg C)
> 
> Then you mention the Buick folks running .83v OK, I'll
> agree with you on that,  do you think a turbo Buick Sedan
> running 12's is doing it at ANYWHERE NEAR 14.2:1 AFR..
> AIN'T GONNA happen.  Or are your numbers just garbage,
> when considering high performance tuning....

Of course not. See above where 1500 deg C, probably a fairly typical
exhaust temp for a turbo GN, would interpolate to about 12.8 a/f.
I believe 12.8 is probably a resonable # for a turbo a/f.
I used to tune high compression race motors which have lower exhaust
temps on the order of 1200-1300 degs to about 13.4-13.8 a/f. Plug
readings suggested the #'s were correct.
> 
> If you want to look at a dampened response meter fine,
> but remember it's lag time...  Maybe you don't light dancing
> lights, but the reponse time is a hellva lot faster, and you
> don't have to refocus eyes to read them...

I agree and that way I used one to keep a check on bad gas and
do some tuning. You soon learned which led was correct when
everything was correct. I never really meant that one should try
and read a dvm. Only trying to say that the small differences you see
at wot with turbolink, Diacom-P, or a datalogger are important. If
fact, I suspect that the 50 mv or so drop that some GN guys have 
reported at higher rpms may be due to the temp rise of the sensor
and thus the lower output of the sensor rather than leaning out that
it appeared like.
> 
> I believe this list is about being resourceful, and being clever
> rather than always throwing as much money as possible at
> a problem.  IE sure a wide range laboratory grade exhaust
> gas analyzer would be neat, but how many list members
> can afford one??..  I offered a workable alternative, and
> to helping a DIY get it right on AFR

I believe you took a different meaning than what I intended. The led
meter has worked well for many and I still use mine. Never intended
any other meaning- just that the #'s only have real meaning at the
ends of the scale and at the rich end thet vary with temp alot.

A LM3914 meter costs justt a few $ if you build your own AND if
you buy the LSM11 sensor for a not unreasonable $180 and get the
corresponding data, both will help the DIY tune in their car.
You can get away with a t/c to measure the temp at the sensor and
then use tables to get a pretty good idea of a/f without having to buy
the high $ interface from Bosch that does it automatically.

Regards,

Frank Parker