interfacing EGT sensor with O2 senor input

[Lawrence Ho]

Hi Johnny 

O2 sensor have two distinctive state

rich	0.6 > 0.9v

lean	0.1 > 0.4v


How about using a micro controller or a Pic to monitor EGT. If you want
more fuel just sent a sent a low voltage (0.1 > 0.4v) to the O2 sensor
input, which tells the computer O2 sensor is lean and hence sent more
fuel.

When the EGT is in the desire range, just oscillate between lean and
rich very fast or 0.5v ?

Of course there will be a limit on how much the computer will compensate
before thinking the sensor is not working or running out of block learn.


Lawrence Ho

Johnny Faubion wrote:

> The main problem I had was getting the EGT sensors I have calibrated to
> something useful for the O2 sensor input on the Haltech box. EGT is wide
> scale, O2 sensor is narrow.  The other issue was picking an EGT sensor that
> I thought I could get in the future as this is to be a production engine. I
> ended up doing a (gasp) simple OPamp circuit to do the conversion which was
> not satisfactory because of the wide range of the EGT sensor and the
> nonlinearity between the two scales. I think I need to go
> analog->digital->analog to get enough control of what the output to the O2
> sensor input of the box is.