AFR Monitoring?

[jacko996]

Can I monitor the afr from a standard sensor on Escort Cosworth??

If so can someone help with connections?

Thanks in advance

[Jimster]

isn't the lamda sensor on the cosworth a narrow band? if so you could simply connect into the signal and connect to to any free analogue input

[jacko996]

isn't the lamda sensor on the cosworth a narrow band? if so you could simply connect into the signal and connect to to any free analogue input

Yes I believe it is narrow band.

Im not that technically minded, can you explain about connections, and if I need to do anything else

Thanks
Dave

[Dan in Saint Louis]

isn't the lamda sensor on the cosworth a narrow band? if so you could simply connect into the signal and connect to to any free analogue input

I'd be a little concerned about the output impedance of the sensor and the input impedance of the data logger. Unless the input impedance of the data logger is at 20 or so times higher, the sensor will be loaded down and produce inaccurate readings.

I have seen various numbers cited for the output impedance of the oxygen sensor. It definitely varies with temperature, and could be over 1 megohm cold, and as low as 10 kilohms hot.

I cannot find an input impedance spec for the DL1. If, like the DL2, it is around 100 kilohms; 10% of the output voltage of a HOT oxygen sensor (or ALL of the output of a cold sensor) would be lost by resistive loading (see also "Thevenin's equivalent").

There is some chance that this loading could work to the racer's benefit, as a lower output voltage would indicate a lean condition and the mixture computer would compensate by adding a little more fuel. Maximum engine power is not at lambda = 1, but more like 0.88. How practical this is will have to be determined by experimentation<G>.

[Turby]

Doesn't a narrow band lambda sensor simply switch produce a square wave output which toggles between rich and lean (stoichiometric air/fuel ratio) ?

See
http://www.lambdapower.co.uk/TechNotes/Tech-4.aspl

Only wideband lambda sensors actually give you a A/F ratio.
http://www.lambdapower.co.uk/TechNotes/Tech-8.asp

[Dan in Saint Louis]

Doesn't a narrow band lambda sensor simply switch produce a square wave output which toggles between rich and lean (stoichiometric air/fuel ratio) ?

See
http://www.lambdapower.co.uk/TechNotes/Tech-4.aspl

Only wideband lambda sensors actually give you a A/F ratio.
http://www.lambdapower.co.uk/TechNotes/Tech-8.asp

The most usual sensor does have a very steep response characteristic, but within some limits you can read lambda if you are willing to program the interpretation.

One designer offered this table:

volts air/fuel Lambda
(open circuit)
=====================================
.250 15.0:1 1.02
.375 14.5:1 0.99
.500 14.0:1 0.95
.625 13.5:1 0.92
.750 13.0:1 0.88
.875 12.5:1 0.85
1.000 12.0:1 0.82

You are correct that more accuracy can be obtained from a separate wide-band sensor, preferably not connected to the ECU.