[Diy_efi] Wide band sensor

[WSCowell at aol.com]

In a message dated 22/08/2005 04:47:03 GMT Standard Time, dsl at airnet.net.nz  
writes:

Can I use a wide band O2 sensor on a diesel to  measure air fuel ratio ?  





I would say "no", assuming you mean the usual WBO2 sensor used in petrol  
engines.  I have two reasons:
 
1.    It's calibrated to provide a response which,  while almost linear 
immediately about the stoichiometric mixture for petrol (c.  14.7: 1? memory fails) 
its response goes rapidly non-linear on either side of  that figure.  Diesel 
engines, AFAIK, run in a regime where there is  always excess air to burn the 
fuel which is expected to be metered by the  injection pump.  So the sensor 
would be stuck "on the end stops" of its  response curve.
 
2    Even if the injection pump is injecting excess  fuel which cannot all be 
burnt, it tends to come out the exhaust as fine  particles of carbon rather 
than as unburnt fuel, which is what the sensor is  looking for.  I'm not 
convinced the sensor would notice, because of the  different combustion process 
(chemically and physically) going on in a  diesel.
 
Good luck on that, as they say.
 
Will C
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