91 vette cross counts
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Burning Brakes
Joined: Jun 2003
Posts: 949
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From: smithtown ny
91 vette cross counts
by increasing fuel pressure will that raise the o2 cross counts or the o2 mv because at idle in closed loop the o2mv never get past 800 even if i bring the rpms up 2000rpms the o2 is and heated?????
Team Owner
Joined: Dec 2000
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From: SE NY
Cruise-In II Veteran
Re: 91 vette cross counts (6spd)
The main thing to remember is that in closed loop mode the ECM maintains nearly a stoch A/F ratio so that the O2 sensor sees the same condition regardless of fuel pressure. Here the O2 sensor is in it's most sensitive region so values swing between say .15 & .8-.8 Vdc.
When you go to WOT, the ECM sets the BLM cell number to #15 where the value is always 128 (quiescent value) and sets the Integrator to 128.
This means that the ECM is no longer moderating injector pulse width based on O2 sensor readings. So under these conditions the O2 sensor readings will go up as you raise fuel pressure. Also, here the O2 sensor does not swing up/down as it does in closed loop, rather the value will go to some rather steady value.
Bottom line, take some O2 sensor readings during a WOT blast, increase fuel pressure by say 4psi and take readings again. You should see a definite increase in O2 sensor readings under these conditions with no cross counts increase during the WOT pass.
When you go to WOT, the ECM sets the BLM cell number to #15 where the value is always 128 (quiescent value) and sets the Integrator to 128.
This means that the ECM is no longer moderating injector pulse width based on O2 sensor readings. So under these conditions the O2 sensor readings will go up as you raise fuel pressure. Also, here the O2 sensor does not swing up/down as it does in closed loop, rather the value will go to some rather steady value.
Bottom line, take some O2 sensor readings during a WOT blast, increase fuel pressure by say 4psi and take readings again. You should see a definite increase in O2 sensor readings under these conditions with no cross counts increase during the WOT pass.
