Nervous O2 readings and missing EGT function.

Tom Kelly

Active Member
Joined
Jun 23, 2016
I’ve been wondering why the O2 voltage on all of our GN’s jumps around so much while the wideband a/f ratio seems steadier. It seems that this is intentional. I have read that the computer adjusts fuel a zillion times a second to cause the voltage in the sensor to jump over and under a central point. It does this (I am told) to enable the catalytic converter to do its job better. It seems that some aspects of catalytic converting are best done at rich conditions and some lean conditions. This intentional jumping around accommodates that while not causing fuel to be too rich or too lean.

This sounds good but that got me to wondering. I don’t think my GN is the only one on the planet without a catalytic converter. Has anyone ever thought of disabling this feature Can it be done? Would it matter?

Another sort of related question. I have read that Eric’s turbotweak chips “disable” EGT function. If this is so what is the advantage of doing that? And does that mean the EGT gear should simply be removed to clean up the driver side of the engine?
 
I’m running a stock ecm with a sd2 chip and I have never heard of this EGT thing you are speaking of . I have added 6 egt probes to monitor my temps . I am also not running a cat . Are you running a stock narrow band sensor? If so that is how they are designed to function. They dip up and down unless you are WOT. I would recommend you upgrade to a wide band sensor which would give you more accurate A/F readings then get Eric’s 6.1 Wideband chip which would allow you to target a specific a certain A/F of your choice .
 
I’m running a stock ecm with a sd2 chip and I have never heard of this EGT thing you are speaking of . I have added 6 egt probes to monitor my temps . I am also not running a cat . Are you running a stock narrow band sensor? If so that is how they are designed to function. They dip up and down unless you are WOT. I would recommend you upgrade to a wide band sensor which would give you more accurate A/F readings then get Eric’s 6.1 Wideband chip which would allow you to target a specific a certain A/F of your choice .
Yes, I have the AEM wideband and that was my point. The ACTUAL a/f ratio is steady compared to the jumping around on the O2 voltage. It is indeed meant to run that way. My point was that I understand it was meant to run that way for only one reason...to enable the CAT to run better and more efficiently. I was just wondering if, for those of us without a CAT, that function (intentional jiggling of the voltage) could be eliminated and, if so, would that serve any useful purpose.
 
I think you’re confusing egt (exhaust gas temperature) with egr (exhaust gas recirculating).

Keep the egr if you need to pass inspection I guess. I think Eric deletes it because most owners put the cat and related emissions items in the garbage, where they belong.
 
I think you’re confusing egt (exhaust gas temperature) with egr (exhaust gas recirculating).

Keep the egr if you need to pass inspection I guess. I think Eric deletes it because most owners put the cat and related emissions items in the garbage, where they belong.
Yes, was thinking EGR when I wrote EGT. I tend to do stuff like that. Yes EGR. The reason I was asking about removing it is because right now it is doing no harm (except taking up space) and I have read of vacuum leaks sometimes resulting from removal. Is that only if the blocking plate is not carefully installed or does that happen a lot?
 
Yes, was thinking EGR when I wrote EGT. I tend to do stuff like that. Yes EGR. The reason I was asking about removing it is because right now it is doing no harm (except taking up space) and I have read of vacuum leaks sometimes resulting from removal. Is that only if the blocking plate is not carefully installed or does that happen a lot?
I should have added that I do not have to pass emissions. Our GN's and all other cars over 25 years old are exempt in Connecticut.
 
The stock narrow band O2 sensor has nothing to do with the Cat. It's what keeps the mixture where it should be and is basically an on off switch. A wide band is linear and much better at doing the job.
 
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