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Need Help O2 & Fuel Trim

chop91vr4

Well-known member
Joined
Jul 31, 2014
Messages
61
Location
new haven indiana
I am trying to tune this thing still I have a data logger a A/F guage that doesn't really tell anything other then rich lean & stotic but I have a better infofrom my TB Timer on the O2 voltage & the A/F & I'm trying to figure out how I get the trim percentage from this. I mean wtf is 100% what mathmatical equation do I need to do to come up with this?>? Thanks I apperciate any help with this
 

tektic

Well-known member
Joined
Dec 19, 2012
Messages
1,497
Location
ronkonkoma, ny
What are you logging and tuning with?
You cant tune with a narrow band o2 sensor.
 

chop91vr4

Well-known member
Joined
Jul 31, 2014
Messages
61
Location
new haven indiana
I have a pda logger & I'm about 98% positive that it has a wideband in it, but that is from the fact that I removed it when I put new down pipe on. ( from knowing what they both look like this was a wideband )
 

prove_it

Well-known member
Joined
Jul 3, 2008
Messages
4,201
Location
Sioux Falls, SD
100% Is basically your centerline for the fuel trim. Anything below 100% and the ecm is pulling fuel, anything over 100% and the ecm is adding fuel to the mix.

Please correct me if I'm wrong, I MAY be backwards as it's been a while since dealing with this old school tuning.

You'll see it won't stay at 100, it will vary 95-105 at idle. Also in WOT the fuel trims are not used. (open loop)
 
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