DataMaster and O2 Sensors
Thread Starter
Instructor
Joined: May 2014
Posts: 152
Likes: 1
From: Fayetteville NC
DataMaster and O2 Sensors
I am completely GREEN with DataMaster, and I have a question. I have a 94 with LT1 engine and recorded data with DataMaster at idle after the engine had fully warmed up. I set the Sample Rate to 4/sec and started recording. Both O2 sensors are flowing between the 50s and 800s changing with each sample. Is this an indication of bad O2 sensors or what? I have read that the reading should be about 450 for a proper AFR - correct? The idle (625 - 650) and AFGS (571 - 614 changing with each sample) are not changing much and the engine seems to idle fairly smooth. Help!!!!!!!
Or, am I just sooooo ignorant!
Thanks in advance.
Or, am I just sooooo ignorant!Thanks in advance.
Racer
Joined: Dec 2007
Posts: 416
Likes: 3
You want the O2 sensors to oscillate. They get an average by going min to max during a very short time period (that I forgot). If you have an O2 making a flat line it's dead, if you have one hanging at one spot too long it's going out or may be running too rich or lean, or theres some other problem.
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
It's supposed to go up and down. However, you will not get a 100% accurate picture of what's going on just by using the laptop. You need to use a graphing meter hooked directly to the signal wire that can view 5 milliseconds or less of what's going on.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Yea the narrow band O2's once heated swing between 0 and 900mV for an average of 450mV = 14.7 stoichiometeric a/f and the average is 450mV (closedloop). So your average of 425mV just a hair rich (something desirable at WOT). I think u mean to say AFGS = Air Fuel Gas Sample rate at idle and would expect idle mixture to be rich rather than lean - but its hard to hurt the engine at idle speeds even going lean so if the car will idle then should be ok. Have u changed anything yet on the tune?
FYI, ya know on the internet u will read a lot of homemade mechanics will tell u tuning is easy to do. Well it is very easy to screw things up and takes quite a bit of experience and reference material to get the tune correct. What i mean is start hitting the books and learn to reference anything u read on the internet.
FYI, ya know on the internet u will read a lot of homemade mechanics will tell u tuning is easy to do. Well it is very easy to screw things up and takes quite a bit of experience and reference material to get the tune correct. What i mean is start hitting the books and learn to reference anything u read on the internet.
Thread Starter
Instructor
Joined: May 2014
Posts: 152
Likes: 1
From: Fayetteville NC
Yea the narrow band O2's once heated swing between 0 and 900mV for an average of 450mV = 14.7 stoichiometeric a/f and the average is 450mV (closedloop). So your average of 425mV just a hair rich (something desirable at WOT). I think u mean to say AFGS = Air Fuel Gas Sample rate at idle and would expect idle mixture to be rich rather than lean - but its hard to hurt the engine at idle speeds even going lean so if the car will idle then should be ok. Have u changed anything yet on the tune?
FYI, ya know on the internet u will read a lot of homemade mechanics will tell u tuning is easy to do. Well it is very easy to screw things up and takes quite a bit of experience and reference material to get the tune correct. What i mean is start hitting the books and learn to reference anything u read on the internet.
FYI, ya know on the internet u will read a lot of homemade mechanics will tell u tuning is easy to do. Well it is very easy to screw things up and takes quite a bit of experience and reference material to get the tune correct. What i mean is start hitting the books and learn to reference anything u read on the internet.
I am at work and do not have my book, but AFGS is measured in gm/Sec so is it Air Fuel Grams/Second? The readings were actually 5.17 to 6.14 gm/sec.
I have not made ANY changes just yet. I am reading/studying everything I can on fuel tuning right now and MAY start making some SMALL minor adjustments to the fueling at idle to start with. Probably will get Cartech's book on tuning before I make any other changes. I realize that if you get too lean at WOT or cruising you can burn up pistons, so I am going real slow and making sure I understand what I am doing BEFORE I do it. Better safe than sorry.
I have only been studying and changing the shift points on my 4L60E so far. Just did not seem right or good to shift to 2nd at 10mph in the middle of an intersection!? I like what I have done with the trans so far, and I will be making some more changes.
