O2 trim = 80 What does it mean?

[3Sfever]

I recently installed 450 injectors. . . . I basically set SAFC to approx 20% reduction in fuel. The O2s are cycling most of the time, trims are near 100 in all three ranges, but I now have an annoying "drivability" issue.

With the new injectors and SAFC fired up, it seems that "transition" from no throttle to slight throttle is "jerky".

Before the new injectors, I do not ever recall seeing the O2 trim = 80. Now it shows that a lot, (when letting off the throttle). . Before these injectors, when I let off the throttle, I seem to remember that it would go straight to "100" (no fuel ?). . . . Now instead, it goes to 80 for a few seconds, THEN goes to 100. (monitored by ScanMaster).

Any ideas what this means?

[75blackray]

100 (or .100 02V) is super rich not lean. Second, do not tune with nb, I was probably the most hard headed person about believing what the scanmaster said for 02V, until I actually got a wideband saw how inconsistent these numbers were to what the wb was reading. What numbers are you getting at WOT?

[RealMcCoy]

100 fuel trim is not "no fuel"... That's the center target the ECU corrects from. 100 is ideal, if you see it hit 80 that means it's running rich at that point and is pulling fuel. If the data on steath316 is correct, 80 trim= 95% fuel (a 5% correction)

Can you log all the data during the problem area and maybe catch what's going on...?

What are the oxygen sensors doing during this event?

[75blackray]

Whoops, sorry I missed that you were talking about 02 trims (even though it is in the title). Your said you were reading it off the scanmaster so I assumed O2V just bc it is usually what people read off of it.

[3Sfever]

I have not had a chance to drive the car much since putting the injectors in. I need to drive it some more and watch more closely.

Basically though it is cycling O2v most of the time I would normally expect it to. Watching the numbers fly by --> it seems to stay in .3 to .8 range. . . . The odd thing is that it stops cycling when idling. (I forget now what it reads). I think it must be going into open loop. Giving it the slightest throttle will get it cycling again.

The long-term trims, L, M, & H are all in the high 90's

The O2 trim cycles around 100 most of the time, but when letting completely off throttle and coasting, it goes to solid 80 for a couple seconds, then goes to solid 100 until I give throttle.

In the past when watching O2trim, it went to solid 100 when coasting or high throttle. I don't remember seeing a solid 80 before.

[RealMcCoy]

When they stop cycling, do they fix low, or stay up around .8v?

If they are going low, they may be dropping out at idle, one of the first signs of them being fubar'd

Take a look at the O2s and O2trim on a graph, they should cycle several times a second, if not they're probably getting lazy.

Edit: you can't worry about what it does under decel, the ECU goes into decel fuel cut, and fixes the trims... You can watch it happen by seeing the O2s drop in the dirt, and the pulse width down to nothing...

[blkvr491]

So what exactly does hte o2 trim numbers mean? i just barely got my sm3 and am not super familiar with it. What are normal numbers for that and will it tell you lean and rich engiine conditions?

[3Sfever]

Originally Posted by blkvr491

So what exactly does hte o2 trim numbers mean? i just barely got my sm3 and am not super familiar with it. What are normal numbers for that and will it tell you lean and rich engiine conditions?

O2 trim is a "instantaneous" measure of fuel adjustment. If 100, then the O2 sensors are reporting back that the ECU sent the correct amount of fuel. If less than 100, the mixture is rich. Over 100 is lean. . . . Note that the O2 trim is constantly changing while in "closed loop". If it seems to be cycling around 100, then everything is normal.

If the O2 trim goes to a solid 100, that means the system has gone to open loop . . . (the ECU is no longer listening to the O2 sensors. . . . .
- This occurs at WOT (uses "maps" to decide how much fuel to send)
- and when coasting, no throttle (no fuel is sent).

Low trim, Med, and High trim are "averages" over time. Again, 100 is normal. Under (80 or 90) is rich, and over (110 or 120) is lean.

.

[Gray Haze]

Originally Posted by 3Sfever

O2 trim is a "instantaneous" measure of fuel adjustment. If 100, then the O2 sensors are reporting back that the ECU sent the correct amount of fuel. If less than 100, the mixture is rich. Over 100 is lean. . . . Note that the O2 trim is constantly changing while in "closed loop". If it seems to be cycling around 100, then everything is normal.

If the O2 trim goes to a solid 100, that means the system has gone to closed loop . . . (the ECU is no longer listening to the O2 sensors. . . . .
- This occurs at WOT (uses "maps" to decide how much fuel to send)
- and when coasting, no throttle (no fuel is sent).

Low trim, Med, and High trim are "averages" over time. Again, 100 is normal. Under (80 or 90) is rich, and over (110 or 120) is lean.

.

Correct that to 'open loop.'

Closed loop is when it uses the o2's to control the injection maps based upon trims, open loop is when it says fuck the o2 sensors and injects based upon pre determined variables from maf input and map table value.

[TurboBob]

during decel the O2 trim will 'stick' at 80 as sort of a decel enleanment.

We need to talk more about what the trims do when not decelerating to know where the tune stands.

If all the main trims are stuck at 100, then the ECU is not 'happy' with what the O2 trims has done to toggle the O2.

So, watch what the O2 trim does at cruise when you go on and off the throttle and see if you can tune things to get the O2 trim to hang around 100 with the O2 toggling.

At idle the O2 trim will try to make the O2 toggle, if it has to adjust too far the ECU gives up.

Generally, richer tunes have better driveability.

Bob