edfiero

Please take a look at the scan in the attached link, of my new 383 LT4 Stroker. (OBD II) I don't know how to correct this inbalance between the left and right bank.

http://members.localnet.com/~jteague/SCAN47.xls

Throttle Position voltage is .68 at idle
Vacuum is good. Haven't been able to locate any vacuum or exhaust leaks.
Plugs and Wires are new. Triple checked they are all hooked up to the correct cylinders.
Fuel Pressure is in the mid 40's at idle
Injectors have all been flow tested and are within 2% of each other
02 sensors are new, AND I've tried switching right and left sides and the problem does NOT move with the sensor.
Although not shown in this scan IAC counts are in the low 40's at idle.

Any suggestions would be appreciated.
(sorry for the double post but I'm not getting any responses over in the computer section.

Injuneer

There's not much in the log. There not much in the post regarding the engine.

Appears you just kept poking the throttle. Since there's no time stamp, its impossible to see what the sample rate is, but if I had to guess, I'd say it was sitting in the driveway and you were goosing the throttle? Is this correct? If so, its not very useful.

Appears you are trying to rationalize the difference between the long term fuel trims on bank 1 and bank 2. It would be more meaningful if you had the fuel cell numbers in the log. Also generally a good idea to include things like MAP, MAF, IAT, CLT, MPH, a time stamp, knock retard, etc.

Other than the fact that its an OBD-II 383, there's no useful info.... how big is the cam? What throttle body? What kind of exhaust?

Finally, what software are you using? Are the column headings the ones provided by the scan software, or did you make your own headings? I've reviewed hundreds of logs, and have never seen one before with this nomenclature.

edfiero

Yes... the question is about the differences in the fuel trims between bank 1 and 2.

File is as produced by the scan software. I didn't modify any column headings.
Software is from http://www.obd-2.com/. You are seeing about 1 line of data per second, recorded while driving around a residential neighborhood. This is why you wont see any high revs.

I didn't want to clutter up the post with all my "mods". Thought I could cut to the chase, but if all that other info is required.... here goes:
2 1/2 inch exhaust
Tri-y headers
Random Technology cats
3200 Yank Converter
Dynomax Muffler
52 MM throttle body
Stock Injectors and MAF
AFR 195 Cylinder Heads (compression ratio should be about 10.8:1)
1.6Ratio Roller Rockers
Cam is 214 / 224 with 112 Lobe (yes I know its mild)

Im not sure what you mean by fuel cell numbers, that appears to be some kind of OBD-1 term. I am supplying all ENHANCED data from an OBD-2 computer relative to fuel and 02's. All other data like MAF, IAC, etc is within spec.

Computer was previously modified by PCMforless, with all mods except the 383. I haven't had any additional tuning done yet.

Injuneer

The "fuel cell" is used in both OBD-I and OBD-II..... Cell 16 is idle, cell 17 is open loop and decel, cell 18 is open loop load and PE mode if upper cells are cutting fuel, cells 01-15 are arranged in a grid with MAP on one axis and RPM on the other. By looking at the specific cell number, and the long term fuel correction that is stored in it, you can sometimes determine the source of the problem.

If you need a bit of background on the concept of "cell", check my online scanner writeup..... its toward the middle in the section on fuel/air control:

http://members.aol.com/InjuneerZZ/ScanMast.htm

The other parameter may be "within spec", but for someone to thoroughly review your data, they'll get the best results if they can see those parameters. Just my thought..... if you don't weant top supply them, its up to you.

edfiero

I've got another scan uploaded with additional data, Fuel Cell, MAP, MAF, IAC etc.

Would appreciate any assistance in understanding why my fuel trims are all over the place.

http://members.localnet.com/~jteague/SCAN3a.xls

Thanks

Injuneer

The sampling rate is so low (approx 3.1 seconds per frame) that is makes it very difficult to analyze the data. The PCM is updating 9 times per second. You need to get the sampling rate below 1 frame per second. At this slow rate, it masks transitions between fuel cells, and there is no certainty that the data in one column bears any relationship to the data in another column, since they are taken so far apart. It becomes a problem with matching the long term fuel corrections up to the cells, because if a data point is in transition between cells, the PCM weights the long terms by looking at both cells.

That said, it appears that all of the cells that show a huge "split" in the long term corrections are low load/low RPM cells - 16, 2, 5, 6, etc. When you look at the high load cells.... 11 - 15, the split disappears. In fact, Cells 10-15 are showing that it has to add major amounts of fuel (10-14%) on both sides, so the tune looks a bit shakey.

So its one of two possibilities. First, how long since your PCM was "reset"? It may not have operated in the high load cells for enough time if it was reset recently. But I don't think it was reset.

Something is affecting the engine to cause the low RPM split. Even though I've asked, you still have not told us anything about the engine, other than its a "383 LT4 Stroker". For starters, what throttle body are you using? What are the cam specs? It doesn't look too big, since MAP is 12"Hg at idle. Both of those can become factors that cause split long terms. Please tell us more about the engine. People aren't going to be able to help you unless you include the info.

And, you obviously have a major problem with knock. Seems like every time you move the throttle, its getting knock retard in the range of 5-11deg. Again, the tune is suspect.

I would also encourage you to include data for coolant and IAT.

edfiero

Thanks for the feedback, but you must have missed the earlier post. I provided the following info about the car. What else are you looking for?

2 1/2 inch exhaust
Tri-y headers
Random Technology cats
3200 Yank Converter
Dynomax Muffler
52 MM throttle body
Stock Injectors and MAF
AFR 195 Cylinder Heads (compression ratio should be about 10.8:1)
1.6 Ratio Roller Rockers
Cam is 214 / 224 with 112 Lobe (yes I know its mild)

The intake air temp was 40F and the car was fully warmed up about 190 / 195

I agree the sampling rate of the scan is slow, but that is a function of how many sensors are being recorded. I think I can record 4 or 5 sensors a second. When I throw 20+ different sensors up there, its going to take a while to read them. If you'd like to give me a more concise list of 5 or 6 sensors that you'd need to provide some feedback, I can provide a new file.

The original tune was done by PCMFORLESS, however I have not had it retuned yet (Since adding the 383) Heads, Intake, Cam were are all part of the original tune. I'm not sure what you mean by RESET of the PCM. I have had the battery disconnected within the last 50 miles, if that will do a reset.

Injuneer

My bad on the "info"... I keep confusing this thread with the duplicate one on "Computer...", which is always a problem. My apologies.

I don't know much about the scan software you are using, other than their advertising. I can tell you that alternative systems like Autotap will run through twice as many sensors as you are logging in under one second. If the system you are using can not accomplish any better than what you have shown, its going to limit its usefulness.

All considered, doesn't seem like we're communicating too well here... more like a disagreement on scan tools and what data is needed, so I'll back off and let someone else follow up on this.

edfiero

Not disagreeing at all. I am attempting to provide what you asked for.... I'm just frustrated at my own lack of knowledge on the subject and that fact that it seems no one wants to "work with me" and the tools I have at my disposal.

Below is a new file, with a slightly higher data rate. (This is as fast at it will scan. I'll have to remove sensors to get a faster refresh rate)

I'd still appreciate any suggestions on where to look for a cause to the differences between the left and right fuel trims. I do see there is some correlation to the Fuel CELLs that you mentioned earlier, but I don't know what that means as to where to look for a problem on the car.

http://members.localnet.com/~jteague/SCAN56.xls