Tuning for headers - B4105 question

[derekf]

Bought a new (to me) LS1 car - 98 Trans Am.

Seller won't respond to questions now that he's got his money, so the only things I know for sure about the engine is that it has LT headers (supposedly Pacesetter) into 3" duals, and it has a giant K&N mostrosity for the filter. Believe the MAF is ported, but I have low expectations as to how well.

Tune compares as identical to the GM tune #19980100 so it doesn't look like anyone's ever done a tune. I've got an LC1, but I haven't installed it yet to do any WB logging.

Using the search, I found several threads that mention that for LT headers, the o2 switch points should be set to more like 450... but {B4105} has different rows for different "CL Modes" and some are above 450 and some are below already. Seems to me that this is something that should probably be set before adjusting other tables; can someone point me at a reference that defines the "CL Modes" or give a pointer as to which rows should be set to 450?

If it matters, my LTFTs are pretty much -10 across the board. Can, of course, get specifics as needed.

[WeathermanShawn]

Hi there..

It gets fairly complicated. For tuning MAF and/or VE utilizing closed-loop, a number of us have had more success utilizing an unilateral mv switch-point reading. Many use 450 mv as that 'equates' to ~14.7 AFR. I occasionally use 550mv. That reading keeps my closed-loop AFR closet to stoich (~14.63 AFR).

I believe the theory is that as you get into higher airflow (CL Modes) the ability of the narrowband to 'cool' increases..hence the differing mv to its respective CL Mode (airflow).

My advice is not to 'sweat the small stuff' too much at this point. Personally, I see no downside to just using 450mv for every CL Mode. The whole process of CL Modes becomes more important if you tune utilizing closed-loop and LTFTBEN's.

It is more of a refinement concept to tuning, than basic. Save it for later would be my advice.

Hope that helps..

[joecar]

Post log and tune files.

[derekf]

Tune is literally the default GM tune 19980100 (98 Trans Am/manual).

No log with me here at work, will post when I am home.

Edit: Are the following the PIDs you'd want to see?

VSS
TP
RPM
DYNCYLAIR or DYNCYLAIR_DMA
DYNAIR
MAF (SAE or GM)
MAP (SAE)
DYNAIRTMP_DMA
IAT
ECT
EQIVRATIO or AFR
SPARKADV
KR
LONGFT1
LONGFT2
HO2S11 (not HO2S12 or HO2S22)
HO2S21 (not HO2S12 or HO2S22)
MFTOTAL

(I don't have the LC-1 installed yet to get WB O2 numbers)

[WeathermanShawn]

If you do not exceed 24 channels, you might try to log MAF Frequency. Perhaps dump Misfire Pid? That way we can compare it against your LTFT's across the MAF Frequency range.

Without starting a huge Internet battle, here are a few points to ponder. Radical air-boxes and filters along with ported MAF's do not always supply more airflow into the engine, but simply disrupt the MAF airflow. And that drives your Trims crazy.

Probably a nice high-flow LS1 Lid and filter along with a stock MAF, will deliver within 5HP of your current setup and be a lot easier to tune. With the headers, the type and location of the narrow-bands will determine how they are switching.

A good log will help.

[derekf]

Couldn't log DYNAIRTMP_DMA - said it wasn't a supported PID.

DEREKF_00.efi

Not really sure how I should be driving while logging - I don't think I got to full throttle, and I'm sure I didn't break 60mph (too many cops around). Looks like I may have been misremembering the LTFTs as it looks like everything is +10ish rather than -10ish.

[WeathermanShawn]

Derek:

Don't worry about logging and driving. I have logged over 30,000 miles without a ticket or incident. By all means, do not stare at your laptop while driving! If you are using a laptop you can set up audible alarms that will sound when you have KR, ECT too high etc.

Use your drive gears as much as possible. There is no law against safely taking an on-ramp in a spirited manner, but if you don't feel comfortable stick to the track or a dyno.

As far as your log..

1. Need a wideband hooked up (mandatory).
2. Your LTFT's are very high. You need to adjust the MAF and VE Table. (see CALC.VE Tutorial in my sig).
3. Your O2's look like they are switching too slow in spots. How old are they, and where are they located?
4. Way too much KR. Some of low RPM. Are you gunning the engine? Once your fueling is down then you can work on spark.
5. Your IAT's are way too high! You need to log in cooler weather, or get some ambient air in there.

I would read through the CALC.VE Table Tutorial. With a wideband and fresh O2's, it should only take 2-3 logs to go from a questionable tune to a very good one.

Good luck (and do not take my criticism personally). Better to get it right by knowing what needs to be addressed..

[derekf]

I appreciate the feedback, and I don't see anything to take personal.

Wideband probably this weekend.

No idea how old the sensors are, but they're in the collectors of the long-tube headers. Is that the problem or do I need to replace them?

Not sure what you're asking when you ask if I'm gunning the engine.

As for IATs - this is Texas in July, cooler weather will have to wait for October or so - ambient air is 101F today or so

[joecar]

+1 NBO2's are switching slowly, less than 2 times/second... good ones will switch faster than 4 times/second.

If the NBO2's are aolder than 60K miles or if they are fouled then they probably should be replaced.

[WeathermanShawn]

I appreciate the feedback, and I don't see anything to take personal.

Wideband probably this weekend.

Good idea!

No idea how old the sensors are, but they're in the collectors of the long-tube headers. Is that the problem or do I need to replace them?

They are switching..they just seemed a little sluggish. New ones can't hurt though.

Not sure what you're asking when you ask if I'm gunning the engine.

Derek..see attachment. On frame 1, you are at 650 Rpm with a TP% of 25% and 5 degrees of KR. I am just trying to understand why?

As for IATs - this is Texas in July, cooler weather will have to wait for October or so - ambient air is 101F today or so

No, I understand. Denver hit 101F this week, but I kept my ambient right at 101F. Might look into a Free Air Mod to get it cooler. 136F is heat soak and will really hurt tuning.

Keep at it. There are just a few issues to ponder..