Adding O2's

[jsm00z28ss]

I have a 427 ci ls1 motor in my 2000 camaro. It was tuned in open loop and I want to put the O2 sensors back in. If I put them in and turn them back on what kind of problems can I run into. Would the car need to be completly retuned or will it be ok.

[joecar]

It should be ok...

If it was tuned right then the LTFT's will be low.

[jsm00z28ss]

Great thanks I will get them back in and see what happens. If things seem to go crazy I will post back any problems that I have.

[WeathermanShawn]

Sometimes those O2's get a little lazy, especially at start-up and until you hit your normal operating temperature. But, that can be easily manged by an accurate VE Table and MAF Calibration Table.

I run closed-loop with a moderately aggressive cam. I personally prefer the concept of a system that is constantly attempting to run your car at or near stoich (~14.7 AFR)..

My only suggestion is that at some point your look at your tune and your O2 Switch Points. After a lot of logging, I chose slightly higher O2 voltages. Using my wideband, that gave me a consistent 14.7 AFR and my LTFT's are right on.

Good luck. I am interested in how that engine runs! Let us know.

[mr.prick]

I agree with using O2s.
I flat-lined the switch point @ 450mV and used LTFTs for non PE areas of the VE & MAF.
LTFTs & PE AFR are right where I want them but
it's the damn transient fueling that I have trouble getting straight. :bangin:

Don't be surprised if you have high LTFTs after enabling CL. :sneaky:

[Frost]

It should be ok...

If it was tuned right then the LTFT's will be low.

Just leave the LTFTs off... If the MAF/VE was tuned well enough for good OL driving, the STFTs will be more than plenty correction and if they wander off positive a bit, they won't interfere with WOT like LTFTs will. :cheers:

[WeathermanShawn]

Just leave the LTFTs off... If the MAF/VE was tuned well enough for good OL driving, the STFTs will be more than plenty correction and if they wander off positive a bit, they won't interfere with WOT like LTFTs will. :cheers:
Yea, I have not had the nerve to try that yet. I see your point about not interfering with WOT..Frost isn't there a point if STFT's exceed a certain value, then the LTFT's become active?

I know you will probably say..if your tune is on, then that will not happen. I am just curious if there is any 'side effect' of turning off LTFT's. What happens if STFT's wander off and your LTFT's are not active?

[Frost]

Yea, I have not had the nerve to try that yet. I see your point about not interfering with WOT..Frost isn't there a point if STFT's exceed a certain value, then the LTFT's become active?

I know you will probably say..if your tune is on, then that will not happen. I am just curious if there is any 'side effect' of turning off LTFT's. What happens if STFT's wander off and your LTFT's are not active?

We are all trying to learn, so anything you can add is helpful.

Thanks.

..WeathermanShawn..


No, they reach the same limit regardless of the state of LTFTs. LTFT's reach the point of updating whenever a defined ECT is met (typically around 149F OE for GenIII) and the STFT correction exceeds 4%.

If you are worried about things, set a lower limit on trim correction, though you shouldn't need to do so.

I think it's a plus in some areas... If you have a misfiring cylinder around idle, the LTFTs will stack on a pile of fuel that will be applied at next cold start if not cleared and further aggravated by the STFT addition.

If his car ran well in OL, it should be fine in CL with just short term trimming.

[WeathermanShawn]

Thanks.

I am going to try it!:cheers:

[jsm00z28ss]

I just turned on the ltft and stft along with using the stock correction values for both. I have yet to get under the car and put them in I hope to do that today. I was curious about the switch point which is at a stock setting also. I will go back and disable the ltft and see where it goes. The cam in there may be small for the motor at 254/254 581/581 112 lsa. Should I try the flat switch point as well.

[WeathermanShawn]

I just turned on the ltft and stft along with using the stock correction values for both. I have yet to get under the car and put them in I hope to do that today. I was curious about the switch point which is at a stock setting also. I will go back and disable the ltft and see where it goes. The cam in there may be small for the motor at 254/254 581/581 112 lsa. Should I try the flat switch point as well.

It is probably best to just start with the stock O2 switch points and see how it goes. We just mentioned a flat-line of 450-550 mv as a switch point as many of us have had better results with that method.

But, for starters (IMO) it is easier and more consistent on your first few tunes to use your stock O2 switch points. You can aways apply the 'flatline' method as you narrow down your STFT's & LTFT's. At some point you can try just disabling your LTFT"S as Frost suggested and just run with STFT's. You can then manipulate your O2 switch points and other parameters to fine-tune it if necessary.

[Frost]

The reason the O2 table is not flat is that their response is relative to both exhaust temperature and pressure (more so temp tho!). I'm still fumbling in the EFIL editor, but that's why their switch points are tied to the airflow mode (HPT terms).

[Frost]

...
As a side note, Frost (and OP) I have played around with those switch points numerous times to see what effect they had. Using a wideband and logging Fuel Trims, the only ones I could successfully manipulate were near Idle. Small changes make a great difference for me at Idle. At cruise the changes were hard to detect.

For my combo, I settled on a 550 mv flat line. While I highly respect the GM engineers that constructed that Table, I think with aftermarket heads and cams, and headers.. it really alters how the O2's react....



That's definitely the case (as far as changes have higher impact near idle/lower airflow modes)... As far as the last sentence, that is definitely the case as well. Pardon the HPT terminology, but another table of relevance is the Closed Loop Integrator Delay (sometimes called transport delay in the broader world of tuning) which is setup in Base Delay vs. airflow mode. The units are time in mS. With headers and the move of the NB O2s, this time clearly needs to be increased. I don't think I have EVER seen a car roll out of another shop with anything but OEM values here.

I am over here at EFIL because HPTuner's is making me insane with the lack of public releases for almost 2 years now. That means that EVERYTHING made in the last few years must be tuned with a beta. There were some beta issues, and I am not rolling the dice with a customer's nice new Vette or Camaro. I will not use beta software for 'production' work, and I can't otherwise tune new Vettes and Camaros... It's kind of sad really. The diesel stuff is a little more 'meaty' with EFIL as well. There are two sides to every coin though... HPTuner's can be purchased and the GenIII car portion unlimited would only cost an additional $1100 in credits where as it's $2500 for the same with EFIL (gag). Also, with HPT, cars can be tuned one at a time with every single-VIN license carrying over at 80% face value towards unlocking the vehicle group so that over time as you do them, you "get" all of the unlimited licenses. EFIL credits HALF of total stream with VIN licenses, so I would still still have to tune like 12-13 GenIII's at $100/car and then still shell out more than the entire cost of HPT's GENIII cars (another $1250) just to unlock the GenIII stuff. In Australia where guys get a bazillion dollars to tune a car it might be fine, but it's awfully steep otherwise.

[mr.prick]

Common knowledge/lore of NBO2 stoich switch point is 450mV :nixweiss:
and if you look at {C2301} you will see the stoich reference is 451mV. (fbody)
The newer OS' have the switch points @ 450mV and
I've heard a few "Pro Tuners" say to set the switch points to 450mV. :gossip:
That's my excuse anyways. :angel_innocent:

OL tuning on the streets = unstable ECT/IAT temps and made VE values vary. :frown:
STFTs seemed too erratic for me altho they are "in the moment" while
LTFTs can carry over to spots that are actually high/low.
STFTs can be high//low with LTFTs near perfect at the same time.
Obviously you don't want LTFTs adding in PE but I think
it can be a good thing in certain situations.
Without a good filter using LTFTs will screw things up. :doh2:

As flawed as it may be this is my reason for using LTFTs.
One is probably not better than the other but LTFTs work best for me.
I'm nowhere near as knowledgeable as Joecar and I can't predict the weather either. :laugh:

In Jesse's sticky I posted a calc_pid that uses STFTs & BEN w/RTACS. (http://forum.efilive.com/showpost.php?p=106498&postcount=88)

[WeathermanShawn]

Thanks for the compliment. Weather Forecasting can be tough too.:)

Mr. Prick,, I think that is a very logical plan you have laid out. You have done a lot of good work.

I have no great insights into why 550 mv (flat line) works for me. One my original stock tune I was +15-+20 LTFT's. Hooking up the wideband confirmed lean spots everywhere. The car ran terribly.

Perhaps with the O2 sensors near the header, my car likes a little higher O2 switch point. I have always battled being too lean on this car, so perhaps it likes it a little rich..or it fools the O2 sensors into keeping my LTFT's happy!

[joecar]

Just leave the LTFTs off... If the MAF/VE was tuned well enough for good OL driving, the STFTs will be more than plenty correction and if they wander off positive a bit, they won't interfere with WOT like LTFTs will. :cheers:Good idea... do you mean have B4206 "semi-open loop" STFT enabled...? I do like that better than CL...:cheers:

How far from stoich can SOL/STFT trimming operate, or can it only trim to stoich...?

[joecar]

...
I'm nowhere near as knowledgeable as Joecar and I can't predict the weather either. :laugh:
...lol... I play with it alot, I read a lot (I don't sleep much anyway), and I ask questions...

LOL, it is easy to predict the weather in So.Cal with 99% certainty... "sunny with no rain"... :hihi:

WeathermanShawn has a tough job there in Co. where people (not just tuners) depend on the weather report, my hat off to you...:cheers:

[joecar]

jsm00z28ss (http://forum.efilive.com/member.php?u=9907),

We are sorry we hijacked your thread... :doh2:

We are easily distracted and goof off a lot (this is how we learn stuff)...:hihi:

[jsm00z28ss]

That is no problem. I am totally new to this so it will help me as well. I put my o2's back in and made the changes to the tune but it never went into closed loop. There has to still be something that I am missing. For now I am just going to pull everything out and put it back to the way it was.

[joecar]

...
How far from stoich can SOL/STFT trimming operate, or can it only trim to stoich...?My understanding is:

- B4206 allows OL STFT trimming to stoich from B3605 (same as SOL in COS).

- B3801 disabled and B4205 temperature enabled allows CL STFT only trimming (to stoich).


So, either way, STFT only trimming will trim to stoich only...


Sanity check: have I got this right, anyone...?

[mr.prick]

It's been a while since I tried this but IIRC
{B4206} Enabled is just CL w/o LTFTs
{B3605} won't come into play even if PE is off.

[Frost]

There is a lot of EFIL specific terminology here that I don't know... The OEM PCM for GenIII can run STFTs in OL (off by OEM default), STFTs, and LTFTs. My suggestion was simply to use STFTs and not LTFTs. If the MAF and VE are close, the driver should not be able to distinguish between the 2 closed loop fuel approaches.

[WeathermanShawn]

l WeathermanShawn has a tough job there in Co. where people (not just tuners) depend on the weather report, my hat off to
you...:cheers:
Thanks for the 'shout out' Joecar. Yes, Colorado is a beautiful state, but can be a tough place to forecast weather. Thanks for recognizing the challenge.

[joecar]

It's been a while since I tried this but IIRC
{B4206} Enabled is just CL w/o LTFTs
{B3605} won't come into play even if PE is off.B4206 description says:
"If this parameter is enabled then O2 feedback (STFT) will be used with the Open Loop table."

[Frost]

B4206 description says:
"If this parameter is enabled then O2 feedback (STFT) will be used with the Open Loop table."

Makes more sense read like that... In HPT the description is just STFTs active in OL.... which seems to be contradictory at face value :shock: This is the same item that I mentioned in my post above (and said off by OEM default but was referring to cars not trucks...).

[WHYTRYZ06]

just do OLSD and be done with it :)

[joecar]

jsm00z28ss (http://forum.efilive.com/member.php?u=9907),

Is there any particular reason why you want to put the O2's back in...?

[jsm00z28ss]

Just something I wanted to do to see if I could and to see how the motor would react. I also want to see if there is any way to improve upon what I have.

[joecar]

Ok we were just curious... in case you had seen some problem.