One More Time: PE VS OLFA Commanded AFR

[WeathermanShawn]

Hello:

Need a double-check.

I have heard various descriptions of how the OLFA Table B3605 and the PE Modifier Based on RPM B3618 interact. I.E., that the PCM will take the richest of the two (Commanded AFR). Lately, I have been wondering if this is true if you are not running Open-Loop.

Attached is a tune and a log where I purposely made OLFA richer than PE. But, yet my Commanded AFR followed PE regardless.

Did I do something wrong, or can I make the assumption that if you are running MAF Closed-Loop, PE commands irregardless?

Thanks..

[joecar]

B3605 is active only in OL.

B3618 is active only when the PE enable tables (B3608-B3616) trigger regardless of OL or CL.

So, if PE activates at PT, the PCM is still in "CL" (see edit below), so the richest of the active tables will be B3618 (since it is the only table active at this moment).

An assumption made is that PE only activates at WOT... but if you look at B3616 for example you will see that is not a valid assumption.

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edit:

since the PE EQR is non-stoich, the PCM can't really be in CL... but it is not in OL either
(otherwise B3605 would have activated, and Shawn's log/tun files shows that it didn't);

if the PE EQR was stoich, then the PCM would stay in CL.

:)

[mr.prick]

If you want to cure a lean/rich cold start through {B3605}
what you can do is use {EXT.EQR1} as a multiplier.
The units in {B3605} must be in Lambda or AFR,
if the are in EQ use {EXT.LAM1}.
You can also make a calc_pid with a desired AFR/EQ/Lambda and
divide actual AFR/EQ/Lambda by that for a multiplier.

This will reduce/increase the value in {B3605} until
AFR/EQ/Lambda is to your liking while waiting for CL.
I see no reason for AFR to be too much richer than stoich and
lean cold starts can be aggravating.

I'm pretty sure GM never meant for actual AFR to be
as rich as what is in {B3605}.

[WeathermanShawn]

All good points Mr. P and Joecar.

What is interesting..If you "Google' LS1 OLFA PE", there are over a dozen pages that state [..the PCM commands the richer of OLFA and PE at WOT..].

It appears the more correct statement might be [..if in closed-loop, the Commanded AFR will be dictated by any residual LTFTBENS and the Commanded AFR as indicated in Table B3618 ]...

Even though technically in PE Mode you are in 'open-loop', it does not appear to trigger the OLFA AFR default (cold open-loop).

Mr. P., I know you do a lot of CLSD tuning. Have you found that to be true? Seems like I was getting the same PE Commanded Fuel Closed-Loop whether I was MAF or SD. I.E. OLFA Table does not dictate AFR when in closed-loop...PE AFR does.

Have you had similar experiences? I know most people normally keep B3618 'richer', but always good to know for sure.

Thanks..

[mr.prick]

I never disabled PE in CL so I don't know if {B3605} comes into play.
In OL {B3618} will override {B3605} if it is richer.

[joecar]

Shawn,

Take another log including the pid FUELSYS... this will indicate which of CL/OL the PCM says it's in.

[joecar]

See my edit above.

[WeathermanShawn]

Shawn,

Take another log including the pid FUELSYS... this will indicate which of CL/OL the PCM says it's in.

Yea, I can do that. A lot of people (including me) have usually kept PE richer than OLFA, so it might not ever come up.

I think I know what you are saying Joe, I may have logged FUELSYS before..it seemed like it was some sort of hybrid OL or CL Loop. Same thing would happen when my car hit EVAP. It would change FUELSYS status.

I will add it and do another log. I think that may be it. Don't know if that is unique to my year or OP, but I will follow through on that suggestion..:)

Thanks.

[WeathermanShawn]

Follow-Up:

Attached are a few screen shots of where I logged FUELSYS as suggested.

Also, attached are my tune and log.

Basically, the car enters OL-Drive..and all Commanded Fuel is dictated by PE Mode Table B3618. For what it is worth OL-Drive is also indicated when the car undergoes EVAP.

Don't know what to really make of that, but occasionally I have had EVAP 'mess' with my WOT. I think they both share FTC Cell 22.

Bottom line is that when you utilize closed-loop PE Commanded AFR will be followed, irregardless of the OLFA Table. Perhaps OL-Drive is a 'hybrid' Open-Loop?

[joecar]

Very interesting... you have a pm.

[WeathermanShawn]

Well, Joecar you finally 'broke' my car..:grin:..just kidding.

For now, I will just post the tune & Log. Joecar had me do an interesting test. I put Table B3618 to the same value as B3601 (stoich). For B3616, Normal PE Mode Enable all TPS values were put to 10%.

Table B3605 was purposely changed to a richer value of 13.0 AFR at normal engine operating temperature.

Results:

1. Car started normally using the Table B3605.
2. Car went into Closed-Loop at 34C (normal).
3. When PE mode was hit, car went into OL-Drive..commanding 14.629 AFR. At 10% TPS it stayed continuously in OL-Drive.
4. 5-10 minutes later it attempted to do its EVAP Purge (FTC cell 22). It was unable to do its EVAP purge (cell 22 is also WOT). Car immediately threw a DTC Code P0131 and P0137..and defaulted into the Table B3605.

Pulled car over, cleared codes..reloaded 'normal' tune. Everything worked out.

Joe, or anybody else who might be interested. PE Mode (in my OS) seems to always initiate OL-Drive. When in OL-Drive, the EVAP Purge is not active. Believe me it was not long before I smelled gas fumes and I went rich. No Trim, no EVAP..it did not like that 10% TPS enabler. To minimize pids, I did not log IPW or H02S11..but my O2 sensors pulled a DTC and I found an unique way to use the OLFA Table:grin:..

Joecar interesting experiment, but the U.S. EPA may have done something tricky with FTC cell 22 and EVAP. Thats my theory. Any thoughts?

[joecar]

Shawn,

Very interesting...

During OL-Drive mode, where TP > 10%, AFR is stoich and I see that FTC is 4 or 5 and the LTFT's are +0.8% and 0% respectively... this tells me it is trimming... BEN is 1.00.

The thing is, I can't tell if PE has enabled... or is that what OL-Drive mode is telling us...?

[joecar]

I was looking thru the descriptions for the STATE/TSTATE pids...

These pids may shed more light on what is going on:
STATE01 (evap command)
STATE04 (cotp mode)
STATE05 (fuel trim learn, fuel loop status)
TSTATE03 (pe mode active)

(that's what I said: "what is pe mode doing in a trans pid).

[WeathermanShawn]

Well Joe, here is the conundrum. For the first 5-10 minutes at normal ECT, Commanded AFR was indeed 14.63. However, when TPS >10 % (irregardless of PE AFR being stoich), it would go into OL-Drive. Perhaps OL-Drive is unique to 2002's, but it appears to go into OL-Drive when in PE Mode and/or EVAP purge.

If you look about 10 minutes into the log, because FUELSYS reads OL-Drive for 5+ minutes at a time (narrow-bands ignored?), whenever TPS ,< 10% EVAP was continuously on (OL-Drive). So, bottom line for 10-15 minutes OL-Drive completely ignored the o2 sensors. I could smell raw fuel (EVAP could not purge?), and about 15 minutes later it DTC'd and went into 'UNKNOWN" Fuel Status..And went to my overly rich OLFA Table..:grin:.

So, here is my 'conclusion'. In the 12212156 OP, EVAP and PE initiates OL-Drive..PE can not default to Closed-Loop (see log) unless you make TPS 100%. Whenever it says OL-Drive..those narrowbands are being ignored..

I know it is bizarre, but I have heard of 1 or 2 others with 2002 Camaro's that have had similar experiences. Believe it or not FTC cell 22 WOT and EVAP is shared. So if you start out with +5% LTFTBEN EVAP, you will see +5% at WOT fueling (FTC cell 22..).

I probably did not explain it well..but the car ended up running 100% Open-Loop at 13.0 AFR. I re-flashed a tune and 'clean' it out, but never did I see PE Mode and CL???

[WeathermanShawn]

Just a follow-up and conclusion:

On my Vehicle's OP system while operating in closed-loop, PE Table B3618 dictates the Commanded AFR Fueling, irregardless of the AFR value commanded in the OLFA Table B3605.

Any initiation of PE Mode, including TPS % in Table B3616 puts the vehicle into a variation of an open-loop. Table B3618 can not be 'disabled' even when commanding an EQ of 1.00.

If for any reason someone wants to initiate PE Mode at very low or part-throttle conditions, be aware that the EVAP purge appears to be disabled while in PE Mode. This may lead to an excessive release of EVAP purge during off throttle and lead to a an overly rich AFR.

Obviously that can significantly limit your ability to properly tune your vehicle while in closed-loop.

If anyone in the future runs into similar problems, at least you will have information to compare to.

Thanks..

[Raven]

hello everyone,
I was wondering if it is ok or wise to disable the PE altogether? if I'm getting the AFR I'm commanding using B6347 without the PE.
I'm using COS5.

--
Regards

[WeathermanShawn]

I have not ran that particular custom OS, but it is probably just a matter of personal preference whether you disable PE or not.

I like my fueling to come on more by TPS %, but if I recall several of the Custom OS's allow that.

In my situation, there does not appear to a PE 'disabling' function, but if you don't need PE.. by all means do what you need to do. My thread was just to illustrate that sometimes there are unusual consequences that you are not always aware of.

Hope that helps..

[Raven]

in this COS5 you command RPM-MAP instead of ECT-MAP.
I use B3613 to disable the PE.
I'm going to enable the PE above 80 kPa and set it to match my WOT commanded AFR.

unless you fully understand how something works it can be hard to track back the consequences.

thanks

--
Regards

[joecar]

You can disable PE as long as you set the high load columns of B3647 suitably rich.

[WeathermanShawn]

You know I guess even in my OS you can 'disable' it by changing B3613 (MAP threshold) to a higher MAP. Not really the original point, but as Joecar says..just make sure you have the correct fuel commanded regardless of what Table is controlling.

Good luck..

[Raven]

I've been driving with the PE disabled for the last couple of years with no problems at all.
and to tell you how do I know , I'm using the xD16 from Innovate AFR digital gauge connected to my LC-1 to watch my AFR all the time. very handy!

now I want to enable it again at 80 kPa and more and set it as rich as my WOT commanded AFR which is rich enough in B3647, though I'm enabling it I wont see any difference since it will kick in at my WOT and match my already commanded AFR in B3647.

I'm done with running mafless, soon I'll dial in my maf and see if I like it.
--
Regards

[voda1]

if the are in EQ use {EXT.LAM1}.


I don't see this in my pid parameter list. Where could I find it?

[mr.prick]

It's {EXT.WO2LAM1} :doh2: and it's in the WO2 Serial section.