E38 LS7 EQ_RAT and EOILTS Issues

[hapnermw]

When the ECM goes into PE I'm getting commanded EQ values of .829. I have dual LC-1s and these read AFRs in the low 11s so I know PE commanded EQ can't be what EQ_RAT is logging.

Has anyone seen this?

I was not logging commanded AFR so I don't know whether this is correct or not. In previous logs, closed loop AFR/EQ is 14.68/1.

Also the GM.EOILTS always reads -40. ENGOILP and TFT read as expected and the oil temp gauges work. Is there another PID for oil temp that I'm missing.

[gmh308]

When the ECM goes into PE I'm getting commanded EQ values of .829. I have dual LC-1s and these read AFRs in the low 11s so I know PE commanded EQ can't be what EQ_RAT is logging.

Has anyone seen this?

I was not logging commanded AFR so I don't know whether this is correct or not. In previous logs, closed loop AFR/EQ is 14.68/1.

Also the GM.EOILTS always reads -40. ENGOILP and TFT read as expected and the oil temp gauges work. Is there another PID for oil temp that I'm missing.

Are you using an LS7 Corvette calibration? Year? They typically dont have an oil temp PID, as the sensor does not connect to the ECM :doh: .

[GMPX]

As was in the previous post, the Oil Temp on most E38 applications is calculated. I am pretty sure the GM.EOILTS PID only shows what a real sensor would be reading if there was one fitted.

Cheers,
Ross

[gmh308]

As was in the previous post, the Oil Temp on most E38 applications is calculated. I am pretty sure the GM.EOILTS PID only shows what a real sensor would be reading if there was one fitted.

Cheers,
Ross

And have only seen one calibration so far that expects to see an Oil Temp Sensor.

:(

[GMPX]

I have a feeling it might be used on what GM call the heavy duty applications. They might have even wanted it for the Workhorse series, like Motorhomes etc.

Cheers,
Ross

[hapnermw]

Are you using an LS7 Corvette calibration? Year? They typically dont have an oil temp PID, as the sensor does not connect to the ECM :doh: .

It's a 2007 C6Z06 stock calibration. I suppose that ECT and oil pressure is sufficient for the ECM.

[hapnermw]

No one has commented yet on my issue with the PE values being output by the EQ_RAT PID.

This is supposed to report the commanded EQ Ratio but its PE values don't seem to make sense. Has anyone else encountered this?

[gmh308]

No one has commented yet on my issue with the PE values being output by the EQ_RAT PID.

This is supposed to report the commanded EQ Ratio but its PE values don't seem to make sense. Has anyone else encountered this?

That difference is typically what drives the re-scaling of the MAF so that the commanded value = the measured value for lambda.

But there may be other factors, as you have not mentioned what mods are done on the car/engine, and someone who does this everyday may have some more feedback on whether the difference, which, though not knowing what low 11's is (11.05 or 11.35?) you may only be looking at a 7-9% error, and whether that is normal.

:cheers:

[swingtan]

Just a thought on the EQ_RAT PID. Is there a chance that its actually...

"The commanded EQ ratio referenced to Stoich"

14.68 x 0.825 = 12.17:1 AFR. Would this be what you are commanding in PE mode?

Simon

[joecar]

I may be wrong, but it seems to me that EQ_RAT is behaving like Lambda instead of EQ.

Sanity check: have you set your fueling units to AFR or EQ and not Lambda...?

[hapnermw]

I may be wrong, but it seems to me that EQ_RAT is behaving like Lambda instead of EQ.

Sanity check: have you set your fueling units to AFR or EQ and not Lambda...?

The E38 calibration is the latest stock calibration for my VIN from TIS so whatever EQ_RAT is reading is whatever GM has set it to.

[joecar]

In the scantool, on the PIDs tab, it shows the units of EQ_RAT being Lambda.

[hapnermw]

In the scantool, on the PIDs tab, it shows the units of EQ_RAT being Lambda.

The 'lambda' units just mean that the range of EQ is the same as the range of lambda which it is. Clearly EQ is the inverse of lambda.

The .829 PE reading I'm getting doesn't make sense for either EQ or lambda. If it were lambda it would be 12.1 AFR. I know for a fact that the stock commanded PE EQ is in the low 11s. Readings on my scan vary but one .829 reading corresponds to LC1 Bank 1 11.11 Bank 2 10.96.

As soon as my beta BB Logging starts working again I'll scan both commanded EQ and AFR and report back the results.

The reason I was scanning commanded EQ instead of AFR was I thought it might be more accurate since California gas is 91 Octane and Stoich differs from the 14.68 the ECM assumes. I'm assuming commanded AFR should be exactly 14.68/EQ_RAT.

[joecar]

EQ_RAT is in Lambda, so commanded AFR should be 14.68 * EQ_RAT, assuming your stoich AFR is 14.68.

Edit: I meant to say 14.68.

[hapnermw]

EQ_RAT is in Lambda, so commanded AFR should be 14.68 * EQ_RAT, assuming your stoich AFR is 14.63.

Version 8.1.2 correctly lists the units of EQ_RAT as EQR.

[swingtan]

Here's a log I just did comparing the the following...

AFRATIO_DMA
EQ_RAT
WB_AFR


http://farm4.static.flickr.com/3316/3408185055_18e55c769f_o.jpg

As you can see, EQ_RAT tacks AFRATIO_DMA and it does it precisely. I have bumped the scale for EQ_RAT as if I set it directly match AFRATIO_DMA, the 2 lines lie directly over the top of each other. Also note that the default units for EQ_RAT is "lambda".

So going back to post #9 as well as post #14....

EQ_RAT=Commanded AFR / Stoich AFR

[hapnermw]

Thanks swingtan,

Now that 8.1.2 logging is working for me and it has changed EQ_RAT units to EQR, possibly it will correctly show commanded EQ as the inverse of commanded AFR.

I'll check this out.

[hapnermw]

With an 8.1.2 BB log of commanded AFR and EQ displayed with Scan 7.5, the EQ_RAT PID is still displaying Lambda instead of EQ. Perhaps Scan 8.1.2 will fix this.

[joecar]

I notified Paul.

[Blacky]

Apart from the EQ_Ratio units showing up as lambda, I can't see any other problems.

EQ Ratio is directly proportional to AFR, so EQ Ratio should track AFR.
Lamba is inversely proportional to AFR, so Lambda should inversely track AFR.

Or am I missing something? (It happens, often :( )

Regards
Paul

[hapnermw]

Apart from the EQ_Ratio units showing up as lambda, I can't see any other problems.

EQ Ratio is directly proportional to AFR, so EQ Ratio should track AFR.
Lamba is inversely proportional to AFR, so Lambda should inversely track AFR.

Or am I missing something? (It happens, often :( )

Regards
Paul

Actually, Lambda is proportional to AFR. EQ is inversely proportional to AFR.

Lambda is the ratio of AFR/AFR Stoich - EQ is 1/Lambda. Lambda > 1 is lean; EQ > 1 is rich.

Having EQ reported as Lambda is completely wrong.

I'm assuming this hasn't been caught earlier because everyone has been using the AFR PID for tuning.

See http://en.wikipedia.org/wiki/Air-fuel_ratio

[Blacky]

Me->:bangin:<-Math
I'll fix the PID to be correct :angel_innocent:

Regards
Paul

[Blacky]

Ok, so I'm going nuts here...

Wiki says:
http://en.wikipedia.org/wiki/Air-fuel_ratio
To calculate AFR from a given lambda, multiply the measured lambda by the stoichiometric AFR for that fuel.

The SAE specification says:
(see image)
To obtain the actual A/F ratio being commanded, multiply the stoichiometric A/F ratio by the equivalence ratio.

Which one is correct? What am I missing?

Regards
Paul

[hapnermw]

Ok, so I'm going nuts here...

Wiki says:
http://en.wikipedia.org/wiki/Air-fuel_ratio
To calculate AFR from a given lambda, multiply the measured lambda by the stoichiometric AFR for that fuel.

The SAE specification says:
(see image)
To obtain the actual A/F ratio being commanded, multiply the stoichiometric A/F ratio by the equivalence ratio.

Which one is correct? What am I missing?

Regards
Paul

Lambda = AFR/AFR Stoich so AFR=AFR Stoich*Lambda
EQ=AFR Stoich/AFR so AFR=AFR Stoich/EQ

The SAE spec is in error. Somewhere it must say that EQ=1/Lambda. EQ is proportional to fuel so it doesn't make sense that increasing EQ would increase the air/fuel ratio - increasing EQ must decrease AFR.

[joecar]

Paul,

In the SAE document:

if 0.95 was Lambda, then 14.64 * 0.95 = 13.9 would be true (gets richer with Lambda < 1).
if 0.95 was EQR then 14.64 * 0.95 = 13.9 would be strange (should have gotten leaner with EQR < 1).

So the SAE paper seems to be treating EQ_RAT as Lambda, or it could be a typo in the paper (as said by hapnermw (http://forum.efilive.com/member.php?u=8579)).

In Heywood ("ICE Fundamentals") on page 71: φ = FAR/FARs and λ = 1/φ = AFR/AFRs

so from those 2 we can then deduce: φ = AFRs/AFR = FAR/FARs = 1/λ or λ = AFR/AFRs = FARs/FAR = 1/φ

[joecar]

There is an updated SAE J1979 paper:



...

Differences from SAE J1979 APR2002:
...

• Appendix B – Consistent use of "LAMBDA" instead of "EQ_RAT" for external test equipment to display equivalence ratio for PIDs $24 to $2B, $34 to $3B, and $44
...

[Blacky]

That'll teach me for blindly trusting the specification :nixweiss:
SAE spec -> :crash: <- Me

Not sure why I never got the updated doc, have to check my subscription. Joe where did you get/find the update?

Regards
Paul

[joecar]

I searched the web for "SAE J1979" and it showed me a site where the update could be purchased, and it showed a list of changes since the 2002 edition...

(http://global.ihs.com/doc_detail.cfm?currency_code=USD&customer_id=2125432C4B0A&shopping_cart_id=282428372A4B404C4F5A4D38260A&rid=Z56&input_doc_number=SAE%20J1979&mid=W094&input_doc_number=SAE%20J1979&country_code=US&lang_code=ENGL&item_s_key=00144768&item_key_date=920731&input_doc_number=SAE%20J1979&input_doc_title=)SAE J1979 Edition: 07 Chg: Date: 05/00/07 (http://global.ihs.com/doc_detail.cfm?currency_code=USD&customer_id=2125432C4B0A&shopping_cart_id=282428372A4B404C4F5A4D38260A&rid=Z56&input_doc_number=SAE%20J1979&mid=W094&input_doc_number=SAE%20J1979&country_code=US&lang_code=ENGL&item_s_key=00144768&item_key_date=920731&input_doc_number=SAE%20J1979&input_doc_title=)

<hmmm.... when I went to that same link last night it showed what changed since the 2002 edition>


I don't actually have the document itself.

[Blacky]

I just updated our subscription with SAE, the new documents are on their way...

Regards
Paul

[gmh308]

I just updated our subscription with SAE, the new documents are on their way...

Regards
Paul

Hey Paul, Any further feedback on this?

Does the GM ECM run on Lambda as a base unit or EQ Ratio or ..... AFR no less?

Every PID I have seen looks to be lambda, but is usually, if not always labelled EQ_Rat or EQ Ratio or something similar.

And the actual value is always lambda. Via EFILive and alternate scanner device/s.

Cheers :cheers:

[Blacky]

All the SAE PIDs display LAMBDA for their value.

Those PIDs are:
SAE.LAMBDA displays lambda, even though (in EFILive) the description says "Commanded Equivalence Ratio". The description needs to be updated.

SAE.WO2Sxx displays lambda, even though (in EFILive) the sub PIDs are called EQ_RATIO and the description says "Equivalence Ratio (Lambda)". The name and description needs to be updated. However, these PIDs are not supported on any vehicles that FlashScan is designed for - as the factory controller does not support wide band O2 sensors.

The confusion stems from the fact that in previous docs the explanation of those PIDs was ambiguous. Sometimes it refered to air-fuel equivalence ratio (which is what we call EQ_RATIO) and sometimes to fuel-air equivalence ratio (which is what we call Lambda). Sometimes it even mixed up lambda and equivalence ratio.

The latest SAE doc I have explain that it was wrong in previous docs and is now corrected.

I should have updated the descriptions in the latest release but it slipped off the "whiteboard list" I've put it back on the list.

Regards
Paul

[gmh308]

All the SAE PIDs display LAMBDA for their value.

Those PIDs are:
SAE.LAMBDA displays lambda, even though (in EFILive) the description says "Commanded Equivalence Ratio". The description needs to be updated.

SAE.WO2Sxx displays lambda, even though (in EFILive) the sub PIDs are called EQ_RATIO and the description says "Equivalence Ratio (Lambda)". The name and description needs to be updated. However, these PIDs are not supported on any vehicles that FlashScan is designed for - as the factory controller does not support wide band O2 sensors.

The confusion stems from the fact that in previous docs the explanation of those PIDs was ambiguous. Sometimes it refered to air-fuel equivalence ratio (which is what we call EQ_RATIO) and sometimes to fuel-air equivalence ratio (which is what we call Lambda). Sometimes it even mixed up lambda and equivalence ratio.

The latest SAE doc I have explain that it was wrong in previous docs and is now corrected.

I should have updated the descriptions in the latest release but it slipped off the "whiteboard list" I've put it back on the list.

Regards
Paul

Thanks Paul, appreciate the clarification. If even the SAE gets this out of whack, what hope have the rest of us mortals got? :hihi:

[JAY4SPEED]

All the SAE PIDs display LAMBDA for their value.

Those PIDs are:
SAE.LAMBDA displays lambda, even though (in EFILive) the description says "Commanded Equivalence Ratio". The description needs to be updated.

SAE.WO2Sxx displays lambda, even though (in EFILive) the sub PIDs are called EQ_RATIO and the description says "Equivalence Ratio (Lambda)". The name and description needs to be updated. However, these PIDs are not supported on any vehicles that FlashScan is designed for - as the factory controller does not support wide band O2 sensors.

The confusion stems from the fact that in previous docs the explanation of those PIDs was ambiguous. Sometimes it refered to air-fuel equivalence ratio (which is what we call EQ_RATIO) and sometimes to fuel-air equivalence ratio (which is what we call Lambda). Sometimes it even mixed up lambda and equivalence ratio.

The latest SAE doc I have explain that it was wrong in previous docs and is now corrected.

I should have updated the descriptions in the latest release but it slipped off the "whiteboard list" I've put it back on the list.

Regards
Paul

Paul, has this been corrected as of 8/29/2009?

[Blacky]

No, but it has been corrected in the next update.
Regards
Paul

[JAY4SPEED]

No, but it has been corrected in the next update.
Regards
Paul

Thanks Paul. I'm trying to shed my AFR "training wheels" and trying to start working in EQ ratio. Looks like the next update is going to be a good one :).

[Blacky]

Actually, I just went to update those PID's descriptions and it has already been done in the previous release for generic (i.e. SAE) PIDs. Sorry for the confusion.

Regards
Paul