After 14yrs, I'm second-guessing MAF tables and would like some feedback
Thread Starter
Junior Member
Joined: Feb 2008
Posts: 21
Likes: 1
After 14yrs, I'm second-guessing MAF tables and would like some feedback
First of all, I'm running a 383 in an 89 Vette. Came over here due to better tuning "presense" (vs the CF). Mostly, I'm revisiting tuning in prep for intake/exhaust changes...but I also had an issue a while back where I bought & installed an OEM Bosch MAF. In 2010, I launched my 383 build with a descreened MAF and used it up until 2022. That's when the car wouldn't start/run quite right. In short, I put a screened MAF on it (thinking the sensor wires looked a bit "loose"). But, I also figured out a big part of my problem was a failing O2 sensor. Probably a grounding problem too. I did that at the end of the "season" going into 2022's winter.
I never got around to remounting the descreened MAF. Instead, I ran a screened unit in 2023 and even 2024. (When I plugged my laptop in AFTER the O2 swap, it was mostly in range -- meaning BLMs weren't that "bad". And, I'll be honest, I never decided if the problem might have been that descreened MAF. Because I'm in my 60's, I might not obsess about these things as much. Not until now anyway! LOL
So, I put my descreened unit back on and realized IMMEDIATELY that the screened unit ran better in low-rpm 6th gear cruise...to lower-mid-range moderate accel. I let the descreened MAF "relearn". It was better the next day -- but it will never have the "torque" of the screened unit -- driving on the hwy. As such, (without a wideband), I'm trying to figure out what might be happening...or if I did something wrong in 2010? Note: A member here showed me how to center the tune by watching BLMs and the O2 readings IIRC, i was trying to hit 800-900mV? I'm thinking I thought I was leaning it out a bit?
Common sense would suggest the need to ENRICHEN MAF tables for a descreened unit. As I look at it again (now), the MAF values (gms) are actually lower-than-stock. WTF? Am I thinking backwards?
This is my point of confusion. Should the MAF values be lower for a descreened MAF? In the rich/lean offset table, are those millivolts the stated "swingpoint" to determine what's rich or lean? If I moved each value up, would it get richer? (or leaner?) When I look at an online graphic of lamda vs millivolts, it LOOKS like higher voltage means richer I'd think it would read oxygen and be getting leaner?
Mostly, this is me asking if the MAF tables could be botched/backwards, if I might be better off reinstalling the screened MAF -- WITH THE STOCK ARAP/AYPY MAF VALUES -- and wait until next spring when I plan to install a WB sensor? The engine made it 35k miles -- so you'd THINK I didn't "F" it up too bad!
FWIW, I'm running 24# SVOs with the bin set to 25.5 FI constant If anything my FP is a couple pounds LOW. I'd think that would make it run a hair lean? The descreened MAF could add to that? (Especiallly if the MAF table entries should indicate MORE grms of air -- so the ECM would see it By contrast, the oil filter smelled a HAIR rich, the tips show mild black soot wthin 50-100 miles, and one other person who TRIED my bin in 2011 said it ran PIG RICH for them (They also had a 383 with 24# SVOs -- though it had a miniram vs my hogged SLP setup)
None of this adds up as I revisit my tune. It might just take a WB to figure it out....But I thought WTH, I should post and see if I can get some pointers -- so I head bad into a "retune" with the correct facts in my head!
Thx!!!
I never got around to remounting the descreened MAF. Instead, I ran a screened unit in 2023 and even 2024. (When I plugged my laptop in AFTER the O2 swap, it was mostly in range -- meaning BLMs weren't that "bad". And, I'll be honest, I never decided if the problem might have been that descreened MAF. Because I'm in my 60's, I might not obsess about these things as much. Not until now anyway! LOL
So, I put my descreened unit back on and realized IMMEDIATELY that the screened unit ran better in low-rpm 6th gear cruise...to lower-mid-range moderate accel. I let the descreened MAF "relearn". It was better the next day -- but it will never have the "torque" of the screened unit -- driving on the hwy. As such, (without a wideband), I'm trying to figure out what might be happening...or if I did something wrong in 2010? Note: A member here showed me how to center the tune by watching BLMs and the O2 readings IIRC, i was trying to hit 800-900mV? I'm thinking I thought I was leaning it out a bit?
Common sense would suggest the need to ENRICHEN MAF tables for a descreened unit. As I look at it again (now), the MAF values (gms) are actually lower-than-stock. WTF? Am I thinking backwards?
This is my point of confusion. Should the MAF values be lower for a descreened MAF? In the rich/lean offset table, are those millivolts the stated "swingpoint" to determine what's rich or lean? If I moved each value up, would it get richer? (or leaner?) When I look at an online graphic of lamda vs millivolts, it LOOKS like higher voltage means richer I'd think it would read oxygen and be getting leaner?
Mostly, this is me asking if the MAF tables could be botched/backwards, if I might be better off reinstalling the screened MAF -- WITH THE STOCK ARAP/AYPY MAF VALUES -- and wait until next spring when I plan to install a WB sensor? The engine made it 35k miles -- so you'd THINK I didn't "F" it up too bad!
FWIW, I'm running 24# SVOs with the bin set to 25.5 FI constant If anything my FP is a couple pounds LOW. I'd think that would make it run a hair lean? The descreened MAF could add to that? (Especiallly if the MAF table entries should indicate MORE grms of air -- so the ECM would see it By contrast, the oil filter smelled a HAIR rich, the tips show mild black soot wthin 50-100 miles, and one other person who TRIED my bin in 2011 said it ran PIG RICH for them (They also had a 383 with 24# SVOs -- though it had a miniram vs my hogged SLP setup)
None of this adds up as I revisit my tune. It might just take a WB to figure it out....But I thought WTH, I should post and see if I can get some pointers -- so I head bad into a "retune" with the correct facts in my head!
Thx!!!
Thread Starter
Junior Member
Joined: Feb 2008
Posts: 21
Likes: 1
Re: After 14yrs, I'm second-guessing MAF tables and would like some feedback
I might need to simplify this....
1) Can raising the rich/lean offset values make an engine run richer or leaner? Is that the only way (besides parms out of range (bad tune) to enrich/enlean closed loop operation?)
2) When running a descreened MAF, are your values higher than stock? (Wouldn't mind seeing your descreened MAF tables for comparison to mine)
3) If a screened MAF seems to run better in lower rpms (despite what appears to be good BLMs), would you enrich lower LV8s via MAF table adjustments, rich/lean offset, or ???
4) So you know, I'm running a 383 with AFR195 heads which (I'd think) would flow more than a screened MAF "allows". (600cfm vs 500cfm??)
5) Do any changes in commanded AFR really do anything? (I've heard to leave it at 14.7:1 regardless of ethanol percentage.
6) Does anyone run a RICHER than stoich mixture in lower LV8s...just for better response.
Note: I have a very small performance cam...214/214 with 540 lift.
1) Can raising the rich/lean offset values make an engine run richer or leaner? Is that the only way (besides parms out of range (bad tune) to enrich/enlean closed loop operation?)
2) When running a descreened MAF, are your values higher than stock? (Wouldn't mind seeing your descreened MAF tables for comparison to mine)
3) If a screened MAF seems to run better in lower rpms (despite what appears to be good BLMs), would you enrich lower LV8s via MAF table adjustments, rich/lean offset, or ???
4) So you know, I'm running a 383 with AFR195 heads which (I'd think) would flow more than a screened MAF "allows". (600cfm vs 500cfm??)
5) Do any changes in commanded AFR really do anything? (I've heard to leave it at 14.7:1 regardless of ethanol percentage.
6) Does anyone run a RICHER than stoich mixture in lower LV8s...just for better response.
Note: I have a very small performance cam...214/214 with 540 lift.
Supreme Member
Joined: Jun 2012
Posts: 1,367
Likes: 193
From: Canada
Car: '18 Chev Camaro SS 1LE
Engine: LT1 6.2L
Transmission: T56
Axle/Gears: 3.91
Re: After 14yrs, I'm second-guessing MAF tables and would like some feedback
Hi,
No offence, but I am reading your posts and I am getting a head ache just trying to sort out what you are saying.
I'll get back to you.
Peace
No offence, but I am reading your posts and I am getting a head ache just trying to sort out what you are saying.
I'll get back to you.
Peace
Supreme Member
Joined: Jun 2012
Posts: 1,367
Likes: 193
From: Canada
Car: '18 Chev Camaro SS 1LE
Engine: LT1 6.2L
Transmission: T56
Axle/Gears: 3.91
Re: After 14yrs, I'm second-guessing MAF tables and would like some feedback
Hey!
I'm not trying to be an a** or anything like that. I am straight to the point tonight. No hard feelings.
I'm going to try answering the best I can in a short format. Your questions are loaded and indicate little knowledge of tuning. It is very hard, trying, explaining everything in one post. But the hardest part is having to repeat over and over and over again. All the information you need is scattered all over TGO. It has been asked by many over 2 decades. It's all there for you to grab. Some of the pioneers are no longer on this board because they are either, deceased, or just left, exhausted having to repeat the same information over and over. Personally, I don't know why I still do it. I can tell you that you are barely touching the tip of the iceberg. There is way more.
I suggest you take the time to read as much as you can on TGO. It takes many, many, many, many.... and many hours of reading and testing to get a real grip on these antiquated EFI systems. Ask me how I know? If not, I recommend you contact @Tuned Performance and for a fee, he will help you with your tuning. It is well worth it, believe me.
So here we go (again):
“In 2010, I launched my 383 build with a descreened MAF and used it up until 2022.”
I assumed everything worked well for 12 years with what ever tune you had.
“...but I also had an issue a while back where I bought & installed an OEM Bosch MAF.”
After 2022? What year is a “while back”? What issue?
“That's when the car wouldn't start/run quite right. In short, I put a screened MAF on it (thinking the sensor wires looked a bit "loose"). But, I also figured out a big part of my problem was a failing O2 sensor. Probably a grounding problem too. I did that at the end of the "season" going into 2022's winter.”
If I understand correctly, the car ran fine for 12 years (2010-2012) and then, ran into the above-described problem, right? Problem was fixed I assume?
“ (When I plugged my laptop in AFTER the O2 swap, it was mostly in range -- meaning BLMs weren't that "bad".”
What ever interpretation “mostly in range” and “weren’t that bad” mean!!! To me it means nothing.
“I let the descreened MAF "relearn".”
This makes no sense from a tuning perspective with a ‘165 $6E. There is no relearn procedure with this antiquated EFI system
“but it will never have the "torque" of the screened unit -- driving on the hwy. As such, (without a wideband), I'm trying to figure out what might be happening...or if I did something wrong in 2010?”
Are you talking about WOT condition, cruising condition or both?
“Note: A member here showed me how to center the tune by watching BLMs and the O2 readings IIRC, i was trying to hit 800-900mV? I'm thinking I thought I was leaning it out a bit?”
You must be talking about WOT condition, right? “centre a tune” is not a known tuning terms. I have no clue what you are talking about.
“Common sense would suggest the need to ENRICHEN MAF tables for a descreened unit. As I look at it again (now), the MAF values (gms) are actually lower-than-stock. WTF? Am I thinking backwards?”
You are touching a complex subject here. You can not compare MAF tables from tune to tune. You have to take into consideration other parameters that comprise the INJ PBW calculation. Also, from MAF to MAF, there could be a difference in the voltage range vs real mass airflow. The ECM does not know what the mass airflow is. All it sees is a voltage sent by the MAF sensor. A human attributes a value (g/sec) to a voltage in the MAF tables (6 of them). But, yes, common sense (or logic) would suggest the need to enrichen MAF tables if one was to descreen a MAF, as long as it’s the same MAF unit.
“Should the MAF values be lower for a descreened MAF?
Question already answered above
“In the rich/lean offset table, are those millivolts the stated "swingpoint" to determine what's rich or lean?
They are used in closed loop operation only to determine rich/lean condition. They are used for Integrator (INT) and BLM calculation. They have no impact in open loop or PE (WOT) condition.
“If I moved each value up, would it get richer? (or leaner?) When I look at an online graphic of lamda vs millivolts, it LOOKS like higher voltage means richer I'd think it would read oxygen and be getting leaner?”
Higher = richer, lower = leaner. I would not temper with those parameters in the tune for now. If BLM’s are too low/high, generally, MAF tables need retuning, but not necessarily.
“Mostly, this is me asking if the MAF tables could be botched/backwards,”
No clue what this means!
“if I might be better off reinstalling the screened MAF -- WITH THE STOCK ARAP/AYPY MAF VALUES”
Why?
“and wait until next spring when I plan to install a WB sensor? The engine made it 35k miles -- so you'd THINK I didn't "F" it up too bad!”
WB sensor in closed loop will indicate if MAF tables, INT and BLM are doing a good job at accomplishing stoichiometric combustion (Lambda 1). In PE (WOT), it would help tuning AFR for performance (need chassis dyno). Why not reinstall the original set-up that worked for 12 years?
“FWIW, I'm running 24# SVOs with the bin set to 25.5 FI constant If anything my FP is a couple pounds LOW.”
What ever “a couple of pounds low” means! Do you have a real fuel pressure number? What brand of injectors? Do you have the datasheet for them? Why set 25.5 if the injectors are 24? What fuel pressure are your injectors rated at?
“I'd think that would make it run a hair lean?”
What would make it run “a hair lean”?
“The descreened MAF could add to that?
Add to what? The “a hair lean?”
“(Especiallly if the MAF table entries should indicate MORE grms of air -- so the ECM would see it By contrast, the oil filter smelled a HAIR rich, the tips show mild black soot wthin 50-100 miles, and one other person who TRIED my bin in 2011 said it ran PIG RICH for them (They also had a 383 with 24# SVOs -- though it had a miniram vs my hogged SLP setup)”
Man, I don’t follow you there! Sorry.
1) Can raising the rich/lean offset values make an engine run richer or leaner? Is that the only way (besides parms out of range (bad tune) to enrich/enlean closed loop operation?)
Yes. Like I said above. MAF tables are the starting point to tune closed loop condition. The O2 voltage parameters could be retuned, only in specific situations.
2) When running a descreened MAF, are your values higher than stock? (Wouldn't mind seeing your descreened MAF tables for comparison to mine)
Depends on the tune to tune comparison and MAF to MAF. Not necessarily. See explanation above.
3) If a screened MAF seems to run better in lower rpms (despite what appears to be good BLMs), would you enrich lower LV8s via MAF table adjustments, rich/lean offset, or ???
???... You have to datalog and verify why the screened MAF “run better” than what ever you are comparing to. Why is it running better” You need to compare identical engine conditions in terms of CT, Voltage, MAT, RPM, TPS and IAC position.
4) So you know, I'm running a 383 with AFR195 heads which (I'd think) would flow more than a screened MAF "allows". (600cfm vs 500cfm??)
Probably. The $6E system has its limits for MAF tables. The only way around it in PE condition is to tune PE commanded AFR vs RPM using a wideband AFR.
5) Do any changes in commanded AFR really do anything? (I've heard to leave it at 14.7:1 regardless of ethanol percentage.
Ethanol content should be compensated by INT/BLM in closed loop. However, in open loop and PE, it will not. The more ethanol, the leaner the fuel mixture gets, all else being equal. Again, wide band AFR will tell you if leaner in PE (WOT) but you can also estimate with 02 voltage in PE WOT condition with the following:
830 mv = 13.0:1
880 mv = 12.5:1
930 mv = 12.0:1
6) Does anyone run a RICHER than stoich mixture in lower LV8s...just for better response.
I do run richer on my 383 and stock 305 LB9 in idle condition. Runs smoother. I achieved that by modifying the O2 parameters and monitoring the wide band sensor.
I found that datalogging the MAF voltage really helps with diagnostic. You can accomplish that by modifying your BIN and ADX (see topic in stickies). That is key to trouble shooting. I've seen MAF sending voltage = 0 with no SES code. In this case, ECM relies on other sensors and defaults to another routine yielding different MAF g/sec readings.
Good Luck and Peace
I'm not trying to be an a** or anything like that. I am straight to the point tonight. No hard feelings.
I'm going to try answering the best I can in a short format. Your questions are loaded and indicate little knowledge of tuning. It is very hard, trying, explaining everything in one post. But the hardest part is having to repeat over and over and over again. All the information you need is scattered all over TGO. It has been asked by many over 2 decades. It's all there for you to grab. Some of the pioneers are no longer on this board because they are either, deceased, or just left, exhausted having to repeat the same information over and over. Personally, I don't know why I still do it. I can tell you that you are barely touching the tip of the iceberg. There is way more.
I suggest you take the time to read as much as you can on TGO. It takes many, many, many, many.... and many hours of reading and testing to get a real grip on these antiquated EFI systems. Ask me how I know? If not, I recommend you contact @Tuned Performance and for a fee, he will help you with your tuning. It is well worth it, believe me.
So here we go (again):
“In 2010, I launched my 383 build with a descreened MAF and used it up until 2022.”
I assumed everything worked well for 12 years with what ever tune you had.
“...but I also had an issue a while back where I bought & installed an OEM Bosch MAF.”
After 2022? What year is a “while back”? What issue?
“That's when the car wouldn't start/run quite right. In short, I put a screened MAF on it (thinking the sensor wires looked a bit "loose"). But, I also figured out a big part of my problem was a failing O2 sensor. Probably a grounding problem too. I did that at the end of the "season" going into 2022's winter.”
If I understand correctly, the car ran fine for 12 years (2010-2012) and then, ran into the above-described problem, right? Problem was fixed I assume?
“ (When I plugged my laptop in AFTER the O2 swap, it was mostly in range -- meaning BLMs weren't that "bad".”
What ever interpretation “mostly in range” and “weren’t that bad” mean!!! To me it means nothing.
“I let the descreened MAF "relearn".”
This makes no sense from a tuning perspective with a ‘165 $6E. There is no relearn procedure with this antiquated EFI system
“but it will never have the "torque" of the screened unit -- driving on the hwy. As such, (without a wideband), I'm trying to figure out what might be happening...or if I did something wrong in 2010?”
Are you talking about WOT condition, cruising condition or both?
“Note: A member here showed me how to center the tune by watching BLMs and the O2 readings IIRC, i was trying to hit 800-900mV? I'm thinking I thought I was leaning it out a bit?”
You must be talking about WOT condition, right? “centre a tune” is not a known tuning terms. I have no clue what you are talking about.
“Common sense would suggest the need to ENRICHEN MAF tables for a descreened unit. As I look at it again (now), the MAF values (gms) are actually lower-than-stock. WTF? Am I thinking backwards?”
You are touching a complex subject here. You can not compare MAF tables from tune to tune. You have to take into consideration other parameters that comprise the INJ PBW calculation. Also, from MAF to MAF, there could be a difference in the voltage range vs real mass airflow. The ECM does not know what the mass airflow is. All it sees is a voltage sent by the MAF sensor. A human attributes a value (g/sec) to a voltage in the MAF tables (6 of them). But, yes, common sense (or logic) would suggest the need to enrichen MAF tables if one was to descreen a MAF, as long as it’s the same MAF unit.
“Should the MAF values be lower for a descreened MAF?
Question already answered above
“In the rich/lean offset table, are those millivolts the stated "swingpoint" to determine what's rich or lean?
They are used in closed loop operation only to determine rich/lean condition. They are used for Integrator (INT) and BLM calculation. They have no impact in open loop or PE (WOT) condition.
“If I moved each value up, would it get richer? (or leaner?) When I look at an online graphic of lamda vs millivolts, it LOOKS like higher voltage means richer I'd think it would read oxygen and be getting leaner?”
Higher = richer, lower = leaner. I would not temper with those parameters in the tune for now. If BLM’s are too low/high, generally, MAF tables need retuning, but not necessarily.
“Mostly, this is me asking if the MAF tables could be botched/backwards,”
No clue what this means!
“if I might be better off reinstalling the screened MAF -- WITH THE STOCK ARAP/AYPY MAF VALUES”
Why?
“and wait until next spring when I plan to install a WB sensor? The engine made it 35k miles -- so you'd THINK I didn't "F" it up too bad!”
WB sensor in closed loop will indicate if MAF tables, INT and BLM are doing a good job at accomplishing stoichiometric combustion (Lambda 1). In PE (WOT), it would help tuning AFR for performance (need chassis dyno). Why not reinstall the original set-up that worked for 12 years?
“FWIW, I'm running 24# SVOs with the bin set to 25.5 FI constant If anything my FP is a couple pounds LOW.”
What ever “a couple of pounds low” means! Do you have a real fuel pressure number? What brand of injectors? Do you have the datasheet for them? Why set 25.5 if the injectors are 24? What fuel pressure are your injectors rated at?
“I'd think that would make it run a hair lean?”
What would make it run “a hair lean”?
“The descreened MAF could add to that?
Add to what? The “a hair lean?”
“(Especiallly if the MAF table entries should indicate MORE grms of air -- so the ECM would see it By contrast, the oil filter smelled a HAIR rich, the tips show mild black soot wthin 50-100 miles, and one other person who TRIED my bin in 2011 said it ran PIG RICH for them (They also had a 383 with 24# SVOs -- though it had a miniram vs my hogged SLP setup)”
Man, I don’t follow you there! Sorry.
1) Can raising the rich/lean offset values make an engine run richer or leaner? Is that the only way (besides parms out of range (bad tune) to enrich/enlean closed loop operation?)
Yes. Like I said above. MAF tables are the starting point to tune closed loop condition. The O2 voltage parameters could be retuned, only in specific situations.
2) When running a descreened MAF, are your values higher than stock? (Wouldn't mind seeing your descreened MAF tables for comparison to mine)
Depends on the tune to tune comparison and MAF to MAF. Not necessarily. See explanation above.
3) If a screened MAF seems to run better in lower rpms (despite what appears to be good BLMs), would you enrich lower LV8s via MAF table adjustments, rich/lean offset, or ???
???... You have to datalog and verify why the screened MAF “run better” than what ever you are comparing to. Why is it running better” You need to compare identical engine conditions in terms of CT, Voltage, MAT, RPM, TPS and IAC position.
4) So you know, I'm running a 383 with AFR195 heads which (I'd think) would flow more than a screened MAF "allows". (600cfm vs 500cfm??)
Probably. The $6E system has its limits for MAF tables. The only way around it in PE condition is to tune PE commanded AFR vs RPM using a wideband AFR.
5) Do any changes in commanded AFR really do anything? (I've heard to leave it at 14.7:1 regardless of ethanol percentage.
Ethanol content should be compensated by INT/BLM in closed loop. However, in open loop and PE, it will not. The more ethanol, the leaner the fuel mixture gets, all else being equal. Again, wide band AFR will tell you if leaner in PE (WOT) but you can also estimate with 02 voltage in PE WOT condition with the following:
830 mv = 13.0:1
880 mv = 12.5:1
930 mv = 12.0:1
6) Does anyone run a RICHER than stoich mixture in lower LV8s...just for better response.
I do run richer on my 383 and stock 305 LB9 in idle condition. Runs smoother. I achieved that by modifying the O2 parameters and monitoring the wide band sensor.
I found that datalogging the MAF voltage really helps with diagnostic. You can accomplish that by modifying your BIN and ADX (see topic in stickies). That is key to trouble shooting. I've seen MAF sending voltage = 0 with no SES code. In this case, ECM relies on other sensors and defaults to another routine yielding different MAF g/sec readings.
Good Luck and Peace
Last edited by SbFormula; Dec 11, 2024 at 08:50 PM.
Thread Starter
Junior Member
Joined: Feb 2008
Posts: 21
Likes: 1
Re: After 14yrs, I'm second-guessing MAF tables and would like some feedback
Hey!
I'm not trying to be an a** or anything like that. I am straight to the point tonight. No hard feelings.
I'm going to try answering the best I can in a short format. Your questions are loaded and indicate little knowledge of tuning. It is very hard, trying, explaining everything in one post. But the hardest part is having to repeat over and over and over again. All the information you need is scattered all over TGO. It has been asked by many over 2 decades. It's all there for you to grab. Some of the pioneers are no longer on this board because they are either, deceased, or just left, exhausted having to repeat the same information over and over. Personally, I don't know why I still do it. I can tell you that you are barely touching the tip of the iceberg. There is way more.
I suggest you take the time to read as much as you can on TGO. It takes many, many, many, many.... and many hours of reading and testing to get a real grip on these antiquated EFI systems. Ask me how I know? If not, I recommend you contact @Tuned Performance and for a fee, he will help you with your tuning. It is well worth it, believe me.
So here we go (again):
“In 2010, I launched my 383 build with a descreened MAF and used it up until 2022.”
I assumed everything worked well for 12 years with what ever tune you had. AFAIK, yes
“...but I also had an issue a while back where I bought & installed an OEM Bosch MAF.”
After 2022? What year is a “while back”? What issue? Turned out to be a bad O2 sensor and/or iffy ground.
“That's when the car wouldn't start/run quite right. In short, I put a screened MAF on it (thinking the sensor wires looked a bit "loose"). But, I also figured out a big part of my problem was a failing O2 sensor. Probably a grounding problem too. I did that at the end of the "season" going into 2022's winter.”
If I understand correctly, the car ran fine for 12 years (2010-2012) and then, ran into the above-described problem, right? Problem was fixed I assume? Correct
“ (When I plugged my laptop in AFTER the O2 swap, it was mostly in range -- meaning BLMs weren't that "bad".”
What ever interpretation “mostly in range” and “weren’t that bad” mean!!! To me it means nothing. BLMs were in range with an occasional "blip" out of range. That was probably before I addressed the ground.
“I let the descreened MAF "relearn".”
This makes no sense from a tuning perspective with a ‘165 $6E. There is no relearn procedure with this antiquated EFI system Once electricity is removed, it's my understanding fuel trims are lost and they have to be "relearned". It's an expression that's probably not the best.
“but it will never have the "torque" of the screened unit -- driving on the hwy. As such, (without a wideband), I'm trying to figure out what might be happening...or if I did something wrong in 2010?”
Are you talking about WOT condition, cruising condition or both? The descreened MAF I tuned it with in 2010, does everything better EXCEPT low-rpm responsiveness (torque) in 6th gear around 1400-1500rpms.
“Note: A member here showed me how to center the tune by watching BLMs and the O2 readings IIRC, i was trying to hit 800-900mV? I'm thinking I thought I was leaning it out a bit?”
You must be talking about WOT condition, right? “centre a tune” is not a known tuning terms. I have no clue what you are talking about. No...during closed loop....adjusting MAF tables to get BLMs in the middle of the upper/lower limits of correctability. IIRC, around 130? Where 100 is getting too rich and 160 too lean? (Don't hold me to that memory of 14yrs)
“Common sense would suggest the need to ENRICHEN MAF tables for a descreened unit. As I look at it again (now), the MAF values (gms) are actually lower-than-stock. WTF? Am I thinking backwards?”
You are touching a complex subject here. You can not compare MAF tables from tune to tune. You have to take into consideration other parameters that comprise the INJ PBW calculation. Also, from MAF to MAF, there could be a difference in the voltage range vs real mass airflow. The ECM does not know what the mass airflow is. All it sees is a voltage sent by the MAF sensor. A human attributes a value (g/sec) to a voltage in the MAF tables (6 of them). But, yes, common sense (or logic) would suggest the need to enrichen MAF tables if one was to descreen a MAF, as long as it’s the same MAF unit. Same style MAF unit with screens removed. Stock style. Seems more complicated than I'd think. Isn't that "human attribution of g/sec" what we call calibrating? BTW...It seems odd there are multiple MAF tables but maybe the assembler code runs faster with smaller tables...or more likely I don't know something else going on....Or the main array area for assembler is "full" with the spark table...or something unimportant. And, yeah, I get the scalers contain hex values pointing to the limits for each table.
“Should the MAF values be lower for a descreened MAF?
Question already answered above
“In the rich/lean offset table, are those millivolts the stated "swingpoint" to determine what's rich or lean?
They are used in closed loop operation only to determine rich/lean condition. They are used for Integrator (INT) and BLM calculation. They have no impact in open loop or PE (WOT) condition.
“If I moved each value up, would it get richer? (or leaner?) When I look at an online graphic of lamda vs millivolts, it LOOKS like higher voltage means richer I'd think it would read oxygen and be getting leaner?”
Higher = richer, lower = leaner. I would not temper with those parameters in the tune for now. If BLM’s are too low/high, generally, MAF tables need retuning, but not necessarily.
“Mostly, this is me asking if the MAF tables could be botched/backwards,”
No clue what this means! Many of the sentences I wrote were poorly conceived...me thinking out loud as it were. I was wondering if (after doing calculations to determine estimated adjustment to shift MAF values -- where each would result in higher/lower DESIRED BLM "counts", I've started to wonder if I subtracted where I should have added. I would have THOUGHT I would have double-checked after changes....so it's a damn longshot. This all comes back to WTF are my MAF values lower than "stock" with the screened unit -- when I took the OEM unit and descreened it. I would THINK the MAF "calibration would increase for the extra air passing through. Then again...all this was done after going from a 350 to a 383.
“if I might be better off reinstalling the screened MAF -- WITH THE STOCK ARAP/AYPY MAF VALUES”
Why? Because, after running a screened MAF (same style) for a while, I could tell it feels different....in lower rpms probably stronger? NOT A LOT THOUGH.
“and wait until next spring when I plan to install a WB sensor? The engine made it 35k miles -- so you'd THINK I didn't "F" it up too bad!”
WB sensor in closed loop will indicate if MAF tables, INT and BLM are doing a good job at accomplishing stoichiometric combustion (Lambda 1). In PE (WOT), it would help tuning AFR for performance (need chassis dyno). Why not reinstall the original set-up that worked for 12 years? That's the way it sits right now. But, the consumate tinker-er in me is curious to try the stock MAF tables with a stock MAF -- just to observe for a short run...LOL (Partly because it's probably what would have been suggested if I didn't descreen the MAF in 2010). Why? Most people think it's enough to "get by"?
“FWIW, I'm running 24# SVOs with the bin set to 25.5 FI constant If anything my FP is a couple pounds LOW.”
What ever “a couple of pounds low” means! Do you have a real fuel pressure number? What brand of injectors? Do you have the datasheet for them? Why set 25.5 if the injectors are 24? What fuel pressure are your injectors rated at? Maybe not common knowledge anymore? 24# SVO are FORD injectors that were rated at a lower-than-GM pressure. In a GM fuel rail, they flow more like 25.5 -- which I calculated with the formula used to predict flow based on change in pressure. 2-3yrs after the build, I checked FP for some reason and it sat around 41# vs 43 IIRC? And, yes, I loaded the datasheet values in my BIN.
“I'd think that would make it run a hair lean?”
What would make it run “a hair lean”? If more air were flowing thru the sensor than a possible erroneous "calibration" would suggest. And, yeah, the 02 feedback SHOULD "fix" that UNLESS BLMs got "out of maximum correction "range" for the +/- 15% correction that I've been told is possible. THEN AND ONLY THEN...might it get richer/leaner AFAIK. (FWIW, I don't have a laptop setup for scanning right now)
“The descreened MAF could add to that?
Add to what? The “a hair lean?”
“(Especiallly if the MAF table entries should indicate MORE grms of air -- so the ECM would see it By contrast, the oil filter smelled a HAIR rich, the tips show mild black soot wthin 50-100 miles, and one other person who TRIED my bin in 2011 said it ran PIG RICH for them (They also had a 383 with 24# SVOs -- though it had a miniram vs my hogged SLP setup)”
Man, I don’t follow you there! Sorry.
1) Can raising the rich/lean offset values make an engine run richer or leaner? Is that the only way (besides parms out of range (bad tune) to enrich/enlean closed loop operation?)
Yes. Like I said above. MAF tables are the starting point to tune closed loop condition. The O2 voltage parameters could be retuned, only in specific situations.
2) When running a descreened MAF, are your values higher than stock? (Wouldn't mind seeing your descreened MAF tables for comparison to mine)
Depends on the tune to tune comparison and MAF to MAF. Not necessarily. See explanation above.
3) If a screened MAF seems to run better in lower rpms (despite what appears to be good BLMs), would you enrich lower LV8s via MAF table adjustments, rich/lean offset, or ???
???... You have to datalog and verify why the screened MAF “run better” than what ever you are comparing to. Why is it running better” You need to compare identical engine conditions in terms of CT, Voltage, MAT, RPM, TPS and IAC position.
4) So you know, I'm running a 383 with AFR195 heads which (I'd think) would flow more than a screened MAF "allows". (600cfm vs 500cfm??)
Probably. The $6E system has its limits for MAF tables. The only way around it in PE condition is to tune PE commanded AFR vs RPM using a wideband AFR.
5) Do any changes in commanded AFR really do anything? (I've heard to leave it at 14.7:1 regardless of ethanol percentage.
Ethanol content should be compensated by INT/BLM in closed loop. However, in open loop and PE, it will not. The more ethanol, the leaner the fuel mixture gets, all else being equal. Again, wide band AFR will tell you if leaner in PE (WOT) but you can also estimate with 02 voltage in PE WOT condition with the following: Is this linear giving the following values added to your list?
650mV = 14.7:1 (stoich for gas)
680mV = 14.5:1
720mV = 14.1:1 (stoich for 10% ethanol)
730mV = 14.0:1
780mV = 13.5:1
830 mv = 13.0:1
880 mv = 12.5:1
930 mv = 12.0:1
BTW...I notice ARAP (rich/lean threshold) has higher values for lower MAF flow -- than the Corvette's AYPY stock BIN (as found online). I'm thinking the ARAP is an automatic BIN vs a manual bin for the AYPY. Since an automatic aids in torque conversion (torque converter), I'm almost think THAT is backwards too! :-) I'll post them if you're curious.
6) Does anyone run a RICHER than stoich mixture in lower LV8s...just for better response.
I do run richer on my 383 and stock 305 LB9 in idle condition. Runs smoother. I achieved that by modifying the O2 parameters and monitoring the wide band sensor. O2 parameters? Rich/lean threshold is the only method I can see in the 6E 1989 BIN.
I found that datalogging the MAF voltage really helps with diagnostic. You can accomplish that by modifying your BIN and ADX (see topic in stickies). That is key to trouble shooting. I've seen MAF sending voltage = 0 with no SES code. In this case, ECM relies on other sensors and defaults to another routine yielding different MAF g/sec readings. I haven't seen any error codes since reinstalling the descreened MAF which I used to tune it in 2010...but I suppose it's possible one or the other (MAFs...screened or not) caused the ECM to ignore it's values???
Ironically, I notice more drone with the descreened unit. AFR might change exhaust note (according to AI) but it suggests richer = louder. LOL Again, I'd expect the screened unit to pass LESS air -- resulting in a slightly richer AFR -- if anything!
Good Luck and Peace
I'm not trying to be an a** or anything like that. I am straight to the point tonight. No hard feelings.
I'm going to try answering the best I can in a short format. Your questions are loaded and indicate little knowledge of tuning. It is very hard, trying, explaining everything in one post. But the hardest part is having to repeat over and over and over again. All the information you need is scattered all over TGO. It has been asked by many over 2 decades. It's all there for you to grab. Some of the pioneers are no longer on this board because they are either, deceased, or just left, exhausted having to repeat the same information over and over. Personally, I don't know why I still do it. I can tell you that you are barely touching the tip of the iceberg. There is way more.
I suggest you take the time to read as much as you can on TGO. It takes many, many, many, many.... and many hours of reading and testing to get a real grip on these antiquated EFI systems. Ask me how I know? If not, I recommend you contact @Tuned Performance and for a fee, he will help you with your tuning. It is well worth it, believe me.
So here we go (again):
“In 2010, I launched my 383 build with a descreened MAF and used it up until 2022.”
I assumed everything worked well for 12 years with what ever tune you had. AFAIK, yes
“...but I also had an issue a while back where I bought & installed an OEM Bosch MAF.”
After 2022? What year is a “while back”? What issue? Turned out to be a bad O2 sensor and/or iffy ground.
“That's when the car wouldn't start/run quite right. In short, I put a screened MAF on it (thinking the sensor wires looked a bit "loose"). But, I also figured out a big part of my problem was a failing O2 sensor. Probably a grounding problem too. I did that at the end of the "season" going into 2022's winter.”
If I understand correctly, the car ran fine for 12 years (2010-2012) and then, ran into the above-described problem, right? Problem was fixed I assume? Correct
“ (When I plugged my laptop in AFTER the O2 swap, it was mostly in range -- meaning BLMs weren't that "bad".”
What ever interpretation “mostly in range” and “weren’t that bad” mean!!! To me it means nothing. BLMs were in range with an occasional "blip" out of range. That was probably before I addressed the ground.
“I let the descreened MAF "relearn".”
This makes no sense from a tuning perspective with a ‘165 $6E. There is no relearn procedure with this antiquated EFI system Once electricity is removed, it's my understanding fuel trims are lost and they have to be "relearned". It's an expression that's probably not the best.
“but it will never have the "torque" of the screened unit -- driving on the hwy. As such, (without a wideband), I'm trying to figure out what might be happening...or if I did something wrong in 2010?”
Are you talking about WOT condition, cruising condition or both? The descreened MAF I tuned it with in 2010, does everything better EXCEPT low-rpm responsiveness (torque) in 6th gear around 1400-1500rpms.
“Note: A member here showed me how to center the tune by watching BLMs and the O2 readings IIRC, i was trying to hit 800-900mV? I'm thinking I thought I was leaning it out a bit?”
You must be talking about WOT condition, right? “centre a tune” is not a known tuning terms. I have no clue what you are talking about. No...during closed loop....adjusting MAF tables to get BLMs in the middle of the upper/lower limits of correctability. IIRC, around 130? Where 100 is getting too rich and 160 too lean? (Don't hold me to that memory of 14yrs)
“Common sense would suggest the need to ENRICHEN MAF tables for a descreened unit. As I look at it again (now), the MAF values (gms) are actually lower-than-stock. WTF? Am I thinking backwards?”
You are touching a complex subject here. You can not compare MAF tables from tune to tune. You have to take into consideration other parameters that comprise the INJ PBW calculation. Also, from MAF to MAF, there could be a difference in the voltage range vs real mass airflow. The ECM does not know what the mass airflow is. All it sees is a voltage sent by the MAF sensor. A human attributes a value (g/sec) to a voltage in the MAF tables (6 of them). But, yes, common sense (or logic) would suggest the need to enrichen MAF tables if one was to descreen a MAF, as long as it’s the same MAF unit. Same style MAF unit with screens removed. Stock style. Seems more complicated than I'd think. Isn't that "human attribution of g/sec" what we call calibrating? BTW...It seems odd there are multiple MAF tables but maybe the assembler code runs faster with smaller tables...or more likely I don't know something else going on....Or the main array area for assembler is "full" with the spark table...or something unimportant. And, yeah, I get the scalers contain hex values pointing to the limits for each table.
“Should the MAF values be lower for a descreened MAF?
Question already answered above
“In the rich/lean offset table, are those millivolts the stated "swingpoint" to determine what's rich or lean?
They are used in closed loop operation only to determine rich/lean condition. They are used for Integrator (INT) and BLM calculation. They have no impact in open loop or PE (WOT) condition.
“If I moved each value up, would it get richer? (or leaner?) When I look at an online graphic of lamda vs millivolts, it LOOKS like higher voltage means richer I'd think it would read oxygen and be getting leaner?”
Higher = richer, lower = leaner. I would not temper with those parameters in the tune for now. If BLM’s are too low/high, generally, MAF tables need retuning, but not necessarily.
“Mostly, this is me asking if the MAF tables could be botched/backwards,”
No clue what this means! Many of the sentences I wrote were poorly conceived...me thinking out loud as it were. I was wondering if (after doing calculations to determine estimated adjustment to shift MAF values -- where each would result in higher/lower DESIRED BLM "counts", I've started to wonder if I subtracted where I should have added. I would have THOUGHT I would have double-checked after changes....so it's a damn longshot. This all comes back to WTF are my MAF values lower than "stock" with the screened unit -- when I took the OEM unit and descreened it. I would THINK the MAF "calibration would increase for the extra air passing through. Then again...all this was done after going from a 350 to a 383.
“if I might be better off reinstalling the screened MAF -- WITH THE STOCK ARAP/AYPY MAF VALUES”
Why? Because, after running a screened MAF (same style) for a while, I could tell it feels different....in lower rpms probably stronger? NOT A LOT THOUGH.
“and wait until next spring when I plan to install a WB sensor? The engine made it 35k miles -- so you'd THINK I didn't "F" it up too bad!”
WB sensor in closed loop will indicate if MAF tables, INT and BLM are doing a good job at accomplishing stoichiometric combustion (Lambda 1). In PE (WOT), it would help tuning AFR for performance (need chassis dyno). Why not reinstall the original set-up that worked for 12 years? That's the way it sits right now. But, the consumate tinker-er in me is curious to try the stock MAF tables with a stock MAF -- just to observe for a short run...LOL (Partly because it's probably what would have been suggested if I didn't descreen the MAF in 2010). Why? Most people think it's enough to "get by"?
“FWIW, I'm running 24# SVOs with the bin set to 25.5 FI constant If anything my FP is a couple pounds LOW.”
What ever “a couple of pounds low” means! Do you have a real fuel pressure number? What brand of injectors? Do you have the datasheet for them? Why set 25.5 if the injectors are 24? What fuel pressure are your injectors rated at? Maybe not common knowledge anymore? 24# SVO are FORD injectors that were rated at a lower-than-GM pressure. In a GM fuel rail, they flow more like 25.5 -- which I calculated with the formula used to predict flow based on change in pressure. 2-3yrs after the build, I checked FP for some reason and it sat around 41# vs 43 IIRC? And, yes, I loaded the datasheet values in my BIN.
“I'd think that would make it run a hair lean?”
What would make it run “a hair lean”? If more air were flowing thru the sensor than a possible erroneous "calibration" would suggest. And, yeah, the 02 feedback SHOULD "fix" that UNLESS BLMs got "out of maximum correction "range" for the +/- 15% correction that I've been told is possible. THEN AND ONLY THEN...might it get richer/leaner AFAIK. (FWIW, I don't have a laptop setup for scanning right now)
“The descreened MAF could add to that?
Add to what? The “a hair lean?”
“(Especiallly if the MAF table entries should indicate MORE grms of air -- so the ECM would see it By contrast, the oil filter smelled a HAIR rich, the tips show mild black soot wthin 50-100 miles, and one other person who TRIED my bin in 2011 said it ran PIG RICH for them (They also had a 383 with 24# SVOs -- though it had a miniram vs my hogged SLP setup)”
Man, I don’t follow you there! Sorry.
1) Can raising the rich/lean offset values make an engine run richer or leaner? Is that the only way (besides parms out of range (bad tune) to enrich/enlean closed loop operation?)
Yes. Like I said above. MAF tables are the starting point to tune closed loop condition. The O2 voltage parameters could be retuned, only in specific situations.
2) When running a descreened MAF, are your values higher than stock? (Wouldn't mind seeing your descreened MAF tables for comparison to mine)
Depends on the tune to tune comparison and MAF to MAF. Not necessarily. See explanation above.
3) If a screened MAF seems to run better in lower rpms (despite what appears to be good BLMs), would you enrich lower LV8s via MAF table adjustments, rich/lean offset, or ???
???... You have to datalog and verify why the screened MAF “run better” than what ever you are comparing to. Why is it running better” You need to compare identical engine conditions in terms of CT, Voltage, MAT, RPM, TPS and IAC position.
4) So you know, I'm running a 383 with AFR195 heads which (I'd think) would flow more than a screened MAF "allows". (600cfm vs 500cfm??)
Probably. The $6E system has its limits for MAF tables. The only way around it in PE condition is to tune PE commanded AFR vs RPM using a wideband AFR.
5) Do any changes in commanded AFR really do anything? (I've heard to leave it at 14.7:1 regardless of ethanol percentage.
Ethanol content should be compensated by INT/BLM in closed loop. However, in open loop and PE, it will not. The more ethanol, the leaner the fuel mixture gets, all else being equal. Again, wide band AFR will tell you if leaner in PE (WOT) but you can also estimate with 02 voltage in PE WOT condition with the following: Is this linear giving the following values added to your list?
650mV = 14.7:1 (stoich for gas)
680mV = 14.5:1
720mV = 14.1:1 (stoich for 10% ethanol)
730mV = 14.0:1
780mV = 13.5:1
830 mv = 13.0:1
880 mv = 12.5:1
930 mv = 12.0:1
BTW...I notice ARAP (rich/lean threshold) has higher values for lower MAF flow -- than the Corvette's AYPY stock BIN (as found online). I'm thinking the ARAP is an automatic BIN vs a manual bin for the AYPY. Since an automatic aids in torque conversion (torque converter), I'm almost think THAT is backwards too! :-) I'll post them if you're curious.
6) Does anyone run a RICHER than stoich mixture in lower LV8s...just for better response.
I do run richer on my 383 and stock 305 LB9 in idle condition. Runs smoother. I achieved that by modifying the O2 parameters and monitoring the wide band sensor. O2 parameters? Rich/lean threshold is the only method I can see in the 6E 1989 BIN.
I found that datalogging the MAF voltage really helps with diagnostic. You can accomplish that by modifying your BIN and ADX (see topic in stickies). That is key to trouble shooting. I've seen MAF sending voltage = 0 with no SES code. In this case, ECM relies on other sensors and defaults to another routine yielding different MAF g/sec readings. I haven't seen any error codes since reinstalling the descreened MAF which I used to tune it in 2010...but I suppose it's possible one or the other (MAFs...screened or not) caused the ECM to ignore it's values???
Ironically, I notice more drone with the descreened unit. AFR might change exhaust note (according to AI) but it suggests richer = louder. LOL Again, I'd expect the screened unit to pass LESS air -- resulting in a slightly richer AFR -- if anything!
Good Luck and Peace
Thread Starter
Junior Member
Joined: Feb 2008
Posts: 21
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Re: After 14yrs, I'm second-guessing MAF tables and would like some feedback
(You hitting me) Supreme Member
Joined: Jun 2012
Posts: 1,367
Likes: 193
From: Canada
Car: '18 Chev Camaro SS 1LE
Engine: LT1 6.2L
Transmission: T56
Axle/Gears: 3.91
Re: After 14yrs, I'm second-guessing MAF tables and would like some feedback
My bad!
I meant:
830 mv = 13.0:1
880 mv = 12.5:1
930 mv = 12.0:1
With ethanol free gasoline.
Translated in lambda:
830 mv = 0.88
880 mv = 0.85
930 mv = 0.82
Use lambda, not AFR on your gauge. It will compensate for ethanol content
I meant:
830 mv = 13.0:1
880 mv = 12.5:1
930 mv = 12.0:1
With ethanol free gasoline.
Translated in lambda:
830 mv = 0.88
880 mv = 0.85
930 mv = 0.82
Use lambda, not AFR on your gauge. It will compensate for ethanol content
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Supreme Member
Joined: Jun 2012
Posts: 1,367
Likes: 193
From: Canada
Car: '18 Chev Camaro SS 1LE
Engine: LT1 6.2L
Transmission: T56
Axle/Gears: 3.91
Re: After 14yrs, I'm second-guessing MAF tables and would like some feedback
“I let the descreened MAF "relearn".”
This makes no sense from a tuning perspective with a ‘165 $6E. There is no relearn procedure with this antiquated EFI system Once electricity is removed, it's my understanding fuel trims are lost and they have to be "relearned". It's an expression that's probably not the best.
This is a myth. There is a Stay Alive Memory feature (SAM). It retains the last BLM number that was used in each BLM cells (15 of them) before shut down. Once engine is restarted, in open loop, SAM will definitely have an effect because instead of "128" BLM, you could get any other value. However, in closed loop, the INT kicks in and immediately corrects fuel mixture + BLM value. So this "relearn" thing does not exists. The BLM learn feature is very short term and constantly varies. From experience, SAM is inaccurate and a real pain in the b** when tuning open loop and PE. I always disable SAM to make sure BLM is locked at 128 on every cold start or hot restart. I also rearrange BLM cells to make sure when entering PE at WOT, BLM is locked at 128. That way I get consistency. Reseting the ECM by cutting power to it resets SAM to 128.
While on the topic of BLMs, they are inaccurate at best! The BLM cells cover a large area of engine operation. They will swing from rich to lean depending in which quadrant of the BLM cell the engine operation is at. BLMs also react with a delay, so it makes it harder to pin point where the adjustment to MAF tables needs to be done. I always rely on the integrator average to adjust MAF tables, not BLMs. If anything I slow down the BLM update rate to prevent wild swings. BLM are overrated. They actually are pretty useless. What counts is having the O2 sensor in the right location and operating properly in close loop. Then watch the INT average at different engine operation.
“but it will never have the "torque" of the screened unit -- driving on the hwy. As such, (without a wideband), I'm trying to figure out what might be happening...or if I did something wrong in 2010?”
Are you talking about WOT condition, cruising condition or both? The descreened MAF I tuned it with in 2010, does everything better EXCEPT low-rpm responsiveness (torque) in 6th gear around 1400-1500rpms.
That's when you need to datalog and figure out why this is. You need to compare data and see where the differences are all else being equal. In close loop, there should not be much difference in BLM from MAF to MAF unless something major is happening. Example would be a significant difference in voltage range which would make BLM max out and prevent fuel mixture correction. Again datalogging is key.
“Common sense would suggest the need to ENRICHEN MAF tables for a descreened unit. As I look at it again (now), the MAF values (gms) are actually lower-than-stock. WTF? Am I thinking backwards?”
You are touching a complex subject here. You can not compare MAF tables from tune to tune. You have to take into consideration other parameters that comprise the INJ PBW calculation. Also, from MAF to MAF, there could be a difference in the voltage range vs real mass airflow. The ECM does not know what the mass airflow is. All it sees is a voltage sent by the MAF sensor. A human attributes a value (g/sec) to a voltage in the MAF tables (6 of them). But, yes, common sense (or logic) would suggest the need to enrichen MAF tables if one was to descreen a MAF, as long as it’s the same MAF unit. Same style MAF unit with screens removed. Stock style. Seems more complicated than I'd think. Isn't that "human attribution of g/sec" what we call calibrating? BTW...It seems odd there are multiple MAF tables but maybe the assembler code runs faster with smaller tables...or more likely I don't know something else going on....Or the main array area for assembler is "full" with the spark table...or something unimportant. And, yeah, I get the scalers contain hex values pointing to the limits for each table.
It does not matter if it's the same style of MAF, etc... Each MAF could be different depending on which company manufactured it (tolerances & quality) and when. The intake track differences could make the exact same MAF behave differently. Lot of people assume that the MAF will adapt to a new engine and it does not. Especially at lower rpm. Also, GM tuned the MAF tables for different engine and intake track.
“I'd think that would make it run a hair lean?”
What would make it run “a hair lean”? If more air were flowing thru the sensor than a possible erroneous "calibration" would suggest. And, yeah, the 02 feedback SHOULD "fix" that UNLESS BLMs got "out of maximum correction "range" for the +/- 15% correction that I've been told is possible. THEN AND ONLY THEN...might it get richer/leaner AFAIK. (FWIW, I don't have a laptop setup for scanning right now)
The only way to see if BLM is out of range is by datalogging and looking at the actual number.
Factory ARAP/AYPY = 108min 160max
They can be changed to accommodate more correction. Problem again with BLM is they can swing wildly. Follow the Integrator instead.
BTW...I notice ARAP (rich/lean threshold) has higher values for lower MAF flow -- than the Corvette's AYPY stock BIN (as found online). I'm thinking the ARAP is an automatic BIN vs a manual bin for the AYPY. Since an automatic aids in torque conversion (torque converter), I'm almost think THAT is backwards too! :-) I'll post them if you're curious.
What do you mean by rich/lean threshold? It's a confusing term. There are no rich/lean thresholds in the MAF tables.
APYP = 89 vette 5.7TPI 6 speed with 3.33 or 3.54
ARAP = 89 vette 5.7TPI auto with 3.07
6) Does anyone run a RICHER than stoich mixture in lower LV8s...just for better response.
I do run richer on my 383 and stock 305 LB9 in idle condition. Runs smoother. I achieved that by modifying the O2 parameters and monitoring the wide band sensor. O2 parameters? Rich/lean threshold is the only method I can see in the 6E 1989 BIN.
Again what do you mean by rich/lean threshold method?
I found that datalogging the MAF voltage really helps with diagnostic. You can accomplish that by modifying your BIN and ADX (see topic in stickies). That is key to trouble shooting. I've seen MAF sending voltage = 0 with no SES code. In this case, ECM relies on other sensors and defaults to another routine yielding different MAF g/sec readings. I haven't seen any error codes since reinstalling the descreened MAF which I used to tune it in 2010...but I suppose it's possible one or the other (MAFs...screened or not) caused the ECM to ignore it's values???
If you don't datalog and compare, you'll never know and just keep guessing
Ironically, I notice more drone with the descreened unit. AFR might change exhaust note (according to AI) but it suggests richer = louder. LOL Again, I'd expect the screened unit to pass LESS air -- resulting in a slightly richer AFR -- if anything!
You might have more drone because you have more air. Who knows? In close loop, the AFR should be the same even if more air is entering the engine the close loop operation tries to maintain Lambda 1.0. I feel that you don't understand the close loop operation. By descreening the MAF you add a bit more air and probably modify air velocity as well. However, it should not be significant enough to have material change on the tune. The close loop feature via INT/BLM will adjust the fuel mixture. Thus, you should not run leaner or richer in close loop. I will repeat again, lol, you need datalogging to see what is going on. There is also SA that is affected by LV8. If you have more air = higher LV8 = different SA. Maybe that plays a role in responsiveness.
Datalogging will tell you what the MAF, RPM, LV8 and resulting SA are for a comparable engine operation. You will be able to determine a delta in MAF and LV8 for sure.
This makes no sense from a tuning perspective with a ‘165 $6E. There is no relearn procedure with this antiquated EFI system Once electricity is removed, it's my understanding fuel trims are lost and they have to be "relearned". It's an expression that's probably not the best.
This is a myth. There is a Stay Alive Memory feature (SAM). It retains the last BLM number that was used in each BLM cells (15 of them) before shut down. Once engine is restarted, in open loop, SAM will definitely have an effect because instead of "128" BLM, you could get any other value. However, in closed loop, the INT kicks in and immediately corrects fuel mixture + BLM value. So this "relearn" thing does not exists. The BLM learn feature is very short term and constantly varies. From experience, SAM is inaccurate and a real pain in the b** when tuning open loop and PE. I always disable SAM to make sure BLM is locked at 128 on every cold start or hot restart. I also rearrange BLM cells to make sure when entering PE at WOT, BLM is locked at 128. That way I get consistency. Reseting the ECM by cutting power to it resets SAM to 128.
While on the topic of BLMs, they are inaccurate at best! The BLM cells cover a large area of engine operation. They will swing from rich to lean depending in which quadrant of the BLM cell the engine operation is at. BLMs also react with a delay, so it makes it harder to pin point where the adjustment to MAF tables needs to be done. I always rely on the integrator average to adjust MAF tables, not BLMs. If anything I slow down the BLM update rate to prevent wild swings. BLM are overrated. They actually are pretty useless. What counts is having the O2 sensor in the right location and operating properly in close loop. Then watch the INT average at different engine operation.
“but it will never have the "torque" of the screened unit -- driving on the hwy. As such, (without a wideband), I'm trying to figure out what might be happening...or if I did something wrong in 2010?”
Are you talking about WOT condition, cruising condition or both? The descreened MAF I tuned it with in 2010, does everything better EXCEPT low-rpm responsiveness (torque) in 6th gear around 1400-1500rpms.
That's when you need to datalog and figure out why this is. You need to compare data and see where the differences are all else being equal. In close loop, there should not be much difference in BLM from MAF to MAF unless something major is happening. Example would be a significant difference in voltage range which would make BLM max out and prevent fuel mixture correction. Again datalogging is key.
“Common sense would suggest the need to ENRICHEN MAF tables for a descreened unit. As I look at it again (now), the MAF values (gms) are actually lower-than-stock. WTF? Am I thinking backwards?”
You are touching a complex subject here. You can not compare MAF tables from tune to tune. You have to take into consideration other parameters that comprise the INJ PBW calculation. Also, from MAF to MAF, there could be a difference in the voltage range vs real mass airflow. The ECM does not know what the mass airflow is. All it sees is a voltage sent by the MAF sensor. A human attributes a value (g/sec) to a voltage in the MAF tables (6 of them). But, yes, common sense (or logic) would suggest the need to enrichen MAF tables if one was to descreen a MAF, as long as it’s the same MAF unit. Same style MAF unit with screens removed. Stock style. Seems more complicated than I'd think. Isn't that "human attribution of g/sec" what we call calibrating? BTW...It seems odd there are multiple MAF tables but maybe the assembler code runs faster with smaller tables...or more likely I don't know something else going on....Or the main array area for assembler is "full" with the spark table...or something unimportant. And, yeah, I get the scalers contain hex values pointing to the limits for each table.
It does not matter if it's the same style of MAF, etc... Each MAF could be different depending on which company manufactured it (tolerances & quality) and when. The intake track differences could make the exact same MAF behave differently. Lot of people assume that the MAF will adapt to a new engine and it does not. Especially at lower rpm. Also, GM tuned the MAF tables for different engine and intake track.
“I'd think that would make it run a hair lean?”
What would make it run “a hair lean”? If more air were flowing thru the sensor than a possible erroneous "calibration" would suggest. And, yeah, the 02 feedback SHOULD "fix" that UNLESS BLMs got "out of maximum correction "range" for the +/- 15% correction that I've been told is possible. THEN AND ONLY THEN...might it get richer/leaner AFAIK. (FWIW, I don't have a laptop setup for scanning right now)
The only way to see if BLM is out of range is by datalogging and looking at the actual number.
Factory ARAP/AYPY = 108min 160max
They can be changed to accommodate more correction. Problem again with BLM is they can swing wildly. Follow the Integrator instead.
BTW...I notice ARAP (rich/lean threshold) has higher values for lower MAF flow -- than the Corvette's AYPY stock BIN (as found online). I'm thinking the ARAP is an automatic BIN vs a manual bin for the AYPY. Since an automatic aids in torque conversion (torque converter), I'm almost think THAT is backwards too! :-) I'll post them if you're curious.
What do you mean by rich/lean threshold? It's a confusing term. There are no rich/lean thresholds in the MAF tables.
APYP = 89 vette 5.7TPI 6 speed with 3.33 or 3.54
ARAP = 89 vette 5.7TPI auto with 3.07
6) Does anyone run a RICHER than stoich mixture in lower LV8s...just for better response.
I do run richer on my 383 and stock 305 LB9 in idle condition. Runs smoother. I achieved that by modifying the O2 parameters and monitoring the wide band sensor. O2 parameters? Rich/lean threshold is the only method I can see in the 6E 1989 BIN.
Again what do you mean by rich/lean threshold method?
I found that datalogging the MAF voltage really helps with diagnostic. You can accomplish that by modifying your BIN and ADX (see topic in stickies). That is key to trouble shooting. I've seen MAF sending voltage = 0 with no SES code. In this case, ECM relies on other sensors and defaults to another routine yielding different MAF g/sec readings. I haven't seen any error codes since reinstalling the descreened MAF which I used to tune it in 2010...but I suppose it's possible one or the other (MAFs...screened or not) caused the ECM to ignore it's values???
If you don't datalog and compare, you'll never know and just keep guessing
Ironically, I notice more drone with the descreened unit. AFR might change exhaust note (according to AI) but it suggests richer = louder. LOL Again, I'd expect the screened unit to pass LESS air -- resulting in a slightly richer AFR -- if anything!
You might have more drone because you have more air. Who knows? In close loop, the AFR should be the same even if more air is entering the engine the close loop operation tries to maintain Lambda 1.0. I feel that you don't understand the close loop operation. By descreening the MAF you add a bit more air and probably modify air velocity as well. However, it should not be significant enough to have material change on the tune. The close loop feature via INT/BLM will adjust the fuel mixture. Thus, you should not run leaner or richer in close loop. I will repeat again, lol, you need datalogging to see what is going on. There is also SA that is affected by LV8. If you have more air = higher LV8 = different SA. Maybe that plays a role in responsiveness.
Datalogging will tell you what the MAF, RPM, LV8 and resulting SA are for a comparable engine operation. You will be able to determine a delta in MAF and LV8 for sure.
Last edited by SbFormula; Dec 12, 2024 at 11:20 AM.
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Re: After 14yrs, I'm second-guessing MAF tables and would like some feedback
Other than adding lamda, I don't see that your AFR vs mV values are different than your prior post???
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Rich/Lean Threshold tables for your perusal....
Notice the differences in values between APYP and ARAP. And, yeah, the differences MIGHT be attribute to trans type...meaning some need to enrich lower air flow (rpms/LV8s) to perform richer/leaner depending on trans type. TO ME, it would appear manual trans requires less of a "boost" to launch the vehicle (or lightly accel) compared to auto (ARAP). I make this guess because ARAP's higher voltage thresholds imply a richer target -- in closed loop.
Which is to say I'm assuming it's possible to alter AFR even in closed loop. If I'm right, that's what you weren't understanding when you thought I don't get closed loop vs open loop.
Last edited by greggpenn; Dec 12, 2024 at 01:22 PM.
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Car: '18 Chev Camaro SS 1LE
Engine: LT1 6.2L
Transmission: T56
Axle/Gears: 3.91
Re: After 14yrs, I'm second-guessing MAF tables and would like some feedback
You multiply lambda by stoichiometric AFR for the type of gasoline you have and that gives you the AFR.
Example of E10 Gasoline = 14.1
14.1 x 0.85 = 12.0
So 880mv = 12.0
I always use lambda now.
Last edited by SbFormula; Dec 12, 2024 at 06:13 PM.
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Joined: Jun 2012
Posts: 1,367
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From: Canada
Car: '18 Chev Camaro SS 1LE
Engine: LT1 6.2L
Transmission: T56
Axle/Gears: 3.91
Re: Rich/Lean Threshold tables for your perusal....
Notice the differences in values between APYP and ARAP. And, yeah, the differences MIGHT be attribute to trans type...meaning some need to enrich lower air flow (rpms/LV8s) to perform richer/leaner depending on trans type. TO ME, it would appear manual trans requires less of a "boost" to launch the vehicle (or lightly accel) compared to auto (ARAP). I make this guess because ARAP's higher voltage thresholds imply a richer target -- in closed loop.
Which is to say I'm assuming it's possible to alter AFR even in closed loop. If I'm right, that's what you weren't understanding when you thought I don't get closed loop vs open loop.
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Re: After 14yrs, I'm second-guessing MAF tables and would like some feedback
Riddle me this: Is this example rich or lean? What is the dominant source of error (MAF, NBO2, WBO2, Fuel, Fuel pressure, injector calibration, temperature, alcohol, other)? Who's driving the bus? Will obsessing over certain numerical values make it better?
https://datazap.me/u/tequilaboy/400-...7022-6790-6906
Not really expecting answers, but fun to think about.
https://datazap.me/u/tequilaboy/400-...7022-6790-6906
Not really expecting answers, but fun to think about.
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Joined: Feb 2008
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Re: After 14yrs, I'm second-guessing MAF tables and would like some feedback
Riddle me this: Is this example rich or lean? What is the dominant source of error (MAF, NBO2, WBO2, Fuel, Fuel pressure, injector calibration, temperature, alcohol, other)? Who's driving the bus? Will obsessing over certain numerical values make it better?
https://datazap.me/u/tequilaboy/400-...7022-6790-6906
Not really expecting answers, but fun to think about.
https://datazap.me/u/tequilaboy/400-...7022-6790-6906
Not really expecting answers, but fun to think about.
Last edited by greggpenn; Dec 13, 2024 at 02:52 PM.
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