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Thread: LS1 CL Fueling question

  1. #1
    Tuner evolmotorsprt's Avatar
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    Question LS1 CL Fueling question

    I'm still green when it comes to tuning and am hoping someone can give me clarification on something.

    When driving around town in closed loop, where I assume the MAF and O2's are doing the majority of calcs, what table(s) are telling the computer what AFR to shoot for? I know the MAF reads the air coming in and the O2's lean or rich, but is the commanded AFR controlled simply by the calibration of the MAF Hz in relation to the set stoich value and O2 switch points, or are the values being pushed from somewhere like the FA table?

    This is on a C5. Thanks.
    Last edited by evolmotorsprt; 10-10-2018 at 03:55 PM.

  2. #2
    Senior Tuner cobaltssoverbooster's Avatar
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    depends on if you forced it into maf only mode or speed density mode.
    when in closed loop the ecu always targets the stoich fuel ratio which is a general fuel setting.
    when in enrichment mode, the ecu will switch to OL-enrichment mode and stop using the inputs from the oxygen sensors. in order to tune any enrichment zone fueling you must have a wideband. the target in enrichment mode is derived by stoich fuel setting divided by the pe enrichment value. Enrichment values get set to a target afr and then dont get adjusted after they are set.

    do you have a tune file for us to analyze and help push you in a progressive direction?
    2000 Ford Mustang - Top Sportsman

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    Tuner evolmotorsprt's Avatar
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    Quote Originally Posted by cobaltssoverbooster View Post
    depends on if you forced it into maf only mode or speed density mode.
    when in closed loop the ecu always targets the stoich fuel ratio which is a general fuel setting.
    when in enrichment mode, the ecu will switch to OL-enrichment mode and stop using the inputs from the oxygen sensors. in order to tune any enrichment zone fueling you must have a wideband. the target in enrichment mode is derived by stoich fuel setting divided by the pe enrichment value. Enrichment values get set to a target afr and then dont get adjusted after they are set.

    do you have a tune file for us to analyze and help push you in a progressive direction?
    The reason I asked is because at cruise and light throttle I'm at a lambda of 1.08ish. At full throttle my lambda is .84. I'm wondering if I should try to get my lambda at cruise closer to 1, or if being a little lean is okay.

    Thanks, and here's the tune:

    My Corvette Tune 10052018 Timing Dialed.hpt

  4. #4
    While cruising in closed loop your WB should switch between lean and rich, just like a narrowband.

  5. #5
    Tuner evolmotorsprt's Avatar
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    I'll hook everything up and go log today. I'm still waiting on HP Tuners to release the pro package for the MPVI2 so I can easily log my UEGO in the software. I'll report back.

  6. #6
    Senior Tuner cobaltssoverbooster's Avatar
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    sorry i just got time to go through the tune.
    so it should show a commanded lambda of 1.0 unless enrichment mode is triggered then it will be richer (obviously). the only time commanded would be leaner would be defco or cfco. cfco transitions are disabled but it looks like defco is active so if the settings are too sensitive and triggering fuel cuts then you could disable it by raising its threshold temp and then come back and turn it on when your done. in my yukon defco was good for a solid 1.5 mpg and your project has half the weight so id say in the long run keep the feature enabled. i dont think this is your issue for stoich swings though.

    i notice your closed loop is still active in the tune file. you have not raised the closed loop thresholds high enough to disabled closed loop operation. also the ltft tables seem to be still active. if you tune off the wideband make sure you shut that stuff down so it doesnt interfere with your wideband error analysis.
    this is likely the reason your wideband values keep dancing around stoich when in closed loop operation.

    the only time i wander the pe settings is if i do dyno runs and find the vehicle desires a different target afr. for the most part it should be very happy around 12.5-12.8. you could go higher and test towards the 13 but i usually stop at 12.7 if i dont have forged pistons. just a personal preference on that but its worth testing if you have time as a shop.
    1.125 is your 12.7 afr value and 1.144 is your 12.5 value since you have the stoich set to 14.3.
    you wideband lambda at wot seems to track your rich pe fairly well considering thats a 12 flat afr value with your commanded stoich value. commanded stoich * lambda recorded = actual afr

    personal opinion here but i dont prefer the torque trigger for pe. i usually shut torque delay off and go old school gen3 and rely on the map and tps thresholds. typically a map limit of 65-75 and a similar tps of 60ish depending on the behavior. i adjust enrichment ramp in value to try and target a transition afr around the low to mid 12's (12-12.5)


    as for controlling fuel your still running in SD enhanced mode which is the factory setup. in this mode the ve table is used up until 4000 rpm (high rpm disable value) and then the maf sensor takes over.
    its best to tune these as separate entities so pick either maf or ve to tune in one at a time and then when your done you can come back and set the high rpm value to return to the stock blended airmass prediction mode.
    2000 Ford Mustang - Top Sportsman

  7. #7
    Tuner evolmotorsprt's Avatar
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    Quote Originally Posted by cobaltssoverbooster View Post
    sorry i just got time to go through the tune.
    so it should show a commanded lambda of 1.0 unless enrichment mode is triggered then it will be richer (obviously). the only time commanded would be leaner would be defco or cfco. cfco transitions are disabled but it looks like defco is active so if the settings are too sensitive and triggering fuel cuts then you could disable it by raising its threshold temp and then come back and turn it on when your done. in my yukon defco was good for a solid 1.5 mpg and your project has half the weight so id say in the long run keep the feature enabled. i dont think this is your issue for stoich swings though.

    i notice your closed loop is still active in the tune file. you have not raised the closed loop thresholds high enough to disabled closed loop operation. also the ltft tables seem to be still active. if you tune off the wideband make sure you shut that stuff down so it doesnt interfere with your wideband error analysis.
    this is likely the reason your wideband values keep dancing around stoich when in closed loop operation.

    the only time i wander the pe settings is if i do dyno runs and find the vehicle desires a different target afr. for the most part it should be very happy around 12.5-12.8. you could go higher and test towards the 13 but i usually stop at 12.7 if i dont have forged pistons. just a personal preference on that but its worth testing if you have time as a shop.
    1.125 is your 12.7 afr value and 1.144 is your 12.5 value since you have the stoich set to 14.3.
    you wideband lambda at wot seems to track your rich pe fairly well considering thats a 12 flat afr value with your commanded stoich value. commanded stoich * lambda recorded = actual afr

    personal opinion here but i dont prefer the torque trigger for pe. i usually shut torque delay off and go old school gen3 and rely on the map and tps thresholds. typically a map limit of 65-75 and a similar tps of 60ish depending on the behavior. i adjust enrichment ramp in value to try and target a transition afr around the low to mid 12's (12-12.5)


    as for controlling fuel your still running in SD enhanced mode which is the factory setup. in this mode the ve table is used up until 4000 rpm (high rpm disable value) and then the maf sensor takes over.
    its best to tune these as separate entities so pick either maf or ve to tune in one at a time and then when your done you can come back and set the high rpm value to return to the stock blended airmass prediction mode.
    Thanks for the reply, I'm with you on most of what you said. I just want to check some math.

    EQ=1.144 comes out to a lambda=0.874
    That would mean @14.68, PE=12.83
    and @14.32, PE=12.52
    Does that seem correct?

    I'm going to try EQ=1.16 and log today because I road race the car and want a little more safety factor at sustained high loads.
    That should put me at lambda=0.862, and respectively @14.68, PE=12.655

    Also, clarifying the PE torque trigger, do you set the "enable torque" to zero and then set "map" to 65-75kpa? What does this accomplish? are you doing this for feel or greater control?

    Thanks for you guidance. I appreciate it.

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    Cruising slightly on the lean side of stoichiometric will not hurt a thing. With Tri-Y headers and the mild cam that I have in my 350 powered Express van my factory 02 sensor target voltages gave a 1.02-1.05 lambda in closed loop at idle and cruising down the road. In lean cruise mode I run around 1.15 Lambda or about 16.25:1 with E10s ~14.1 stoichiometric value. As long as it richens up under throttle and load it will not hurt a thing to cruise a little lean. A lean mixture actually burns cooler than a mixture a stoich. I run the 420 HP HO Marine cammed 8.1 in my 1999 Tahoe about the same.

  9. #9
    Senior Tuner cobaltssoverbooster's Avatar
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    Quote Originally Posted by evolmotorsprt View Post
    Thanks for the reply, I'm with you on most of what you said. I just want to check some math.

    EQ=1.144 comes out to a lambda=0.874
    That would mean @14.68, PE=12.83
    and @14.32, PE=12.52
    Does that seem correct?

    I'm going to try EQ=1.16 and log today because I road race the car and want a little more safety factor at sustained high loads.
    That should put me at lambda=0.862, and respectively @14.68, PE=12.655

    Also, clarifying the PE torque trigger, do you set the "enable torque" to zero and then set "map" to 65-75kpa? What does this accomplish? are you doing this for feel or greater control?

    Thanks for you guidance. I appreciate it.
    The math looks right. Is stoich changes so does the target afr.
    I disable pe torque triggers because it's a calculation. I just personally feel better about triggering pe soley off the map and tps because those are not calculations. You can use the torque threshold just lower it from 100% so it will trigger sooner.

  10. #10
    Senior Tuner cobaltssoverbooster's Avatar
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    Lambda eq is different than afr eq only when you change the stoich value away from 14.7 afr.

    14.7/12.6= 1.162
    1/.86=1.162
    14.3/12.6=1.134
    14.3*.86=12.298
    You set your targets based on afr eq in the ecu not lambda so make sure you always change your target value to match new stoich.

    Hope that clears it up

  11. #11
    Senior Tuner kingtal0n's Avatar
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    Quote Originally Posted by Fast4.7 View Post
    Cruising slightly on the lean side of stoichiometric will not hurt a thing. With Tri-Y headers and the mild cam that I have in my 350 powered Express van my factory 02 sensor target voltages gave a 1.02-1.05 lambda in closed loop at idle and cruising down the road. In lean cruise mode I run around 1.15 Lambda or about 16.25:1 with E10s ~14.1 stoichiometric value. As long as it richens up under throttle and load it will not hurt a thing to cruise a little lean. A lean mixture actually burns cooler than a mixture a stoich. I run the 420 HP HO Marine cammed 8.1 in my 1999 Tahoe about the same.
    This. I recommend open loop target of 14.8 to 15.2 air fuel ratio for all cruising/idle positions using gasoline. Personally I checkerboard my fuel map in these regions to alternate between them, so the wideband never sits too long on 14.8 or 15.2 but rather wanders between them naturally as you drive, as if it were still some form of 'closed loop'.

    I do not keep the engine run at 16:1+ extremely lean air fuel ratios for extended period is because even though it will run normal, there is some concern of 'pre-heating' the combustion chamber, raising EGT while cruising, and seems to wear the plugs faster although that could just be my imagination. I also get more misfires at idle once the engine's been 'warmed over' by the lean air fuel ratios (turbo engines). I do not recommend chasing over 15.8:1 and tend to consider 15.2 as a 'boundary' of sorts. there is very little fuel to be saved going from 15:1 to 16:1, something like 0.23% I believe. It is for all practical purposes negligible.

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    Quote Originally Posted by kingtal0n View Post
    This. I recommend open loop target of 14.8 to 15.2 air fuel ratio for all cruising/idle positions using gasoline. Personally I checkerboard my fuel map in these regions to alternate between them, so the wideband never sits too long on 14.8 or 15.2 but rather wanders between them naturally as you drive, as if it were still some form of 'closed loop'.

    I do not keep the engine run at 16:1+ extremely lean air fuel ratios for extended period is because even though it will run normal, there is some concern of 'pre-heating' the combustion chamber, raising EGT while cruising, and seems to wear the plugs faster although that could just be my imagination. I also get more misfires at idle once the engine's been 'warmed over' by the lean air fuel ratios (turbo engines). I do not recommend chasing over 15.8:1 and tend to consider 15.2 as a 'boundary' of sorts. there is very little fuel to be saved going from 15:1 to 16:1, something like 0.23% I believe. It is for all practical purposes negligible.
    As you go richer or leaner than stoich your EGTs will drop as will your peak combustion chamber temps. The burn of the mixtures slows considerably. Read up on lean of peak egt cruise mixture settings on airplanes. Airplane pilots adjust mixture for peak EGT, then lean them out enough to drop EGT about 50?F. Leaner mixtures at cruise power settings increase engine life. 14.7 to 16.5 is about 2-3 mpg highway in my 350 powered Express van. My 8.1 Tahoe sees 3-4 mpg better running in lean cruise. Running leaner reduces the torque output, requiring more throttle opening and the engine has less pumping loss, similar to how an EGR works except without the carbon buildup.

  13. #13
    Senior Tuner kingtal0n's Avatar
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    Quote Originally Posted by Fast4.7 View Post
    As you go richer or leaner than stoich your EGTs will drop as will your peak combustion chamber temps. The burn of the mixtures slows considerably. Read up on lean of peak egt cruise mixture settings on airplanes. Airplane pilots adjust mixture for peak EGT, then lean them out enough to drop EGT about 50?F. Leaner mixtures at cruise power settings increase engine life. 14.7 to 16.5 is about 2-3 mpg highway in my 350 powered Express van. My 8.1 Tahoe sees 3-4 mpg better running in lean cruise. Running leaner reduces the torque output, requiring more throttle opening and the engine has less pumping loss, similar to how an EGR works except without the carbon buildup.
    I read about that but I didn't have good luck with it in my application. Perhaps because all of my cars are turbocharged has something to do with it. I get similar to superior economy with 15-16 rather than 16+. As for mpg I only seem to gain 0.5~ if that from 14.7 to 15.3. 8.1L huh? maybe that also has something to do with it it. DI by any chance? I've never used Di.

    do you mind sharing weight/gear/economy stats? I am an economy freak.
    Mine is
    5.3L Gasoline, 3200lbs, 4l80e, 3.5:1 rear, 26" tires. Approx 2500rpm cruise 70~mph, 22-23mpg max so far.
    basically what I am always looking for a 800ft*lbs of torque capable drivetrain for < $1000 with 26+mpg and so far I am a long way off at 22~
    Last edited by kingtal0n; 10-15-2018 at 12:18 AM.