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Thread: ran out of airflow for maf (512g/s) just reduce IFR?

  1. #1
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    ran out of airflow for maf (512g/s) just reduce IFR?

    As title would state maf is getting pegged at (512g/s) and its about 2-3% too lean at 512 g/s.

    I dont need much more headroom. can i just whack the IFR vs KPA table globally and multiply by .95, and then do the same for the entire maf curve (x .95) Does that make sense?

    is .95 even enough to significantly skew spark airmass numbers (cyl air)? Is that literally all i do? I have enough maf HZ headroom btw. Any other tips appreciated. e67 on MAF. No i dont want to use the vve for "SD".


    Thanks

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    can u use 2bar OS and then get the higher limit, i dont use maf but tried to max mine out and i can get double that in mine

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    Advanced Tuner jsllc's Avatar
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    Post log and tune. e67 should not have an issue with MAF until 655. VE will max out at 512. Either way if car is configured correctly the Dynamic which is what is used always keeps going.

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    Bump.

    There is no 2bar OS patch for my e67. This is a 2006 ctsv. Not the 2nd gen CTS-V (2009+) e67 that most are familiar with and has much better support.

    If i run in vve only ("SD") the PCM wants to nuke my motor (https://forum.hptuners.com/showthrea...080#post572080). So lets not go down that route.

    Attached is a logfile example. It's MAF only. I did reduce IFR by 20%, it did help. But still leaning out when 512 g/s approaches. But im not sure how much more resolution i want to sacrifice in the ignition timing table..

    Can i adjust cyl charge bias, any of the prediction coefficient biases to work in my favor here? Any other tables or items im missing? CYL or displacement size?
    Attached Files Attached Files

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    looking at your other thread using SD do u have your 02 sensors unplugged ? as the MV is 450ish all the time which could be causing the issue if the ecu freaks out because of it once it hits a curtain airflow, also your dynamic airflow in those logs is not even getting to 400g/s @6500rpm so im not sure why the maf could be maxing out so much higher now unless something off, also in your SD log the maf still shows a really small reading so it may be stuffing some calcs maby if u can disconnect it but keep the iat sensor see if that helps

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    Quote Originally Posted by 07GTS View Post
    looking at your other thread using SD do u have your 02 sensors unplugged ? as the MV is 450ish all the time which could be causing the issue if the ecu freaks out because of it once it hits a curtain airflow, also your dynamic airflow in those logs is not even getting to 400g/s @6500rpm so im not sure why the maf could be maxing out so much higher now unless something off, also in your SD log the maf still shows a really small reading so it may be stuffing some calcs maby if u can disconnect it but keep the iat sensor see if that helps
    Yeah both o2's are unplugged. Car is turbo and essentially only has 1 bank now. If youre looking at the logs from this thread you'll see dynair maxed too from what i can see. This log has 10-11# of boost. old logs were like half that on a different maf etc (old thread).

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    ok, i have herd of some dont like the 02's to be unplugged and can cause strange issues if u can plug them back in even if not in exhaust and give it a go see if it helps, couldnt see a log in this thread only a tune file ?

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    Quote Originally Posted by 07GTS View Post
    ok, i have herd of some dont like the 02's to be unplugged and can cause strange issues if u can plug them back in even if not in exhaust and give it a go see if it helps, couldnt see a log in this thread only a tune file ?
    I'll consider that for down the road. Really want to see if there's a way to gain more headroom in the airflow numbers running maf only for now though. Anything else besides IFR i can adjust?

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    Don't know how hard it would be but, If you put your maf sensor in a bigger tube that will slow the air down and extend your readings. Shouldn't hurt your power. Just a thought.

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    Quote Originally Posted by openwheel25 View Post
    Don't know how hard it would be but, If you put your maf sensor in a bigger tube that will slow the air down and extend your readings. Shouldn't hurt your power. Just a thought.
    Already did that. It's ls7 card maf in 4in housing.

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    Although it's really not recommended and I can't believe I'm even suggesting it - it is more tune-able or beneficial for you to just skew your injector flow rate table rather than doing the half / double stuff... It may not get you the head room your after and you'll need to skew your torque model in the opposite fashion so other airflow dependent torque calculations are somewhat correct... Then if needed you can still scale based on how much of the spark table your wishing to retain
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

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    This is a basic LS2 with a single 7875 and you've maxed out a LS7 MAF in a 4" tube? Does that sound right?

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    Quote Originally Posted by GHuggins View Post
    Although it's really not recommended and I can't believe I'm even suggesting it - it is more tune-able or beneficial for you to just skew your injector flow rate table rather than doing the half / double stuff... It may not get you the head room your after and you'll need to skew your torque model in the opposite fashion so other airflow dependent torque calculations are somewhat correct... Then if needed you can still scale based on how much of the spark table your wishing to retain
    Ghuggins - thanks. I know it hurts you to say that. You have given me good advice in the past on here.

    I reduced IFR by 20% and have enough headroom now, except cold days it still hits 512g/s. Worse case ill pull back on more IFR.

    But on the torque tables you mentioned? which ones could be massaged?

    Could I pull say 20% on all 4x air mass coefficients? (airmass A,b,c,d) to get headroom? I'm manual, and dont use any stability or traction on the car either. I know correct torque modeling is good for auto. But am i really needing that to be perfect in a m6? Or can i cheat it to my advantage? Im not sure what adverse effects this could cause. I haven't played with that stuff much. Any info, guides, links etc on those tables would be interesting.
    Last edited by itsdaveonline; 10-18-2019 at 02:22 PM.

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    Quote Originally Posted by blindsquirrel View Post
    This is a basic LS2 with a single 7875 and you've maxed out a LS7 MAF in a 4" tube? Does that sound right?
    Yes, its not that hard to believe. It's maybe 6-700hp. Im not sure what your getting at here. There is room in the Hz, just not in the airmass.

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    You would need to increase the torque model instead of decreasing it - This is also required even when doing something like putting the maf in a larger tube - all the same end effect - you just did it via injector skewing vs inlet tube changing... Depending on turbo size - even though it's not making a lot of boost - it can still be flowing a lot of air ;D

    There are still calc's in the ecm based off of the torque model even on manuals - although it's not that directly evident in the 4th gens they do exist to control throttle opening and closing on simple events such as coast and idle for example... If your happy with how the car is running and you've already tuned in a lot of things like these, then unless you just want it more "OE" - you should be good with what you have... I would focus on better blow offs and bypasses at this point...
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

    ~Greg Huggins~
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