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Lets talk in depth tuning

This is a discussion on Lets talk in depth tuning within the Computer & Tuning forums, part of the LSx Technical Help Section category; Figured I would stop high jacking the other thread (s) and make one for myself and others to ask questions, ...

  1. #1
    Veteran Hi-Po's Avatar
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    Thumbs up Lets talk in depth tuning

    Figured I would stop high jacking the other thread (s) and make one for myself and others to ask questions, be it in depth or a general question about specific tuning areas. Would like to keep the questions more specific so that we can all learn some specifics about HPT.

    Mrr23, I will start this and say that I dont know exactly what you mean when you say, "change your injector constant table to match." I assume you mean the Injector Flow Rate Vs KPA VAC. I only say that because I mine are 27.41 from 10 KPa to 65 KPa. Cant say I know exactly what to change when swapping my 26's out for 42 lb'ers. I have them sitting next to me.

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    Senior Member mrr23's Avatar
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    this should be what your injector table should be right now.




    a quick and dirty method is just to increase the number to 42. only thing is the injector flow rate are based on 45 psi. the LSx fuel pressure is 58 psi. using the injector calculator in the hptuners editor, the new flow rate for the 42# injectors are 47.68 lbs/hr now. take 47.68 and subtract the first number in the table to get the new flow rate start point for the table. 47.68 - 26.41 = 21.27. now take that number and put it into the box next to the = + x. left click the empty box above the word FLOW in the injector table. this will highlight all the boxes. now click the + sign and it will increase the whole table by 21.27. now you will be real close to correct. again this is a dirty and quick way to do this. your new numbers in the table will be these, but in 2 decimal places you'll see

    47.68217 47.86819 48.05421 48.17822 48.36423 48.55025 48.67426 48.86028 48.98429 49.17030 49.29431 49.48033 49.60434 49.79036 49.91437 50.10038 50.22440

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    24.43014 24.43014 27.40640 27.40640 27.40640 27.40640 27.40640 27.40640 27.40640 27.40640 27.40640 27.40640 27.40640 27.40640 29.32857 29.32857 29.32857

    Well, those are my numbers now. Pretty close. That is awesome, I will do the equation for my numbers and also for the numbers you posted. I figured with the higher PSI fuel pressure of the LSx's it was going to change the number. Awesome.

    When I do my numbers with th nifty equation you showed me, Of course my first two numbers are a tad lower and my other numbers are slightly higher. Either way, I now can change my injectors and get them changed correctly ( or semi dirty) Thanks so much!

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    TunedbyFrost.com Tuner Frost's Avatar
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    I setup flow rate tables using a spreadsheet that Doug Stalter modified from 'the' original uncredited injector spreadsheet. He did a fantastic job to the point where I use it as-is. I have attached it. It is based on (a variant of) the Bernoulli Equation (Google it!).

    The better and more accurate your base injector tables, the easier the rest of the operation falls in line. Remember, ALL final fueling decisions (pre CL) are based on this one table. Fudge here makes fudge in tables that we can't even correct. That's not to say that it doesn't happen to some extent with every setup, but it is best practice to minimize error wherever possible.

    There are many ways to skin a cat.

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    Veteran 0rion's Avatar
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    what's your thoughts on using the iat modifier for injectors over 63.5#'s? Do you know what people are doing for the LS2's because it's my understanding that IAT modifier won't work on the LS2's.

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    TunedbyFrost.com Tuner Frost's Avatar
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    Scale the injector and the VE by the same % (and MAF if in use).

    It's the same principal used to limit dynamic airflow in the GENIII's.

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    TJEA Retirement Home Dr.Crash's Avatar
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    Quote Originally Posted by mrr23 View Post
    this should be what your injector table should be right now.

    Click for full size


    a quick and dirty method is just to increase the number to 42. only thing is the injector flow rate are based on 45 psi. the LSx fuel pressure is 58 psi. using the injector calculator in the hptuners editor, the new flow rate for the 42# injectors are 47.68 lbs/hr now. take 47.68 and subtract the first number in the table to get the new flow rate start point for the table. 47.68 - 26.41 = 21.27. now take that number and put it into the box next to the = + x. left click the empty box above the word FLOW in the injector table. this will highlight all the boxes. now click the + sign and it will increase the whole table by 21.27. now you will be real close to correct. again this is a dirty and quick way to do this. your new numbers in the table will be these, but in 2 decimal places you'll see

    47.68217 47.86819 48.05421 48.17822 48.36423 48.55025 48.67426 48.86028 48.98429 49.17030 49.29431 49.48033 49.60434 49.79036 49.91437 50.10038 50.22440


    Thanks for the info!!!

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    Moderator Firebirdjones's Avatar
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    I was doing really good understanding everything thanks to Mrr23,,,,,and then Frost jumped in and got all technical,,,now I'm completely lost.
    Then Orion came in and put the icing on the cake and made my head spin.

    Actually I love reading this stuff and trying to learn some of the more in depth tuning capabilities Hptuner has. Even for a computer dummy like me it's still interesting.

    All 3 of these guys have helped me out tremendously with some of the more basic stuff Hi-po,,,you are in good hands.

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    Well, I flashed my new file withthe new injectors and the MAF zero'd out with the fail frequency set to zero. Also with the MAF unplugged. Started it up and it ran horrible. Blue smoke and idling way worse then before. I have my idle set at 1100 across the board for now, and for some reason it still idles at 800/850. Should it be pushing this much blue smoke? Never did that before, it worried me and I shut it off after a few seconds. Also, I was watching my scanner and at 400 RPM it went lean all the way up to 21.6 at 95 and 100 Cylinder airmass. When I saw that I immeaditely dhut it down. Any ideas?

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    Senior Member mrr23's Avatar
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    with the MAF out of the scenario, the PCM relies solely on what the VE tables have. take the VE tables and increase by 10 to get a starting point. alsos what did you set the Base Running Airflow table to?

    blue smoke is an oil consumption issue.

    also, email me your file to mrrjjdh03@aol.com i want to look at it.

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    Veteran Hi-Po's Avatar
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    Well, I dont have a real long one yet with the new injectors or the MAF disabled. Maybe 20 seconds. I will send you the ones after cam along with the very short scans with MAF disabled.

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    TunedbyFrost.com Tuner Frost's Avatar
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    Blue smoke is not tuning related. If it is misfiring as a result, it's not going to run great. I would investigate the smoking...

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    Senior Member mrr23's Avatar
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    Quote Originally Posted by Hi-Po View Post
    Well, I dont have a real long one yet with the new injectors or the MAF disabled. Maybe 20 seconds. I will send you the ones after cam along with the very short scans with MAF disabled.
    i want your PCM file not a log. i want to see your stock file and the modified one you just did.

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    Veteran 0rion's Avatar
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    Quote Originally Posted by Frost View Post
    Scale the injector and the VE by the same % (and MAF if in use).

    It's the same principal used to limit dynamic airflow in the GENIII's.
    Can you explain this, I'm not grasping it. If your new injectors are 25% larger than 63.5# you scale the VE up by that 25%?? If so what do you then do with your IFR table?

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    TunedbyFrost.com Tuner Frost's Avatar
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    Quote Originally Posted by 0rion View Post
    Can you explain this, I'm not grasping it. If your new injectors are 25% larger than 63.5# you scale the VE up by that 25%?? If so what do you then do with your IFR table?
    I haven't had to do it specifically for this, but have have needed to lower dynamic airflow and it works the same. Your assertion here about scaling the VE is correct, and scale the MAF down as well if you are using it.

    Here's a tip for your future 2bar tunes... If you want to be able to better control timing VS. boost this is useful. You can run more timing at lower boost levels, but a turbo slams the timing map early at 1.2g/cyl. If you log dynamic airflow and see it around 1.8-1.9g/cyl at your peak, multiply the IFR and VE by about 70% to keep it off of the bottom of the timing map until max boost. This principal can be used on a genIII PCM with a properly selected MAF to allow MAF operation past 512g/sec
    Last edited by Frost; 04-17-2009 at 06:14 AM.

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    Veteran 0rion's Avatar
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    well, I had a big reply typed up but kind of answered my own question in the middle of it somewhere.
    Let me ask this. If the pcm thinks you have 63# injectors and you actually have 79lb the car should go real rich correct? What would your IDC look like in that case?

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    TunedbyFrost.com Tuner Frost's Avatar
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    Quote Originally Posted by 0rion View Post
    well, I had a big reply typed up but kind of answered my own question in the middle of it somewhere.
    Let me ask this. If the pcm thinks you have 63# injectors and you actually have 79lb the car should go real rich correct? What would your IDC look like in that case?
    It normally would, but this is how the 24% reduction in VE balances it out.

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    Veteran Hi-Po's Avatar
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    Well, I cant get this car idling for nothing. Mrr, I uploaded those files and it didnt really do anything. Im getting KR in places I never have before, If I rev it up and let it idle down, it WILL die everytime.

    Ive added 2 to the idle airflow
    Ive put 6.0 from -300 to -200 in the idle underspeed spark vs RPM error
    Ive added 2 to the base spark vs airmass and copied it to my in drive
    I have the desired idle set at 1050.

    This car will not idle for shit. It still dies on me over and over again. Mrr, when you get the config for idle control I would love to see it. Does anyone have any suggestions, where I am missing some much needed changes?

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    Senior Member mrr23's Avatar
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    how we doing now?

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    Better. im going back down to write again. Why should I be making it leaner in my STFT? Im gonna go play with it alittle more.

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