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Thread: NEW TO TUNING I HAVE QUESTIONS, its a long post.

  1. #1
    Carb and Points!
    Join Date
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    NEW TO TUNING I HAVE QUESTIONS, its a long post.

    First i want to let everyone know how thankful i am that this forum exist. I have a 2004 Corvette base model 6 speed convertible. I recently rebuilt the engine due to a lifter failure and metal in everything. I decoded to to up the HP and torque with some aftermarket goodies since it was going to be apart. I kept the stock displacement 347 CI went with forged pistons and rods, PRC225 heads with 62cc chamber with .051" head gaskets my compression ratio should be right at 11.0-1, i picked the Texas Speed torquer V4 camshaft, 231/234 .629"/.615" 111 LSA, i wanted to build naturally aspirated engine with good torque and HP. Other supporting mods are Johnson lifter, hardened pushrods, Che precision trunnion upgrade in the stock rocker arms, melling oil pump, new timing chain and gears, ARP head bolts, bosch 42lb injectors, long tube headers and x pipe, summit racing twin disk clutch, fast 92 intake manifold and LS2 throttle body. When i took the car to the tuner they could never get the idle right, chasing, and hunting, car never started the first try, they said it was the throttle body and intake. They did the dyno tuning and the finals numbers 450/450 are pretty good, car drives really good but when you come to a stop it tries to die.
    After a lot of research and reading and re-reading the same articles i knew something could be done with the tune but i did not want to pay them again. I found tuner pro and pc hammer and did more research. I was able to locate the XDF file , pulled the bin file for my tune and started making some small adjustments, idle timing was set at 16 degrees between 400-1200 rpm, i am currently at 26 degrees of advance and the car has never started this good. I adjusted the idle to 925, might turn that up to 950, VE tables taking out 10% and 10% air at the same time, i currently have removed 15% total from both and the hunting is minimal, coming off throttle it drops smooth but dips 100-200 rpm, not every time, before it would drop 400-600 rpm and try to die.
    So my questions are as follows.
    1. What should i use to data log, i want to check and make sure everything is operating as it should fuel mixture is correct at cruise and WOT. What is the most critical information i should be looking at when i data log?
    2. For final idle tuning what should i be looking at to get that last 100 rpm dip cleared up? More Air adjustments, something in the fuel and VE tables, as a newbie i am sure there are some tables that can be adjusted i am not sure where to start.
    3. COLD IDLE SPEED, even though i added some rpm to the full range from cold to warmed up the engine never idles at or above 1000 rpm's, should i leave it as is?
    I am sure i will have more questions,
    If you read all of this i appreciate you taking the time.
    Thank you

  2. #2
    Fuel Injected!
    Join Date
    Feb 2013
    Location
    Euless, TX
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    Quote Originally Posted by Seans04Vette View Post
    First i want to let everyone know how thankful i am that this forum exist. I have a 2004 Corvette base model 6 speed convertible. I recently rebuilt the engine due to a lifter failure and metal in everything. I decoded to to up the HP and torque with some aftermarket goodies since it was going to be apart. I kept the stock displacement 347 CI went with forged pistons and rods, PRC225 heads with 62cc chamber with .051" head gaskets my compression ratio should be right at 11.0-1, i picked the Texas Speed torquer V4 camshaft, 231/234 .629"/.615" 111 LSA, i wanted to build naturally aspirated engine with good torque and HP. Other supporting mods are Johnson lifter, hardened pushrods, Che precision trunnion upgrade in the stock rocker arms, melling oil pump, new timing chain and gears, ARP head bolts, bosch 42lb injectors, long tube headers and x pipe, summit racing twin disk clutch, fast 92 intake manifold and LS2 throttle body. When i took the car to the tuner they could never get the idle right, chasing, and hunting, car never started the first try, they said it was the throttle body and intake. They did the dyno tuning and the finals numbers 450/450 are pretty good, car drives really good but when you come to a stop it tries to die.
    After a lot of research and reading and re-reading the same articles i knew something could be done with the tune but i did not want to pay them again. I found tuner pro and pc hammer and did more research. I was able to locate the XDF file , pulled the bin file for my tune and started making some small adjustments, idle timing was set at 16 degrees between 400-1200 rpm, i am currently at 26 degrees of advance and the car has never started this good. I adjusted the idle to 925, might turn that up to 950, VE tables taking out 10% and 10% air at the same time, i currently have removed 15% total from both and the hunting is minimal, coming off throttle it drops smooth but dips 100-200 rpm, not every time, before it would drop 400-600 rpm and try to die.
    So my questions are as follows.
    1. What should i use to data log, i want to check and make sure everything is operating as it should fuel mixture is correct at cruise and WOT. What is the most critical information i should be looking at when i data log?
    2. For final idle tuning what should i be looking at to get that last 100 rpm dip cleared up? More Air adjustments, something in the fuel and VE tables, as a newbie i am sure there are some tables that can be adjusted i am not sure where to start.
    3. COLD IDLE SPEED, even though i added some rpm to the full range from cold to warmed up the engine never idles at or above 1000 rpm's, should i leave it as is?
    I am sure i will have more questions,
    If you read all of this i appreciate you taking the time.
    Thank you
    Needs the IAC area adjusted and then an idle relearn. Had to do this on a DBW 6.0L S10 with a 102.

  3. #3
    Carb and Points!
    Join Date
    Apr 2022
    Age
    53
    Posts
    6
    Quote Originally Posted by Fast355 View Post
    Needs the IAC area adjusted and then an idle relearn. Had to do this on a DBW 6.0L S10 with a 102.
    Thank you, I will do some iac adjustment research and do the relearn on it tomorrow. Should I clear the fuel trims before the relearn?

  4. #4
    Carb and Points!
    Join Date
    Apr 2022
    Age
    53
    Posts
    6
    Quote Originally Posted by Fast355 View Post
    Needs the IAC area adjusted and then an idle relearn. Had to do this on a DBW 6.0L S10 with a 102.
    I am trying to figure out the IAC area adjustment, very new to all of this, one thing to note I did drill a small hole in the throttle blade, should I swap that blade out and start over. I know old school carb guys used this method to help with big cams, and it did help before I started trying to learn to do this myself. I can put a blade in it, how much will it change the settings I have already started with? I saved the original tune from the tuner so loading that is not an issue.
    I am having a hard time understanding the iac area and how it is calculated and adjusted. I appreciate any guidance you can share.

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