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Thread: Let's talk air filters & air intakes and how they affect an engines tune..

  1. #1
    Advanced Tuner HartRod's Avatar
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    Let's talk air filters & air intakes and how they affect an engines tune..

    K&N? Spectre? AEM?

    What do you have and why are you using it?

    What about air intake tubing? 3"? 4" straight? bends?

    I bring this up because I never realized the drastic affect that changing the air intake tube and the air filter would have on how the motor AND transmission runs.......!!!!!! I was using a temporary K&N setup on my LS3 in my 68 and had the motor/tranny tuned pretty well. I finally got around to building a cold air intake for it and used a Spectre filter due to size of the box. After getting everything built, I did a test run on and could not believe the difference it made in the truck!! All the fuel trims were messed up, the transmission was shifting all weird, looks like everything we did to the tune was wrong and needs to be done again! Gen IV's are very particular to airflow, and I knew that changing the intake setup up would require some fine tuning, but not to the extent that it did. What do you guys think has the most affect on the engine, the shape of the air intake or the filter you put on? Just thought I would bring this up to generate some discussion and remind people to make sure they finish up the intake setup prior to any tuning. I can post the before and after logs if anyone is interested.
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    68 Farm Truck build thread-LS3/6L80/TVS1900: http://67-72chevytrucks.com/vboard/s...d.php?t=358692

  2. #2
    Changing the intake tube size will affect the airflow across the MAF which will need to be retuned against a wideband for accuracy.
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    Advanced Tuner HartRod's Avatar
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    Quote Originally Posted by Z06-Hammer View Post
    Changing the intake tube size will affect the airflow across the MAF which will need to be retuned against a wideband for accuracy.
    Thank for the input! That makes sense. I'm sure the shape of the tubing affects it as well. How much does the size and type of air filter affect the tune? Is there a way to determine the optimal size of filter if adding a CAI? Here's a picture of my original breather setup and the custom CAI I built, comments and critiques are welcome and encouraged!
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    69 Suburban Bagged & Blown: http://67-72chevytrucks.com/vboard/s...d.php?t=200387
    68 Farm Truck build thread-LS3/6L80/TVS1900: http://67-72chevytrucks.com/vboard/s...d.php?t=358692

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    Advanced Tuner gn2beatu's Avatar
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    I have seen it change it enough to throw lean codes 25%+ off - if thats what your asking by how far off.

    It throws the airflow off a ton as you have the bigger tube, the speed of the air crossing the MAF is slower, so the MAF sees less air (while flowing more), yet the O2's are screaming the opposite that its lean.

    Its not uncommon on LS2 to see a 25hp increase going to 4" tubing and blade style MAF. Less with the 4" and 3.5" stock MAF.
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    You also need to take into account where the MAF is placed in the tube. You went from a accordion style tube to a smooth aluminum one. That alone changes the way the air travels across the MAF. Then you add more bends and a longer tube and things can be way off.

    There is another thread about tuning a 100mm MAF and they get into honeycomb inserts in order to straighten the airflow across the MAF. It a good read, I'll see if I can dig up a link.

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    Advanced Tuner HartRod's Avatar
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    Quote Originally Posted by gn2beatu View Post
    I have seen it change it enough to throw lean codes 25%+ off - if thats what your asking by how far off.

    It throws the airflow off a ton as you have the bigger tube, the speed of the air crossing the MAF is slower, so the MAF sees less air (while flowing more), yet the O2's are screaming the opposite that its lean.

    Its not uncommon on LS2 to see a 25hp increase going to 4" tubing and blade style MAF. Less with the 4" and 3.5" stock MAF.
    Thanks! Not quite 25% but close, lol. I knew it would change things, but didn't think it would be that drastic. How big of filter should I use and what brand?


    Quote Originally Posted by doc350 View Post
    You also need to take into account where the MAF is placed in the tube. You went from a accordion style tube to a smooth aluminum one. That alone changes the way the air travels across the MAF. Then you add more bends and a longer tube and things can be way off.

    There is another thread about tuning a 100mm MAF and they get into honeycomb inserts in order to straighten the airflow across the MAF. It a good read, I'll see if I can dig up a link.
    Thanks for the info! Did you find the other thread?
    69 Suburban Bagged & Blown: http://67-72chevytrucks.com/vboard/s...d.php?t=200387
    68 Farm Truck build thread-LS3/6L80/TVS1900: http://67-72chevytrucks.com/vboard/s...d.php?t=358692

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    Don't mind me asking how HOT does that intake pipe get

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    Advanced Tuner HartRod's Avatar
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    Quote Originally Posted by ultimate lsx tuning View Post
    Don't mind me asking how HOT does that intake pipe get
    Honestly, I haven't driven it enough to get it hot, lol. I should have it back from the powder coaters next week. Then we can finish up the tune, and if the weather cooperates, I'll start driving the heck out of it and let you know!
    69 Suburban Bagged & Blown: http://67-72chevytrucks.com/vboard/s...d.php?t=200387
    68 Farm Truck build thread-LS3/6L80/TVS1900: http://67-72chevytrucks.com/vboard/s...d.php?t=358692