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Thread: IAT's kinda high

  1. #1
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    IAT's kinda high

    Digging around I have found a lot of mixed info. I'm trying to narrow down the reason I have something going on that absolutely kills power in my truck. Those of you that know, know it's a L83 in a 89 suburban.

    So after having a local shop go ahead and adjust my driveshaft and put some new coil springs in my truck, he drove it back over to me and said it felt like a dog. So out of curiosity, I hop in the truck and try to drive. It won't even barely get out of it's own way. I immediately think that the trans is slipping or something its so slow and sluggish.

    Well I go ahead and flash a good known stock file that I pulled from the ECM and I just touched up a few things before flashing.

    Now, truck felt great until it got hot enough again and the IAT's get high again. It was pretty warm today here in NC like 85-90 and my IAT's are up to 130+ almost cresting 140. It is at this time that I realize the IAT's are probably pulling timing a bunch or something. Well stupid me, I don't have my scanner set up perfectly but I went ahead and scanned it some. This is later in the evening and the temps outside have come down a bit.

    Here's the log file I got, and if anyone has a good tutorial for setting up VCM scanner so I can go get a better read with more info it would be greatly appreciated. Aside from just making a Cold air intake setup for my truck, where it's actually seperated from the engine bay, is there any thing I Can do to help prevent it from being so sluggish when the IAT's get up to such a high temp?

    I am thinking of zero'ing out the IAT retard table up to 140* then lowering the reatard after 140 some as I don't have an aggressive tune at all, in fact it's stock for the most part. Also there is a Mult vs IAT under burst knock retard that may have an effect but I am not sure I should be messing with it.

    Let me know what you think. Thanks!

    iat high.hpl

  2. #2
    Tuning Addict 5FDP's Avatar
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    You need to log more channel related to timing advanced. Like intake air temp, coolant temp, torque mngt avdanced and if there are others add those that could remove timing.

    There is literally zero or negative timing under heavy load and it's not all related to just the IAT's being high. The computer is also pulling out a ton of fuel, like all the time. Your fuel trims are -20%.

    What is your current air intake setup as? Is the current intake tube the same size as the stock intake or is it something custom and is the MAF in a straight section near no bends?

    If the air tube is a different size or the MAF isn't placed right it will skew the readings and cause you issues. If the tube diameters is a different size you will have to alter the MAF curve to make it not rich anymore.

    What is your fuel pressure??


    Post your tune file.
    Last edited by 5FDP; 08-14-2021 at 08:02 PM.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  3. #3
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    Thanks for the quick reply. I might be a victim of the MAF bend issue as I do have it close to a bend. Here is the tune file.

    The engine is from a 2015 silverado and the Cold Air Intake is made for that truck. It's the same diameter.

    8-14-21.hpt

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  5. #5
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    Oh, and to answer your question about fuel pressure it's a Corvette 58 psi fuel filter / regulator setup. I know that these engines can require more psi but I have read that they work fine on 58 psi setups.

  6. #6
    Tuning Addict 5FDP's Avatar
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    The fuel pressure should be fine then. A factory truck would have a fuel pump control module that would increase/decrease fuel pressure on demand but so long as you have steady pressure that isn't like 70+ psi, you should be okay.

    Why was the driver demand tables messed with? If everything is stock, put that back to stock.

    Scaling back the IAT pull is okay, but having it start at 140 is not okay. Delay it back to 104 degrees instead of 86 degrees. At 140+ you will want a fair amount if timing pull, atleast 5 degrees.

    Once there is a better data log with more timing channels it will help. Also add some torque channels like peak torque, delivered engine torque, predicted torque and ones like that.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  7. #7
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    Awesome. Thank you for taking the time to reply. I am going to put the Driver Demand tables back to stock. Trying to add all the pertinent info to log, don't know what I'd be missing. here is a screenshot

    scanner.PNG

  8. #8
    Advanced Tuner Shrek's Avatar
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    Quote Originally Posted by Kalvin.I95Muscle View Post
    ... I might be a victim of the MAF bend issue as I do have it close to a bend ...

    That is about the worst place that the MAF Sensor could have possibly been located. It is near a bend, and near where a rubber connector is slid over the metal tubing, and has welded seams close to, and on both sides of, the MAF Sensor.

    All of these conditions will contribute to localized airflow turbulence. You have quite a good length of straight tubing - the MAF Sensor should be placed in the middle of this straight section of tubing (see attached photo). This would afforded you a decent length of straight tubing on either side of the MAF Sensor - which should promote both accuracy and easy tuning.

    Over the years I have seen people use this type of air intake system on their LS or LT project. This configuration will breathe hot under hood air - which increases the likelihood of detonation (knock) and will decrease power potential. Hot air holds less atomized fuel than does cold (dense) air, and due to detonation tendency, will required reduced spark advance (timing).

    The best place for the air filter is ahead of the radiator support, just behind the grill. This location is not always possible. The next best option is to build a sealed box around the air filter, with an intake snorkel that will pull air from the area ahead of the radiator support (just behind the grill).

    Gen 5 - MAF location.jpg

  9. #9
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    Alright. Looks like it's on my list of things to get figured out. Since this is what I have at the moment, what if I was to flip this air intake tube around therefore putting it closer to the throttle body and at the end of the straight run, before a bend instead of right after a bend?

    Either way I can do some research and try to find an air intake tube that accepts this maf iat in the middle, or end up cutting this one up and using couplers but that doesn't seem very efficient.

    Thanks for all the input guys.

  10. #10
    Advanced Tuner Shrek's Avatar
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    Flipping the air intake tubing won't help - you would only be moving the problem.

    If you are on a tight budget, you could build on what you already have - no need to purchase an entirely new system. You can purchase a weld on bung for the MAF Sensor (from GM and other sources). Then you, or your local welder, need to drill a hole in middle of the straight run of the tubing, and weld on the new MAF Sensor bung.

    The existing bung will need to be capped off. Then look at fabricating an enclosure around the air filter - that draws ambient air from outside of the engine compartment.

  11. #11
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    Thanks for all the input. I'll update you guys of the progress as I have time to get things done. Again, I really appreciate all the help.

  12. #12
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    I updated the wrong thread on this. Figured I'd just update on what I've done.

    So, I haven't been able to mess with the MAF tube or anything yet, but I did throw the little divider things in the engine bay that separate the air cleaner from the engine bay. Not sure it helped any but it's not made for that truck anyway. Time to fab something up.

    Anyway, I started looking into the low octane tables and looking around (I know I might catch flak for this) and decided to copy the high octane table to the low octane table and subtract 4* giving me a little cushion.

    I noticed on the low octane table it was like a 15-20* difference under load at low rpms and that was where I was experiencing the most issues with drivability. I am running a stock setup and not boosted or anything so I'm thinking I should be fine as long as I keep my eyes on Knock Retard and make sure it's not pinging or anything. Here's a couple logs and the tune. Drivability wise it is waaaayyyyy better.

    I'll keep driving and logging and get this hptuners thing figured out lol.

    8-18-21 #2.hpl
    8-18-21.hpl
    8-14-21 stock octane table dfco.hpt