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Thread: GMPP LS3/480 idle issues

  1. #1
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    GMPP LS3/480 idle issues

    Seems I?m tuning engine swaps lately.
    This LS3 is in a 59 Apache panel truck.
    Auto trans with a stall and separate controller.

    Car was dyno tuned by another shop, so I don?t have the orig tune file. Can?t seem to find the LS3/480 tune in the repository. So if someone has one, or knows where it might be in the repository, I?d appreciate it.

    Commanded idle is 875. And it does idle there. I am just trying to tame it a bit.

    Using the VCM controls, I told it to idle at 700. Desired idle complies and shows 696 rpm.
    The engine remains at approx 900.
    Timing doesn?t change, neither does the tps. Tps desired however does drop.

    I can speed it up, that works fine.

    The VCM controls also let us manipulate the throttle through its range with the engine off. Although the tps won?t go to 0, it will go to 12%.

    When I tell it to idle at 700 from 900, the tps sits at 20%.

    So something is limiting the tps from going lower.

    I lowered the final airflow min table but no change there.

    Ideas?

    I?d like to tune the MAF below 900 rpm, just can?t get there.

    BTW, it?s MAF only and my research says GM set these up that way.

    Ron
    Y2K C5 A4 Coupe (10.78 @ 127) Cathedral port 6.2
    S476 L33 5.3 69 Nova 8.76 @ 158 Drive to the track street race car
    06 Cobalt SS bought new

  2. #2
    Ron,
    Here is the one I have.
    LS376/480 file
    -Greg
    2009 Maverick Silver G8 GXP M6 - 586hp
    Engine Mods: TVS 2300 Magnacharger ARH 1 7/8" long tubes with catted x-pipe
    Drivetrain Mods: Ram Dual Disc Clutch
    Suspension Mods: Pedders/Wretched basic drag pack - BMR trailing arms
    Misc Mods: Jamesbiz Catch can - GRRRR8 Heater hose relo kit

  3. #3
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    Thanks Greg!

  4. #4
    if you have a cam I would not lower the idle as vacuum becomes unstable but I do not know what you are trying to accomplish? Maf tuning below 2000 rpm is unstable and causes tip in enrichment latency issues are you sure you want to mess with the tune you have???

  5. #5
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    I am trying to understand why this setup won?t idle where I tell it to. If I tell it 700, it should go there, it won?t. I?ve tuned a few of these MAF only, one a turbo 2010 Camaro, and they follow commanded idle rpm.

  6. #6
    This is an ecm hard coded issue for the GMPP stuff, LS3 and LSX. The reason I stopped using the GMPP controller, especially when using an automatic trans. The GMPP trans controller sucks IMO.

  7. #7
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    Thank you! I had suspected as much. Now I can quit spinning my wheels and get to fixing the myriad of other issues on this install.

    Like the MAF too close to a bend, and the air filter tucked down next to the radiator. IAT?s went above 160 while driving it yesterday, with ambient temps in the 60?s......

    Thanks again.

    Ron

  8. #8
    Ouch, I understand tight fits and heat. If my guys have to put the MAF any closer than 8in from a bend I use a 3mm honeycomb straightener in the exit of the bend, honestly end up with a straightener in 90%.

    In that Apache is there enough room in the inner fender for shrouded cone filter? I've used the rectangular filters mounted to inner fender with a nice plenum to pull across the filter. I attached a couple pics showing this, not LS but Hemi powered 47 Power Wagon, shows the concept.

    Good Luck
    Attached Images Attached Images
    Last edited by DHC; 10-19-2018 at 04:59 PM.

  9. #9
    Move the maf up to 2500 then tune vve and youll have a good idle. Use the oem diameter intake tubing and 6 inches before transition is not the issue as look as at zl1 rotofab intake as it has a flex fitting 3 inches after the maf and its only 3 inches from full opening. The MAF is Not designed for part throttle its a blended application build your VVE From open and closed then tune your maf WOT. If its got all the original sensors and your tubing is oem size you should have NO problems with this If you have headers You need a wideband. this be comes your flow variance and incorrect ltft along with stft and including cam changes. Im not going to get into this unless your open minded to really tuning this vehicle in depth. Im getting tired or trying to help others who discard me. Do you see all these modified honey comb products in stock apps? Its has STOCK a flex fitting right after the maf and its almost at the end of piping right by a square filter. Do you really think that doesnt cause turbulance??? Why do you think its set to take control at 4000 rpm stock.
    I want you to look at one chart and it will explain my reason for tuninng VVE .
    Intake valve temperature gas gain under fuel open loop base. The intake valve multiplier is changed by open loop and tuning VVE compensates for this You must tune this.
    Also transient fuel meaning how the fuel is effected by temperate and flow passed valve changes and fuel evaporation based on intake valve temp vs rpm is all effected not by total airflow cause you can have higher valve temps at higher rpm at 1/4 throttle say at 3200 vs you 1/3 throttle at 2600 do you think fuel evaporation and transient fueling is the same??? Please tune your vve not just maf it will run fabulous.

  10. #10
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    You know, there's a reason people discard you. Ending a rhetorical question with "???" or using all caps or using "!!!" makes you seem like the kind of guy most people would ignore.

    It is also very hard to follow your posts. Lots of run on sentences, no spacing within huge posts, continuing to harp on ivt and vve when people ask a question about idle, etc.

    I know it's hard to understand tone on a forum, but your "e-tone" is pretty abrasive, brother.

    Just trying to help.

  11. #11
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    Thanks DHC. That was actually the first solution I thought of. It's a 4x4 so there is plenty of room. The owner built the truck, and he can fabricate.
    Should move the MAF too. The alum intake tube is literally 1/2" from the radiator core.

    It really needs to be fixed before I finish tuning it. The KR table lit up red, and I was just driving normally. I had to call the customer to make sure he didn't put regular in it!
    Not sure what GM was thinking on this tune, but cooler air will certainly help.

    The customers main complaint was that when he drove it over the mountains to eastern Oregon in 90 degree plus temps, it was a stone. I wonder why...…..

    Hemi? Ha! I've tuned lots of them. Boss is a MOPAR guy.

    jpierro79

    GM ships this calibration with these crate engines MAF only. I would think since they sell it as "Plug and Play", it should work fine.
    Obviously it doesn't.
    No headers btw.
    If, if this were my car, I'd delve into tuning the VE. I wonder if it's even close in this cal?
    However, the only area it doesn't run fabulous, is at idle. I understand the GM hot cam isn't know for great idle quality.
    Everywhere else though, it runs excellent.

    Ron
    Y2K C5 A4 Coupe (10.78 @ 127) Cathedral port 6.2
    S476 L33 5.3 69 Nova 8.76 @ 158 Drive to the track street race car
    06 Cobalt SS bought new

  12. #12
    Anytime Ron, glad to be of some assistance. We use a lot aluminum tube for intakes and the more we do the more I want a plastic extrusion machine. Extrude and mold the shape as you go. Huge pipe dream, pun intended.

    I wonder if when GM did this engine and tune they must have intended for light 2wd stuff. Just an assumption, we all know what that does. I know the heavy stuff we have put this combo in really takes some time in the timing tables and PE fueling and still kind of lazy.

    Yes it has a Hemi. I've tuned my fair share and hate the damn things. We do a lot of 6.4 JK conversions and we see them all back for lifter failure and ring lands broken on "stock" tunes.

    Good Luck and keep up the good work