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Thread: Need help with a tune before Monday 12 Jan 15

  1. #1
    Member Dirktdolman's Avatar
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    Default Need help with a tune before Monday 12 Jan 15

    I have a 03 Silverado 6.0 4L80 4X4. I am towing a 6 X 12 enclosed trailer to SoCal on Monday (12 Jan) and want to see if there can be some changes to my tune to get a little better MPG. I have attached my current tune and a couple scans. I wanted to do a WBO2 scan but I have not heard back from PLX Tech Dept.

    LS1B_0041.efi
    LS1B_0042.efi
    2003 Chevrolet 2500 HD LT 6.0L Auto 4X4 LS1B (OS 12593058) 2015 01-Jan 07.ctz

  2. #2
    Joe (Moderator) joecar's Avatar
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    B3616: set this same as 2002 Camaro (i.e. 65% TP below 3200 rpm, 35% TP above 3200 rpm).
    B3618: this is quite rich (EQR 1.23); if you keep seeing positive LTFT's you can probably be safe by setting B3618 to 1.18, but keep an eye on KR.

    As long as it goes to CL and trims, it should be ok for now (until you get your wideband going), just use light throttle if possible.

    What is the problem with your wideband...?

  3. #3
    Member Dirktdolman's Avatar
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    Thanks you for the quick response. I will make the changes and run the V2 going down to keep an eye on the KR.

    I contacted PLX on Dec 17th asking if two SM-AFRs can be connected to a V2. They said they would have to ask the Tech Dept. I have not heard back from them.

  4. #4
    Joe (Moderator) joecar's Avatar
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    You have to make it clear to them that you want to "serial comms daisy chain" to a logging device...

    if they come back and tell you the format, then we'll have to pass this on to Paul.

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    Member Dirktdolman's Avatar
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    I asked "Can I connect two of these to a EFILived V2 scanner via Serial?" I was referring to the SM-AFR Gen 4. This is the units they had on sale during the holidays.

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    Lifetime Member Steve Bryant's Avatar
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    Dirktdolman,
    Your tune could use some refinement, but I don't see anything that should cause you a problem during your trip towing the trailer or using the vehicle for daily driving before you do some more work on the tune. In my estimation, you're going to get about 9 - 10 MPG at best towing the trailer (especially if there is any hilly/mountainous terrain involved.

    When you do start working on the tune, here are some things that I would work on:
    1. Set the Parameter {B4206} Use O2 With Open Loop Commanded Fuel Table to Disable (currently Enabled in your tune). With this parameter enabled, it will always foul up any open loop tuning you may ever do because it constantly uses short term fuel trim to try to steer the mixture back to stoichiometric no matter what you have {B3618} Power Enrichment Modifier Based on RPM or any other open loop mixture modifier. Believe me, I've fought this battle and I have scars.
    2. Your LTFT value could use some work. They need to be much closer to zero across the board. The first thing that I would do to fix this is to calibrate the MAF Table {B5001}. Use the portions of the CALC.VET post 1 that relate to calibrating B5001 using LTFTBEN. This can be done without a wideband AFR of any type. Since you likely have the stock cam and induction system (you didn't mention any mods to the engine), your stock VE table is probably very acceptable as is. Also, the dynamics of driving a truck like yours don't demand the VE table to be spot-on as would be desirable on a sportier car.
    3. The PLX SM-AFR units have 0-5 VDC analog outputs and two of them could be connected to a V1 or a V2 without any modification. However, for the kind of tuning that you're trying to do (improve drivability and perhaps gas mileage), a WBO2 of any type is not really going to be necessary unless you want to refine the AFR using PE in the upper throttle/RPM range.

    You may already be on the road by now since it's January 12. However, if you read this post before, try to relax and enjoy the trip as much as possible! Remember to use TOW/HAUL mode for the transmission and keep you speed below 60 for the best fuel economy. You can do some more tuning later if you want!

    All my best,

    Steve

  7. #7
    Member Dirktdolman's Avatar
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    Thank Joe and Steve. I did some mileage checks for the trip. Pulling an empty trailer down I averaged 11 mpg and 10 mpg pulling a full trailer back up (Boise Idaho to Palm Desert California).

    I scanned both ways. I tried to break up the run down into 30 min to 1 hour blocks. On the way back up I scanned from fuel up to fuel up. Also when I left Idaho I was on 87 oct. I bummed up to 89 after the first fill up. I used 91 for the trip backup. I kept the speed at about 65 of below.

    I was hoping I could hook the PLX units together for a serial input to the V2.

  8. #8
    Member Dirktdolman's Avatar
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    2003 Chevrolet Silverado 2500HD 6.0L Automatic 4 X 4

  9. #9
    Joe (Moderator) joecar's Avatar
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    Your WOT shift points are upside-down... the downshift MPH has to be below the corresponding upshift MPH...

    i.e. require the following relationships:
    - D0925-27 < D0910-12,
    - D0930-32 < D0915-17,
    - D0935-37 < D0920-22,
    - D0966 < D0963,
    - D0967 < D0963,
    - D0968 < D0965.

    Also, set the D0960,1,2 to 100% all across.

    Also, set D1101 to 256 mph all across, in all columns (it is a bad idea to lock the TCC in 2nd gear, especially at high TP/torque).

  10. #10
    Joe (Moderator) joecar's Avatar
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    Take note of this in general:

    PT shift table relationships:

    basic relationships:
    1->2 curve should be above 2->1 curve;
    2->3 curve should be above 3->2 curve;
    3->4 curve should be above 4->3 curve;
    . . .

    additional relationships:
    3->2 curve should be above 1->2 curve;
    4->3 curve should be above 2->3 curve;
    . . .

    this can be summarized as: the curves cannot cross anywhere;

    if they cross anywhere, then you will not be able to predict what gear the TCM selects when the operating point hits the cross.
    It applies to the PT and WOT shift curves/points.

    Also remember that WOT shift requires both the WOT MPH and WOT RPM to be met.
    Last edited by joecar; February 19th, 2015 at 03:30 AM. Reason: spelling

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