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Thread: Hot start trouble LT1

  1. #1
    Tuner in Training
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    Nov 2019
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    Hot start trouble LT1

    Hey guys,
    I have a 2018 Grandsport here with heads, cam, MSD manifold, etc.. def a steep learning curve to figure out. Many thanks to the folks on here that shared their experience with a LT newb

    Anyway this car makes 533/476 on our dyno. Spent a lot of time on the VVE and MAF, LTFTs look great. Drive-ability is excellent. Cold starts nice, however once warmed up I have to dab the throttle to get it to start. Otherwise if I don't apply throttle it will just crank until the autostart runs out.

    The attached log has a hotstart with throttle input, idle, shutoff and restart attempt without throttle.

    Any suggestions on what to try greatly appreciated!
    Attached Files Attached Files

  2. #2
    Same issue here on my 17 GrandSport. I just finished installing my cam and started tuning. Cold start fine, need to dab the throttle hot otherwise it won't start. I changed base idle and startup N and rolling idle with no effect. I did not try yet to hot start at 1200 rpm though. It is probably timing/fueling/torque related

    Since I'm just starting would you mind sharing tips or even better your tune with a fellow GS owner ?

    Anyway curious to see the answer from the experts...

  3. #3
    Keep adding grams of air in the base airflow under crank in the 176F and up columns.

  4. #4
    I would start with 3 grams

  5. #5
    Tuner in Training
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    Thanks, I'll give that a try.

  6. #6
    Tuner in Training
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    Broken record but.... Put it in SD mode and tune the VVE with a wideband. Then put it in MAF only and tune MAF with wideband. I've shared the tune above, feel free to compare with a stock tune to see what has changed.

    Also fee free to reach out with questions.

    Quote Originally Posted by Sachs View Post
    Same issue here on my 17 GrandSport. I just finished installing my cam and started tuning. Cold start fine, need to dab the throttle hot otherwise it won't start. I changed base idle and startup N and rolling idle with no effect. I did not try yet to hot start at 1200 rpm though. It is probably timing/fueling/torque related

    Since I'm just starting would you mind sharing tips or even better your tune with a fellow GS owner ?

    Anyway curious to see the answer from the experts...

  7. #7
    Advanced Tuner
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    Aug 2014
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    Central, LA
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    737
    Try setting cranking ve to 80, but I would also say that the tune posted above probably doesn't have enough cranking airflow in the hot ranges.

  8. #8
    Tuner in Training
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    Quote Originally Posted by regorih View Post
    Keep adding grams of air in the base airflow under crank in the 176F and up columns.
    That worked like a champ, had to add a lot but just went in 3g/s at a time til it started up great.

    Thank you!
    Attached Files Attached Files

  9. #9
    Quote Originally Posted by joshua@arcflashllc View Post
    Broken record but.... Put it in SD mode and tune the VVE with a wideband. Then put it in MAF only and tune MAF with wideband. I've shared the tune above, feel free to compare with a stock tune to see what has changed.

    Also fee free to reach out with questions.
    Thanks. I tried again yesterday to make my LM2 Wideband work with HP tuners with no success despite trying all good grounding pratices. Voltage jumping all around the place. I bought an AEM 30-0334 known to work with HP tuners yesterday night.
    My current file is not stock as I tuned with ARH headers/MSD mani/AFE intake/Ported TB last year. I just used the narrow band for the MAF tuning and the LM2 Wideband for WOT but without datalogging, just looking at it live... Anyway this will help me a lot, along with goat rope garage tuturials, which are really good for beginners like me

    Thanks

    Edit / which cam do you have on this GS ?
    Last edited by Sachs; 02-20-2020 at 07:04 PM.

  10. #10
    Quote Originally Posted by joshua@arcflashllc View Post
    That worked like a champ, had to add a lot but just went in 3g/s at a time til it started up great.

    Thank you!
    Good to know !!! this will help me a lot as well !

  11. #11
    Quote Originally Posted by Sachs View Post
    Good to know !!! this will help me a lot as well !
    Worked really good for me as well. I added 6g/s