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Thread: Startup flare on warm start with video

  1. #1
    Tuner in Training
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    Startup flare on warm start with video

    I'm still trying to perfect my idle and startup and have gotten it almost squared away except for a warm startup flare where the rpm flares high and then falls really low and hunts back and forth until it stabilizes where it wants to be. I have smoothed out the over/under speed timing to help with the cam idle. My BRAF and fueling are really good and the initial airflow adder isn't causing it.

    Do I maybe need to adjust the frictional airflow or the startup timing flare tables?

    https://youtu.be/bWby9sKoDvM
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  2. #2
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    Well I tried to play with the frictional airflow or the startup timing flare tables until I completely zeroed them out. This did absolutely nothing to fix my issue. It would be great to get someone experienced to look at my vid, log, and tune file that has some experience. I don't understand why it does this on warm start but on cold start it slowly falls to the desired idle rpm with no swinging high and low.

    forgot to include applicable information about the car:
    99 corvette
    stock ls1 bottom end
    FAST 102
    Ls2 throttle body
    232/234 .600"/.600" cam
    799 heads mildly ported and milled to 59cc
    Cometic .040 MLS gaskets

  3. #3
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    With some guidance from a user over on the corvette forums I may have found something to attribute to my issue. Even though I can't seem to get help or insight on these forums I will document my trials to possibly help someone out in the future.

    Briefly reading through this thread, http://www.hptuners.com/forum/showth...ghlight=clutch, and thinking about the values in my tune then comparing my tune file to a stock 04' z06 file and some other ls2 throttle body c5's from the tune repository I am seeing something that is jumping out at me. My off idle scalar from my factory tune was 0 as well as the startup airflow decay and every other tune file I'm finding has the scalar set to 1 and the decay set to .800.

    Do you think the car is jumping to an off idle transition early on during the initial startup and this is why my previous attempts at adding more air via startup airflow initial with up to a 100 cam revolution delay did nothing for me? I'm going to attempt this when I get off work this evening.

  4. #4
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    Well I adjusted my startup off idle scalar and set it to 1, set the idle airflow decay to 0, set the airflow adder table to 2 g/s across the table, and airflow delay to 100 cam revolutions. I even zeroed out the startup flare table so that it wouldn't interfere. This did not do anything for my warm start issues still the exact same problem as in the first log I posted.

    My BRAF numbers seemed suspiciously high. To me this seems like a calculated airflow problem and looking into solutions for the discrepancy between desired idle airflow and the dynamic airflow I found that to align these my ETC scalar needed adjustment. The ETC value that brought these back together actually was the stock value of .0255. Getting these back in line also brought my BRAF back into a more reasonable territory.

    Could this mean my injector data is wrong? I have 36lb/hr bosch part number #0280155811 and everything I found when setting this said to use the part number #0280155868 injector data so that is what I did.

    Here is a log from tonight with my tune and a modified .cfg file:
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  5. #5
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    Took some logs this morning before work. I ran the idle airflow config just to get the cooler temps lined up and then once it was warm I shut it down and then tried warm starting the car with the stock cranking fuel numbers for a 04' Z06 thinking that the i may have a rich starting issue. It doesn't appear to be rich on startup but actually a bit lean according to my b1s1 nbo2 sensor.

    I forgot about how my wideband has to do its warm up cycle after starting the car and that's why it reads pig rich at first and then comes out of it. I also noticed that I have a b2s1 nbo2 issue where its locked at 447mv. This wasn't there previously so I don't think it is contributing to my issues but I will address this tonight.

    Well I converted everything over to VCM Suite v3 so that anyone runnig the newest version can view my logs better and view the wideband data. My wideband is placed on the same side as my non functioning o2 sensor.
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  6. #6
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    So I've always seen when I start the car the STIT is 0 and then after 2-3 seconds it sky rocketed to over 2 g/s. I decided to give messing with the startup airflow initial another shot and worked my way up to 6 g/s until I gave up that because it made no change to the issues at all. I figured what the hell I'll start going at the frictional airflow table. Well I definitely saw a hanging idle issue after adding 4 g/s across the board so I slowly worked it down to an added 2.25 g/s over the original values. It warm starts great every time now.

  7. #7
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    start up flare

    I know this is 3 yrs old but in 2019 after my first ls swap im facing the same issue I noticed my timing jumps to 50 during this time of high rev ill try what you did and see what happens. hard to get any help on here for newbies