Results 1 to 6 of 6

Thread: First Cold Start Long Crank

  1. #1
    Tuner in Training
    Join Date
    Aug 2014
    Posts
    22

    First Cold Start Long Crank

    Hello All,

    I recently got my build together and got the idle calibration pretty dialed in. The only issue is the very first cold crank is very long. Any cold start after that, and the motor immediately fires. I've included a log file that shows the very first long key crank event, I let the engine run for ~10 seconds, and then after its off for a few seconds, I crank it again and it immediately fires. I am trying to figure out what tables need adjustment for the very first crank event after the car has been sitting for a while. I've attached my log, config, and tune file. The car is a 2002 Trans AM, LS1, 228/232 .600"/.600", 112 LSA CAM, 799 heads, full exhaust.


    Thanks in advance!
    first_cks_2nd_start_quick_fire.hpl02_ws6_Cam_Startup.hptAutoCross_r1.Layout.xml

  2. #2
    Advanced Tuner
    Join Date
    Oct 2008
    Location
    Mebane NC
    Posts
    475
    Check your fuel pressure at the rail. It may be bleeding off after a long shutdown, mine does that.

  3. #3
    Advanced Tuner
    Join Date
    Jan 2004
    Location
    Columbus, Ohio
    Posts
    213
    I have the same issue on a couple of cars running aftermarket HPFPs. In these cases, on cold starts, the commanded fuel injector pulsewidth will show 0.0 milliseconds for five to ten seconds of cranking, even though there is rail pressure. Then, all of a sudden, like a switch was flipped, the commanded injector pulsewidth fires, then the car starts.
    2022 Cadillac CT5-V Blackwing (733 whp)
    2022 Cadillac CT4-V Blackwing (716 whp), 10.750 @ 134.77 mph
    2016 Cadillac ATS-Vs (eleven ATS-Vs in the 9s)
    2008 Pontiac G8 (first G8 in the 10s), 10.727 @ 129.87 mph
    2000 Bonneville SSEi (first 3800 Bonneville in the 10s), 10.711 @ 125.71 mph
    1999 Grand Prix GT (first 3800 FWD in the 8s), 8.902 @ 154.90 mph
    1998 Firebird (first 3800 RWD in the 8s), 843 whp, 8.991 @ 152.12 mph
    1998 Grand Prix GTP (first 3800 FWD in the 10s), 9.499 @ 145.13 mph

  4. #4
    Tuner in Training
    Join Date
    Aug 2014
    Posts
    22
    Quote Originally Posted by DrLoch View Post
    Check your fuel pressure at the rail. It may be bleeding off after a long shutdown, mine does that.
    That was one of the initial thoughts I had, but a few times I would key cycle the pump on before cranking and still had the same issue.

    Quote Originally Posted by Tapout Tuning View Post
    I have the same issue on a couple of cars running aftermarket HPFPs. In these cases, on cold starts, the commanded fuel injector pulsewidth will show 0.0 milliseconds for five to ten seconds of cranking, even though there is rail pressure. Then, all of a sudden, like a switch was flipped, the commanded injector pulsewidth fires, then the car starts.
    Injector pulsewidth was active during the crank. I believe I am onto something though, the motor needed more fueling on the crank. Instead of messing with the cranking VE, I made changes to the first and second "pulse fuel mass" by increasing the fueling 20% and blending in the ECT ranges I currently see. The cranktime after a long soak is now cut in half. The engine used to take 1+second to fire after a very long soak, now it's anywhere from 3-500ms and I see the narrowbands reading much quicker. I think it needs a little more fuel on the pulse mass tables to be perfect, but it's much better than when I first made this post yesterday. I've attached a log from tonight to show the start improvement.first_cks_morefuelmassincrease_fullsoak.hpl

  5. #5
    Senior Tuner kingtal0n's Avatar
    Join Date
    Feb 2017
    Location
    miami
    Posts
    1,799
    I've got something for this


    You know you are using hptuners when you spend 3 years and 200 revisions trying to perfect the cold start, finally manage to do it, and still have no clue what or how any of the cranking fuel tables work or interact.


    Theres a table called 'FA cranking multiplier' or something like that. The first row for whatever reason is numerically very low, even in cold. I just copied the cells below it and maybe added a bit to that (for the cam and increased airflow at idle) and it starts what I consider adequately in the cold now. takes around 6 to 8 compression strokes. I could never get it to do better than that, but I am still trying new things. In hot it will go with just 2 or 3 compression events, its almost too good when its warmed up.

  6. #6
    Tuner in Training
    Join Date
    Aug 2014
    Posts
    22
    I've pretty much got the cold soak start dialed in now. Modifications to the Prime,First, and Second Pulse Mass volume did the trick. I ended up having to add 20-23% more fuel in the ECT ranges. Crank time went from 1+ seconds on Sunday, to now around 300ms and I see the narrowbands come up and start reading much quicker after the start. Hopefully this thread helps others who face similar initial cold start issues. Here is my start from today(24 hr soak). 032001_coldstart.hpl