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Thread: After Start Holdoff Settings

  1. #1

    Default After Start Holdoff Settings

    I’ve been working on my cold starts and wanted to play with After Start Holdoff as mentioned by Chris at EFI System Pro in his excellent article. Anyway, I changed mine from the default setting of 90 milliseconds to 500 milliseconds in three different cells (60-100°F) just to test. Datalogged a cold start, and I see zero change in when the After Start fuel kicks in. It’s almost instantaneous after hitting Crank To Run RPM. 500 ms should be a noticeable delay, but I’m not seeing it. Has anyone experienced this? I double checked that I had the right GCF loaded and did an Overlay with the datalog. My startup temp was right where it should have been for this to work. I’ll mess around some more, but it seems the ECU is not doing what I’m telling it so far.

  2. #2
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    In my experience, the default After Start Holdoff settings are never a problem.
    http://forums.holley.com/showthread....7913#post77913 (Related Cranking/Startup Tuning Post)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 200A 3G alternator, Optima Red battery, R134a A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, B&M Hammer shifter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 M/T Street Comp tires.

  3. #3
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    Did you verify the GCF uploaded to the ECU or are you live tuning it with a laptop? Did you Zoom in your datalog to around 2 to 3 seconds of info? Remember, you went from one tenth of a second hold off to 5 tenths of a second hold off. You're not gonna see a huge change if your combination doesn't have major issues or there's another piece of the puzzle overpowering that time frame. You could stretch out the hold off to one and a half to two seconds and when you zoom in on the datalog you'll see what some of the other pieces are, that are controlling that time frame. Then work your way backwards to get the result you want.

  4. #4

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    That was my first thought. Figured I uploaded the wrong file or something. So I pulled it out of the ECU last night, and it was the proper file with the Holdoff changes. I use the SD card method for what it’s worth.

    I did zoom way in on the datalog, and compared it to a previous startup datalog. Both have the After Start Fuel kicking in almost instantly. So that 90 ms seems about right. The half second I changed it to should be really obvious I’d think.

    Anyway, I just thought maybe this was one of those weird glitches that was less well known. I’ll try changing the whole table to see what happens, or extend it even further just for testing. I know this setting may not be of any benefit, but I want to see if this can be something that helps my overly rich cold restarts. Like when starting it up cold and backing it out of the garage, then shutting it off and starting it 15 minutes later. It’s not the prime shot, so it has to be in the After Start or Cranking Fuel settings I’d think.

  5. #5
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    Cranking Fuel is probably still too high.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 200A 3G alternator, Optima Red battery, R134a A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, B&M Hammer shifter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 M/T Street Comp tires.

  6. #6

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    I feel like I have it near ideal for the initial cold start. Fires in less than one second from when the starter solenoid is energized. Less Cranking Fuel makes it do a weird semi-start/stutter thing before it fires. I thought maybe it was the After Start since it seems to coincide with hitting the Crank to Run setting. Maybe you’re right and my slightly warmer temp Cranking Fuel settings are too high. Just trying to find a happy medium.

  7. #7
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    Quote Originally Posted by BMWM.D. View Post
    I did zoom way in on the datalog, and compared it to a previous startup datalog. Both have the After Start Fuel kicking in almost instantly. So that 90 ms seems about right. The half second I changed it to should be really obvious I’d think.
    If you start the datalog and don't leave the start/stop screen, your datalog will be in full resolution after you stop it and want to view it. Should be near 60 bites per second. When you view the datalog, if you zoom in to where your X axis is in .1 resolution steps, then select your After Start Enrichment parameter to view, you can step through your datalog near 16ms steps. You'll be able to tell exactly from the time the RPM gets above the Crank-To-Run parameter to when the ASE kicks in.

    Anyway, I just thought maybe this was one of those weird glitches that was less well known.
    Very well may be, I haven't looked at it this close before, but I'll now.

    I know this setting may not be of any benefit, but I want to see if this can be something that helps my overly rich cold restarts. Like when starting it up cold and backing it out of the garage, then shutting it off and starting it 15 minutes later. It’s not the prime shot, so it has to be in the After Start or Cranking Fuel settings I’d think.
    Another table for time between starts wouldn't hurt that's for sure, that would help with a wet manifold vs a dry one. I'd like to have a fuel temp table also. I think both could be done in the current system with enough thought by the end user. If we say "Necessity is the mother of all invention", the question becomes, how necessary is the solution? I'm willing to compromise so it's not necessary at this time for me. In the meantime keep working on the compromise.

  8. #8
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    When the Startup Enrichment parameters are tuned properly, the engine starts very well, every time, any time.

    If you take the time to study this, you'll be a startup tuning expert, and read the "TIP" in post #6:
    http://forums.holley.com/showthread....6254#post36254 (Good Starting Advice Thread - Especially posts #2, #4 & #6.)

  9. #9

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    I went back and set the After Start Holdoff to 500 ms for 100°F & below. Took another datalog, and it doesn’t seem right to me. It hits Crank To Run at 11.040 seconds into my datalog, and the After Start Fuel is all in by 11.056 seconds. I’m not sure what the deal is. The Overlay bubble is clearly in the 500 ms range.

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