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Thread: Which tables for cold start?

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  1. #1
    Fuel Injected! CDeeZ's Avatar
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    Which tables for cold start?

    It was 19*F this morning and my TBI truck with the single plane did NOT want to start. Cranked on it for a while and it was chugging bad and very rich on the wideband. After it's been running from me keeping my foot on the pedal it does ok. But before that it really did not want to start. Seems way too rich. I have been experiencing this even on warmer days, a little bit. but this morning with it being so cold it was very pronounced.

    7427 $0E using Gregs Advanced $0E TP5 v252.xdf

    It had been mentioned that adjusting Open Loop Idle Lean Limit VS Temp ---AND--- Open Loop AFR VS Vacuum might help with these cold start scenarios. I'm not sure what I might need to change in these tables though.

    Since it seems to be loading up from being way too rich when cold starting it, I was wondering if taking those two tables and increasing the AFR a full point in every cell below 40*C might help this?

    Also, wondering about Choke AFR VS Temp, Choke AFR Decay Time VS Temp, and Choke AFR Decay Time Multiplier vs. Airflow.
    Last edited by CDeeZ; 02-07-2019 at 04:09 PM.

  2. #2
    Fuel Injected! CDeeZ's Avatar
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    Well I tried monkeying around with those tables and it didn't help. Seems to have made it worse. I also bumped the whole AE MAP and AE TPS tables up by 30+ percent since I'm still having a lean pop or bog when you snap the throttle open. But changing the AE tables hasn't helped that either. Not sure what to do at this point?

    Here are the latest two BINs and datalogs I have from trying to get this thing to work correctly. I'm hoping someone will take a look at this and point me in the right direction with the cold start rich issue and the lean pop on throttle opening
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  3. #3
    Fuel Injected! sturgillbd's Avatar
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    Look at your open loop afr vs temp vs vacuum table. You have your open loop afr quite a bit lower than stock. The screenshot in yellow is your bin.

    Edit: I see you have a 4L80. Are you using $31 or $0E? Part odf that table is wrong in the screenshot of yours
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    Last edited by sturgillbd; 02-07-2019 at 07:35 PM.

  4. #4
    Fuel Injected! sturgillbd's Avatar
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    Attached is the table with proper xdf... At 19 F its -7 C. Your afr is commanding quite bit lower than stock either way. Interpolating the table, it is commanding 11.6 'ish afr and there are probably other modifiers lowering it more. If the map is fluctuating, it is adding AE along with the cranking fuel during the startup. My 355 is a $0D based tbi with a single plane intake and Howards 180245-10. Cold start is finicky but it just has to be warmed up for a couple minutes before it does ok. I added a MAT sensor and blended it with the CTS and it helps during cold weather.I also increased the idle rpm at colder temps. Setting the minimum throttle blade opening for less than 10 IAC counts on a fully warmed engine helps a lot also.
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    Fuel Injected! CDeeZ's Avatar
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    Man I'm glad that you responded with your insight. Thank you so much!

    I think that my AFR is actually leaner than what was stock. At least for the bin that I started with which I will post. It's a 350 4L80 bin.

    Yes, good point about the fluctuating map causing AE during cranking and startup, I had not even thought of that.

    I'm not sure why, but I have chased my tail with the IAC counts. The last time I set it with a fully warmed engine it was around 20 or so counts on the scanner..... I was shooting for 10 counts but I either coulnd't get it that low or it would go to 0 or near 0, or maybe 1, 2 counts IAC... Maybe that's what I ought to shoot for here?

    Your 355 having a single plane intake is likely very similar to mine I have here, even though I'm $0E and you're $0D.....

    The engine I have is a 355 with flattop pistons (no idea what the compression ratio is, I need to figure that out but I'm thinking about 9.5:1 maybe??) Lunati 20080660 cam, Weiand 7547 single plane intake, Summit SUM-162108 62cc chamber heads, long tube headers and a Holley 670 CFM throttle body running a Marine 28 PSI FPR spring and 61 PPH injectors.

    Would you mind sharing your tune so that I can look at it?
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  6. #6
    Fuel Injected! sturgillbd's Avatar
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    I'll have to get it posted tomorrow. I don't have it on this machine. Will try to post it before I head to work in the morning.

  7. #7
    Fuel Injected! brian617's Avatar
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    Quote Originally Posted by CDeeZ View Post
    I think that my AFR is actually leaner than what was stock. At least for the bin that I started with which I will post
    Keep in mind if your VE tables arent accurate your commanded AFRs and actual AFRs wont match. With no O2 feed back in open loop the commanded AFR is being modified by temp and your VE as a baseline.
    89 K1500 Scottsdale 5.7L 5spd 3:42

    Build specs: 97 4 bolt main block 350ci, Eagle rotating assembly with flat tops and 4 valve reliefs, Dart 165cc/67cc Iron Eagle heads, Manely SS valves and springs 110lbs seat @1.7, GM Ram Jet cam 196/206 @.50 .431/.451, stock intake and throttle body, heads and intake gasket matched, Delco EP377 fuel pump @ 22 psi, 427 PCM.

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