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Thread: Cold start tuning?

  1. #1
    Join Date
    Apr 2018
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    41

    Default Cold start tuning?

    Is there a way to make adjustments to the cold start settings at all on these? Mine runs awesome!!! As long as I don't drive it for the first minute or two when I start it first thing in the morning or in the afternoon leaving work. If I do it'll likely stall the first time I come to a stop sign or light and have to push the clutch in.

    Yes, I have timing control working...

  2. #2

    Default

    What's your IAC count at idle? If it's pretty high, there's a chance that you're tapping out the capabilities of the system. Frankly, mine is a little temperamental but I can compensate with just a little more throttle or lazy de-clutching to avoid it.

    I've usually seen the stalling when coming to a stoplight shortly after resetting the tune, and it figures itself out in a few tries.

    What is your idle and cruise target AFR as well?

  3. #3
    Join Date
    Apr 2018
    Posts
    41

    Default

    Yeah, if this is something I can't dial in and fix I can absolutely live with it cause it runs great otherwise! It's a minor issue in reality but figured worth asking.

    Idle AFR is 13.8
    Cruise AFR is 14.0

    I know my IAC is typically in the 12-18 range at idle when at operating temp, it seems to flucuate. I'll try to remember to look and see what it's at when I fire it up to leave work this afternoon on a "cold start".

    I haven't made any changes to the tune or settings in probably a week and a half if not longer and I daily drive it.

    '67 Mustang with a 302, pretty much stock...

  4. #4

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    If it's really stock, it should be easy to maintain a leaner AFR. Try 14.5 on both and see if it improves at all. My thinking is that snapping the throttle shut is causing it to go over-rich and shut down. I'm not confident it will help, but this should get you better fuel economy anyways.

    I'm running a not-so-stock Chevy 400 with AFR heads, headers, mild cam (218/224-112) and I am running 14.5 idle, 15.0 cruise and 12.6 WOT. I'd like to play with the WOT numbers (try leaning them out a bit), but I think that's an exercise best served on a dyno someday.

  5. #5
    Join Date
    Apr 2018
    Posts
    41

    Default

    Yeah, I'm not engine savvy enough to totally understand exactly what these settings are affecting. I definitely will say I was hoping for better fuel mileage than I'm currently getting though that's for sure! So the higher the AFR number the more air it's dumping in to lean it out it sounds like based on your comment? I was thinking that lean vs. rich was not the pump squirt but that other variable you can change that I can't think of the name of right now off the top of my head! LOL

    I'll try messing with the AFR this afternoon. I had been driving about 2 minutes this morning when it dawned on me to look at my cold start IAC number so I missed that...

    My engine, 302, stock iron heads with a mild port and polish on them. 351 cam so I guess that makes it the 302"HO". Other than that, name brand quality internals but nothing performance wise. It's bored .040 over... I had it built to be a solid reliable daily driver cruiser, didn't do anything for crazy power or anything. Anything power adding is all bolt on stuff, long tube headers, intake manifold, this EFI, MSD stuff, etc...

  6. #6

    Default

    Quote Originally Posted by sirhk100 View Post
    Yeah, I'm not engine savvy enough to totally understand exactly what these settings are affecting. I definitely will say I was hoping for better fuel mileage than I'm currently getting though that's for sure! So the higher the AFR number the more air it's dumping in to lean it out it sounds like based on your comment? I was thinking that lean vs. rich was not the pump squirt but that other variable you can change that I can't think of the name of right now off the top of my head! LOL

    I'll try messing with the AFR this afternoon. I had been driving about 2 minutes this morning when it dawned on me to look at my cold start IAC number so I missed that...

    My engine, 302, stock iron heads with a mild port and polish on them. 351 cam so I guess that makes it the 302"HO". Other than that, name brand quality internals but nothing performance wise. It's bored .040 over... I had it built to be a solid reliable daily driver cruiser, didn't do anything for crazy power or anything. Anything power adding is all bolt on stuff, long tube headers, intake manifold, this EFI, MSD stuff, etc...
    AFR is air to fuel ratio. Higher number = more particles of air. The computer essentially guesses how much air is going through based off of a reading from a MAP sensor. Based on your commanded AFR, it then opens the injectors for a set period of time so that that ratio is hit. Think back to high school chemistry; PV=nRT. Pressure times Volume = (molecules) * R(a constant value) * Temperature. The computer gets pressure from MAP, volume from the engine size (CID), temperature from IAT, constant is known. So it's essentially solving for molecules by guessing from a different table (speed-density in a system like this).

    I could go into a bit more detail, but I think I'm derailing a bit here.

    14.7 is the "stoichiometric" value, or the ratio in which all fuel should be consumed completely in a combustion reaction. I went a little learner for cruise - 15.0.

    I don't know the specs of the 351 cam and I'd imagine there are a few, but I don't have a strong knowledge bank of 60's/70's engines. I owned an 83 F-250 4x4 4-spd 460 once. It used a lot of gas - but it was worth it.

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