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  1. #1
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    Default Lean Tip In w/OBD1

    Wondering if anyone has a preferred method for combating lean tip in with the 051 OBD1 pcm with a MAF tune, specifically at sudden WOT? I seem to be getting a lean spike when quickly mashing the gas so the throttle response could be better. The car will occasionally stutter (maybe once every 25 times) if I roll into it fast enough. The AFR adjusts pretty quickly and it has no problem getting high 12's AFR until redline, but it takes several cells to get there on both the narrow and wideband.

    TPS voltage is normal, no vac leaks or other weird things. I also noticed a MAF spike a while back when it happened and thought the MAF was going out. It didn't seem to affect the inj pw that much though. Swapped to a different one with the same results. I also redid the MAF wiring with no change.

    Other details:
    -Burst knock is disabled. I'll probably re-enable it as a bandaid and see if the occasional stutter goes away.
    -Never had a problem with a stutter until swapping to a 58mm tb and ported intake. Probably allows me to get too much air too quickly. Guessing the lean spike was always there, now it's just more pronounced.
    -Transient fueling is enabled.
    -I think the PE thresholds are 20% tps and 80kpa? I'll have to double check.

    I read about a mysterious pump shot adder that dumps fuel based on sudden changes in throttle position. AFAIK it's not in EEX or EEXtra, so I'm unsure how I'd go about changing it without a definition.
    96Z M6, ERE-383 #60, AFR 210s, LE cam, 9", 414whp sae, awaiting boost
    95 Roadmaster T-56 swap, LE1s, cc304 w/1.7rr, 4.56s, "The Cammaster"
    95 Firehawk hooptie, soon to be track car

  2. #2
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    Default

    Mike, have you figured this out yet? Any info you have would be good learning. How is the forced induction tuning coming along?

  3. #3
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    Default

    Quote Originally Posted by Karl Ellwein View Post
    Mike, have you figured this out yet? Any info you have would be good learning. How is the forced induction tuning coming along?
    I did some digging and found out that a pump shot adder does exist in the tune but I haven't had a chance to play with it yet. There's a 3x3 table called 1240a that has the MAF coefficients in them with MAP/RPM boundaries defined by scalars elsewhere in the tune (just like closed loop fueling cells 0-15 and their respective MAP/RPM boundaries). I saw values ranging from 0.09-0.12 but wasn't entirely sure what the numbers correlate to. Allegedly, a lower # corresponds to more enrichment but there's a lot of uncertainty around this.

    I compared the values between a LT1 and LT4 bin and noticed that the LT4 values were generally higher (ie less enrichment) which seems counter intuitive. I'm also unsure if it's a simple adder that dumps fuel based on %TPS or %airflow change or if it's some sort of dampening coefficient that allows MAF spikes to have more impact on fueling in the short term. I'm going to do some experimenting with it and see what happens because burst knock seems like a crappy bandaid.

    1240a and the other scalars aren't in the regular EEX definition. There was some goofy modified version of EEXtra posted on gearhead-efi that I found it in, I'll have to check my XDF's and see which one it was because I don't remember off the top of my head.

    I'm still running around NA at the moment but I have pretty much everything to put the D1 on. Once the weather gets cold and I figure the tip in issue out, I'm gonna throw it on as a low boost setup... this winter hopefully.
    96Z M6, ERE-383 #60, AFR 210s, LE cam, 9", 414whp sae, awaiting boost
    95 Roadmaster T-56 swap, LE1s, cc304 w/1.7rr, 4.56s, "The Cammaster"
    95 Firehawk hooptie, soon to be track car

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    Default

    Here's a link to the XDF I found it in. I tried uploading it here but the forum doesn't support .xdf attachments.

    http://www.gearhead-efi.com/Fuel-Inj...5&d=1508791730
    96Z M6, ERE-383 #60, AFR 210s, LE cam, 9", 414whp sae, awaiting boost
    95 Roadmaster T-56 swap, LE1s, cc304 w/1.7rr, 4.56s, "The Cammaster"
    95 Firehawk hooptie, soon to be track car

  5. #5
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    Thanks for the link. I need to subscribe to that Gearhead efi form.

  6. #6
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    Quick update... I've come to the conclusion that higher #'s in 1240a mean more enrichment or a larger pump shot. I increased all of the values and it seems to have minimized the lean spike I was getting when the throttle snaps open suddenly. Feels snappier than before, although I'm still tinkering with it.

    Also, I had to jump through some hoops to enable burst knock again. Burst knock wasn't working with the low octane tables is zero'd until I changed parameter 1234c to zero. I think I found it in the same XDF that 1240a was in.
    96Z M6, ERE-383 #60, AFR 210s, LE cam, 9", 414whp sae, awaiting boost
    95 Roadmaster T-56 swap, LE1s, cc304 w/1.7rr, 4.56s, "The Cammaster"
    95 Firehawk hooptie, soon to be track car

  7. #7

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    Don't get too tied up in calculations, All can be controlled via MAF or VE, Ive been running boost since around 97, stock PCM, Stock MAF, 1st supercharged, made 722 RWHP on 15 lbs now Turbo, 710 RWHP on 10lbs, all thru stock PCM, MAF. Where I see a lot of issues is when someone pulls fuel thru PE, then adds fuel thru the IFR, then pulls fuel on the MAF then adds thru VE, I'll never understand what they are trying to accomplish this way. Ported heads can cause some slight issues due to velocity, tumble and swirl so you may never get is 100% perfect..

  8. #8
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    Default

    Maybe this problem is less pronounced with an auto car with a torque converter to dampen it? The fueling looks fine once the car gets going (mid 12's AFR @ WOT), but I was getting a pretty nasty lean spike if I quickly mashed the throttle with the car in gear. Sometimes the car would stumble/buck/backfire for an instant if I rolled into it too fast, but playing with the 1240a pump shot and reenabling burst knock seemed to quell this. I will do more experimenting with it though because the pump shot might be too rich.

    I did try adding fuel to the VE tables to see if it would improve throttle response, but I couldn't tell if it helped or not. I think the inj flow rate is set properly and I generally like to tune WOT with the PE tables and try to avoid touching the MAF unless I absolutely have to. Is there an advantage to fueling at WOT through the MAF? Also, my thresholds are set pretty low for PE, it enters pretty quick so this slow obd1 computer can respond.
    Last edited by Catmaigne; 06-24-2020 at 09:52 PM.
    96Z M6, ERE-383 #60, AFR 210s, LE cam, 9", 414whp sae, awaiting boost
    95 Roadmaster T-56 swap, LE1s, cc304 w/1.7rr, 4.56s, "The Cammaster"
    95 Firehawk hooptie, soon to be track car

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