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Thread: BLM not moving

  1. #1
    Electronic Ignition!
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    Mar 2016
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    BLM not moving

    Hey guys im having a problem tuning my TBI in my 94 suburban BB. I just put 063 mark IV heads on it and a new cam, 227 int and 241 ext at .050 and 0.498/0.483 lift. I am finally in my tuning stage and trying to even things out. Running mask $31 and BMHM bin. My main problem is my BLM's are at about 90 and its just dumping fuel at idle. Map sensor is at about 60-70 at idle. I went into the VE table and changed my values for 60-70kpa at 600-1000 RPM. After I make the change and burn and reinstall, I see no change at all and I am still at about 110-90 BLM. Ive changed my values about 3 times. Which my VE values were at about 70 and i lowered them to 55-60. Still no change of BLMs. I am tuning in closed loop as my funds are very limited for a WB02 at the moment. I am pretty new at this but ive done tons of research. Now the correct table I should be in is Idle VE vs. MAP vs RPM, correct? Also tried changing the values in Open Throttle VE vs MAP vs RPM table and also no change. Ive researched and I heard something about VE learning and wonder if that pertains to me or not. Is there something im missing here? I attached my log just incase you would like to see a log. Thanks guys
    Attached Files Attached Files

  2. #2
    Super Moderator dave w's Avatar
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    Feb 2011
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    6,268
    I would return the VE tables back to stock. I would adjust the Injector Flow Rate to lean all the BLM's.

    Increasing the injector flow rate, for example, from 65 lbs / hr to 68 lbs / hr should lean all the BLM's. The basic idea behind increasing the injector flow rate to a higher number, has the effect of "making the computer think" the injector "On Time" (measured in milliseconds) will need to be fewer milliseconds.

    Sometimes the statement below is true:
    What an injector is rated to flow vs. what an injector is actually flowing vs. what is programmed into the chip, is like trying to win at a slot machine. Just like the slot machine, injector settings seldom get all three to match.

    dave w

  3. #3
    Fuel Injected!
    Join Date
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    60-70kPa at idle sounds like you're not making enough vacuum. That doesn't sound like a radical cam at all for a big block so the MAP at idle should be much lower.

    I've never used or tuned $31. How/when does it decide to go into power enrichment mode?

  4. #4
    Fuel Injected!
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    Honestly I would not touch the BPC atleast not yet. It is probably lean once you get on the throttle and get it above idle. Easier to fix a rich idle than it is to replace pistons.

    Look at your VE% down the 40 kpa/600 rpm range this engine likely idled at when it was stock. You will see the numbers are dramatically lower than what you are seeing in the 60-70 kpa range. You may have to lower the new idle VE area as low if not lower than where it was with the old stock cam.

  5. #5
    Electronic Ignition!
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    Mar 2016
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    Well the cam has a 107* lobe separation. It's a little radical. I do change the VE settings and im getting no feedback of BLM's moving after tuning. It is running rich especially when I decel at about 1600-2000 rpm. BLM's go into the 80-90 range. I also have a horrendous stumbling problem when I step on the gas about mid throttle. If I goto 75%-WOT i can get through the stumbling. I pulled the plugs and they look pretty lean. But my BLM's are telling me im rich and I have a 02 sensor code i think its code 44 saying: 02 sensor rich.

  6. #6
    Electronic Ignition!
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    Mar 2016
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    Also my IAC counts are pretty high. It's at about 80 counts at idle and 160 when im going down the road

  7. #7
    Fuel Injected! sturgillbd's Avatar
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    You probably haven't pulled enough fuel out yet in that area. The calibration probably blocks the BLM from dropping any lower than 90. You can add some timing at idle and see if that helps. Add 3 degrees in the idle area from 50-80 kpa and see if the vacuuum improves. Bigger cams seem to like more idle timing advance. I have a cam with around 230/230@.05 on 110. It likes approximately 25 degrees at idle. You probably still need lower the VE table in those areas. Compare your values to what the normal idle area VE is on a stock engine (20-40kpa at 600-750 rpm). You may have to adjust your idle settings up higher too. Try to target the idle at about 800 rpm. May help if you post your bin, xdf, adx along with a current log file.

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