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Thread: BLM Learn is working

  1. #1
    Fuel Injected! jim_in_dorris's Avatar
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    BLM Learn is working

    I finally have my truck back on the road. Drove to town today, and on the way home decided to log the trip. I started out with a BLM of 153 cruising down the hiway, but it soon went to 126 at the same speed and rpm. I guess that 12 psi will work ok. It still needs a little bit of tuning, but for a stock BIN I shouldn't complain. Here is the log. Comments please.
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  2. #2
    RIP EagleMark's Avatar
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    Sorry I missed your post Jim...

    I thought you put 5.7L injectors in that 5.0L? Sure is adding fuel?

    The way it is, whatever injectors it is learning but BLM is awful high in 15x, idle and lower is 114. All stock I would expect closer. If it's adjustable add a pound to 13 PSI. Another thing to look at when idle is low BLM and drive and cruise is high BLM is fuel filter. Could this be getting plugged with all the fuel system work you have done?

    Looked again and batt voltage may be what's keeping fuel pump a little low. At cruise you have about 13.4? Should be closer to 14.1... then at the little idle at end of log it was 12.4, when you turned it off it went to 11.8... so do you have a weak battery or questionable alternator? Lower voltage = less fuel from electric fuel pump.

    Also the little idle at end of log showed IAC count of 35ish... I'd turn the throttle blade screw in 1/4 turn and get that lower. Lower IAC always helps idle quality.

    It's doing it's job! But BLM shows a high low difference in some cells of up to 14! That's a big spread. It's in the ballpark and should be running OK?

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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  3. #3
    Fuel Injected! jim_in_dorris's Avatar
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    Yes those are 5.7L injectors, I don't currently have the adjustable regulator in the throttle body, it was one of the variables I eliminated while I was trying to figure out what was wrong. The battery could be a problem, it's an old battery as my battery died in the middle of all this and I pulled the battery out of my son's ford pu which isn't being driven. I will check the output of the alternator as soon as I get a chance. The truck is running quite well, and the log showed improvement in the BLMs at cruise towards the end of the run. I am driving it to work this week just to see how things go. The idle quality seems okay, still does that funny shudder thing, but no worse than when I started. I will put the adjustable regulator on and try 13 psi when I can take it into my son's work, or I can borrow the snap-on tool overnight. I really think that I want to spend the money and put an external regulator on it when I can, it is a real pain to check the fuel pressure the way I do it now. Thanks for responding.
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  4. #4
    RIP EagleMark's Avatar
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    Something is wrong then? Those BLM should be all pulling fuel = under 128 with 5.7L injectors!

    I always like 13 PSI over 12, but there's no reason to be adding pressure right now. You should have way to much fuel.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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  5. #5
    Fuel Injected! jim_in_dorris's Avatar
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    I agree with that, I have always thought that it should be way richer than it is showing. I just don't know what to look at next. The fuel pump is new, the fuel filter is new, the injectors were cleaned by witchhunter, and I know they flow lots of fuel (when it had the return line problem, it looked like a fire-hose at the injectors). Any thing I should be looking at in particular? It has alway run really lean on data logs. This particular bin has been superceeded, maybe there was something in it? Do you think that there is a mechanical problem I need to look for?
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  6. #6
    RIP EagleMark's Avatar
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    Quote Originally Posted by jim_in_dorris View Post
    This particular bin has been superceeded, maybe there was something in it?
    Maybe? But normally superceded bins were emmissions or driveability... what is it again? Let me, or you can too, compare it to another 5.0L Manual? I'd compare the entire bin but especially the fueling tables.

    Quote Originally Posted by jim_in_dorris View Post
    Do you think that there is a mechanical problem I need to look for?
    Just the voltage issue is all I can see. How about that dam complcated dual tank switch? Is it still in there? Wonder if it could be slowing down fuel flow?

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  7. #7
    Fuel Injected! jim_in_dorris's Avatar
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    It's a 5.0L 700R4 with 3.73 gearing. Mods are true dual exhaust with 2.5" pipe, dual cats, and flowmaster 40's. Also ultimate mods on TBI with 1" spacer and salad bowl. Lots of air moving thru. I don't think the fuel rate is an issue. If I pinch the return hose, it darn near floods the truck. I think it may be a combination of voltage (low battery volts) and the amount of extra air from my mods.
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  8. #8
    RIP EagleMark's Avatar
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    Your exhaust is letting it breath out easier. Your TBI mods are letting it breath in easier. SHould still be same amount of air at cruise speed... may help lower TPS% and raise MAP, all good for MPG. But it does not explain why you have more then enough injector and still have high BLM? High BLM is adding fuel.

    You sure those were 5.7L injectors? I'd never be able to geuss that with that log... I would have expected BLM to be lower then 128 all over.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  9. #9
    Fuel Injected! jim_in_dorris's Avatar
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    They are gm5235206's I am pretty sure those are 350 injectors. I looked them up and they are 55#/hr 5.7L injectors. My temperature shows 180-183 on the log, but I have a 195 thermostat. That would seem like it would run rich if the temp was a problem. Question, if it is a 5.7L engine with 5.7L injectors, with a 5.0L calibration, would that cause that? Or if a PO had changed the cam, would that cause it? I can't see the block casting # to tell for sure exactly what block is in it. I do have an ASDU prom I could try to see what happens.
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  10. #10
    RIP EagleMark's Avatar
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    I had noticed the CTS reading 180 and was going to suggest a 195. You would not be the first to run at 180 with a 195 T stat... seems like some cheap brands just use one and stamp it both temps?

    5235206 are 5.7L injectors. But GM says they are 61 Lb/hr in $0D bins so I go by that.

    I'm not really sure what would happen with 5.0L chip in 5.7L as far as data? Your not really sure about this motor are you? Idle shows 35 MAP at 550 RPM, so I really doubt this cam is more then stock.

    Yeah stick the ADSU in and data log!

    Leave a minute or so idle at end of log this time. Did you turn TB screw in 1/4 turn to lower IAC counts yet? Does not have to be near as big as last log unless your driving that route anyway.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  11. #11
    Fuel Injected! jim_in_dorris's Avatar
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    I will try that. Supposedly 2 owners ago the engine was "freshened up" whatever that means, so i really don't know.
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  12. #12
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    Quote Originally Posted by jim_in_dorris View Post
    I will try that. Supposedly 2 owners ago the engine was "freshened up" whatever that means, so i really don't know.
    Could have TPI heads on it. I know first hand that a TBI 305 with TPI heads will run lean on a stock TBI 305 calibration even with 350 injectors. Even a 350 calibration ran lean. I had a stock 350 cam, TPI heads and headers at the time.

    There maybe a simpler explanation than that. Is this truck equipped with an air pump? If it is are you sure it is diverting the air back into the air cleaner with a warm engine?

  13. #13
    Fuel Injected! jim_in_dorris's Avatar
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    No air pump. I will have to look at the heads to see if they are tpi heads. Do the TPI heads flow that much more than TBI? Actually thinking about it, they are centerbolt heads, were any of the tpi heads centerbolt?
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  14. #14
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    Quote Originally Posted by jim_in_dorris View Post
    No air pump. I will have to look at the heads to see if they are tpi heads. Do the TPI heads flow that much more than TBI? Actually thinking about it, they are centerbolt heads, were any of the tpi heads centerbolt?
    Yes casting number ending in 081 are TPI 305 centerbolts used from 87-92.

    Its not that the flow that much more, they are non swirl and that really changes the timing and fueling requirements.

    I will put it this way... I saw more of a difference tune wise going from TBI to TPI heads then there was going from TPI to Vortec. The swirl ports have a very odd tune that is both lean and retarded when used with any other head.

    I would be willing to bet it has the hotter 350 cam in it if it has TPI heads. The 305 TPI longblock makes 230-260hp depending on whats bolted to it where the stock TBI is lucky to make 190-200.
    Last edited by Fast355; 10-16-2013 at 07:00 AM.

  15. #15
    Fuel Injected! jim_in_dorris's Avatar
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    Well, we guessed wrong. I pulled a valve cover today and have 193 heads. I really hope that the block is 350 also. No wonder it's lean, a 350 with a 305 calibration. i will swap to my 350 prom and see what happens
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