Page 1 of 10 123456 ... LastLast
Results 1 to 15 of 136

Thread: choke adjustment on 7747

  1. #1
    Fuel Injected!
    Join Date
    Jan 2012
    Location
    ny
    Age
    48
    Posts
    154

    choke adjustment on 7747

    hey guys id like to adjust my choke on my tbi. i get some backfires in the exhaust when i first start the engine for about 5 mins or so. doesnt do it every day. i see there are several places to adjust in tunerpro so im not sure which to mess with.

  2. #2
    RIP EagleMark's Avatar
    Join Date
    Feb 2011
    Location
    North Idaho
    Age
    63
    Posts
    10,477
    It doesn't do it every day? Was weather changing dramatically each day?

    First you have to get VE table correct because everything is an adjustment off that.

    I've been helping Hammertime get his tune in order and the last BLM data adjusted some VE tables over 100, so you don't have enough fuel yet for your engine. No need to find choke issues if your going to change VE fuel table.

    I'll attach a bin with items turned off for recording BLM and have raised the BPW a little to see if it can get enough fuel at your setting of 19 PSI fuel pressure.

    If this does not work the calculater says you need 23 PSI with 5.7L 61 PPH injectors to support 300ish HP on your 5.7L Chevy engine.

    So run this bin and do another data log and we will see how it does. Start log after totally warmed up and driven a little, then start a recording and do varied driving and a wot run.

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

  3. #3
    Fuel Injected!
    Join Date
    Jan 2012
    Location
    ny
    Age
    48
    Posts
    154
    well infact its been about 35-40 in the morning and 70's by the time i leave work. today it was raining and 50 and didnt get any pops... yesturday it was clear sky and about 40 in the morning and got multiple backfires. even at 10am when i go out for break it pops a few times on the way to the store. only when light on the throttle.. if get on it a bit it clears right up. by afternoon its fine... ill try what you posted. i didnt mean to get ahead of you. i thought it was something that could be adjusted while i waited for you to get a min and look at my log. sorry ill be more patient. thanks mark

  4. #4
    Fuel Injected!
    Join Date
    Jan 2012
    Location
    ny
    Age
    48
    Posts
    154
    so by raising the bpw i get how that puts more fuel into motor. by doing that it should raise my duty cycle as well right? I was only using about 30% anyway. I have an adjustable regulator so what would make more sense, high pressure with low duty cycle 30% or use less pressure with a dc more around 60-70%?

  5. #5
    RIP EagleMark's Avatar
    Join Date
    Feb 2011
    Location
    North Idaho
    Age
    63
    Posts
    10,477
    With your VE hitting 100%, DC% showing 30+% and logs still lean I'm not sure the DC % gauge is correct, so just leave that out of the picture for now.

    Guys here have raised BPW a little and it worked for more fuel. We had one that was raised a lot and never got it right. I then took a perfect tune car and raised BPW and went rich idle and lean under load, so big changes do not work. I had always set BPW per calculater and then tuned engine, if I hit 90% VE I add another 1 PSI and recalculate BPW. Retune and it has always worked.

    BPW is a calculation of injector size, fuel pressure and engine displacement. Not a tuning tool. There are so many other things to take into account I've just never played with it.

    So if you have time try the bin with slight raise in BPW and datalog and we will see. Then if you want to do it as per calculation raise pressure to 23 PSI and BPW to 107 and data log.

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

  6. #6
    Fuel Injected!
    Join Date
    Jan 2012
    Location
    ny
    Age
    48
    Posts
    154
    well i tried the new bin and no backfires!!! seems to have cleared up the off idle stumble and feels like it has more power... still getting better.

  7. #7
    RIP EagleMark's Avatar
    Join Date
    Feb 2011
    Location
    North Idaho
    Age
    63
    Posts
    10,477
    I got your log via email. Next time just post it up here so I can keep track.

    Well adding to BPW did add a lot of fuel low rpm and load but hardly anything where you needed it. So again another test shows messing with BPW is not a good tuning tool.

    Raise your fuel pressure to 23 PSI and change BPW to 107, leave rest of bin alone and do another log. Does not have to be as long as last one. 1/3 of it would be fine.

    Little to many knock counts for my liking so I pulled some timing and did the BPW for you so here's the bin to run with new fuel pressure.

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

  8. #8
    RIP EagleMark's Avatar
    Join Date
    Feb 2011
    Location
    North Idaho
    Age
    63
    Posts
    10,477
    Have to get the switches right so your not in ALDL mode for data!

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

  9. #9
    Fuel Injected!
    Join Date
    Jan 2012
    Location
    ny
    Age
    48
    Posts
    154
    ya i feel stupid...forgot the switch on autoprom...youd think by now id have it down! anyway ill give it a another try

  10. #10
    Fuel Injected!
    Join Date
    Jan 2012
    Location
    ny
    Age
    48
    Posts
    154
    I seem to have some kind of fuel problem. I grabbed another guage at work and it says I was currently running 17 psi. guage at home said 19psi. well anyway the range of adjustment is 14 to 19. i bought a 18 to 40 psi spring from ebay so im not sure whats wrong. I have an external pump that is rated to 45psi however im still using the stock intank pump to feed the external pump. perhaps the internal pump cant flow enough for the external to build enough pressure. at this point im ready to just get a high pressure internal pump and get rid of the external. i think someone said a 94-95 pump was a good choice. what you think? I could just remove the internal pump but if i drop the tank i think im better off with 1 from a multiport efi application. besides im tired of listening to the external pump. its very noisy. despite all this i did raise pressure 2 psi more than it was so ill drive it this way for now and see if theres an improvement. maybe thats all i needed.

  11. #11
    Fuel Injected! PJG1173's Avatar
    Join Date
    Nov 2011
    Location
    Jacksonville NC
    Age
    50
    Posts
    641
    I would ditch the intank pump or both. I run a pump from a 99 vortec truck in my tank. Just a warning though the the vortec pump isn't as quiet as the tbi pump.
    87 4Runner, 15" spring lift, 3" body, chevy vortec 355, 5.29 gears, 38.5x15.5x15" Boggers, 280hr, 16168625 running $0D
    93 S10, 36x12.5x15 TSL's, custom turbo headers, 266HR cam, p&p vortec heads, $0D Marine MPFI with 8psi boost.
    05 Silverado, 2' lift, 4" exhaust, Bully Dog programmer,

  12. #12
    RIP EagleMark's Avatar
    Join Date
    Feb 2011
    Location
    North Idaho
    Age
    63
    Posts
    10,477
    I forget what year your truck is but I seem to remember it being a square body Chevy with TBI tank. If so a TPI pump (like same year Camaro) will replace the intank pump and your done. They look identical and bolt in. AC Delco or Carter. Anything else is a crap shoot? New sock and filter, re set fuel pressure, data log and repeat!

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

  13. #13
    Fuel Injected!
    Join Date
    Jan 2012
    Location
    ny
    Age
    48
    Posts
    154
    hey not change the subject but heres a pic of my engine. if you notice i adapted the plow pump to where the ac compresser would go. its nice so i just press the ac button on dash to turn on the clutch and go plowing!
    Attached Images Attached Images

  14. #14
    Fuel Injected!
    Join Date
    Jan 2012
    Location
    ny
    Age
    48
    Posts
    154
    my truck is the rounded nose btw

  15. #15
    RIP EagleMark's Avatar
    Join Date
    Feb 2011
    Location
    North Idaho
    Age
    63
    Posts
    10,477
    Simalar year MPFI, PFI or SFI intank pump will bolt in.

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

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •