Bringing TBI and Multi Port Fuel Injection to a New Level.     EFI Conversions and Tuning! Seattle to Portland! E-mail Tuning Consultant!
Results 1 to 5 of 5

Thread: 16.5psi Fuel Pressure too much?

  1. #1
    Fuel Injected! TheApocalyptican's Avatar
    Join Date
    Mar 2012
    Location
    Las Vegas
    Age
    30
    Posts
    66

    16.5psi Fuel Pressure too much?

    Now that I have gotten my voltage issues sorted....I'm getting 16.5 psi fuel pressure. I've got a stronger spring(stock one broke) in the fpr, and it's bottomed out. Is this psi too high(obviously it is for sure without tuning)to tune the fuel out? Basically....should I go back to a stock spring, or should I just tune the fuel tables as is?

    Edit: Forgot to add that I'm currently running rich. So fuel WILL need to be taken out of the tables if I stay at this psi.

  2. #2
    EFI GearHead ! EagleMark's Avatar
    Join Date
    Feb 2011
    Location
    North Idaho
    Age
    57
    Posts
    10,477
    Best way to get close and stay a little on high side for tuning is to use this speadsheet attached. I tend to loose track with guys but think you were TBI? What ECM? Engine? Mods?
    Attached Files Attached Files

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

  3. #3
    Fuel Injected! TheApocalyptican's Avatar
    Join Date
    Mar 2012
    Location
    Las Vegas
    Age
    30
    Posts
    66
    350 TBI, 7747, Only real mods are exhaust and dual snorkel intake. I know that I am pretty much stock, so 13 is ideal. Just wondering if I can get away with 16.5, or if a new stock spring is better.

  4. #4
    EFI GearHead ! EagleMark's Avatar
    Join Date
    Feb 2011
    Location
    North Idaho
    Age
    57
    Posts
    10,477
    13 is not ideal, it's minimum. I've done this to many times on stock, toatally stock engines and if not 13, not enough fuel. But like GM says between 9 and 13 is OK. Well I don't like what data says for OK so no it's not OK. Yes it will run, not to optimum.

    Found there's a little more room to play with newer ECM/PCM and MPFI/TPI. But not with this 7747.

    16.5 is more than you will need but yes you could tune it very nicely.

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

  5. #5
    Fuel Injected! pmkls1's Avatar
    Join Date
    May 2012
    Location
    Sevierville, TN
    Age
    38
    Posts
    291
    I agree with Mark, 16.5 is well within the manageable range. Having dealt with similar pressure issues on my 305 TBI 8746 setup, I'm thinking that you won't be removing as much fuel as you think. I installed a high pressure/high volume walbro 255lph pump in the car (virtually completely stock) without first thinking things through (my first TBI car) and drove the car 2 weeks before I even checked the pressure. I knew the car was running a little rich, but was more than a little surprised to find that the pressure was ~23psi. I could not lower the pressure any lower than that by any means other than installing an expensive external return-style regulator or uninstalling the pump and replacing it with a different unit. Due to money constraints and/or not wanting to wrestle the tank back out (3rd gen F-body = massive PITA), I could not/would not go with either of those options so I elected to make an attempt to tune for that pressure. The only area that had an issue would be at idle, but the idle was still perfectly smooth as it was rich but still within reason. Jump to the present about 3 years later and I am still running the same setup (TBI unit, injectors, pump, and ecm) albeit with a recent 350 vortec swapped in and a base pressure even higher at ~27psi (long story, but was running a billet vafpr housing for running on E85 fuel). With you having a slightly better breathing engine and at that pressure I would think that you shouldn't have much trouble. Heck, I'd even take advantage and throw on any upgrades within your budget.

    Just my 2 cents, but regardless let us know how it works out,
    Phil

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
  •