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Thread: Bitchin' TBI

  1. #1
    Fuel Injected! CDeeZ's Avatar
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    Bitchin' TBI

    Well after playing with 3 bar SD OBDII stuff in my LS swapped S475 truck for a while, among other things, I'm back to working on another TBI build for the first time in a while.

    Here's the build: I screwed together a nice little 355... Flat tops, WND-7547-1 single plane intake, SUM-162108 heads,LUN-20080660 cam 279/287, Lift .447/.471, longtube headers. 7427 PCM









    I started it for the first time a few days ago, and as expected the tune is going to need some work. Last night I got my wideband installed and wired up and got some more of the exhaust welded up. I also added another busbar like these trucks have from the factory but this one is switched by a relay to power gauges and such. Should be fun getting this thing tuned! It's going to be a running son of a bitch once I get it dialed in though, I can already tell. Probably going to run in in OL fulltime but we'll see how it goes.

    I have a Walbro 255 pump which is probably overkill but it's already laying around so I'm going to install it and just try to regulate it down. Fast has told me about some of his builds which push a LOT of PSI compared to the factory configuration so I think it's doable. Need to figure out some combination of injectors or regulators and whatnot. I'm looking for a marine regulator that I can push up to maybe 30 PSI and see how that goes.
    Last edited by CDeeZ; 02-28-2018 at 03:12 AM.

  2. #2
    Super Moderator dave w's Avatar
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    What TBI computer are you using?

    dave w

  3. #3
    Fuel Injected! CDeeZ's Avatar
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    Hi dave,

    I converted it to a 7427. It had some weird ECM service number I don't recall ever seeing before, basically same as 747 IIRC?

  4. #4
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    How come you didn't use the MAP vacuum port on the back of the throttle body? I think that's a ported vacuum spot you're using. And did you have the PCV hooked up when you cranked it?

  5. #5
    Super Moderator dave w's Avatar
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    Quote Originally Posted by CDeeZ View Post
    Hi dave,

    I converted it to a 7427. It had some weird ECM service number I don't recall ever seeing before, basically same as 747 IIRC?
    You have the option to tune with a Wide Band O2 Sensor (WBO2) with the 16197427 type PCM; http://www.gearhead-efi.com/Fuel-Inj...g)-Spreadsheet

    That's how I would tune your engine.

    dave w

  6. #6
    Fuel Injected! CDeeZ's Avatar
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    Quote Originally Posted by notime2d8 View Post
    How come you didn't use the MAP vacuum port on the back of the throttle body? I think that's a ported vacuum spot you're using. And did you have the PCV hooked up when you cranked it?
    Hmmm... I looked at an extra throttle body I have and I see what you mean. It looks like they're still connected to both of the throttle bores at some point though? I have moved the MAP line connection back to it's original position to experiment with later tonight. I need to look more closely at one of the throttle bodies I have laying around, perhaps the location I was using for the MAP was ported as you say, and not below the throttle plates..... Good catch on that one for sure. Not running a PCV on this one. Will probably do a catch can later but just a breather for now.



    Quote Originally Posted by dave w View Post
    You have the option to tune with a Wide Band O2 Sensor (WBO2) with the 16197427 type PCM; http://www.gearhead-efi.com/Fuel-Inj...g)-Spreadsheet

    That's how I would tune your engine.

    dave w
    Yes, I actully downloaded your spreadsheet a couple weeks ago, when I was getting ready for this thing haha. It's a nicely put together easy to use spreadsheet. Thanks for sharing it!

  7. #7
    Fuel Injected! CDeeZ's Avatar
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    Quote Originally Posted by notime2d8 View Post
    I think that's a ported vacuum spot you're using.
    You are most definitely right about that it turns out. Thank you for pointing that out. After several days of I would have figured that out and been

  8. #8
    Fuel Injected! CDeeZ's Avatar
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    Well after sorting out a few bugs I got the engine to idle half decent without really changing much in the tune. So that will require more work at some point.

    I have installed the 28-30 PSI spring in the regulator and fiddled around with the BPC a little bit to see what it might like..... It's running pretty poor now with that spring in there. Probably getting way too much fuel even though my wideband says 12ish... Still too rich for idle.

    After putting that spring in the regulator, the injectors make a howling sound while pulsing, and the fuel pump sound WAY different compared to before. Also getting a fuel pump relay error after this.

    Don't know what the fuel pressure is actually running at, I ordered one of the adapters to install a gauge and it will be here in a few days so I can nail that factor down.

    I have been away from TBI for so long while dialing in my 3 bar 411 PCM S475 6.0 that I have become quite rusty with the OBD1 side of things.... It is commanding an AFR at idle of like 12 or lower.... I can't remember what table(s) are responsible for this?

    Attached are several tunes and logs THe tunes are both using different experimental values of BPC since I'm not exactly sure what it should need. ANd the logs are when it was started and idling decent BEFORE the 30 PSI spring, and then AFTER the 30 PSI spring was installed in the regulator.
    Attached Files Attached Files

  9. #9
    Fuel Injected! CDeeZ's Avatar
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    It was a vacuum leak at the TBI base gasket. Now back to dialing this thing in..... 4L80 parts should be here tomorrow for the trans also.

  10. #10
    Fuel Injected! woody80z28's Avatar
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    I had a TBI leak on my truck recently. Didn't cause any driveability issues, but it was SUPER loud and annoying. Sounded like a goddam train whistle!
    80 Camaro Z28 - 550hp AFR 383 / T56 6spd (Holley HP EFI)
    91 Beretta "SS" - 260hp 3400 MPFI / HM282 5spd (7730/$A1) sold! for crazy money...but I miss it
    94 Silverado Z71 - 300hp Vortec 357 TBI / NV4500 5spd (7427/$0D) gone but not forgotten
    96 Beretta "T56" - 4.8 LS RWD swap / 6spd (0411/2156)
    01 Silverado 2500HD - stock Vortec 8.1 / ZF6 6spd (0411/8322)
    https://www.youtube.com/c/GEARHEADdezign

  11. #11
    Fuel Injected! CDeeZ's Avatar
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    That's about what this one sounded like!!

    I found your thread http://www.gearhead-efi.com/Fuel-Inj...uestions/page3

    Tell me more about this setup if you would?

    I found a Holley TBI for damn near free and I'm going to try to use it with the GM injector pod to fuel this 355 TBI I'm working on dialing it. Check this out and let me know what you think...

    http://z28boy.cz28.com/throttlebody.htm

  12. #12
    Fuel Injected! woody80z28's Avatar
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    I don't think I have a thread for my truck on here, I built that a couple years before I found this site. I scrounged around third-gen.org for a lot of TBI info back then.

    My TBI is just a stock one with smoothed inlets and the adjustable regulator mod. I put in a TPI pump and used the stock 350 injectors at 20psi.

    Seems like a solid option to use the Holley base with the GM pod. That vacuum-referenced FPR makes some sense too, but I've never had any issues with my idle at 20psi. It's so long ago I don't recall the stock lb/hr of the 350 injectors, but I know I calculated 20psi to be 80% duty cycle at 300hp.
    80 Camaro Z28 - 550hp AFR 383 / T56 6spd (Holley HP EFI)
    91 Beretta "SS" - 260hp 3400 MPFI / HM282 5spd (7730/$A1) sold! for crazy money...but I miss it
    94 Silverado Z71 - 300hp Vortec 357 TBI / NV4500 5spd (7427/$0D) gone but not forgotten
    96 Beretta "T56" - 4.8 LS RWD swap / 6spd (0411/2156)
    01 Silverado 2500HD - stock Vortec 8.1 / ZF6 6spd (0411/8322)
    https://www.youtube.com/c/GEARHEADdezign

  13. #13
    Fuel Injected! CDeeZ's Avatar
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    Yes I'm thinking it will be pretty solid. I'll know tonight if the GM pod will interface easily with it.

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    More or less of the same from the link you posted... https://www.thirdgen.org/forums/tbi/...od-holley.html

  15. #15
    Fuel Injected! CDeeZ's Avatar
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    Thanks for posting that. I'm thinking it will work!

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