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Thread: My Dual TBI Camaro Project

  1. #1
    Fuel Injected! gregs78cam's Avatar
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    Cool My Dual TBI Camaro Project

    Ok, I have been working on this for a few months now, everything is together, the engine runs but has some issues that I am working through. A little bit about the setup: 2pc rear main, 385 i built about 8 years ago, 10.5:1, 6" rods, TFS 23* heads, jesel belt drive, roller cam with 4/7 swap. It spent most of it's life in front of a T-56 with 4.10 gears,(dynoed 340hp/370Tq, and rich) until I just got tired of always shifting. So I found a 4L80E and decided while I was at it I might as well do the EFI since it could all be done with the same PCM. Now I know I could have used a 454 TBI with 454 injectors, but they are usually either hard to find, or cost more than I was willing to spend. So one day I stumbled across a CL ad selling 6 TBIs off various vehicles. I went go to get them and it turned out to be 7 for $35. So after cleaning up two matching ones(for the linkages) my Dual TBI was born(and inexpensively too) I am using a '7427, with Rbob's 4-injector upgrade, APU1, and TPV5. I could have used Rbob's fantastic EBL, but again the cost issue.

    1. It was running way too rich at a "idle", I got this issue corrected by changing the injector size from 55 in the original .bin to 120, due to using 4 injectors

    2. "Idle", I use this term loosly right now (1300-2200rpm). I am pretty sure it is an IAC issue, this morning when I put the ecm in diagnostic mode(jump A/B on ALDL), the pintle on the IAC remained retracted. ??? When key off the pintle extended. I have read on another site that some oldsmobile IACs were wired opposite. IDK if that is true but tends to make sense with way the engine idled(temps went up, idle went up instead of down) So with it extended, I unplugged the IAC and will try again tonight when I get off work. EDIT: problem found and fixed in Post#9.

    3. Datastream communication. I am having a difficult time getting useful data consistantly from the AutoProm to the PC. Friday, before work, I hooked up the PC, loaded TP, and got everthing connected, car started, idled high but I had good data coming out. I let it run for a couple of minutes and shut it off. At the next key on all data was wrong, or flashing stupid numbers, like 345 degrees spark advance????. Any who, my next step will be to just burn a chip with Cyl. count, injector flow, and displacement changed from the original .bin, put the chip in, and start it with the IAC disconnected. EDIT: Found that you need to do it in this order: Open bin., Change MASK ID to AA, upload to Emulator, Then Emulate.

    Where I go after that depends on what happens.
    Last edited by gregs78cam; 04-04-2012 at 10:15 AM.
    1978 Camaro Type LT, 383, Dual TBI, '7427, 4L80E
    1981 Camaro Z-28 Clone, T-Tops, 350/TH350
    1981 Camaro Berlinetta, V-6, 3spd
    1974 Chevy/GMC Truck, '90 TBI 350, '7427, TH350, NP203, 6" lift, 35s

  2. #2
    RIP EagleMark's Avatar
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    Re: My project

    Hey! Another North Idaho guy! Where you at?

    What's the cam specs at .050 ? Idle is a lot of work with big cams. They usually have to idle high to get enough STEADY vacuum for the MAP sensor to give ECM reading it can deal with.

    Your IAC has to be correct first of course. Also Big Block Chevy TBI came from factory wired with 2 wires switched. Should be enough diagrams in our library to figure out all you have there.

    Some things I do with big cammed engines, in no particular order because you usually do them all several times is. IAC closed, set min air on throttle blades, set with bypass wire disconnected,timing, sent min air, set timing, look at vacuum reading, is it steady? probably not, but give it what it wants with no interference from IAC and timing to get an idle.

    In the chip disable EGR because you probably don't have one. Disable closed loop idle. Match base timing to what you have at distributor or it will not know and you will end up with more than total advance. Look for timing advance for that motor and better if the cam manufacturer has a timing table, plug that into the chip tables. With a 427 type ECM you will plug in injectors size and cubic inches and I forget what else. But a 7747 ECM puts them all in one lump called Base Pulse Width constant and is harder to figure out to start.

    If you have a wide band O2 sensor use it for idle.

    Go back to first part and start all over with IAC, timing and O2 sensor all disabled and set min air, set timing. Give the motor what it wants! Get it to idle at whatever RPM even if it's 2000. Then drop min air, drop timing. Play with both of these. Since you have an AutoProm use it emulating and usually drop fuel. Then min air, then timing. There may be a set procedure but I have never seen one and I have watched experienced tuners and they did exactly what I did and learned and am telling you.

    While your doing all these things motor has to be warmed up to start and then rev the motor up once in awhile to clean it out so you are getting true idle, not adjusting a loaded up engine.

    HTH!

    Oh yaeh I forgot...

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

  3. #3
    Fuel Injected! gregs78cam's Avatar
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    Re: My project

    I am up in Spirit Lake, you are in CDA right? I am pretty sure we conversed a bit on TGO.

    I did not know the BBC IAC had two wires swapped. But yes first thing is to get it to idle at a decent rpm, and not pig-rich. It idled at about 700rpm with a carb, so that is my target with efi. As of Friday, my problem was more with getting a solid data link between the PCM and laptop.

    Cam is 224/230 @.050, 0.525/0.524 lift. Not real big for two reasons. I knew I wanted to go EFI eventually, and the engine was built for lots of torque down low, not HP @6500rpm.

    I do have an LM-1 and it is running through the PCM in the datastream.

    I am at work so i don't have any more pics but here is one from 2003 when I built the engine and another from my post on TGO.
    Attached Images Attached Images
    1978 Camaro Type LT, 383, Dual TBI, '7427, 4L80E
    1981 Camaro Z-28 Clone, T-Tops, 350/TH350
    1981 Camaro Berlinetta, V-6, 3spd
    1974 Chevy/GMC Truck, '90 TBI 350, '7427, TH350, NP203, 6" lift, 35s

  4. #4
    RIP EagleMark's Avatar
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    Re: My project

    I think I remember talking to you on TGO as well because of that adapter you made!

    What's this motor in ?

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

  5. #5
    Fuel Injected! gregs78cam's Avatar
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    Re: My project

    It is in my '78 Camaro rust bucket test mule. Once I get the drivetrain sorted out, it will all go into an '81 T-top, Z-28 clone.
    1978 Camaro Type LT, 383, Dual TBI, '7427, 4L80E
    1981 Camaro Z-28 Clone, T-Tops, 350/TH350
    1981 Camaro Berlinetta, V-6, 3spd
    1974 Chevy/GMC Truck, '90 TBI 350, '7427, TH350, NP203, 6" lift, 35s

  6. #6
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    Re: My project

    FWIW ,

    454 TBI IAC wiring :

    PIN A - Coil A Low - Lt Blu/blk
    PIN B - Coil A High - Lt Blu/wht
    PIN C - Coil B High - Lt Grn/wht
    PIN D - Coil B Low - Lt Grn/blk

    This is the 454 IAC wiring at the valve , trace back to the proper pins on your ECM to be sure

    HTH

    TOM
    1994 3500 Dually , 502 (509) , 264HR , Edelbrock MPFI , PFI '7427
    1992 S-10 434 SBC/Tremec - '7427
    1986 Monte Carlo SS
    1984 S-10 , SAS, 496/700R4/205 , D44/14BFF -'7427
    1980 Z-28 496/700R4
    1979 Corvette 496/700R4
    1977 Olds 98 Regency 403/700R4

  7. #7
    Super Moderator dave w's Avatar
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    Re: My project

    Quote Originally Posted by gregs78cam
    Ok, I have been working on this for a few months now, everything is together, the engine runs but has some issues that I am working through. A little bit about the setup: 2pc rear main, 385 i built about 8 years ago, 10.5:1, 6" rods, TFS 23* heads, jesel belt drive, roller cam with 4/7 swap. It spent most of it's life in front of a T-56 with 4.10 gears,(dynoed 340hp/370Tq, and rich) until I just got tired of always shifting. So I found a 4L80E and decided while I was at it I might as well do the EFI as well since it could all be done with the same PCM. Now I know I could have used a 454 TBI with 454 injectors, but they are usually either hard to find, or cost more than I was willing to spend. So one day I stumbled across a CL ad selling 6 TBIs off various vehicles. I went go to get them and it turned out to be 7 for $35. So after cleaning up two matching ones(for the linkages) my Dual TBI was born(and inexpensively too) I am using a '7427, with Rbob's 4-injector upgrade, APU1, and TPV5. I could have used Rbob's fantastic EBL, but again the cost issue.

    1. It was running way too rich at a "idle", I got this issue corrected by changing the injector size from 55 in the original .bin to 120, due to using 4 injectors

    2. "Idle", I use this term loosly right now (1300-2200rpm). I am pretty sure it is an IAC issue, this morning when I put the ecm in diagnostic mode(jump A/B on ALDL), the pintle on the IAC remained retracted. ??? When key off the pintle extended. I have read on another site that some oldsmobile IACs were wired opposite. IDK if that is true but tends to make sense with way the engine idled(temps went up, idle went up instead of down) So with it extended, I unplugged the IAC and will try again tonight when I get off work.

    3. Datastream communication. I am having a difficult time getting useful data consistantly from the AutoProm to the PC. Friday, before work, I hooked up the PC, loaded TP, and got everthing connected, car started, idled high but I had good data coming out. I let it run for a couple of minutes and shut it off. At the next key on all data was wrong, or flashing stupid numbers, like 345 degrees spark advance????. Any who, my next step will be to just burn a chip with Cyl. count, injector flow, and displacement changed from the original .bin, put the chip in, and start it with the IAC disconnected.

    Where I go after that depends on what happens.
    The '7427 has two VE tables and two SA tables. Maybe for the time being it might be a good idea to set both tables to the same value? I think I would try using one IAC, and leave the other IAC unplugged. As for the '7427 injector flow, I've had to set stock 55 lb injectos to 61 lbs, and 90 lb injectors to 85. Setting the injector flow in the PCM does not always match the injector flow rating!

    Personally, I like DataMaster TTS for data logging the '7427. I use the DataMater Histogram to set the injector flow until most cells are in the ideal mixture.

    dave w

  8. #8
    Super Moderator dave w's Avatar
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    Re: My project

    An excellent picture of a TBI running WAYYYYYYYY to RICH.

    dave w
    Attached Images Attached Images

  9. #9
    Fuel Injected! gregs78cam's Avatar
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    Re: My project

    OK, Let's try this for the second time.

    IT RUNS!!!!. The High idle was two problems. Vacuum tube on back of rear TB (MAP connection) was plugged. And in order to plug off the rear IAC passage, I gutted an IAC, threaded the inside, and used a 1/2"NF set screw with a jam nut to simulate a pintle seated against the TB. Well the set screw was not screwed in all the way, hence a vacuum leak. Idle is little high yet ~825-950 when desired is 788-850, but I think it is because the IAC won't extend past 27 counts, no matter what. It's livable though.

    I am still having issues with the AutoProm. I can burn a chip, put it in and datalog though APU1 and TP, and start it as many times as I want. It's emulating that is messed up. If I disconnect battery to reset PCM, hook up AP, open TP, load .bin, and keep verifying until succeed, turn on emulate, turn on Data Aq., then start engine, I can emulate, but as soon as I turn off ignition it's done. Key on after that and nothing, won't start, no data, FUBAR.

    I am going back out to clean up get it off the blocks and hopefully take it for a drive tomorrow.
    1978 Camaro Type LT, 383, Dual TBI, '7427, 4L80E
    1981 Camaro Z-28 Clone, T-Tops, 350/TH350
    1981 Camaro Berlinetta, V-6, 3spd
    1974 Chevy/GMC Truck, '90 TBI 350, '7427, TH350, NP203, 6" lift, 35s

  10. #10
    Super Moderator Six_Shooter's Avatar
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    Re: My project

    When emulating you need to disable checksum by changing the mask id byte from whatever it is (I.E. OD, A1, 8D, 58, etc) to AA.
    The man who says something is impossible, is usually interrupted by the man doing it.

  11. #11
    Fuel Injected! gregs78cam's Avatar
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    Re: My project

    Tried that, didn't work. Do I need to change it in the .bin that I load into the Autoprom, along with the .bin that I have loaded in TP? I don't think I have tried that. I just figured if it were emulating it would update the checksum just like anything else I change while emulating. I will try that tomorrow.

    Another thing does any one else have problems with this website? Every time I try do something I have to login again, and start over, it took me almost an hour to get my last post to be submitted, I was going to upload some pics, but I kept having to login and start over. Anywho, I will post up tomorrow on how it goes.

    Greg
    Attached Images Attached Images
    1978 Camaro Type LT, 383, Dual TBI, '7427, 4L80E
    1981 Camaro Z-28 Clone, T-Tops, 350/TH350
    1981 Camaro Berlinetta, V-6, 3spd
    1974 Chevy/GMC Truck, '90 TBI 350, '7427, TH350, NP203, 6" lift, 35s

  12. #12
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    Re: My project

    Greg,
    The website issue sounds like you may need to clear the "cookies" in whatever browser you are using.

    Other than that I have nothing to add except that the dual TBI adapter is awsome! Cool project.

  13. #13
    Fuel Injected! gregs78cam's Avatar
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    Re: My project

    I thought maybe the cookies too, but that didn't help, I think it is my ISP.
    Thanks for the compliments, I would make it slightly different if I had do it again, but it seems to work well so far. I was kind of hoping that the extra common plenum volume would help extend the RPM range a bit. We'll see though.
    1978 Camaro Type LT, 383, Dual TBI, '7427, 4L80E
    1981 Camaro Z-28 Clone, T-Tops, 350/TH350
    1981 Camaro Berlinetta, V-6, 3spd
    1974 Chevy/GMC Truck, '90 TBI 350, '7427, TH350, NP203, 6" lift, 35s

  14. #14
    RIP EagleMark's Avatar
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    Re: My project

    I looked into website issues and a lot of things went on at server yeasterday. Lets hope your issue goes away.

    What are you doing for an air cleaner?

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

  15. #15
    Fuel Injected! gregs78cam's Avatar
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    Re: My project

    Well I was lazy yesterday, and did very little on the car. But today I finished up a whole bunch of wiring. Just have to vacuum it out, put the seats in, the hood on, and take it off the blocks.

    For an air cleaner, I am going to modify a standard 14" to fit over both TBs. If everything works ok then I will make another base for my triangular Edelbrock one. I may have to make the cowl induction scoop taller, or put a forward facing scoop on it, that is what I would actually like to do. I like the looks of the '67 427 Corvette scoop but nobody makes a hood so I will have to attach a scoop.

    And the website seems to be better today, so far. We'll see how many times I have to write and submit this post.

    I'll get some more pics tomorrow.
    1978 Camaro Type LT, 383, Dual TBI, '7427, 4L80E
    1981 Camaro Z-28 Clone, T-Tops, 350/TH350
    1981 Camaro Berlinetta, V-6, 3spd
    1974 Chevy/GMC Truck, '90 TBI 350, '7427, TH350, NP203, 6" lift, 35s

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