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Thread: Vortec EGR System?

  1. #1
    EFI GearHead ! EagleMark's Avatar
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    Vortec EGR System?

    Does anyone have a understanding of the mechanical end of the EGR system in a Vortec Engine? It's a 98 but I think mechanically 96-00 are all the same.

    I'm wondering if there is a possibility of it feeding one bank more then the other? Or could something get plugged?

    Why? Well I have my tune dialed in for fueling, did so with WB in Open Loop and EGR off. Back to Closed Loop fueling is still spot on. With EGR enabled Bank 1 STFT/LTFT is off by about 3.1% all the time EGR is on.

    Side topic: I'm wondering if the EGR being on from 3 MPH is hurting my around town mileage? My understanding and testing shows EGR to give better mileage on highway for sure! But it does produce less HP, so why would I want it on when HP/Torque is most important? From a standstill it is on at 3 MPH with a varying % based on TPS, more TPS = higher EGR%. I'm thinking this would hurt mileage? Maybe turn it on at 25 after vehicle has made it up to speed and HP/torque requirements are much lower...

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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    I suppose the EGR could get plugged in a way that tends to direct exhaust gas one way but I wouldn't suspect that first. Are you using the stock TB with the diffuser plate on the bottom? Check to see if the plate highly carboned up.

    Most of our GM buses are mainly around town, stop and go. My testing has shown improvements in mileage if EGR is disabled during these conditions. Unfortunately I can't leave them set that way.

    My suburban is showing about 10-12% rich in closed loop. Initially I suspected across the board timing changes were needed for the 302 but those are not bringing O2 into line. I'm going to return to stock timing and see if the EGR is sticking open next.

  3. #3
    EFI GearHead ! EagleMark's Avatar
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    Are you using the stock TB with the diffuser plate on the bottom? Check to see if the plate highly carboned up.
    It is stock. Can you see that with air cleaner off or have to remove TB?

    I'm doubting it, the intake gaskets and spider were recently done, not by me, before I got it. Very nice work too along with everything else, I have maintenece records since new, no expense was ever spared on care of this truck... but you never know?

    It is EGR related as I can turn off EGR and no more Bank 1 fuel trim changes?

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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  4. #4
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    No, you can't see it without pulling the TB.

    Are you also seeing O2 readings that are different between the banks? Does that cal have an option to turn off individual bank fuel trims?

  5. #5
    EFI GearHead ! EagleMark's Avatar
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    O2 readings are same both banks... I even swapped the new O2 sensors awhile back. I know why your going there as I had the issue with post cat O2 sensor which was also same bank. Replaced it and went away... I thought, well the O2 swing of that post Cat sensor went away but this fuel trim issue came back. Post CAT 02 sensors are removed now for testing. Finally tracked it to EGR On/Off.

    Wide Band is only in driver side bank which is bank 1 as well. Runs a steady .98-.99 on gauge and logs and no change when fuel trims go to 3.1%. That's well within boundaries of correction and well within goals of a good tune. Just very strange one bank sees correction only when EGR on?

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

  6. #6
    EFI GearHead ! EagleMark's Avatar
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    There is a Two Bank Fuel Control flag in TunerCat! Just like everything else so much more usable parameters then EFI Live.

    TunerCat is also where I found the EGR enable speed. EFI Live only has one parameter for EGR... Enable/Disable...

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

  7. #7
    Fuel Injected! gregs78cam's Avatar
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    So with that flag you can run in Batch fuel control, or Bank fuel control?
    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

  8. #8
    EFI GearHead ! EagleMark's Avatar
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    From what 1project2many says below it sounds like just trim, not a bank/batch change.

    Quote Originally Posted by 1project2many View Post
    Does that cal have an option to turn off individual bank fuel trims?

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

  9. #9
    Fuel Injected! Lextech's Avatar
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    It's too bad we don't have any EGR related TPS and RPM parameters available to us. That way we could use the PCM's EGR circuit as a switching circuit.

    Jeff
    98 GMC RCSB, 5.0, 4L80e, Moser M60, 4.10 gear, Homemade twin turbo w/Junkyard T3 turbos, 24x CNP, 12200411 PCM.

  10. #10
    Fuel Injected! gregs78cam's Avatar
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    Quote Originally Posted by EagleMark View Post
    From what 1project2many says below it sounds like just trim, not a bank/batch change.
    That's what I meant, it can trim each bank, or both as one?
    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

  11. #11
    EFI GearHead ! EagleMark's Avatar
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    Quote Originally Posted by 1project2many View Post
    My suburban is showing about 10-12% rich in closed loop. Initially I suspected across the board timing changes were needed for the 302 but those are not bringing O2 into line. I'm going to return to stock timing and see if the EGR is sticking open next.
    That's about the same amount of change in cubic inches too? Have you done the VE tables? You still have the 98-00 Vortec PCM?

    I've confirmed my issue once again as EGR. Turned it off yesterday and fuel trims were back to as close to 0 as possible all over but more importantly same bank to bank.

    Going to try turning off the individual bank trims and see what happens, more curiosity. Seems like it would be a patch for a known EGR issue?

    Also going to check MPG on this tank with EGR enable MPH raised to 25 MPH

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

  12. #12
    Fuel Injected!
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    Quote Originally Posted by EagleMark View Post
    That's about the same amount of change in cubic inches too? Have you done the VE tables? You still have the 98-00 Vortec PCM?

    I've confirmed my issue once again as EGR. Turned it off yesterday and fuel trims were back to as close to 0 as possible all over but more importantly same bank to bank.

    Going to try turning off the individual bank trims and see what happens, more curiosity. Seems like it would be a patch for a known EGR issue?

    Also going to check MPG on this tank with EGR enable MPH raised to 25 MPH
    My MPG is better EVERYWHERE with the EGR turned off and always has been.

  13. #13
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    Sorry, Mark. Didn't mean to leave you hanging. Had a road trip to visit family.

    Change that bit and you should see fuel trims follow only bank 1. I have been told the selection for 1 or 2 O2 sensors will do the same thing but haven't played with it.

    Spent time with my cal. Problem was solved with engine displacement per cylinder. The displacement step size is 10CC so I bumped it from 630 to 640CC.

    Imported trans module from 99 Envoy for faster response to throttle changes. I need it due to reduced torque at lower rpm. Much more driveable now and less fuel wasted. Still need to work on a few things but better overall. Didn't realize TC can do that until this weekend. V. Cool.

    The EGR helping / hurting mileage has been a back and forth issue for years. Claims on both sides by respected individuals lead me to believe there are more than simple variables involved. I look at cam overlap and exhaust configuration to decide how much is needed. Decent overlap and mufflers indicate EGR already present at part throttle without opening valve so why add more?
    Last edited by 1project2many; 05-28-2013 at 08:27 PM.

  14. #14
    EFI GearHead ! EagleMark's Avatar
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    Hope your trip went well.

    I tried the bank fueling bit and no change? Still had difference on 1 and 2... I'll give it a shot again tomorrow. Also asked John at TC to verify it's purpose.

    As you found TunerCat will do the Import Calibration of Engine/trans or... which others call a segment swap. It will also do it table by table if the table is open. The more I use it the more I like it.

    The EGR helping / hurting mileage has been a back and forth issue for years. Claims on both sides by respected individuals lead me to believe there are more than simple variables involved. I look at cam overlap and exhaust configuration to decide how much is needed. Decent overlap and mufflers indicate EGR already present at part throttle without opening valve so why add more?
    That is the first time I've ever heard a theory on why! Makes perfect sense as well.

    I just can't pull the TB off right now to check EGR/diffuser issue you asked about, can't chance the vehicle being down. Have no idea when I may have to leave town and bring wife to OR for surgery... The Suburban just has to many issues for a trip...

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

  15. #15
    Fuel Injected! pmkls1's Avatar
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    Well Mark, I may be a little late chiming in here, but I just happen to be resealing the intake on my grandfather-in-law's '99 suburban. I snapped some pics of the bare intake to illustrate what I believe may possibly be the issue. The particular truck that I'm working on is a 1999 Chevy C2500 Suburban with an L31 5.7 (obviously) and a 4L80E. Mechanically, the '96-'02 L30 and L31 intakes are essentially identical AFAIK. Anyway, I've got a couple things to do and then I'll upload my pics to the computer and post them with a few notes showing the passages and such.
    1999 GMC Sierra 1500 standard cab long bed 4.8 V8 2WD - A work in progress.
    2000 Grand Prix GT sedan 3800 - My new daily driver inherited from the wife via the insurance company totaling it out after a minor collision.
    2006 Grand Prix GT sedan 3800 Supercharged - The wife's new grocery getter.

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