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Thread: L67 Injector IFR help

  1. #1

    L67 Injector IFR help

    I'm running 42.5 injectors and having a hard time scaling this thing right. Does anyone have a table for these injectors handy?
    Thanks.... John
    2000 Grand Prix GTP 11.586 @ 118.20
    Best MPH: 121.72

    New Ride: 04 GTO no times or anything yet

  2. #2

    Re: L67 Injector IFR help

    OK. adjusted the stock IFR table, multipied it by 1.19 and its pretty damn close now. A little rich at idle and cruise and a bit lean at WOT. Close enough for now.
    Anyone have any tips for fine tuning the IFR table?
    Like which ones need to be raised or lowered for the fine tuning....
    2000 Grand Prix GTP 11.586 @ 118.20
    Best MPH: 121.72

    New Ride: 04 GTO no times or anything yet

  3. #3
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    back in the day thread but it's lookin like im gunna need help on this also
    2004 GTO LS1~HP Tuners~AFX W/B~PRC 227 heads~.644/.598-231/234-111(TQV3)~Kooks 1 7/8 headers~Stock injectors~Fast 102 LSXR Intake~Fast 102 TB~CAI cold air intake~Yella Terra Roller Rockers~Fast Fuel Rails~

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  4. #4
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    The proper multiplication factor is 1.18055, not 19%.
    '99 Black GTP Sedan
    3.4-2.6" PB Quick Change pulleys, Custom CAI, XP Cam, N* TB, LQ4 MAF, SLP headers, 42.5# Injectors, 180/195* thermostat.

    13.501 @ 103.392 on 91 (2.4 60-foot).
    13.82 @ 105.28 on 87 octane! (2.42 60-foot).
    263kph top end as shown on the GPS.
    All this and 39MPG to boot. What more can a man ask for?
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  5. #5
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    Why can't you jut put 42.5 in that table? if the injectors are 42.5 pound hour injectors then why can't you just put 42.5 in all the way across the table?

    I don't understand why some cars have some scaling from 36.10 at 0-kpa to 38.40 at 100-kpa and other cars will have 38.16 all the way across on GTP's for example.

    Sorry for the hyjack but it seemed like the right time & place to ask.
    Best 60' = 1.716
    Best ET = 12.186
    Best MPH = 112.98


  6. #6
    Senior Tuner 5_Liter_Eater's Avatar
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    It depends on two things:

    A. The pressure that the injectors were rated at and what they will be run at. If they were rated to flow 42.5#/hr at 43.5 PSI (3 bar) of fuel pressure and they will be run at 58 PSI (4 bar) of fuel pressure then they will be flowing more than 42.5 #/hr and the flow increase is not linear, it's exponential.

    B. If the fuel system does not change the fuel pressure based on manifold pressure and manifold vacuum (boost and/or vacuum referenced) then the injectors flow more (at idle when manifold vacuum helps to suck the fuel out of the injector) or less (under boost when the fuel has to work against the manifold pressure).
    Bill Winters

    Former owner/builder/tuner of the FarmVette
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  7. #7
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    Quote Originally Posted by JerryH
    The proper multiplication factor is 1.18055, not 19%.
    So your saying 18.055%?

    100% = 1
    Mitchell

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  8. #8
    Tuner krunchss's Avatar
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    Hey 5 Liter Eater...

    Seeing as someone else brought this topic up, can you answer this?

    OEM L36 has the IFR set all the same in all cells.

    L67, or at least newer version seem to have this "Ramping" IFR table.

    A person with an L36 with boost (Turbo) should run which type of these tables? Ramping because now it's boosted? Still running a 1 bar MAP though.

    If the ramping table is better how would you figure out the ramp?

    Thanx,
    Krunch
    2002 Monte Carlo SS "Project Intimidator"

    [*DHP PowerTuner*] [L36] [180 TStat] [ZZP HVTB] [HV3] [Resonator & U-Bend Delete] [Carsound Hi Flow Cat] [Corsa Catback] [P&P OEM Manifolds] [Precision PT61] [ZZP Trans] [3000 Stall] [2.93 Gears] [F-Body Calipers] [Water-To-Air IC] [AFCO Ford SVT HE] [IAT Post-IC] [Bosch IC Pump] [9.5L System Fluid Capacity]

  9. #9
    Senior Tuner 5_Liter_Eater's Avatar
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    If the system is not vacuum/boost referenced (all returnless systems that I am aware of are not referenced) then the IFR table needs to be sloped. If you have a return style system that references vacuum and boost then you should have a flat IFR table because the regulator is accounting for the fueling differences based on manifold vacuum/pressure.

    For the ramp rate, search for injector.xls and plug in your numbers and it figures it out for you.
    Bill Winters

    Former owner/builder/tuner of the FarmVette
    Out of the LSx tuning game

  10. #10
    Tuner krunchss's Avatar
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    While I appreciate your answer, I must admit, I don't understand it

    I'm not sure which of those two criteria is met on my car. My car has vacumm AND boost, but the MAP only sees from vacumm up to 1 bar, it doesn't see the boost. Some day I might upgrade to a 2 or more bar MAP, but not right now.

    Could you clarify your answer better on how it relates to an L67 car with boost that the PCM sees, a NA car which has no boost at all, and my car that has boost, but only a 1 bar MAP.

    Thanx,
    Krunch
    2002 Monte Carlo SS "Project Intimidator"

    [*DHP PowerTuner*] [L36] [180 TStat] [ZZP HVTB] [HV3] [Resonator & U-Bend Delete] [Carsound Hi Flow Cat] [Corsa Catback] [P&P OEM Manifolds] [Precision PT61] [ZZP Trans] [3000 Stall] [2.93 Gears] [F-Body Calipers] [Water-To-Air IC] [AFCO Ford SVT HE] [IAT Post-IC] [Bosch IC Pump] [9.5L System Fluid Capacity]

  11. #11
    Tuner CTX-SLPR's Avatar
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    An injector works as an electronically controlled nozzle across a pressure difference. In an engine with a return style fuel system with a fuel pressure regulator with a connection to manifold vacuum/pressure the regulator keeps the pressure drop across the injector constant at whatever the "line off" setting is. This means for an engine under vacuum the fuel pressure drops to compensate for the pull on the engine side of the injector and when an engine goes to possitive pressure the pressure in the rail rises to compensate for the push on the injector. The MAP sensor has nothing to do with the injector tables as best I know (a bit new to the practical world of tuning these cars). When GM, and every other manufacturer for that mater, went to returnless systems for emissions reasons the rail is at a constant pressure and to maintain the same amount of fuel comming out of the injector the table must be skewed to match the change in pressure drop and the equivilent change in fuel flow. In this there would be MAP input but they didn't change that till the L29/32 in 2004.
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  12. #12
    Advanced Tuner louvered97gtp's Avatar
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    Quote Originally Posted by 5_Liter_Eater
    If the system is not vacuum/boost referenced (all returnless systems that I am aware of are not referenced) then the IFR table needs to be sloped. If you have a return style system that references vacuum and boost then you should have a flat IFR table because the regulator is accounting for the fueling differences based on manifold vacuum/pressure.

    For the ramp rate, search for injector.xls and plug in your numbers and it figures it out for you.
    This is interesting info. I've seen and heard only the 97 L67 PCM's use the flat IFR table, whereas 98 and up switched to sloped IFR tables. My 97 has flat rate and my 99 has sloped. I'ma have to look into thos a bit further now.
    99GTP: Flowmasters, ZZP Power log & Ported rear, 9.5:1, Bored over .010, removed balance shaft, Dbl roller chain, Intense S1X, custom ported heads, 45#inj., 105lb springs, 1.7 rockers, A103's, 180-stat, Gen V swap, 97 Cadillac TB & Custom machined alum. spacer, 95 GTP Hood louvers
    97GTP: Stock engine, 95 GTP Hood louvers

  13. #13
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    Quote Originally Posted by louvered97gtp
    This is interesting info. I've seen and heard only the 97 L67 PCM's use the flat IFR table, whereas 98 and up switched to sloped IFR tables. My 97 has flat rate and my 99 has sloped. I'ma have to look into thos a bit further now.
    Indeed, you are correct.

    I switched my 97 over to the sloped table for IFR (amongst other matching changes in other tables) a long time ago.. Been using the sloped table for more then 1.5 years now.
    97 Grand Prix GTP (not going to bother listing mods in detail) 1 messed up 97 PCM with about 30-50% of a 2003 calibration and parts of a few others.

  14. #14
    Senior Tuner 5_Liter_Eater's Avatar
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    Quote Originally Posted by CTX-SLPR
    An injector works as an electronically controlled nozzle across a pressure difference. In an engine with a return style fuel system with a fuel pressure regulator with a connection to manifold vacuum/pressure the regulator keeps the pressure drop across the injector constant at whatever the "line off" setting is. This means for an engine under vacuum the fuel pressure drops to compensate for the pull on the engine side of the injector and when an engine goes to possitive pressure the pressure in the rail rises to compensate for the push on the injector.
    Very well said.

    Returnless fuel system=sloped IFR
    Return fuel system (with a vacuum line attached to the regulator)=flat IFR
    Bill Winters

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  15. #15
    Tuner krunchss's Avatar
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    So, is the shorter, less technical answer...

    The L67 uses a sloped IFR as it has a returnless fuel system, but the L36 uses the flat IFR because it has a return fuel system?

    Now I suspect that just because I added a turbo kit to my car, there were no modifications to the fuel system itself to justify a sloped IFR, but again, I'm running a flat IFR in a car that wasn't boosted, but now is. Fuel demands are way greater now under heavy throttle conditions due to the boost.

    I also know that if you made a change in IFR, you could undo that change again with MAF adjustments, so would running a sloped IFR in a boosted L36 produce a smoother looking MAF table?

    Is running a sloped IFR table in a boosted L36 good or bad?

    Krunch
    2002 Monte Carlo SS "Project Intimidator"

    [*DHP PowerTuner*] [L36] [180 TStat] [ZZP HVTB] [HV3] [Resonator & U-Bend Delete] [Carsound Hi Flow Cat] [Corsa Catback] [P&P OEM Manifolds] [Precision PT61] [ZZP Trans] [3000 Stall] [2.93 Gears] [F-Body Calipers] [Water-To-Air IC] [AFCO Ford SVT HE] [IAT Post-IC] [Bosch IC Pump] [9.5L System Fluid Capacity]

  16. #16
    Senior Tuner 5_Liter_Eater's Avatar
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    To be honest I have no idea what the L36 and L67 are. You will need to verify whether each has a returnless or return fuel system. Acutally you just need to know what your car has.

    Sure adding a turbo or blower will increase fuel requirements but this should not be accomplished by editing the IFR table. The IFR table defines how much fuel the injectors are flowing at different levels of vacuum (and on a natively FI car this table extends into boost).

    So it was elegantly explained by CTX above and I made the very dumbed down version of it above.

    Returnless fuel system=sloped IFR
    Return fuel system (with a vacuum line attached to the regulator)=flat IFR


    So if you know what type of fuel system your car has and what size the injectors are (as well as what pressure they were rated at) then you can determine whether to use flat or sloped and what numbers to use.
    Bill Winters

    Former owner/builder/tuner of the FarmVette
    Out of the LSx tuning game

  17. #17
    Tuner in Training JFDugal's Avatar
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    The L67 uses a sloped IFR as it has a returnless fuel system
    L67 is a return type fuel systsm. L32 is returnless.

  18. #18
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    Quote Originally Posted by JFDugal
    L67 is a return type fuel systsm. L32 is returnless.
    Really?? wow... I didn't know that the L32 doesn't have a return.
    Ok... knowledge adjustment is now complete... Thanks for the info guys..
    Best 60' = 1.716
    Best ET = 12.186
    Best MPH = 112.98


  19. #19
    Advanced Tuner louvered97gtp's Avatar
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    Quote Originally Posted by 5_Liter_Eater

    Returnless fuel system=sloped IFR
    Return fuel system (with a vacuum line attached to the regulator)=flat IFR


    So if you know what type of fuel system your car has and what size the injectors are (as well as what pressure they were rated at) then you can determine whether to use flat or sloped and what numbers to use.
    Sorry but I seem to be a bit thickheaded in trying to figure this out.
    So i have Siemens 60# injectors rated at 43.5psi
    I have a 99GTP with return style fuel system and vacuum on stock FPR
    Based on this I should have a flat graph line in my injector table but I don't. What are the consequences of this?

    Also, how is the sloped rate properly calculated.
    Stock GTP injector 36lbs divided by new injector 60lbs, so 60/36=1.6667
    We multiply our current injector by new upgraded scale factor..
    36x 1.6667 = 60.012 lbs new IFR linear chart?

    Now, If the above is correct, how do we turn this into a sloped table? We don't use the HPT conversion chart do we. It asks for current and new fuel pressure. Most of us change injectors, not fuel pressure so this conversion chart seem useless you raise fuel pressure correct?
    99GTP: Flowmasters, ZZP Power log & Ported rear, 9.5:1, Bored over .010, removed balance shaft, Dbl roller chain, Intense S1X, custom ported heads, 45#inj., 105lb springs, 1.7 rockers, A103's, 180-stat, Gen V swap, 97 Cadillac TB & Custom machined alum. spacer, 95 GTP Hood louvers
    97GTP: Stock engine, 95 GTP Hood louvers

  20. #20
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    Yeah, it's not making sense to me either. I understand what is being said, but the L36 (3800 NA) and L67 (3800 SC) are both return fuel systems, and by that rationale should both have flat IFR. Although in practice, they don't...why not?

    And krunchss, this may be a silly question, but if you've got the ability to tune, why are you still running a 1 bar MAP on a boosted engine? You could start with an L67 tune and work it from that, right?
    Last edited by eclipse5302; 06-23-2008 at 09:56 PM.

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