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  • #1

    TB and MAFS causing issues

    Hey Guys,

    Thanks for all your replies to my previous two posts. As I mentioned, last weekend I installed a Holley 58mm TB and a Granatellie MAFS on my stock 97 TA M6. Now from I read they really are meant for the car when she has larger/ported intake but I got crazy to do something on her and well on they both went. Well, now the revs dip below 1000 and the car seems like its about to stall out. I am not getting any SOTP fun I thought I would get rather just alot more popping coming out my Borla exhaust. Are the issues causing this the lack of proper tuning (which will happen when I upgrade the topside of the motor) and the fact that the car has these parts on when it can't really fully utilize them? I am thinking of putting on the stock stuff this weekend and until I have the engine rebuild under way before putting them back on.

    Thanks for your insight.

    Jorge
    97 TA, M6, JBA ceramic coated headers, Borla Cat-back exhaust, 1.6 RR, 160 Thermo, LT4 knock sensor, CAI, Bils, Hotchkis all around, GT rotors, B&M shifter, Magnecor wires, Granatelli MAF
    In the shop LT4 Intake and heads.
    Tags: None
  • #2
    If you dont have any major internal mods, then the 58mm T.B is way overkill and will probably not make any more power for you. The stock T.B. is more than adaquate for a stock engine. The PCM and IAC is probably having a hard time maintaining the idle in your car due to the throttle blades not being adjusted properly. The minimum air rate through the T.B. needs to be matched with the correct number of IAC counts (5-15) at idle. If the blades are allowing too much/ too little air through, the PCM will be "confused". The change of MAF at the same time is probably not helping issues. If at all possible, do mods one at a time.....and you may want to put the stock throttle body back on.
    96 WS6 Formula: Ram Air, 383 Stroker, Ported LT4 Heads and Manifold, 1.6 Crane Rollers, 58MM T.B., AS&M Headers, Borla Exhaust, Meziere Elec. H2O Pump, Canton Deep Sump Oil Pan, 100 HP OF TNT N2O!! , T56 Conversion w/ Pro 5.0 shifter, SPEC Stage 3 Clutch, Hotchkiss Subframe Conn., Lakewood Adj. Panhard Bar, Spohn Adj. LCA's, BMR Adj. T.A., Custom 12 bolt w/ 3:73's, Moser Axles, Eaton Posi, Moser Girdle
    11.6 @ 123mph (1.6 60' - getting there )

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    • #3
      N20LT4Bird ..
      Thanks for the reply. I think I will do just that and restore it back to stock until I take her in to get all the work done. On a different note, do you have any regrets going the LT4 Intake/heads route? I have an LT4 intake and was thinking of going down the ported route similar to yours. Would you go with other heads in retrospect?

      Thanks,

      Jorge
      97 TA, M6, JBA ceramic coated headers, Borla Cat-back exhaust, 1.6 RR, 160 Thermo, LT4 knock sensor, CAI, Bils, Hotchkis all around, GT rotors, B&M shifter, Magnecor wires, Granatelli MAF
      In the shop LT4 Intake and heads.

      Comment

      • #4
        I like the LT4 heads. Unported LT4 heads flow just as well, if not better, than a well ported set of LT1 heads. There are guys making some serious power with worked LT4 heads. There are other nice aftermarket heads out there that will make good power too, but are a bit more pricey....
        96 WS6 Formula: Ram Air, 383 Stroker, Ported LT4 Heads and Manifold, 1.6 Crane Rollers, 58MM T.B., AS&M Headers, Borla Exhaust, Meziere Elec. H2O Pump, Canton Deep Sump Oil Pan, 100 HP OF TNT N2O!! , T56 Conversion w/ Pro 5.0 shifter, SPEC Stage 3 Clutch, Hotchkiss Subframe Conn., Lakewood Adj. Panhard Bar, Spohn Adj. LCA's, BMR Adj. T.A., Custom 12 bolt w/ 3:73's, Moser Axles, Eaton Posi, Moser Girdle
        11.6 @ 123mph (1.6 60' - getting there )

        Comment

        • #5
          OK .. good to hear. I have been leaning towards ported LT4 intake and heads and appreciate your input.

          Jorge
          97 TA, M6, JBA ceramic coated headers, Borla Cat-back exhaust, 1.6 RR, 160 Thermo, LT4 knock sensor, CAI, Bils, Hotchkis all around, GT rotors, B&M shifter, Magnecor wires, Granatelli MAF
          In the shop LT4 Intake and heads.

          Comment

          • #6
            You can attempt to straighten out the 58mm TB problem by putting a scanner on the PCM. SLOWLY back off on the throttle stop screw until the PCM indicates the specified 800rpm idle speed for your M6. Don't trust the tach, they read 100-200rpm higher than actual.

            With the idle speed correct, check for IAC counts in the range of 20-40. I personally think 5-15 is too low). Then, finally check for a TPS voltage between 0.20-0.90V with the car at idle, blades closed against the stop.

            Also, check your long term fuel corrections (BLM's) for Cell 16. With an oversize throttle body, it isn't unusual to get into problems with "split" BLM's due to poor idle air distribution. If the BLM's differ by more than 10 counts, you need to address the idle air flow.

            The 58mm TB is gross overkill for a stock car. The shop that built my engine sort of laughed at my 58mm TB, and were able to show me on an engine dyno, that even with 381 cubic inches, and the capability to rev over 7,000rpm, the engine got all the air it needed to produce 500HP with the blades only open 77%. Back calculating, you can see that I could have used a 52mm TB and just about max'd it out at 500HP.

            The Granatelli MAF is a VERY hit-or-miss mod. It doesn't gain HP because it can flow more... it gains HP at WOT because it is "recalibrated" at high flow levels, to show less than actual air flow compared to the stock MAF, leaning out the power enrichment (PE) mode target A/F ratio, which is way too rich with the stock PCM programming. While this leaning out MAY produce 15HP, the recalibration in the Granatelli alledgedly is done very crudely, and a lot of people do not see the 15HP gain. You could send your stock PCM to one of the "mail order" tuners, have them lean out the PE mode tables, and gain the same 15HP as the Granatelli, and guaranteed, for about 1/2 the cost of the Granatelli.
            Fred

            381ci all-forged stroker - 10.8:1 - CNC LT4 heads/intake - CC solid roller - MoTeC engine management - 8 LS1 coils - 58mm TB - 78# injectors - 300-shot dry nitrous - TH400 - Gear Vendor O/D - Strange 12-bolt - 4.11's - AS&M headers - duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP/800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117MPH straight motor

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            • #7
              well that sucks ...... so basically both are no good even with the upcoming motor work. I will see if I can return the MAF and get my money back. The Holley was a cash and carry deal so I will have to post it on ebay.

              darn darn darn darn darn.....

              Thanks for the information guys.
              97 TA, M6, JBA ceramic coated headers, Borla Cat-back exhaust, 1.6 RR, 160 Thermo, LT4 knock sensor, CAI, Bils, Hotchkis all around, GT rotors, B&M shifter, Magnecor wires, Granatelli MAF
              In the shop LT4 Intake and heads.

              Comment

              • #8
                Always better to do your research before just throwing parts on the car. As you can see there is a wealth of f-body knowledge on this board. never be afraid to ask a question here about a planned mod. It may save future headaches!
                Dave M
                Life, liberty, and the pursuit of all who threaten it!


                Comment

                • #9
                  The 58mm TB isn't hurting anything.... why sell it? Its just gonna be too big. With an M6, it causes no problems. With an A4, is could cause trans-damaging problems with line pressures and shift points.
                  Fred

                  381ci all-forged stroker - 10.8:1 - CNC LT4 heads/intake - CC solid roller - MoTeC engine management - 8 LS1 coils - 58mm TB - 78# injectors - 300-shot dry nitrous - TH400 - Gear Vendor O/D - Strange 12-bolt - 4.11's - AS&M headers - duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP/800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117MPH straight motor

                  Comment

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