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when dropping throttle (WOT -> no T) there's a "bump" / brief surge?

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  • #16
    I'll bump those two, thanks.

    Without removing the heat shield, and without a known-CA car to compare, it's hard to tell. This was sold in Kentucky, one of the first 99s, and I can't find a California sticker. The O2 sensor is just below the heat shield, and from what I've read the Cali version would be further down, behind that midpipe cat. So I think i'm clear. Existing literature is hard to sort out -- some of it says *all* 99s had both cats, some says just California, some says NY+CA had the same rules.

    Either way, it'll be a one-cat car when I'm done.
    '99 + stock Coldside

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    • #17
      Most likely it was not a CA car. They had a special sticker under the hood for 99-00. Your sticker should read 49 state. The CA version called out 50 state. Also, if you had the front cat, it is not easy to hide. :-) It is short and fat and seriously obvious.
      sigpic


      1990 with FFS Coldside. At least 260 WHP NON-INTERCOOLED

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      • #18
        I replaced the cat with a magnaflow, but lost the o2 port; we ran it for a little with the post-cat sensor in the air, and I think the ECU got confused. In closed loop at low RPM / low speed, it would get down into 12s (I didn't have an OBD reader running). We installed the bung + O2 sensor, cleared the P0140 code, and did more testing hot. The car idled well for about 10 minutes, then we took a test run with a live OBD reader. It took a few minutes / miles at ~ 50mph in cruise to get LTFT to settle down; it had been around 14.8% and sending occasionally rich mixture. After a bit LTFT settled down to -1% to 1% range, STFT was within 3%, and it was pretty normal 14.7 in closed loop mode.

        Under hard acceleration in 2nd / 3rd / 4th, it seems to be doing the same as before: AFR drops to 10ish when boost peaks around 12#. If I roll on around 2k + roll off around 6k RPM, AFR will settle around 10.0, and as I roll off it can drop below 10 (to like 9.8 briefly). At lower boost it seems to pretty quickly drop into 12s. Unfortunately I don't have RPM hooked into my O2 sensor, so I don't have a great way to show both together.

        The old / original cat looks OK, visually; I can see the mesh and light gets through it. I don't know a good way to test the silencer in the midpipe or the muffler, though.

        Unless you have other suggestions, I'm gonna try to repeat the above testing with the muffler disconnected -- that may help me see if there's a problem downstream of the cat.

        I have a new header in my garage, but I don't want to make too many changes until I figure out what's going on.
        '99 + stock Coldside

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        • #19
          Turn down the yellow/blue on boost fuel card 1 light. From 6 to 5.

          LTFT & STFT look great.
          sigpic


          1990 with FFS Coldside. At least 260 WHP NON-INTERCOOLED

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          • #20
            I will, thank you. I assume I should also make the recommended changes to the boost and Ecool card?

            Boost Fuel
            G-B: Green = 4 , Blue = 8

            Ecool
            G-B: Green = 4 , Blue = 8
            '99 + stock Coldside

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            • #21
              (taking notes here for my own benefit)

              Factory header, magnaflow cat, factory silencer, no muffler: 3rd from 2500 -> 6k+ RPM, AFR starts around 12.5 and levels out around 11-11.5 at peak boost / top RPM. When rolling off, AFR increases to ~10.5 briefly.

              I'll let it cool down, will reconnect the muffler, and make the settings changes + another run.
              '99 + stock Coldside

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              • #22
                the change:
                Turn down the yellow/blue on boost fuel card 1 light. From 6 to 5.
                test run: Factory header, magnaflow cat, factory silencer, factory muffler: third from 250->6k+ RPM, AFR starts around 13 and levels out around 11 at peak boost/RPM; will inconsistently dip to 10:1 briefly during spinup and after rolling off throttle.
                '99 + stock Coldside

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                • #23
                  Sounds about perfect.
                  sigpic


                  1990 with FFS Coldside. At least 260 WHP NON-INTERCOOLED

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                  • #24
                    Numbers can be anything when you lift. Only numbers that are meaningful are at WOT.
                    sigpic


                    1990 with FFS Coldside. At least 260 WHP NON-INTERCOOLED

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                    • #25
                      Awesome, thanks for the help! I've updated the numbers based on your recommendation. I'll get the new header in place and will check back in if I have further questions.
                      '99 + stock Coldside

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                      • #26
                        Glad to help.
                        sigpic


                        1990 with FFS Coldside. At least 260 WHP NON-INTERCOOLED

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