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  • #1

    Comment on scan from Autoxray pls.

    Motor is together and running strong. Much traction problems with GSCs in 1st and 2nd. Thought I would gather some feedback on a scan or three (more later) prior to taking it in for smog.

    Half throttle - on ramp to hwy, slowed by traffic
    Link to PDF or Excel of scan data

    Here is what is stock (for now) ....ran outa $$
    Cam
    Entire Fuel System (much new)
    Tune
    Bottom End

    Mods in sig,
    Thank you
    1994 Z28, 6 spd, LE2 Heads, GM 1.6 RR, .026" head gasket, SLP: CAI-Headers (CARB legal)-ypipe-2 on the left-lightweight flywheel-short throw, Random tech cat, CF dual friction, LT-4 KM.
    Tags: None
  • #2
    Not a lot of data, and the 1 frame/sec scan rate sort of masks a lot of things. Its got 3% longer pulse widths on the left side, and its running leaner on the left side than the right side, but I suspect you've already picked that up. Look for an exhaust leak on that side to see if its really running lean or its "false". The knock retard shows up pretty quickly when you push the throttle on the shift to 2nd. Possibly the result of the thinner head gasket and stock tune, plus the left side being lean. Have you estimated the CR with that gasket and the LE2 heads?
    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

    • #3
      As Fred mentioned, check for exhaust leaks, make sure your EGR and AIR fittings are tight too.

      Comment

      • #4
        Thank you both!

        Fred,
        The Autoxray is limited for sure. I didn't post more runs right now because I will borrow a friends Autotap setup this weekend. I did get a chance to get under the car last night and found that the passenger y-pipe flange was tapping the nearby heatshield under load, so I rotated it in a more favorable position. That may or may not be a knock source (it was on the other side earlier this week - see below). The compression may be high for the 91 available around here, Kevin told me in a previous post 11.04:1, although I don't if that thakes the head work into account. It was the gasket Lloyd said to use and other CA people have the same combination.

        Joe / Fred,
        I have really been careful about the leaks. I am definately leaking at the y-pipe to cat and am getting those welded today. Do you think O2 could get back to the sensor? Would it only be on one side? The other problem area is on the right side. The SLP EGR extender pipe is not flush on its mating surface, and may be a leak source. Unfortunately that is not on the suspect side. All other leak sources have been tightened and cycled, the checked last night.

        Thanks to the person with the SLP header to y-pipe tip in another post. The one about leave one side tight, then loosen the other almost all the way, rotate the assembly until the tight bolt is in the unreachable position, and finally tighten the side that is no longer hitting the chassis. Worked awesome! I had 4-5 degress of KR when that puppy was hitting.

        BTW, I just followed the instructions for the GM RR (with brand new LT-4 lifters)and went slightly more than 1/2 turn past zero lash. Directions said 1/2-1. They seem quiet enough, but is that too much preload? Should I redo it with the engine running to get best results?

        Any tips for routing plug wire on #5 with these headers. If I shield it with anything, the shield material touches. If I leave it alone, there is only about 1/8" of clearance.

        Anybody think I should go ahead and get a tune before I SMOG it?

        Thanks, I'll see if I can get a video up soon too.
        1994 Z28, 6 spd, LE2 Heads, GM 1.6 RR, .026" head gasket, SLP: CAI-Headers (CARB legal)-ypipe-2 on the left-lightweight flywheel-short throw, Random tech cat, CF dual friction, LT-4 KM.

        Comment

        • #5
          Originally posted by Joe 1320
          As Fred mentioned, check for exhaust leaks, make sure your EGR and AIR fittings are tight too.
          The air fittings that attached to the headers are tight. The SLP hoses that join those to the air system fit like crud because those metal AIR tubes are a smaller OD. I'll try to find something air-tight to wrap around those tubes to get a better seal. I had a lapse of logic regarding that (AIR) system, that your post caused me to re-think. It is probably a source of a leak at the moment.
          Thanks
          1994 Z28, 6 spd, LE2 Heads, GM 1.6 RR, .026" head gasket, SLP: CAI-Headers (CARB legal)-ypipe-2 on the left-lightweight flywheel-short throw, Random tech cat, CF dual friction, LT-4 KM.

          Comment

          • #6
            Autotap is for OBD-II, so it won't work with your 94. You need either TTS DataMaster, FreeScan, EFI Live V4 or Diacom for OBD-I.

            A leak at the collector to cat connection shouldn't be backflowing to the O2 sensor... how far is the leak from the sensor? Any "slip fits" on your headers? AIR connections sound like they need to be looked at.

            I can't comment on the valve adjustment, but if they're staying open a little, they can bleed air into the exhaust. The leaking EGR connection could be serious, but as you pointed out, its the wrong side.
            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

            • #7
              Originally posted by Injuneer
              Autotap is for OBD-II, so it won't work with your 94.
              Oh, Nevermind (In my best Emily Latella voice).

              Originally posted by Injuneer
              A leak at the collector to cat connection shouldn't be backflowing to the O2 sensor... how far is the leak from the sensor?
              24" minimum, I was on the weld to keep it easy to take apart until things were running smooth.

              Originally posted by Injuneer
              Any "slip fits" on your headers?
              Only the one discussed above. It is single cat, and the Y-pipe to header connections use them fancy donuts. Similar but not the same ones as stock.

              Originally posted by Injuneer
              I can't comment on the valve adjustment, but if they're staying open a little, they can bleed air into the exhaust.
              I'll address the other issues tonight and see where I am at.

              Thanks again!
              1994 Z28, 6 spd, LE2 Heads, GM 1.6 RR, .026" head gasket, SLP: CAI-Headers (CARB legal)-ypipe-2 on the left-lightweight flywheel-short throw, Random tech cat, CF dual friction, LT-4 KM.

              Comment

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