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Thread: Sanity check, please...

  1. #131
    Lifetime Member BLK02WS6's Avatar
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    Looks like it is coming around! You were rollin during that run for sure...
    GM EFI Tuner
    02 WS6 9.41 @ 143 MPH 3675#, drag radials, pump gas, through the mufflers - sold


  2. #132
    Lifetime Member Rich Z's Avatar
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    Quote Originally Posted by BLK02WS6 View Post
    Looks like it is coming around! You were rollin during that run for sure...
    Yeah, it still startles me when the turbos kick in. It's like a giant hand on the back of the car giving a huge push.

    Well, I'm going to go ahead and start changing out the wastegates, and pulling the compressor housings off of the turbos to drill and tap the fitting holes I need. Weather forecast is calling for heavy rains over the next several days anyway.

    CorvetteFlorida.com

    2002 Corvette Z06
    427 RHS block built by LME
    STS rear mounted twin turbos
    It nearly died on the operating table, but I'm bringing her back.

  3. #133
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    You can't put a hose connection in your last intake pipe before the throttle body? That way you are still referencing pressure very near the manifold.

  4. #134
    Lifetime Member Rich Z's Avatar
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    Quote Originally Posted by ACCLR8N View Post
    You can't put a hose connection in your last intake pipe before the throttle body? That way you are still referencing pressure very near the manifold.
    Attaching the wastegates directly to the turbos just seems more efficient to me. I am using 14 lb springs, expecting there to be some loss to compensate for at the intake. These are rear mounted turbos so I would like to keep those boost lines controlling the wastegates local unless there is a real good reason not to. Besides, it's cluttered enough under the hood as it is. One reason I wanted rear mounted turbos was because I didn't want all that stuff crammed into the engine compartment. I've seen some people's engine compartments that looked like they would be absolute nightmares to do ANY work on the engine.

    CorvetteFlorida.com

    2002 Corvette Z06
    427 RHS block built by LME
    STS rear mounted twin turbos
    It nearly died on the operating table, but I'm bringing her back.

  5. #135
    Lifetime Member Rich Z's Avatar
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    Sorry, been away for a while. Mostly because of rainy weather.

    Anyway, got the new wastegates installed and did a couple of runs with them. Boost is now hitting 11.6 and 11.7 psi. Everything seems to be holding together OK, too. No couplers coming loose and the plastic airbridge didn't pop like I feared it might.

    Found an EXCELLENT road to let it all hang out on yesterday. Virtually the middle of nowhere and nice and straight and flat. So I dropped it into fourth gear from a rolling idle and once the rpms were high enough where I didn't think it would bog, I opened it up to 100 percent until just over 6500 rpm. I didn't take it to redline because the slight curve in the road was coming up pretty darn quickly.

    Log and latest tune are attached. I started pushing it into boost around frame 11920.

    Car feels REALLY good lately. Throttle response is good, no errors showing up and the scans look OK to my untrained eye. Looks like car speed is pretty linear with engine rpm till I took my foot off of the accelerator pedal. Looks like a couple of rich spots in the AFR when I am in boost, though, but doesn't look too bad to me. Only thing I still have nagging me as some slight engine surging around 1200 rpm at 40 to 50 kpa while in higher gears. But that just might be the nature of the beast with this engine, perhaps. If it's something that I CAN fix, I would like to.

    So can you guys take a look at this and see if I am overlooking something or just doing it the wrong way? I know there is more than one way to skin this kind of cat, but I just want to make certain I am not doing something just really dumb while learning this stuff.

    Thanks.
    Attached Files Attached Files

    CorvetteFlorida.com

    2002 Corvette Z06
    427 RHS block built by LME
    STS rear mounted twin turbos
    It nearly died on the operating table, but I'm bringing her back.

  6. #136
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    Couple things I noticed: A0009 you have dropping off above 185 kPa. You should extrapolate that up by hand so you don't lean out if you over boost. If anything ramp it higher for protection.

    There is a pretty steep step between 35 and 40 kPa, 800-2400 RPM in your B0101. My guess is that is your surging.

    In your log it jumps up to peak nice and quick but then falls off. Turbo's might be a little small for racing, but good low end for the street.

  7. #137
    Lifetime Member Rich Z's Avatar
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    Quote Originally Posted by ACCLR8N View Post
    Couple things I noticed: A0009 you have dropping off above 185 kPa. You should extrapolate that up by hand so you don't lean out if you over boost. If anything ramp it higher for protection.

    There is a pretty steep step between 35 and 40 kPa, 800-2400 RPM in your B0101. My guess is that is your surging.

    In your log it jumps up to peak nice and quick but then falls off. Turbo's might be a little small for racing, but good low end for the street.
    Thanks.

    I see what you mean by B0101. I smoothed out that range to make smoother transitions between cells, so I'll see if that helps. And I'll take a look at A0009 as well and increase the values up top too.

    Yeah, I was more interested in low end responsiveness than top end power with the turbos. When I did that run I logged, I was at 105 kPa at just over 1750 rpm. So I'm happy with that.

    Thanks for your help.

    BTW, I did a little video of that run I did. -> http://www.youtube.com/watch?v=LUhun5zl1e8

    CorvetteFlorida.com

    2002 Corvette Z06
    427 RHS block built by LME
    STS rear mounted twin turbos
    It nearly died on the operating table, but I'm bringing her back.

  8. #138
    Lifetime Member Rich Z's Avatar
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    Well, didn't help much when I smoothed out B0101. Been trying a bunch of stuff. Actually lost track of what exactly as I was just pulling over and making changes, so I didn't jot down any notes. I thought perhaps the values were wrong on B4349 indicating the change made from the 75mm to 90mm throttle body. I had 0.0330 there and changed it to 0.0157. Car didn't want to idle at all if I did anything to the gas pedal. And even just sitting at idle, I watched the AFR gradually creeping up into the lean zone. Played around with B4403 too, with no positive results.

    Wound up disabling LTFTs as that seemed to be causing some surging on me. Still had some, so I disabled STFTs as well, but that didn't change anything.

    One thing I noticed was that if the engine stalled on me, I had a devil of a time getting it started again. Seems like I had to let it set for a period of time before it would want to start right up, so I changed the relevant settings (I think) at B3201 and B3203. Haven't stalled it since then so I don't know if that helped or not. But I do know I still have that annoying surging at low speeds. Seems to be low RPM and light load on the engine where it is most noticeable. Which is often just barely over idle driving at under 10 mph, or in any gear that is at the lower limit of the RPM range in that gear.

    The answer is in there somewhere, but I just can't figure out where yet....

    CorvetteFlorida.com

    2002 Corvette Z06
    427 RHS block built by LME
    STS rear mounted twin turbos
    It nearly died on the operating table, but I'm bringing her back.

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