Turbo for a hot 6nz

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by matneyenterprises, Sep 6, 2021.

  1. matneyenterprises

    matneyenterprises Bobtail Member

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    I have a 6nz in a Pete, 13spd, 3.55s and a solid steel piston IPD overhaul kit with about 75k on it and its got a 7cz 600 brakesaver file in it thats got some extra fuel and timing. Dont know what it dynos at, but no 600 hp rated truck, older or newer can pull with it. Naturally I've fought heat with it during summer time and I continuously get conflicting information on what I need for a turbo. Was running a 78/1.32 and it grenaded in a big way and was sold an 80/1.32 to "slow it down". Boost pressure dropped a little with the bigger wheel as did the pyrometer but my water temp builds faster and runs a little warmer overall. The 80 did clean up the smoke a little bit over the 78. This is in Colorado at over 5000 ft and loaded to 85-97k lbs. I always thought the turbine housing was what you wanted to change to properly slow a turbo and let the engine breathe. Seems to me like an 80 would just create even higher drive pressures. I've recently been reading that a 14.6 Liter would be much happier with a 1.45 exh housing so it can breathe and slow the turbo down as a whole, when I asked my tuner about it I was told the bigger housing takes more fuel to make the boost pressure so its less efficient. I always thought boost pressure was a restriction overall and that it is less important than actual airflow. Sooo, is the 1.32 stopping up a bunch of hot air that should just be skating by in a 1.45, or do I need it to keep the intake adequately supplied with charged air to feed the big file and let 'er scream?
    Thanks
     
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  3. MRMTRANS

    MRMTRANS Light Load Member

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    I believe you are getting more air into the engine-particularly in higher gears and under heavy engine load demand- while at the same time getting less back pressure from the turbo. Hence, less smoke, and I bet better performance after the turbo is spooled up some. I would consider buying a high flow radiator. More tubes, more coolant, and maybe with dimpled tubes for better heat transfer.
     
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  4. RockinChair

    RockinChair Road Train Member

    You added more fuel, so you also need to add more air. I don't know what to tell you regarding housing size and impeller size (because I don't understand the finer points of that myself), but the fact that the new turbo lessened the smoke and your EGT dropped indicates that that was a start in the right direction.
     
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  5. swaan

    swaan Road Train Member

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    What are your egts? What are you getting for boost. Water temp? We need numbers .
     
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  6. matneyenterprises

    matneyenterprises Bobtail Member

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    Cruising empty 700-800. Loaded 800-900 until I get into the hills then starts building. I have to keep it at about 825 or cooler in a long pull to Maintain water temp of 210. This is with the fan turned on full time. Cruises at about 200 empty -fan off- and will build to fan temp in rolling hills. Boost is 33-37 depending on what part of the day it is. And it builds plenty fast. These numbers are all summer time numbers. It's a lot happier at 80 degrees and cooler. 180 thermostats,1 year old 4 core radiator and new CAC when the turbo blew up. With the 78 the egt would build to 1000. Boost pressure was the same and water temp was slower to build.
     
  7. lester

    lester Road Train Member

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    I'm running a tune from kurt Murray and was running his turbo as well before switching to a compound setup. With his turbo I stopped watching egts because I couldn't make them get to high. Would run 40-43 lbs of boost. Modified BS file as well.
    Wish I knew the specs on that turbo
     
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  8. swaan

    swaan Road Train Member

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    Your boost seems low. With that file you should be around 42 ish. Your water temp is definitely a big factor also. Have you checked your water pump make sure impeller is not slipping on shaft. ? Also pressure test for boost leaks. Your turbo should be fine.
     
  9. bad-luck

    bad-luck Road Train Member

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    Do you have or have you considered a one piece ported and polished exhaust manifold? I think this would help with your situation.
     
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  10. Brettj3876

    Brettj3876 Road Train Member

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    Just throwing it out there i don't know anything else but you said hot timing. Just a few degrees too far that could be your water temp issue. Did someone reputable do the tune?
     
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