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New VG35E High Compression Build

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  • #16
    I composed this little table of results:

    RPM HP Torque Notes
    -------- ----------- ------------ --------------------
    4800 180 Nissan claim
    2800 202 Nissan claim
    --------------------------------------------------------------------------
    3000 170 Dyno run "before"
    4500 130
    --------------------------------------------------------------------------
    3900 192 207 Dyno run "after"
    --------------------------------------------------------------------------


    Conclusions:
    1. peak horsepower increased 13% going from 170 to 192 (+22 hp on 170)
      1. compared to 19% expected from combined displacement and compression increases
    2. peak torque increased 60% going from 207 to 130 (+77 ft-lb on 130)
    3. and the peak torque moved down from 4500 RPM to 3900 RPM
    #2 and #3 are why the truck feels peppier. It has 60% more available acceleration down at the rev ranges where you typically mash the pedal to get on the freeway.

    I don't understand why the Nissan claim has peak HP at 4800 while you measured it peaking so much earlier at 3000 RPM on the first dyno run. Maybe HP is really flat, so the RPM is irrelevant, or maybe you miss-typed and meant 4000 RPM?? Anyway, this radically lower RPM for reaching peak torque is why the engine feels so different.

    I think the new cams (and maybe the head work) are responsible for allowing the cylinders to fill at lower RPM and get you all that torque earlier. This at the expense of poorer idle performance and perhaps worse low speed emissions performance which might explain why Nissan doesn't build motors that way.

    Maybe you can post the dyno plots from before and after so we can better understand these details.

    Anyway, congratulations on the build. Seems like you really achieved some impressive real-world drive-ability improvement goals. Nice!

    Chris

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    • #17
      Looks like it reformatted my post to be different from the "preview". Let me try again with my little table:

      Nissan claimed 180 HP at 4800 RPM and 202 ft-lbs of torque at 2800 RPM.
      According to Matt, he measured 170 HP at 3000 RPM and 130 ft-lbs of torque at 4500 RPM with a stock engine.
      That's a lot less torque than Nissan claims.
      Then Matt modified the engine and found
      192 HP at 3900 RPM and 207 ft-lbs of torque also at 3900 RPM.

      That's a huge improvement of peak torque, both absolute amount and reduction of RPM where it was available.

      Chris

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      • #18
        In case my prior post was confusing, here's the actual before/after dyno results, taken at the rear wheel...on a Mustang chassis dyno
        r9EO.jpg

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