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2JRacing 200sx new track build

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  • #31
    The reason why the QR probably doesn't like high RPM is that the block is pretty pared down compared to the SR. That lightness comes at the expense of structural stiffness in most cases. High RPMs really stresses how rigid the bottom end is and problems are usually a result of things distorting from high stress.
    '18 Chevrolet Volt - Electric fun hatch for DD duty!


    DefSport Koni Sleeve and Spring Perch Buy!!!
    http://www.nissanroadracing.com/showthread.php?t=5902

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    • #32
      that's a nice theory...

      How bout the rod stroke ratio sucks...yeah there we go back in reality

      The QR is 89X100 with a 143mm rod

      that's a 1.43:1 rod stroke ratio...that is horrendous
      Last edited by Tower240sx; 02-02-2011, 05:13 PM.
      I am SKULLWORKS

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      • #33
        Man.. I thought the KA was bad.. the rods on it are 1" longer and it's a shorter stroke.
        Originally posted by SoSideways
        I don't care what color they are as long as they are LONG AND HARD.
        '04 G35 Sedan 6MT- The DD
        '96 240SX- The Track Toy

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        • #34
          The KA is actually ridiculously good on the rod:Stroke
          I am SKULLWORKS

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          • #35
            so why do they eat bearings?
            Originally posted by SoSideways
            I don't care what color they are as long as they are LONG AND HARD.
            '04 G35 Sedan 6MT- The DD
            '96 240SX- The Track Toy

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            • #36
              I wasn't aware they ate bearings...I've only lost bearings on oiling issues...
              I am SKULLWORKS

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              • #37
                at higher RPM, they have a tendency to eat rod & main bearings. this is even on a Rebello-built engine & dry sump. the KA-E seems much worse than the DE in that regard, so I wonder if it's a block/crank stiffness issue, as well as the 1/2 counterweight.
                Originally posted by SoSideways
                I don't care what color they are as long as they are LONG AND HARD.
                '04 G35 Sedan 6MT- The DD
                '96 240SX- The Track Toy

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                • #38
                  Originally posted by Tower240sx View Post
                  that's a nice theory...

                  How bout the rod stroke ratio sucks...yeah there we go back in reality

                  The QR is 89X100 with a 143mm rod

                  that's a 1.43:1 rod stroke ratio...that is horrendous
                  Rod/stroke differences don't make an absolutely huge difference in absolute forces the bottom end has to resist. Yes, I've done the calculus.

                  The big stroke gives the most of its problems, but with a more rigid bottom end, they'd probably hold up a little better. They made them light because they're good enough for a stock Sentra or Altima.


                  KAs have low bearing area for the forces involved in the bottom end IMO.
                  '18 Chevrolet Volt - Electric fun hatch for DD duty!


                  DefSport Koni Sleeve and Spring Perch Buy!!!
                  http://www.nissanroadracing.com/showthread.php?t=5902

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                  • #39
                    I didn't say the bottom end had any problems resisting the forces....

                    You said the engine didn't like High RPM, I gave you the root cause, you assumed it had something to do with the forces applied to the bottom end...you claimed to have done calculus, you never thought about the rod angle difference and how it loads the piston against the cylinder wall.

                    This isn't the first engine born with a horrible rod:stroke, motors designed for hi rpm use have higher Rod:Stroke.

                    Do you think people would spend the energy it takes to relocate the wrist pin into the ring pack if a better rod:stroke ratio was 15 mins of calculus away from being a useless myth,,,,yeah I didn't think so either....
                    I am SKULLWORKS

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                    • #40
                      in the 2007 Sentra QR25DE, the SPEC V MODEL ONLY, the crankshaft is an 8 counterweight design, vs the old 4 CW design. The 2007 Spec V only also has a factory redline of 6900-7000 rpms and a connecting rod specific to the Spec V also. The old QRs only have a 6200 rpm redline. The old QRs were for the a lot of models in the Nissan line up, the 2007 Spec V has a lot of cool parts only found in that model.

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                      • #41
                        I figured I could update this now because the custom bits are done. Rods took a little longer than expected. Pistons were done months ago because I get special service from JE













                        86mm SR20 crank next to 100mm stroke QR25 crankshaft




                        SR20 crankshaft in QR25 block. Thrust area needs to be widened up, or thrust washers narrowed, or custom thrust washers. Block (or crankshaft) needs a touch a clearnce work due to forging line on crank causing some rubbing. Snout diameter needs to be reduced to accept timing gears, and the register is 8 bolt vs 6 bolt. JWT has a flywheel for this application.

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                        • #42
                          The 200sx is still at our friends shop. We have to finish the car we are working on before i can do the cage in mine. You know, paying customers first.

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                          • #43
                            mmmm 15x9, ordering these ASAP so I can do suspension mock up and start widening the car. BC Racing is on board for this car as the suspension sponsor. Car is still waiting for us to get some free time so we can put the cage in

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                            • #44
                              6UL is a great wheel. It's impressive how far Emilio has come with them.
                              Between rides...unless you count a WD21...

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                              • #45
                                depending on what has to be done for the rims to clear the coilovers, the car is going to get around 4-5 inches of track width I'm willing to bet I can get a 275/35/15 on the car.

                                low vehicle weight: check

                                low CoG: check

                                good wide tires: check

                                added track width: check

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