Announcement

Collapse
No announcement yet.

s15 sr20det

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • s15 sr20det

    Considering rebuilding my 240sx yet again... s15 motor is the same price as s14 motors at my importer. A few questions to start:

    1. http://forums.nicoclub.com/s14-vs-s1...e-t406481.html says s15 motor will work with an s14 wiring harness. I have a wiring specialties s14-into-s14 harness that I paid pretty penny for and would love not to cut it up. Can anyone confirm that I won't need a new wire harness?

    2. Looking at 5 speed vs 6 speed gear ratios, 6 speed fits another gear between 1-4 but 6th on the 6 speed is almost the same as the 5th on a 5 speed. I did not get the impression that 1-4 were particularly far apart, is 6 speed much better for road racing given the diff/final drive stays the same?

    3. http://www.automotiveforums.com/t448..._sr20det_.html says 6 speed is much weaker than 5 speed. Is that weaker at 250 hp or 400 hp? Any personal experiences with 6 speeds failing?

    Should I keep the 5 speed and try to sell the 6 speed? Any market for the 6 speeds?

    4. One issue I had with my s14 sr20det was I did not get OEM boost control parts, and therefore was not getting full OEM hp. Is the same issue likely to happen with the s15 sr20det?

    Not a fan of rebuilding the car for the fourth time but the last explosion was my fault and the car is sitting there staring at me every day... at least it would drive.
    winhpde.com

  • #2
    Lots of questions...

    As far as I know - MOST connectors will be the same S14 to S15. One big difference is in coilpack wiring. The S15 coilpack subharness plugs into the S13/S14 harnesses (once you bypass the igniter). USE THE S15 COILPACK SUBHARNESS. The power and grounds are switched on the smart coils vs. the earlier dumb coils. Alternatively you can repin every coilpack connector. I think most the other stuff should plug up except maybe the TPS? I think the S14 manual TPS was the same 2 connector as the auto S13 etc. My S15 SR had the 4 pin single connector.

    2. 6 speed is pretty weak by all accounts, if you're making over 300-350 rwhp, I'd skip it.

    3. 6 speed = weak

    4. Run a boost controller.
    '18 Chevrolet Volt - Electric fun hatch for DD duty!


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

    Comment


    • #3
      on the 6 spd, Nissan had to cram 6 gears into the same space they previously had 5. so every gear is narrower by about 20%. keep that in mind when you're considering power handling capability.

      At 250whp, it's probably not going to be a huge problem. at 350whp, it's going to be a problem.
      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

      Comment


      • #4
        The case is a little larger by outside appearances, but I do think gear width is less, and I'm not sure on the center to center shaft distances. I doubt it's larger than the 5 speed based on external size.
        '18 Chevrolet Volt - Electric fun hatch for DD duty!


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

        Comment


        • #5
          Originally posted by Matt93SE View Post
          on the 6 spd, Aisin had to cram 6 gears into the same space they previously had 5. so every gear is narrower by about 20%. keep that in mind when you're considering power handling capability.

          At 250whp, it's probably not going to be a huge problem. at 350whp, it's going to be a problem.
          Fixed,

          Same basic format transmission in the RX-8 S2000 and The 86Twins if you believe the spec sheets.

          I'm sure there have been lessons learned and applied so yes this is the first application for the transmission family and is not as strong, but they are a handy transmission if treated properly, i would never pretend to be able to do such a thing though...
          I am SKULLWORKS

          Comment


          • #6
            The 6 speed can break even at stock power, with some abuse and sticky tyres. I'd recommend staying away from it. RB25 gearbox is a little bit better than the CA/SR 5 speed. If you want a nice 6spd gearbox, go z33. Very smooth, closer ratios than the 5 speed, and strong as hell if you don't buy the early versions. There are conversion plates available too, so not that much fabrication required, a bit of grinding here and there, and a bracket for the shifter (and a custom prop shaft). Clutch and flywheel stay the same, no machining on the input shaft either.

            Comment


            • #7
              One other thing, S15 SR 6 speed is about 115-120 lbs, which is only about 10 lbs lighter than a Z33 trans according to internet lore. I think the fully enclosed tailshaft section adds the weight vs. the external shifter of a Z33 trans.
              '18 Chevrolet Volt - Electric fun hatch for DD duty!


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

              Comment


              • #8
                Doing more reading... it looks like the s15 clutch setup with the dual-mass flywheel is an expensive/rare contraption, and the only advantage s15 offers is better oiling. More boost is dependent on ECU and I'm guessing I won't get this without OEM boost hardware.

                Bottom line - s14 engine seems to be the way to go, plus I can use existing parts as spares.
                winhpde.com

                Comment


                • #9
                  Well get rid of the dual mass flywheel and go for an alu/steel one that weighs less.
                  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

                  Comment


                  • #10
                    Originally posted by minspd View Post
                    Doing more reading... it looks like the s15 clutch setup with the dual-mass flywheel is an expensive/rare contraption, and the only advantage s15 offers is better oiling. More boost is dependent on ECU and I'm guessing I won't get this without OEM boost hardware.

                    Bottom line - s14 engine seems to be the way to go, plus I can use existing parts as spares.
                    S15 clutch/flywheel setups are all over the place. Maybe not a TON of options, but there are options.

                    Why are you stuck on using the OEM boost hardware? That stuff is junk - use a proper boost controller/solenoid.

                    You should definitely sell me your S14 SR transmission though...
                    '18 Chevrolet Volt - Electric fun hatch for DD duty!


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

                    Comment

                    Working...
                    X