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Drawbacks to removing speed limiter on S14?

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  • Drawbacks to removing speed limiter on S14?

    So I've been poking around on the various forums about removing the speed limiter since I hit it at the end of the front straight at TWS in clean air.

    This weekend I will likely be running quite a bit faster since we'll be running in a draft, and I'd like to remove the speed limiter before the event.

    I've read over various threads similar to this: http://www.240sx.org/faq/articles/spdgov.htm and several of them mention the ECU goes into a safe mode of sorts...
    I don't want to mess with adding switches and this and that- I just want the damn thing turned off.
    Has anyone had any issues with this, or can recommend a different fix for the stock ECU? (and I don't have time or money to buy a new ECU... unless someone wants to overnight me an SE ECU without the limiter on their dime!)

    Thoughts?
    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

  • #2
    Disabled the speed cut on a few S13s and R32s without issues... The only thing I've found is you can't have HICAS as the HICAS is speed sensitive and if the ECU doesn't know the speed anymore it tends to toe the rear wheels all over the place when it feels like it. :P

    Never done it on an S14 ECU though sorry.

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    • #3
      Don't do it! Your car will fall apart!

      Sorry... someone needs to say it.

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      • #4
        Just do a free test for this weekend. Disconnect the 5th gear sensor and vehicle speed sensor from the tranny. Your speedo won't work but who cares, since you can tell from the tach (115mph on stock tranny/tire is about 5k rpm in 5th). If the ECU doesn't like it, hook the harness back up and live with the limiter for now. Then let us know how it goes.

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        • #5
          put a switch on you speed sensor. So you can turn it off at the track.

          Other wise get a daughterboard and remove it on the tune.

          been there done that. 220 with my 180kph limited car at Mosport.

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          • #6
            The issue is if I hit the speed limiter in the middle of the straight with a bunch of rookies 6" behind me. that would be ugly. very ugly.

            I'm not installing switches and other bull**** on a track car, and I'm not replacing the ECU (yet). When I do, it'll be a full ECU not a daughterboard.

            I want to know if it works permanently by removing the 5th gear sensor or cutting the speed sense wire and NOT go into a limp mode or any of the other horror stories. that's all. I can't risk this thing going into a limp mode and killing throttle at 120mph with someone 6" behind me.

            I don't have time to fiddle with it and check it before the event, so it's do it or not deal (I'm not about to drive the car on the street looking the way it does- especially doing 120 on public roads).
            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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            • #7
              Cut the speed wire by the puter on S13's all the time without incident. The signal goes to the speedo first so it still works. No experience on S14's and don't know if it is the same but you would sure think it would be.

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              • #8
                Yes you cut it between the cluster and the ECU. That way your speedo still works.

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                • #9
                  The way I understood it is that it uses the 5th gear switch on the tranny and then caps RPM at ~5000 or so only when in 5th gear. it says nothing about speed in those descriptions.

                  Other end of that is the articles mention a 4th gear sensor/switch as well, which does not show up in the S14 FSM. I'm also curious as to the difference between an OBD-I and OBD-II car. there's possibly some stuff there.

                  Since that's all internet conjecture, I'm not inclined to believe a whole helluvalot of it. (Thus my asking here. You guys are actually intelligent. )

                  I *like* having my speedo but it's not a huge issue. I use it to monitor corner-exit speeds but otherwise don't need it.

                  If I can cut the speed sense wire to the ECU and the thing is happy, then I'm fine. I just can't risk the ECU going into a limp mode with someone right behind me.
                  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
                    The only sensor I have plugged into my transmission is my speed sensor. I'm running an E5 ecu on my Redtop SR20. No speed limiter issues at all. Durdan Perfab did the harness for the swap, so perhaps he cut the cable on the ECU side.

                    When on the track, I hit fuel cut @ 120 mph in 4th gear ~5000-6000 rpms. I think the ecu may of been detecting knock, I goes past 120 easily in 5th.

                    I'm hoping the E5 ecu will help with that fuel cut issue in 4th.

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                    • #11
                      Originally posted by WorkInProgressK View Post
                      put a switch on you speed sensor. So you can turn it off at the track.

                      Other wise get a daughterboard and remove it on the tune.
                      As much as Matt didn't like these, my response would've been the same.

                      Matt: WTH's wrong with a switch?

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                      • #12
                        s14 KA doesn't need a 4th gear sensor b/c 115mph in 4th is past the 6.5k redline, so the rev limiter takes care of that.

                        The ECU has a code 14 "VSS circuit is open", so I guess disconnecting the VSS wire by the tranny will throw a code. But if s13 doesn't throw code for cutting the ECU wire, then s14 shouldn't.

                        In any case, play it safe by putting a sign on the rear bumper telling tailgaters to stay away.

                        Comment


                        • #13
                          Originally posted by 2Fass240us View Post
                          As much as Matt didn't like these, my response would've been the same.

                          Matt: WTH's wrong with a switch?
                          Because the only place I drive the car is on track. (Ya know, the roll cage, numbers, and SCCA stickers kinda keep me from cruising to Sonic in it on Friday nights.. )

                          Why should I install a switch to disable something for the 100 feet I drive it from the trailer to the garage? i.e. it will be switched off 99.99% of the time I'm driving the car. If I have to turn it on and off to make the car driveable, then it's not acceptable.
                          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


                          • #14
                            Originally posted by hai1206vn View Post
                            The ECU has a code 14 "VSS circuit is open", so I guess disconnecting the VSS wire by the tranny will throw a code. But if s13 doesn't throw code for cutting the ECU wire, then s14 shouldn't.
                            In any case, play it safe by putting a sign on the rear bumper telling tailgaters to stay away.
                            Actually not a bad idea. might put a sticker on the back that says "120mph governor" or something.
                            But I'm hoping to find a reasonable workaround so that I don't have this issue. There are two tracks in the area where I'll be over 120 on the straights, and if/when I build a faster engine or change rear diff ratio, it will be even more of an issue.

                            A couple other thoughts were (if it had one), split the 4th gear switch to feed into the 5th gear as well so you have a higher rev limit vs. none at all. since that's near redline in 4th gear and you'll never reach redline in 5th gear, it should work okay.

                            also might stick a frequency halver on the VSS signal so that it tells the ECU I'm only going half as fast as I actually am. I'm not paying $100 for one, but I can build one with a couple flip-flops and a 5v regulator. maybe I'll do that later, but I dont' have time to experiment right now. I need a "do this and it'll work" fix.

                            so do I need to cut the VSS wire AND unplug the 5th gear sensor, or just either/or? I've heard both sides of the fence on that one as well.
                            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


                            • #15
                              Originally posted by Matt93SE View Post
                              split the 4th gear switch to feed into the 5th gear
                              s14 doesn't have 4th gear wiring. This would only work with s13 ECU (even with s13 tranny, s14 ECU would think it's 5th gear signal).

                              I know for sure the 5th gear switch does cut fuel: on the road, in 5th, clutch in and rev, it'll bounce at 5k rpm (on s13, 4th gear, will bounce at 6.6k, before the 6.9k redline).

                              So unhook 5th switch, leave VSS wires alone, then you can tell if the limiter uses VSS input at all. With a rear bumper sign to warn fellows.

                              I've reached the limiter on the highway a few years back in some deserted states along my CA-NY drive, in a bone stock s13 with 195 $h!t tires and 300lb of luggage; never gonna do it again.
                              Last edited by hai1206vn; 07-08-2010, 12:08 PM.

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