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    Motec RB knocking issue

    I was road tuning my tarmac rally car last night and can't work out why it's knocking at peak torque.
    The engine is stock except for 9:1 CP's, Hypergear highflow, 740cc injectors, Blitz front mount and splitfires. As the engine reaches peak torque approx 3700 rpm it starts to knock, so I keep pulling timing out at that point in the map. The mixture is fine pretty solid around .81 lambda, but I'm down to 2 degrees timing in the middle of the map to stop it rattling and it's still not great.
    The CRIP and timing are fine at idle, I can't really fault the system when it's idling and I can't believe 2 degrees is right.
    My bet is on a dodgy cam angle sensor, any other thoughts? The CAS is wired directly to the Motec in a shielded cable, not the factory wiring. Is there some sort of weird setup in the factory ignition wiring that can alter the timing (unlikely).
    I'll post a picture of the timing map when get to the office later on.

    #2
    is the CAS new?

    set the whole timing map to 10 put a timing light on it and give it and give it a good rev, is it stable?
    Originally posted by ALLMTR
    the theory is the fuel pump is one of the only things that can fuck out on a diesel

    Comment


      #3
      i dont give a fuck what any ecu manufacturer says the nissan CAS is a piece of shit, there WILL be timing variances of up to 5deg, most ecu manufactures know this, but some still persist to talk shit and tell people lies..

      best bet is to fit a 12 tooth crank trigger and be done with it
      Edit
      no saying motec are telling lies etc just stating in general no point anything at motec
      im a cunt
      and apparently i dont know shit...

      Comment


        #4
        How are you determining that it is knocking? is it audible?

        How much boost are you running at that point?

        What sort of ignition system is it?

        What fuel are your running?

        What sort of RB engine is it?

        -Jamie

        Comment


          #5
          Hi Jamie, it's an rb20 powerhouse. It's a factory ignition system with splitfire coils, running on 98 with 15psi boost.
          The knock is audible when driving.

          Comment


            #6
            Ok, here's a screen shot of the timing map.
            Good ideal re the static timing map, I'll have a look at that.



            In the meantime I'll also have a look at the 24t trigger discs and see if I can find a local distributor.
            One of my other cars has an Autronic and after endless cam angle sensor issues I put a GT101 on the crank and have never looked back. I would like a 'nice' solution like this from Ross, but it's going to be pretty spendy for an RB20.
            http://www.rawbrokerage.com/ross-tuf...b20-rb25-rb26/

            Comment


              #7
              thats pretty low for 14psi... have you put a timing light on it when ramping it up to check it stays matched up? what is the trigger settings ?
              im a cunt
              and apparently i dont know shit...

              Comment


                #8
                That's what I thought.
                The trigger was setup by a Motec "expert" so I haven't changed it. It's setup as Ref/Sync mode 10 (360 optical).
                I haven't checked the timing while ramping, I'll have to head back to the dyno. At this point I'll swap the sensor over and change the map to a single value and see if it holds steady during a free rev, but at the end of the day I will probably have to either change the disc or put a crank trigger on it.
                Fucking RB's, everything is shit on them.

                Comment


                  #9
                  Has it run properly ever? Cam timing changed recently?

                  Comment


                    #10
                    I'll have a look at the cam timing tomorrow it could be wrong but I don't think so.
                    I've never been happy with the Motec tune, it's always had issues but that has more to do with taking it to fuck wits than anything else. I'll just tune it myself, it'll take longer because I'm not great with the Motec software but I'll get there in the end.
                    I might have a look at making a crank trigger setup on the weekend if I have any mojo

                    Comment


                      #11
                      Pretty retarded to say the nissan sensors are bad. In theory and practice they are the best oem sensor available. They older first generation items can fail though but not lead to this problem.
                      Jason Broadhurst

                      Someone once asked me if they could use my mower. I said "sure, so long as it doesn't leave my yard"

                      Comment


                        #12
                        Originally posted by Jason Broadhurst View Post
                        Pretty retarded to say the nissan sensors are bad. In theory and practice they are the best oem sensor available. They older first generation items can fail though but not lead to this problem.
                        So you have zero experience with them hey???
                        im a cunt
                        and apparently i dont know shit...

                        Comment


                          #13
                          Originally posted by Komdotkom View Post
                          I'll have a look at the cam timing tomorrow it could be wrong but I don't think so.
                          I've never been happy with the Motec tune, it's always had issues but that has more to do with taking it to fuck wits than anything else. I'll just tune it myself, it'll take longer because I'm not great with the Motec software but I'll get there in the end.
                          I might have a look at making a crank trigger setup on the weekend if I have any mojo
                          Email me the map and I'll have a look if you want there are a few things that can cause issues like this like choosing rising edge not falling edge
                          im a cunt
                          and apparently i dont know shit...

                          Comment


                            #14
                            Put a new cas on it and its heaps better, still can't get more than 8 degrees timing into it at peak torque but it's much better than previously.
                            I checked the stability during free rev with the timing locked on 10 and it wanders about 3 degrees. I'll make a crank trigger in the next few weeks I think.
                            Thanks for the input gents, much appreciated.

                            Comment


                              #15
                              Originally posted by Komdotkom View Post
                              Put a new cas on it and its heaps better, still can't get more than 8 degrees timing into it at peak torque but it's much better than previously.
                              I checked the stability during free rev with the timing locked on 10 and it wanders about 3 degrees. I'll make a crank trigger in the next few weeks I think.
                              Thanks for the input gents, much appreciated.
                              FWIW we did the same check on my 3SGE in the Fraser and the timing was rock-solid. So yeah it looks like some kind of sensing problem.

                              Comment

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