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Where to put the missing tooth?

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  • Where to put the missing tooth?

    So where do I have to put the missing tooth relative to TDC? Put the first tooth at TDC? Do I line it up with the TDC? With the megasquirt does it really matter?

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    Last edited by TheSilverBuick; August 11th, 2011, 02:13 PM.
    Escaped on a technicality.

  • #2

    Re: Where to put the missing tooth?

    I always tell my kids to put them under the pillow......

    Sorry, I had to do it!
    Of all the paths you take in life - make sure a few of them are dirt.

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    • #3

      Re: Where to put the missing tooth?

      =P


      As I'm thinking more about this, I'm guessing it's relevant to where I place the sensor?
      Last edited by TheSilverBuick; April 28th, 2011, 07:32 AM.
      Escaped on a technicality.

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      • #4

        Re: Where to put the missing tooth?

        Starting with the engine at TDC and then determining ideal placement of the sensor, IIRC the missing tooth was either seven or eight teeth BTDC, that is the missing tooth was already past the sensor in the direction of rotation when the engine is at TDC. I will have to look back at my notes to be sure. This was partly the result of the conversion from the locked out MSD distributor I was using before the conversion to the EDIS wheel and the wasted spark set-up. You can put it about anywhere but this made the trigger angle calculation easier and again IIRC there was a 'latency' issue that gave us a better shot at the 'phasing' based on the available settings in Megasquirt. Scott knows this stuff backwards whereas I forget my name at the end of most days.
        Drag Week 2006 & 2012 - Winner Street Race Big Block Naturally Aspirated - R/U 2007 Broke DW '05 and Drag Weekend '15 Coincidence?

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        • #5

          Re: Where to put the missing tooth?

          My sensor is likely going to be five or six teeth width after TDC, relative to the timing mark on the harmonic balancer being on the zero of the timing tab.
          Last edited by TheSilverBuick; April 28th, 2011, 12:25 PM.
          Escaped on a technicality.

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          • #6

            Re: Where to put the missing tooth?

            Just saw this post, sorry for delay:

            You want the missing tooth to be "under the CKP sensor" when the engine is 60-90 degrees before top dead center. This is so the computer gets the "heads up" signal (missing tooth) far earlier than any actual timing you want to run.

            Randal, it's just like the Trigger Angle - you want it to be either greater than your max ignition advance (mid 40s?) or LESS than your minimum ignition advance, but there's an advantage to placing it as I describe above: the computer picks up on the signal quicker and starts adding fuel and timing during cranking a little quicker. I.e. the computer syncs up faster during cranking.

            Bill's description is another way of looking at it, if the engine is at TDC then you want the crank sensor to be 5-9 teeth PAST the missing tooth.

            Of course, it's not critical to be dead accurate, you make your final adjustments in the computer - by adjusting the Trigger Angle (or equivalent) until the timing light shows the exact same ignition timing as the Megasquirt says it's running.
            www.realtuners.com - catch the RealTuners Radio Podcast on Youtube, Facebook, iTunes, and anywhere else podcasts are distributed!

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            • #7

              Re: Where to put the missing tooth?

              Thanks. Bill's method is a little easier to figure out because I know where TDC is. I could probably ballpark 60-90 degrees though.

              I'm visualizing TDC falling about 12 teeth counter clockwise from the missing tooth for the 90 degrees, and probably around the 9 teeth for the 60 degrees. Ok, I think I could figure this out. I may be experimenting with mounting and such this weekend. Pending the results of that I'll be looking for a sensor.

              One (major) issue I may run into is, I think the ring has a smaller diameter than my pulley, but where I want to mount it on the pulley is flaired, so the sensor potentially will be right next to the pulley to a ~1/4" away to get the right clearance between the sensor and the teeth. I bought a second crankpulley so I can experiment some without completely downing the car. May have to find a larger diameter toothed ring.
              Escaped on a technicality.

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              • #8

                Re: Where to put the missing tooth?

                I don't recall how that worked with my Q-jet
                67 Fairlane 434 ci/464 hp/488 tq-RIP
                05 GTO torrid red/red gut, LS2, Auto (my knees hurt!)

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                • #9

                  Re: Where to put the missing tooth?

                  Has your Ford been pushed lately
                  Escaped on a technicality.

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                  • #10

                    Re: Where to put the missing tooth?

                    Has your Ford been pushed lately
                    sigghhh-no not even pushed lately-returned it to the home garage in feb so we could actually work on cars that pay money, been busy ever since. HOWEVER when it is pushed, it is pushed with a carb on that intake manifold!!
                    67 Fairlane 434 ci/464 hp/488 tq-RIP
                    05 GTO torrid red/red gut, LS2, Auto (my knees hurt!)

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                    • #11

                      Re: Where to put the missing tooth?

                      sigghhh-no not even pushed lately-returned it to the home garage in feb so we could actually work on cars that pay money, been busy ever since. HOWEVER when it is pushed, it is pushed with a carb on that intake manifold!!

                      Cause that's so much better =P
                      Escaped on a technicality.

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                      • #12

                        Re: Where to put the missing tooth?

                        Cause that's so much better =P
                        no no-you misunderstand-BETTER would be if you could hurry up and make this stuff work on your FE so once it is all dialed in you could come make it work on my FE!!
                        67 Fairlane 434 ci/464 hp/488 tq-RIP
                        05 GTO torrid red/red gut, LS2, Auto (my knees hurt!)

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                        • #13

                          Re: Where to put the missing tooth?

                          The postal service tracking says my spare pulleys were in Vegas at 12:30am this morning, hopefully they caught a truck ride up here right after that. Mail delivery is usually around 10am... Hopefully I see it today!
                          Escaped on a technicality.

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                          • #14

                            Re: Where to put the missing tooth?

                            So where do I have to put the missing tooth relative to TDC? Put the first tooth at TDC? Do I line it up with the TDC? With the megasquirt does it really matter?

                            So a few months later I just picked this up from a local machine shop. For $25 they trued up the inside of the crank pulley so it was flat, mostly scraped the paint off of it, and opened up the trigger wheel. The next question becomes, will the inside pulley and/or the balancer interfere with the trigger wheel signal since it's so close?





                            I have some wiggle room between the balancer and the inside pulley. Once I get the balancer back I'll probably see about setting it halfway between the two.


                            It slides on to the pulley real nicely, I should be able to pin or tack weld them together once I figure out where I want the missing tooth to be located. I need my balancer back from the machine shop to set this up.
                            Escaped on a technicality.

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                            • #15

                              Re: Where to put the missing tooth?

                              That is a great start as you can optimize the sensor location and then rotate the wheel to match based on all the conflicting (not really) advice written above.

                              Where did you source your escort ring? I have to set up another wheel as I'm changing dampeners.
                              Drag Week 2006 & 2012 - Winner Street Race Big Block Naturally Aspirated - R/U 2007 Broke DW '05 and Drag Weekend '15 Coincidence?

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