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VSS and EGR, what do they do and where do they go?

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  • VSS and EGR, what do they do and where do they go?

    Trying to get everything ready for my switch over and came across information pertaining to these. Wondering what they do and where they go and are they needed?

    Thanks
    Mark

  • #2
    As far as what they are and where they go, i can probly answer that much of your question. EGR stands for exhaust gas recirculation and consists of a valve in the intake manifold and a vaccumn switch to control its operation. I have been told it can be programed out with the ecm chip? The VSS is vehicle speed sensor and is mounted in the transmission or transfer case output housing. It is a fairly complicated system as it uses a DRAC (Digital ratio ?? I think) that converts the signal to something else so the computer can tell how fast the vehicle is going? The drac is calibrated for your diff ratio and tire speed so a swap from a donor will not be a direct swap, then there is the tone ring (may not be correct name) on output shaft of tranny. I would like to make the vss conversion in my 800 for the cruise out of the donor truck myself. To really get the info you need you probly need to give a few more details about the system you are using. Hope I did'nt confuse you any!! Good luck


    Bill let me in on what if anything John "Rough" did to his scout at Gilmer?
    My "Disasterpiece"
    1970 800A 4X4,HFI'd,304,B/W,27,44,3:73,28's.
    The rest are in my 25 year plan!

    My "Ruedh"
    FREE 1972 1110 4x4,V8(?)727,205,44 drum/60/3.54's,small cheap tires.
    LOOOOADS-O-RUST!! Donor body located. Not!! JY owner played the "crusher value" card. : angry:
    NON-working rear window. Need info!!!

    www.northtexasbinders.com

    Comment


    • #3
      Ok this is my second try at answering this. Computer dumped before I could hit the send button......

      The egr is only needed for emissions. If you have to pass emissions then you need to see if you can even run FI. Some states require a visual insp and if it is not the same as the factory then they wont pass it. Does it make sense???? No, but it is the rule. I think they started in 76 since my 75 does not have one but the 76 does.
      Normally it is hooked up to a thermal switch on the intake then to a vacuum source. With FI, the computer controls it through a solenoid connected to vacuum. It opens the egr based on speed, temp, and map(manifold absolute pressure) settings.

      So how do you get a spd input? VSS(vehicle spd sensor)
      GM used a lot of different types thru out the years like Binderman said. I think the one you need is a 2 pulse magnetic pick up. Try the links on the main FI page. Jags that run.




      1. The two-pulse square unit for all passenger car TBI installations, all computer controlled carbureted engines, and 1985–1989 TPI engines. 7/8-18 thread, .104" square drive.

      Some aftermarket digital speedometers also use them. It just goes inline on the speedometer cable.

      Right now I don't run either. I do plan on running a VSS later but for different reasons.
      HTH

      PS. Heard he laid it on it's side and the light on the windshield frame twisted and smashed the windshield. No pics yet!
      Last edited by Bill usn-1; 04-29-2003, 06:40 AM.
      Bill USN-1

      COMMITED TO TEACHING PEOPLE THE "PROPER" WAY TO EFI
      HAMILTON FUEL INJECTION
      May be the answer to all your fuel injection needs!
      Learn to do it right.

      Comment


      • #4
        Bill
        Thanks for the pic of the cable operated vss, as that would be a lot easier than try to drill and tap the transfer case to accept the sensor and then trying to get the tone ring installed some how. I remenber those now as I looked at a Dakota digital dash one time for a 72 chevy. Two or more heads are better than one for sure.

        I finally got John to fess up and he said exactly what you did. Is he trying for the ugly truck award this year. Contest is pretty close at this time I think , LOL. Were you his spotter this time. Paybacks are @#[email protected] Did you not go?
        My "Disasterpiece"
        1970 800A 4X4,HFI'd,304,B/W,27,44,3:73,28's.
        The rest are in my 25 year plan!

        My "Ruedh"
        FREE 1972 1110 4x4,V8(?)727,205,44 drum/60/3.54's,small cheap tires.
        LOOOOADS-O-RUST!! Donor body located. Not!! JY owner played the "crusher value" card. : angry:
        NON-working rear window. Need info!!!

        www.northtexasbinders.com

        Comment


        • #5
          I just got back from another Navy trip monday afternoon, so I missed all the action. I'll have to find out who the spotter was!!!!

          He has a ways to go to catch me on the ugly contest.
          Bill USN-1

          COMMITED TO TEACHING PEOPLE THE "PROPER" WAY TO EFI
          HAMILTON FUEL INJECTION
          May be the answer to all your fuel injection needs!
          Learn to do it right.

          Comment


          • #6
            Fast responses

            Thanks for the quick responses guys, It sounds like I don't need either one. I don't have to worry about emmisions here 74-older dont have to do it. And I will be using the mechanical speedo, so unless the ECM really needs the input for something I can pass on that too.

            So pretty much can turn those off on the chip, now I just need to figure out where to mount the knock sensor. I saw a post awhile back that had pics but I cant seem to find it.

            Thanks
            Mark

            Comment


            • #7
              use the block drain right in front of the starter. It is 1/4 pipe and screws right in.
              Bill USN-1

              COMMITED TO TEACHING PEOPLE THE "PROPER" WAY TO EFI
              HAMILTON FUEL INJECTION
              May be the answer to all your fuel injection needs!
              Learn to do it right.

              Comment


              • #8
                Ok, what about the MAP sensor?

                OK guys is the MAP sensor needed in this application?

                Thanks
                Mark

                Comment


                • #9
                  absotudally!!!!!!!
                  In other words Yes.
                  It is one of the main inputs to the computer.
                  Bill USN-1

                  COMMITED TO TEACHING PEOPLE THE "PROPER" WAY TO EFI
                  HAMILTON FUEL INJECTION
                  May be the answer to all your fuel injection needs!
                  Learn to do it right.

                  Comment


                  • #10
                    thanks, dumb question

                    Ok, thanks Bill you save me again, now this is a dumb question but i am trying to sort through parts. So I just need to mount it and run a vacume line to it. Where would you sugest I use as the source?

                    thanks
                    Mark

                    Comment


                    • #11
                      Go with the factory port. It is the one on the back of the TB. Right below the regulator.
                      Try to avoid a manifold vacuum. They are not always a constant source. They may be from just 1 cylinder.


                      Bill USN-1

                      COMMITED TO TEACHING PEOPLE THE "PROPER" WAY TO EFI
                      HAMILTON FUEL INJECTION
                      May be the answer to all your fuel injection needs!
                      Learn to do it right.

                      Comment

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