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  • Map sensor

    I have heard that with the SCT tune we will be able to support use of 2 and 3 bar MAP instead of the stock 1 bar. Is this going to ge true and if so how is this accomplished or what will be needed to change over?

    Troy

  • #2
    Yes, I am writing a 2 bar program as we speak with 55lb injectors.
    Marty Fletcher
    SCT DCX Truck Tuner
    KRC Performance, Florida
    www.krcperformance.com
    (321) 635-8866

    Comment


    • #3
      So is it just a setting in the software then? Just plus new map sensor in and tune or do you have to adapt anything?

      Troy

      Comment


      • #4
        Yes it can be done, We have done it on a bunch of blown vipers and viper trucks. What exactly needs to be changed in the calibration is application dependent.

        But the short answer is yes.
        Take Care,
        Mr. Torrie R. McPhail
        www.FastPartsNetwork.com
        www.UnleashedTuning.com
        Ford/GM/Dodge/Chrysler/Jeep SCT Custom Calibrator
        2005 Black Twin hairdryer Ford GT 1105rwhp / 954rwtq
        2010 Roush Hammer 560rwhp / 522rwtq

        Comment


        • #5
          The JTEC was never designed for boosted applications. Nor does it have a mass airflow sensor that can be rescaled to accommodate boost, because it uses a map sensor. In addition, JTEC ecu’s use a relatively complex lookup routine that estimate barometric pressure. This routine not only looks at the map sensor at key on, but under other driving conditions, such as deceleration. This barometric compensation can have a huge influence on all of the fueling calculations. Some companies, such as Split Second and Perfect Power, have products which are known as map calibrators. Basically, they are software mappable two bar map sensors. In theory, if you were two put a two bar map sensor on your JTEC controlled vehicle right now, and install new fuel injectors that are roughly double the flow rating of your current fuel injectors, you could start and drive your vehicle, although it would no doubt not run very well. The reason you could start and drive the car, is that the fuel mapping is fairly linear, and because the two bar map sensor is only giving about half of the load input to the ecu, you are only commanding about half of the pulse width. Unfortunately, it has been my experience that when you do this, even with an adjustable map calibrator, the drivability is never as good as stock, there are always compromises. In fact, I have never seen a car run exceptionally well, whether I have tuned it or someone else that has used a map calibrator. This is because there are so many tables in the factory ecu, not just the main fuel and timing lookup tables, which use engine load for their calculations.

          There are several other problems that I can see arising from trying to tune with a two bar map sensor without a map calibrator. First, the JTEC only has nine breakpoints of resolution in the main fuel table. Most map calibrators give you a much bigger tuning window than that. This means if you were to leave the map scaling relatively linear, you would only have four to five break points in the non boost and boosted areas of the map. Second, you usually set the area in the map calibrator software load map, at key on, engine off, to approximate what the factory pcm would see so that the JTEC can calculate baro. Without this trickery, your JTEC would think that you are somewhere close to 8000 feet. Third, there are many (thousands) other tables and constants in the ecu, many of which may not be adjustable, that would not be scaled correctly, that would lead to drivability issues, similar to those found when using a map calibrator.

          I’m not trying to discourage anyone here, just trying to give a different perspective, and I don’t want people who aren’t especially familiar with factory ecu tuning to think this is an easy task. Most, if not all, factory speed density based computer systems, that have been properly tuned for boost, have had modifications to the actual operating system and have had routines added or modified, as necessary to compensate for these different conditions. I would not doubt if this will be the case for the JTEC.

          - Chris

          www.dcperformance.com

          Comment


          • #6
            Thanks Chris, I did open the normalizers scaling to get more resolution. I am really not concerned with a 2-2.5 bar program, 3/4/5 I would not even want to try. We have been using factory scaled map voltages with the Split Sec, SMT6 and Unichips with great drivability for a long time. I have no doubt all of us can nail it in the ecu tables the same way. Especially with WOT multipliers for boosted areas of the chart.

            I agree, it will not be easy and I am going to wear out a ignition switch!
            Marty Fletcher
            SCT DCX Truck Tuner
            KRC Performance, Florida
            www.krcperformance.com
            (321) 635-8866

            Comment


            • #7
              Knowledge is the key here.
              Take Care,
              Mr. Torrie R. McPhail
              www.FastPartsNetwork.com
              www.UnleashedTuning.com
              Ford/GM/Dodge/Chrysler/Jeep SCT Custom Calibrator
              2005 Black Twin hairdryer Ford GT 1105rwhp / 954rwtq
              2010 Roush Hammer 560rwhp / 522rwtq

              Comment


              • #8
                Originally posted by tmcphail
                Knowledge is the key here.
                tmcphail, what do you mean by this statement ? I don’t know you personally, but as far as I can tell, you don’t have much experience tuning the factory engine controller on these vehicles, as the SCT software has only been out for about a month. As I’m sure you will agree, it takes time to master anything, especially something as complex as a factory engine management system. I have been tuning JTEC engine controllers for over three years, and have been tuning Vipers and other DCX vehicles with alternative means for over seven, and even though “knowledge is key”, I won’t hesitate to say that I’m still learning every time I tune a vehicle.

                I might be misunderstanding something, have you actually done complete two bar calibrations with the JTEC or are you saying that have tuned boosted vehicles? If you have done some two bar calibrations, maybe you can share some information with us?

                Comment


                • #9
                  My simple point was stating the fact that the more you collectively know / understand about recalibration the more effective you can be on all levels.
                  Knowledge is absolutely key in making different combinations work correctly together. I bought my 05 Viper in February of that year and have used it for R&D with various forms of Engine management since I purchased it. I didn't just start working with this platform a month ago.

                  And you are correct; you and I do not at all know each other at all.

                  "I might be misunderstanding something, have you actually done complete two bar calibrations with the JTEC or are you saying that have tuned boosted vehicles?"

                  Both.
                  Take Care,
                  Mr. Torrie R. McPhail
                  www.FastPartsNetwork.com
                  www.UnleashedTuning.com
                  Ford/GM/Dodge/Chrysler/Jeep SCT Custom Calibrator
                  2005 Black Twin hairdryer Ford GT 1105rwhp / 954rwtq
                  2010 Roush Hammer 560rwhp / 522rwtq

                  Comment


                  • #10
                    So can you explain how the tuning is with the 2 bar map sensor then? I hate to spend 1k so I can remove some of my bandaids and mail order flashes only to find out I will still need to keep a bandaid cause of the MAP

                    Troy

                    Comment


                    • #11
                      Kan't we settle this over a pint????


                      I started the 2 bar map program today in the factory Ram 2002 controller.
                      I used the ford 39lbrs,(50psi rail pressure) MSD 2 bar 23121, wired in the MAP signal so I can switch back and forth between the 1 bar and 2 bar for R&D.

                      I remapped the spark tables for 16 vacuum in my case, since I don't have a turbo hanging on the truck. I had to pull alot of fuel out in the WOT tables, part throttle trims are at -10% currently. I had to set the global Fuel multiplier back to 1. Basically I am working on nailing drivability before boost comes on with the resolution I have. But it's up and running.

                      Later I will re-map for the SRT4 injector.


                      EDIT I stand corrected, I have a 3 bar map in there running.
                      Last edited by KRC Tech; 09-26-2007, 01:38 PM.
                      Marty Fletcher
                      SCT DCX Truck Tuner
                      KRC Performance, Florida
                      www.krcperformance.com
                      (321) 635-8866

                      Comment


                      • #12
                        Originally posted by Aves
                        So can you explain how the tuning is with the 2 bar map sensor then? I hate to spend 1k so I can remove some of my bandaids and mail order flashes only to find out I will still need to keep a bandaid cause of the MAP

                        Troy
                        Troy, I installed 39lb injectors, (45-46 flow) and the MSD 2 bar map. I recalibrated the spark tables and fuel tables for idle and part throttle cruise easily. WOT is the easiest part, drivability takes the longest in my opinion. Very nice compared to running aux injectors or FMU's. Part throttle boost will be seamless.
                        Marty Fletcher
                        SCT DCX Truck Tuner
                        KRC Performance, Florida
                        www.krcperformance.com
                        (321) 635-8866

                        Comment


                        • #13
                          Originally posted by KRC Tech
                          Troy, I installed 39lb injectors, (45-46 flow) and the MSD 2 bar map. I recalibrated the spark tables and fuel tables for idle and part throttle cruise easily. WOT is the easiest part, drivability takes the longest in my opinion. Very nice compared to running aux injectors or FMU's. Part throttle boost will be seamless.
                          Quite true the center of the curve is the most time involved. The top and bottom are extremely easy to solve.
                          Take Care,
                          Mr. Torrie R. McPhail
                          www.FastPartsNetwork.com
                          www.UnleashedTuning.com
                          Ford/GM/Dodge/Chrysler/Jeep SCT Custom Calibrator
                          2005 Black Twin hairdryer Ford GT 1105rwhp / 954rwtq
                          2010 Roush Hammer 560rwhp / 522rwtq

                          Comment


                          • #14
                            Originally posted by KRC Tech
                            Troy, I installed 39lb injectors, (45-46 flow) and the MSD 2 bar map. I recalibrated the spark tables and fuel tables for idle and part throttle cruise easily. WOT is the easiest part, drivability takes the longest in my opinion. Very nice compared to running aux injectors or FMU's. Part throttle boost will be seamless.
                            I guess I am not following ya'll on this. So how exactly does the PCM read the 2bar MAP sensor? Is there extra coding in the Pro package software that allows the pcm to see the difference?

                            Troy

                            Comment


                            • #15
                              I believe the 3 bar sends a better signal vs the 1 bar. I put the 3 bar in( takes 5 seconds) and installed 36 lb injectors and truck registered and ran fine before I got it on the dyno. DIYautotune.com and order the gm 3 bar map sensor. It's like 60 bucks.

                              Comment

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