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AAN in T3 Syncro 16 - misfire above 10psi boost

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  • #61
    The test was done with the vacuum pipe fitted, at idle and with the engine off.

    The pump, good question! I specc'd it up for an Audi 4.2 V8 on a previous project that didn't get finished so it should be more than capable.

    Fuel lines, 8mm from the tank to the rail but as the tank is right in front of the engine, the line is only about 1 meter long.

    BOV valve I tested first before the MFTS was changed.

    If I'm seeing 22-23psi boost with the other ECU, why would we assume that I have a boost leak?

    I'll check to see if I'm getting WOT but I tested that when fitting the MFTS. Good to check it vagcom though.

    Altitude sensor is reading 1012. I remember checking that when I plugged in yesterday. No faults in the ECU.

    MG

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    • #62
      AFAIK the ECU does not reduce boost. You either get it or your don't and I believe the only two things that will cut boost (to spring pressure) are an overheat signal from the MFTS (this should not apply in your case with the AAN set-up) or if the ECU detects knock or a fault with the knock sensors. If your boost deviates from what is expected then you have a mechanical fault. Not knowing what boost should be expected (with your modified ECU) is only going to make it harder to trace a fault. So I would stick with standard software for now.
      Another reason not to use unknown software is that some bad tunes are known to defeat the standard safety routines like knock detection and fuel cut, (Superchips for example) and use modified wastegate spring pressure - not good

      I am really surprised you are not getting any fault codes at all. Are you sure the ECU is not being reset every time you turn the car off?

      You also mentioned before you had issues with the engine needing a long crank time to start when hot. Is that still a problem?
      Panthero Coupé quattro 20vt
      Indigo ABY coupé
      Imola B6 S4 Avant

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      • #63
        Also 22-23 psi sounds too much to me on stock fueling system.
        Panthero Coupé quattro 20vt
        Indigo ABY coupé
        Imola B6 S4 Avant

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        • #64
          Ok, I don't know what's good/bad re boost and I can do without killing the engine due to a bad chip set.

          Yes I still have the hot start issue. I have been meaning to wire in a delay to the fuel pump relay so that it continues to circulate the fuel for a couple of minutes after shutdown to try to lower the fuel temps... Not got to that yet.

          Wastegate diaphragm is good also, checked that a while ago.

          MG

          Comment


          • #65
            Originally posted by RS2 View Post
            Yes I still have the hot start issue. I have been meaning to wire in a delay to the fuel pump relay so that it continues to circulate the fuel for a couple of minutes after shutdown to try to lower the fuel temps... Not got to that yet.
            MG
            Not sure why you think that will solve a hot restart problem. In any event, setting up a circuit to do what you think you want. The OE AAN J17 fuel pump relay is only energized by the ECU when the engine is turning at greater than 13 RPM as measured by the G28 engine speed sensor.

            Click on the J17 label in the upper right corner of this live engine bay device map:

            http://members.shaw.ca/ajmills/UrS%2...ice%20Map.html

            RS2'd 93 UrS4 5 spd sedan
            94 UrS4 V8 6 spd manual avant

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            • #66
              Originally posted by RS2 View Post
              The test was done with the vacuum pipe fitted, at idle and with the engine off.
              MG
              If you have 3.95 bar fuel pressure at idle with the vac pipe connected it is too much as referenced by the figures I gave. I think the fuel pressure should drop approx 0.5 bar with the pipe connected to vac under the value with it off. So 3.95 bar is acceptable with vac pipe off and engine running but not with it fitted. So if thats the case it needs investigation. I know its only marginal but we are looking at all the litlle things that add up. Perhaps something as simple as a split pipe.
              Again another baseline is the wastegate spring. I cannot quite see if the cap has been modified or not. So if you disconnect the wgfv electrically by temporarily removing the connector you should be on mechanical boost of 0.4/0.5bar. If not and the wastegate is adjustable it will need tweaking back to the correct setting.
              Glad you are beginning to see the light about the chip set. Its a massive unkown to be honest. As really is the 551D chip set because it is intended for an auto and does have differences such as lower idle speed/lower rev limit etc and probably others we don't know about.. As we are trying to get the engine back to a known configuation its another issue. Its closer to stock but not ideal.
              Based on previous experience with another member, it wasn't until we saw pics of various engine plumbing that we were finally able to help because we noticed various components incorrectly installed because of a need to fit the engine in the space available. So I would double check things like the BOV and WGFV are correctly installed.
              Posting up the basic measurement blocks as we asked might also indicate issues. Block 4 is quite a critical one as its MAF related and needs to be within a certain range at idle or you get issues! A lot of them are related to idle parameters but there may be clues.
              You stil have not answered whether you have done the pressurised leak test which is the first port of call to find loost boost. There are numerous places where it can escape from twixt turbo and engine includng the infamous inject seat issues as an example. It would have also flagged up a split pipe to the FPR which of course is going to cause 2 issues if it exists. The first is incorrect fuel pressure under boost and a boost leak!
              Lastly I had a horrible thought that perhaps as we are dealing with a loom from an automatic that Audi in its wisdom could have wired up the MFTS as a safeguard unlike the manual which does not seem to use this. Its certaintly a posibility as the trans fluid cooler is incorporated into the rad so is doing double duty. Having only examined manual looms which do not have a wire, it certaintly a possibility that IF the wire is there on the auto loom that a faulty MFTS would restrict boost. Only you can answer that question and it would put that issue to bed.
              Last edited by twoqu; 12 December 2015, 21:29.

              Comment


              • #67
                Originally posted by UrS4boy View Post
                Not sure why you think that will solve a hot restart problem. In any event, setting up a circuit to do what you think you want. The OE AAN J17 fuel pump relay is only energized by the ECU when the engine is turning at greater than 13 RPM as measured by the G28 engine speed sensor.

                Click on the J17 label in the upper right corner of this live engine bay device map:

                http://members.shaw.ca/ajmills/UrS%2...ice%20Map.html

                Thanks for the info.

                I believe that the temperature in the engine bay is getting up enough that the fuel is being peculated in the fuel rail (so the hot starting issue is because the fuel pump is having to build up pressure again). My idea is that by allowing the fuel pump to continue to pump after the engine has run, it will cool the fuel and fuel rail as well.

                MG

                Comment


                • #68
                  Originally posted by twoqu View Post
                  ...Lastly I had a horrible thought that perhaps as we are dealing with a loom from an automatic that Audi in its wisdom could have wired up the MFTS as a safeguard unlike the manual which does not seem to use this. Its certaintly a posibility as the trans fluid cooler is incorporated into the rad so is doing double duty. Having only examined manual looms which do not have a wire, it certaintly a possibility that IF the wire is there on the auto loom that a faulty MFTS would restrict boost. Only you can answer that question and it would put that issue to bed.
                  Might be true. I only have manual transmission AAN electrical diagrams so I can NOT confirm or deny that possibility. The only two external connections that normally show for an AAN F76 MFTS are the coolant temp gauge and a link to the climate control head at T12d/11 which will shut off the A/C compressor if the coolant temp is too high in order to protect the engine from increased load and resulting elevated coolant temps.

                  F76 MFTS label on the right side of this live AAN engine bay device map for lots more info: http://members.shaw.ca/ajmills/UrS%2...ice%20Map.html
                  RS2'd 93 UrS4 5 spd sedan
                  94 UrS4 V8 6 spd manual avant

                  Comment


                  • #69
                    Originally posted by RS2 View Post
                    Thanks for the info.

                    I believe that the temperature in the engine bay is getting up enough that the fuel is being peculated in the fuel rail (so the hot starting issue is because the fuel pump is having to build up pressure again). My idea is that by allowing the fuel pump to continue to pump after the engine has run, it will cool the fuel and fuel rail as well.

                    MG
                    Or if there is no issue with the FPR vac pipe, a restriction in the return side pipework.

                    Comment


                    • #70
                      Originally posted by twoqu View Post
                      If you have 3.95 bar fuel pressure at idle with the vac pipe connected it is too much as referenced by the figures I gave. I think the fuel pressure should drop approx 0.5 bar with the pipe connected to vac under the value with it off. So 3.95 bar is acceptable with vac pipe off and engine running but not with it fitted. So if thats the case it needs investigation. I know its only marginal but we are looking at all the litlle things that add up. Perhaps something as simple as a split pipe.
                      Again another baseline is the wastegate spring. I cannot quite see if the cap has been modified or not. So if you disconnect the wgfv electrically by temporarily removing the connector you should be on mechanical boost of 0.4/0.5bar. If not and the wastegate is adjustable it will need tweaking back to the correct setting.
                      Glad you are beginning to see the light about the chip set. Its a massive unkown to be honest. As really is the 551D chip set because it is intended for an auto and does have differences such as lower idle speed/lower rev limit etc and probably others we don't know about.. As we are trying to get the engine back to a known configuation its another issue. Its closer to stock but not ideal.
                      Based on previous experience with another member, it wasn't until we saw pics of various engine plumbing that we were finally able to help because we noticed various components incorrectly installed because of a need to fit the engine in the space available. So I would double check things like the BOV and WGFV are correctly installed.
                      Posting up the basic measurement blocks as we asked might also indicate issues. Block 4 is quite a critical one as its MAF related and needs to be within a certain range at idle or you get issues! A lot of them are related to idle parameters but there may be clues.
                      You stil have not answered whether you have done the pressurised leak test which is the first port of call to find loost boost. There are numerous places where it can escape from twixt turbo and engine includng the infamous inject seat issues as an example. It would have also flagged up a split pipe to the FPR which of course is going to cause 2 issues if it exists. The first is incorrect fuel pressure under boost and a boost leak!
                      Lastly I had a horrible thought that perhaps as we are dealing with a loom from an automatic that Audi in its wisdom could have wired up the MFTS as a safeguard unlike the manual which does not seem to use this. Its certaintly a posibility as the trans fluid cooler is incorporated into the rad so is doing double duty. Having only examined manual looms which do not have a wire, it certaintly a possibility that IF the wire is there on the auto loom that a faulty MFTS would restrict boost. Only you can answer that question and it would put that issue to bed.
                      Hmmm, I took two photos when testing the fuel pressure. My phone has corrupted the first (which was taken when the engine was idling). The photo that I've posted up was from afterwards when the engine was off and I was checking that it held the pressure. From memory, the fuel pressure was slightly lower when it was running but I haven't written the figure down so the only way that I can check it is to test it again. It would make sense that the pressure level would be higher once the engine is off as the vacuum will go - essentially giving the same figures as the vacuum pipe being removed.

                      I have checked the vacuum pipes in the engine bay and they are either good or I've replaced them.

                      Yes, I have used the auto wiring loom, it's the only one that I had as the engine came from an auto car. I will pull off the plug from the MFTS and take a photo to see how many pins are in it.

                      Re boost check. No, I haven't carried out a boost check on the system. Everything is really jammed into the engine bay, it would taken me half a day to just pull it apart and get it back together....

                      You seem to be missing my point about boost. If the system can get up to 22-23psi, why do you think that it has a boost leak at 12psi?

                      I don't think that the original (auto) ECU is socketed. Maybe I should look out for a pair of standard S6 manual chips for that instead?... anyone got any?

                      MG

                      Comment


                      • #71
                        It can still make plenty of boost with a leak. A thorough leak test should be one of your first ports of call
                        Panthero Coupé quattro 20vt
                        Indigo ABY coupé
                        Imola B6 S4 Avant

                        Comment


                        • #72
                          Depending on the SW the ecu will continue to demand boost until it reaches the cut off. The fact that you can get a high figure does not rule out a leak as its easier for the turbo to spin against less restriction. Depending where the leak is will also have an impact. Its hard to comprehend that a boost leak can cause overboost. It also means that you are beating the turbo to death. Perhaps someone will come up with a better analogy.
                          Its really only the software that needs to be changed. These chips can be erased and reprogrammed. So thats not an issue. The problem is that in order to do this the chips need to be removed and the ecu socketed. I could probably do the erase and reprogramming for you BUT I need the OE chips. I would not be prepared to use the other chips in the modified ecu as I don't think the boost chip in particular is correct personally. Thats one option and will give you a stock manual ecu effectively with the possibility of using proven chips for the stock 2.5bar maps. Another alternative would be to see if someone like PRJ could fit the Motorola 4bar internal map sensor to the modified ecu and offer you a chip package to suit. Or find someone to fit the map sensor here and get PRJ to send the files to use. Then you will have a known chip set.
                          Basically you need to find someone with soldering skills!

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                          • #73
                            Originally posted by Error404 View Post
                            It can still make plenty of boost with a leak. A thorough leak test should be one of your first ports of call
                            Ok. I guess I'll be making up some tools to carry out a boost leak check... and find half a day somewhere.

                            MG

                            Comment


                            • #74
                              Originally posted by twoqu View Post
                              Depending on the SW the ecu will continue to demand boost until it reaches the cut off. The fact that you can get a high figure does not rule out a leak as its easier for the turbo to spin against less restriction. Depending where the leak is will also have an impact. Its hard to comprehend that a boost leak can cause overboost. It also means that you are beating the turbo to death. Perhaps someone will come up with a better analogy.
                              Its really only the software that needs to be changed. These chips can be erased and reprogrammed. So thats not an issue. The problem is that in order to do this the chips need to be removed and the ecu socketed. I could probably do the erase and reprogramming for you BUT I need the OE chips. I would not be prepared to use the other chips in the modified ecu as I don't think the boost chip in particular is correct personally. Thats one option and will give you a stock manual ecu effectively with the possibility of using proven chips for the stock 2.5bar maps. Another alternative would be to see if someone like PRJ could fitted the Motorola 4bar internal map sensor and offer you a chip package to suit.
                              Basically you need to find someone with soldering skills!
                              I've socketed ECUs before, that's not an issue. i just don't have another set of chips to fit to it.

                              MG

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                              • #75
                                Bit frustrating as I appreciate you need to keep using it.
                                Certaintly if you can scare up some stock chips and you can socket the ecu that at least gives you options. The chips that come out can then be used for the other ecu if you choose to get a decent known set up. Most reputable reprogrammers tend to use the OE chips as they are superior to domestic computer ones.
                                If we can get the correct manual SW in that stock ecu then personally I think thats a good thing.
                                I have just looked up the stock AAN boost levels which are dependent on altitude and outside temperature. Assuming you are not above 1600M then at 0C boost should be between 1.84-2.00bar absolute and at 20C 1.99bar -2.10 absolute. So as we are nearer the former its not that far out really.

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