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My second T4, operation de-chav

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  • Originally posted by rjhoy02 View Post
    The problem would be the position of the diff/driveshafts as the engine is canted over at a different angle in the T4 to a Volvo


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    I think it's doable.

    Fuckmuppetry & Bodge Award Winner

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    • Nothing is insurmountable! Just needs a bit of engineering guile


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      • There's plenty of that on here.


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        • My second T4, operation de-chav

          Originally posted by Activ8 View Post
          Yep AAN - Still.... its a beauty.... from Holsworthy (?) Dan , one question , what was the one biggest restriction to reaching 250 bhp you encountered?

          Fuckmuppetry & Bodge Award Winner
          There was no ONE big restriction more like LOTs of them lol, to name a few. Lack of knowledge around big power on T4s, sourcing hardware and mapping.

          Yeah definitely a beaut! His new one should be more interesting when done, yeah he’s couped up down here in South Devon as well.


          Sent from my iPhone using Just T4s

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          • Been working with my bits of T4, first job was to weld on the sections of chassis and floor that I cut off because I got a bit grinder happy with the original weight loss job

            Then welded a couple of legs in the form of 40mm box to the front of the chassis rails




            Then I managed to get the subframe into place and fitted back on - even stripped down it's a hefty lump of metal




            Now to weld the rest of the framework on....

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            • Good work !

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              • LOGRUN TIME!

                hooked the new PC up, despite vagcom running fine it would recognise the cable, maybe a windows 10 issue??

                dusted off the old XP laptop and grabbed fault codes first

                17964 - Charge Pressure Control: Negative Deviation
                P1556 - 35-10 - - - Intermittent
                17564 - Manifold Pressure Sensor (G71): Open/Short to Ground
                P1156 - 35-00 - -
                17569 - Manifold Temp Sensor (G72): Open or Short to Plus
                P1161 - 35-00 - -

                The pressure and temp sensor could well be me plugging stuff in a few weeks ago - so ignore.

                cleared codes and took a three log runs

                The first came back with decent data and the other two were empty. Got some odd figures in the first run though

                I was hoping to catch the van going into limp but I couldn't provoke it. Normally happens with full throttle, high revs and load.

                However, pottling back home and it goes into limp about 100 yds from home - so I grabbed the code

                17964 - Charge Pressure Control: Negative Deviation
                P1556 - 35-00 - -

                And so the logrun

                Click image for larger version

Name:	logrun 27 sep 2018.jpg
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Size:	101.4 KB
ID:	265747

                Why is the airmass fixed at 850?
                Why is the N75? fixed at 12.8
                And why are the wish/torque and smoke all saying 51?

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                • Originally posted by regcheeseman View Post
                  LOGRUN TIME!
                  However, pottling back home and it goes into limp about 100 yds from home - so I grabbed the code

                  17964 - Charge Pressure Control: Negative Deviation
                  P1556 - 35-00 - -

                  And so the logrun

                  [ATTACH=CONFIG]10499[/ATTACH]

                  Why is the airmass fixed at 850?
                  Why is the N75? fixed at 12.8
                  And why are the wish/torque and smoke all saying 51?
                  The boost actual against the map target was greater than the mapped tolerance allowed.

                  Airmass of 850 reported is the result of the airmass tables being mapped.

                  N75 at 12.8 is the maps reported and designed closure range. 12.8 to 95%.

                  51 is the throttle torque and smoke control maximums. At that point in time you maxxed out the limits.


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                  • Originally posted by Activ8 View Post
                    The boost actual against the map target was greater than the mapped tolerance allowed.

                    Airmass of 850 reported is the result of the airmass tables being mapped.

                    N75 at 12.8 is the maps reported and designed closure range. 12.8 to 95%.

                    51 is the throttle torque and smoke control maximums. At that point in time you maxxed out the limits.

                    So the limp was down to the N75 not doing enough?

                    Don't get what you mean about "850 reported is the result of the airmass tables being mapped."


                    Is the N75 just closed off then - up to 95%? Seems crude?

                    Maxxed out is a phrase I like.

                    And the airflow looks better than previous runs? Even though the boost isn't there - but we know why that is.

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                    • It looks quick to rev but all looks OK apart from the boost. It's got a lot more left in it but the N75 / actuation control is far from perfect and under boosting. Have you got a logrun where the top port is under pressure from the boost to compare?


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                      • So 'air mass calculated' - is that a volume/mass per rev? And therefore a constant based on engine swept volume?

                        And air mass actual a figure derived from flow past the MAF?

                        Should the figure then increase when boost arrives, is the increase constantly proportional to boost increase, or does the rate of increase fall as the boost rise – seem to remember something about lifting bag volume from my diving days.

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                        • My VCDS states mg/s where as yours displays mg/R? The 850 displayed is the result of making airmass mapping changes and not something I have written. BUT it's just a display and may be limited it could be worth locating the switch/factor used. 850 is the original figure and maximum axis number. There's nothing in the maps or switches that actually changes but something records the change.

                          Yes, MAF flow rate.

                          Yes, actuator or N75 mods can change the airflow. Unsure whether it's a linear increase as other factors are at play, temp being the main one but it does relate to the boost.

                          Last edited by Activ8; 28 September 2018, 12:05 PM.

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                          • Originally posted by Activ8 View Post
                            My VCDS states mg/s where as yours displays mg/R?
                            Surely if it was mg per sec and plotted with revs then it would increase as the double the revs per minute would mean double the air given air pressure remains constant.

                            Whilst mg per rev when plotted against revs would be a constant.



                            Finished my six-speed conversion/big turbo manifold jig.

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                            • Originally posted by regcheeseman View Post
                              Surely if it was mg per sec and plotted with revs then it would increase as the double the revs per minute would mean double the air given air pressure remains constant.

                              Whilst mg per rev when plotted against revs would be a constant.



                              Finished my six-speed conversion/big turbo manifold jig.

                              My VCDS display is mg/stroke not second but the ECU / maps calculate the airmass in kg/Hour.

                              Love the jig.



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                              • Originally posted by rjhoy02 View Post
                                The problem would be the position of the diff/driveshafts as the engine is canted over at a different angle in the T4 to a Volvo


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                                Ah, see i wasnt thinking gearbox. I was thinking 2.5 20v turbo engne 😆

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