08.09.2009 - 19:19
hi kodjo,
Thorsten gave an excellent description of an easy fault diagnosis. I remember that a similar case was discussed earlier in this forum, in the end it turned out to be a somehow faulty valve although it appeared to react like You described (and everybody would guess it would).
As far as I understand the working principle of the valve in a biturbo, there is some backpressure inside the valve created by the restrictor in R-position. This might work "against" the movement of the closing element initiated by the electronics. In fact, in a biturbo the pneumatic valve obviously does not stay closed until a certain pressure level is reached and then open but constantly beeing a little open, depending on the electronic signal and the pressure inside the valve.
Might well be, that either Your restrictor element is too small / too big or electronics imply an opening impulse for some reason.
Easiest way to check is to mount a second valve which is supposed to be working correctly. If not, Your electronic might detect some knocking or at least drives the valve opener as if the engine was knocking. With regards to the latter case, a check is more difficult. If both ECUs work, might be cabling or otherwise caused bad signaling to the valve. Worst case is to detect a faulty knock sensor, which I so far do not have a way to check apart from exchanging with a new one to check as the bloody thing [besides being almost impossible to reach within a running engine compartment] needs ground connection constantly.
cheers,
Veith
Thorsten gave an excellent description of an easy fault diagnosis. I remember that a similar case was discussed earlier in this forum, in the end it turned out to be a somehow faulty valve although it appeared to react like You described (and everybody would guess it would).
As far as I understand the working principle of the valve in a biturbo, there is some backpressure inside the valve created by the restrictor in R-position. This might work "against" the movement of the closing element initiated by the electronics. In fact, in a biturbo the pneumatic valve obviously does not stay closed until a certain pressure level is reached and then open but constantly beeing a little open, depending on the electronic signal and the pressure inside the valve.
Might well be, that either Your restrictor element is too small / too big or electronics imply an opening impulse for some reason.
Easiest way to check is to mount a second valve which is supposed to be working correctly. If not, Your electronic might detect some knocking or at least drives the valve opener as if the engine was knocking. With regards to the latter case, a check is more difficult. If both ECUs work, might be cabling or otherwise caused bad signaling to the valve. Worst case is to detect a faulty knock sensor, which I so far do not have a way to check apart from exchanging with a new one to check as the bloody thing [besides being almost impossible to reach within a running engine compartment] needs ground connection constantly.
cheers,
Veith
an später denken...steine schenken!!