Help. Pulsating boost
11 August 2010, 09:41 PM
#31
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sorry about being slightly off topic, but could you do a quick log with the front O2 sensor being logged and idle speed steps please? i take it yours is pretty much standard and if it is I might be still having issues with mine, as your boosting higher than mine with the wastegate % being the same.
11 August 2010, 11:47 PM
#32
sorry about being slightly off topic, but could you do a quick log with the front O2 sensor being logged and idle speed steps please? i take it yours is pretty much standard and if it is I might be still having issues with mine, as your boosting higher than mine with the wastegate % being the same.
i know what its like when you want to get someting done, something else gets in the way! lol
12 August 2010, 10:53 PM
#35
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Steve, it's difficult to derive too much value from this log given that it's long, and also doesn't appear to have a sustained WOT acceleration run like in your video. There are only two points at which your foot is flat down, one of them only lasts a single sample (so around 0.12 seconds) and the other one two samples (so around 0.25 of a second). That isn't long enough to get a proper idea what's going on.
The only thing I can see is that from samples 8260 to 8291, you give it a bit, and there does appear to be a gentle overshoot - boost appearing to build normally and running over target, peaking at 14.6psi, with solenoid duty cycle seemingly being pulled to drop it back. Relatively mild overboost like that could simply be caused by the decat downpipe. However it is impossible to get a proper idea what's happening as you floor it very briefly (as above) and then trail the throttle back down. That being the case there's no way to tell whether the changes in solenoid duty cycle are being caused by the error correction system, or your foot.
As above it'd be easier to look at a log of a short full throttle acceleration run when you know the turbo is acting up. There's nothing in this one to illustrate it clearly enough.
Oh - incidentally, you might want to be a bit more selective/careful posting this kind of log in future, unless of course the little trip you took happened to be on your private test track. I think you know what I mean.
The only thing I can see is that from samples 8260 to 8291, you give it a bit, and there does appear to be a gentle overshoot - boost appearing to build normally and running over target, peaking at 14.6psi, with solenoid duty cycle seemingly being pulled to drop it back. Relatively mild overboost like that could simply be caused by the decat downpipe. However it is impossible to get a proper idea what's happening as you floor it very briefly (as above) and then trail the throttle back down. That being the case there's no way to tell whether the changes in solenoid duty cycle are being caused by the error correction system, or your foot.
As above it'd be easier to look at a log of a short full throttle acceleration run when you know the turbo is acting up. There's nothing in this one to illustrate it clearly enough.
Oh - incidentally, you might want to be a bit more selective/careful posting this kind of log in future, unless of course the little trip you took happened to be on your private test track. I think you know what I mean.
Last edited by Splitpin; 12 August 2010 at 10:55 PM.
12 August 2010, 11:11 PM
#36
Steve, it's difficult to derive too much value from this log given that it's long, and also doesn't appear to have a sustained WOT acceleration run like in your video. There are only two points at which your foot is flat down, one of them only lasts a single sample (so around 0.12 seconds) and the other one two samples (so around 0.25 of a second). That isn't long enough to get a proper idea what's going on.
The only thing I can see is that from samples 8260 to 8291, you give it a bit, and there does appear to be a gentle overshoot - boost appearing to build normally and running over target, peaking at 14.6psi, with solenoid duty cycle seemingly being pulled to drop it back. Relatively mild overboost like that could simply be caused by the decat downpipe. However it is impossible to get a proper idea what's happening as you floor it very briefly (as above) and then trail the throttle back down. That being the case there's no way to tell whether the changes in solenoid duty cycle are being caused by the error correction system, or your foot.
As above it'd be easier to look at a log of a short full throttle acceleration run when you know the turbo is acting up. There's nothing in this one to illustrate it clearly enough.
Oh - incidentally, you might want to be a bit more selective/careful posting this kind of log in future, unless of course the little trip you took happened to be on your private test track. I think you know what I mean.
The only thing I can see is that from samples 8260 to 8291, you give it a bit, and there does appear to be a gentle overshoot - boost appearing to build normally and running over target, peaking at 14.6psi, with solenoid duty cycle seemingly being pulled to drop it back. Relatively mild overboost like that could simply be caused by the decat downpipe. However it is impossible to get a proper idea what's happening as you floor it very briefly (as above) and then trail the throttle back down. That being the case there's no way to tell whether the changes in solenoid duty cycle are being caused by the error correction system, or your foot.
As above it'd be easier to look at a log of a short full throttle acceleration run when you know the turbo is acting up. There's nothing in this one to illustrate it clearly enough.
Oh - incidentally, you might want to be a bit more selective/careful posting this kind of log in future, unless of course the little trip you took happened to be on your private test track. I think you know what I mean.
If you look from time 977249 that is WOT and it was playing silly buggers at the time.
It was on a private test track
12 August 2010, 11:27 PM
#37
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Nuff said, thought so.. Hmmmm, at the sample with time index 977249, you are at 0.52v on the throttle sensor which is only just above idle, and there's a lot of part throttle-off-part-off stuff from there. The only point at which your throttle sensor says you are at WOT is as I mentioned above - rows 8259 and 8260 (time index 1030539). Then you immediately back off a little.
Are you saying you were actually at full throttle for the entire time?
. Hmmmm, at the sample with time index 977249, you are at 0.52v on the throttle sensor which is only just above idle, and there's a lot of part throttle-off-part-off stuff from there. The only point at which your throttle sensor says you are at WOT is as I mentioned above - rows 8259 and 8260 (time index 1030539). Then you immediately back off a little. Are you saying you were actually at full throttle for the entire time?
12 August 2010, 11:42 PM
#38
Nuff said, thought so.. Hmmmm, at the sample with time index 977249, you are at 0.52v on the throttle sensor which is only just above idle, and there's a lot of part throttle-off-part-off stuff from there. The only point at which your throttle sensor says you are at WOT is as I mentioned above - rows 8259 and 8260 (time index 1030539). Then you immediately back off a little.
Are you saying you were actually at full throttle for the entire time?
. Hmmmm, at the sample with time index 977249, you are at 0.52v on the throttle sensor which is only just above idle, and there's a lot of part throttle-off-part-off stuff from there. The only point at which your throttle sensor says you are at WOT is as I mentioned above - rows 8259 and 8260 (time index 1030539). Then you immediately back off a little. Are you saying you were actually at full throttle for the entire time?
The only thing i can do then is do another log and start it from the second im at WOT with it playing up.. (which i think is what you asked for in the first place) lol
20 August 2010, 12:01 AM
#40
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Indeedy. As I said via pm, low frequency boost oscillation. A few potential causes to look into and eliminate. Oil contamination of the boost control pipework and solenoid is the obvious. I think you've been there and done that already but it's something to double-check. Make sure the return pipe that goes from the solenoid to the inlet pipe is cleaned too.
Might also be worth taking the circlip off the wastegate actuator lever and making sure the wastegate opens and closes freely - that it isn't coked up, or sticking.
In addition, is all the boost control pipework the standard grey Subaru stuff or has any been replaced with aftermarket?
Finally, the other obvious thing to check is the diameter of the air restrictor in the pipe between the compressor actuator and tee piece. Standard MY99-00 should be 1.2mm (if I remember right, have got this wrong before!). Possible that a previous owner might have fitted a smaller one in an attempt to get a bit more boost. One of the downsides of that sort of mod is the sort of symptoms you are seeing. Buy a 1.2mm drill from a hardware store, get the restrictor out, clean it, and make sure the drill will pass through the hole. If not, use the drill to enlarge the bore.
Go through the above and let us know what you find.
Might also be worth taking the circlip off the wastegate actuator lever and making sure the wastegate opens and closes freely - that it isn't coked up, or sticking.
In addition, is all the boost control pipework the standard grey Subaru stuff or has any been replaced with aftermarket?
Finally, the other obvious thing to check is the diameter of the air restrictor in the pipe between the compressor actuator and tee piece. Standard MY99-00 should be 1.2mm (if I remember right, have got this wrong before!). Possible that a previous owner might have fitted a smaller one in an attempt to get a bit more boost. One of the downsides of that sort of mod is the sort of symptoms you are seeing. Buy a 1.2mm drill from a hardware store, get the restrictor out, clean it, and make sure the drill will pass through the hole. If not, use the drill to enlarge the bore.
Go through the above and let us know what you find.
21 August 2010, 12:52 PM
#42
Indeedy. As I said via pm, low frequency boost oscillation. A few potential causes to look into and eliminate. Oil contamination of the boost control pipework and solenoid is the obvious. I think you've been there and done that already but it's something to double-check. Make sure the return pipe that goes from the solenoid to the inlet pipe is cleaned too.
Might also be worth taking the circlip off the wastegate actuator lever and making sure the wastegate opens and closes freely - that it isn't coked up, or sticking.
In addition, is all the boost control pipework the standard grey Subaru stuff or has any been replaced with aftermarket?
Finally, the other obvious thing to check is the diameter of the air restrictor in the pipe between the compressor actuator and tee piece. Standard MY99-00 should be 1.2mm (if I remember right, have got this wrong before!). Possible that a previous owner might have fitted a smaller one in an attempt to get a bit more boost. One of the downsides of that sort of mod is the sort of symptoms you are seeing. Buy a 1.2mm drill from a hardware store, get the restrictor out, clean it, and make sure the drill will pass through the hole. If not, use the drill to enlarge the bore.
Go through the above and let us know what you find.
Might also be worth taking the circlip off the wastegate actuator lever and making sure the wastegate opens and closes freely - that it isn't coked up, or sticking.
In addition, is all the boost control pipework the standard grey Subaru stuff or has any been replaced with aftermarket?
Finally, the other obvious thing to check is the diameter of the air restrictor in the pipe between the compressor actuator and tee piece. Standard MY99-00 should be 1.2mm (if I remember right, have got this wrong before!). Possible that a previous owner might have fitted a smaller one in an attempt to get a bit more boost. One of the downsides of that sort of mod is the sort of symptoms you are seeing. Buy a 1.2mm drill from a hardware store, get the restrictor out, clean it, and make sure the drill will pass through the hole. If not, use the drill to enlarge the bore.
Go through the above and let us know what you find.
Right took all pipe work off again cleaned through with a non residue degreasing agent that i "borrowed" from work. There seemed to be slight oil contamination that came from the boost solenoid and from the inlet pipe. So i sorted all of that.
Then moved onto the the wastegate actuator lever, i was unable to move this freely with my hand. Couple of sprays of the degreaser around the pivot point and i could then move it. Reassembled everything and then went on the usual run i do when testing the car.
There is no longer any oscillation
. One thing i have noticed is that the peak boost is no longer 15 psi but 13. Correct me if im wrong but is that not the normal level of peak boost. So to finish off i believe that my problem is all sorted. I thank everyone for there input. Massive thanks to splitpin who went out of his way to research my problem.
21 August 2010, 03:33 PM
#43
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Nice one Steve, that sounds like a good result. 13-13.6psi or so should indeed be a normal held/peak boost for your car (dependent on gear and ambient temp) so on the face of it - and touching wood - seems like you've identified the cause. Although, thinking of Simonds1's thread, it's probably better to wait a little bit before breaking out the champagne! 
The other question now would be whether it was caused by the oil in the pipework, or the sticky wastegate, or a combination of both. If you do start to get a recurrence, would be worth doing only one or the other and going for a drive straight away and seeing if it's fixed.
Hopefully though it'll be something that you don't have to worry about for a while.
The other question now would be whether it was caused by the oil in the pipework, or the sticky wastegate, or a combination of both. If you do start to get a recurrence, would be worth doing only one or the other and going for a drive straight away and seeing if it's fixed.
Hopefully though it'll be something that you don't have to worry about for a while.
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