Possible Boost Problems.. any ideas ??

[Spec83]

I wrote a large reply out to this. But deleted it. i cant be arsed. All i can say is learn how a turbo works. Thanks.

I don't see the issue...

Air goes through the system forced by the turbo... when the throttle body closes the turbo is still spinning thus it builds up air pressue behind the closed throttle body which can cause surging or boost spike (I am pretty sure this is what causes the 'flutter' sound) which is no good for the turbo as it slows it down and could possibly stall the wheel altogether... And sort of answers the OP's question!!!! The BOV in effect causes a 'closed loop' system where the same volume of air is circulated to both sides of the turbo, which does not cause a boost spike.

If this is not how a turbo / bov works then please enlighten me rather than throwing in a smart ass remake that solves nothing - If you went to the trouble of writing an essay then post the friggen thing and we might all learn something!!!

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Now... at full throttle sometimes I can feel my stock tune car surging (feels like the power goes off then on again very quickly) and like you it happens especially in second gear... This may have something to do with the way the ECU controls the N75 valve and what you are experienceing is the sudden turbo spool then the opening of the wastegate on the turbo as it's modulated by the ECU to control boost pressure. It is PI contol theroy - i've hit 11.2psi and my set point is 11psi so i'll open the wastegate - oppps now pressure is 10.5psi I have opened too much and I'll close it again.. They could have reset your ECU during the service and it may have to 'learn' the control loops over again or the ECU may be experiencing a condition it hasn't seen before and is learning how to correct for it...

As for removing the stock BOV, the VW engineers put it on there for a reason and I am sure they will know better than you what is good for their cars components - why would they waste money fitting it if it wasn't necessary?? Just don't start a "my turbo is f#$%@d and I don't know why" thread

[verbalhologram]

I have encountered a simlilar problem with the boost intermitently seeming to"lull"and then come back on,only does this every now and then.I thought maybe it had something to do with the stinking heat in sydney,but probably not.I think some of you guys have some made some good points ,dont let arguments detract from the sharing of POG info,
peace.

[Blitzen]

I have encountered a simlilar problem with the boost intermitently seeming to"lull"and then come back on,only does this every now and then.I thought maybe it had something to do with the stinking heat in sydney,but probably not.I think some of you guys have some made some good points ,dont let arguments detract from the sharing of POG info,
peace.

Did you find that the problem rectified itself if you turned it off, then started the car again?? This worked for me, but I only found that I had this problem when I had the BOV fitted...Never did it with the stock DV, and it did it both before and after the car was APR Tuned.

[verbalhologram]

Did you find that the problem rectified itself if you turned it off, then started the car again?? This worked for me, but I only found that I had this problem when I had the BOV fitted...Never did it with the stock DV, and it did it both before and after the car was APR Tuned.

Yep totally. If it started happening it would occur for most of the journey,but then I would stop and start te car again later and no problem???
Suppose if a few people have the drama maybe it is just a Polo quirk.I still enjoy the car immensly and haven't even got it chipped yet.

[MR-GTI]

Hey guys,

Thanks for the experiences and advice, just FYI I have contacted VW and they have heard of this issue before, but it's not all that common.
I will be taking the car to them in a week or so, I have also been told to disconnect the battery for 5-10 mins then connect it up and take it for a drive as this has cleared this type of fault and others...(apparently)
Maybe when the temp come down here in Sydney I might try a few things, as for now it will stay like that .TOO DAAM HOT HERE !!!

Regards MR-GTI

[Spec83]

Least they know it's a problem which is a start... Let us know how you go