Possible Boost Problems.. any ideas ??

[MR-GTI]

mmmmm interesting.. I have added a small filter to that hose that runs to the air box when i run the pod... and maybe that and running no DV has thrown a code.

All too weired for me , I might just try take the car back and see what they think.

Thanks again.

[Spec83]

That flutter is the air bouncing back and forward between the impeller wheel and the throttle body. This places a fair ammount of extra load on the turbo bearings / shaft (as ir almost forces the turbo to spin backwards) plus increases lag as the turbo slows to less RPM and takes longer to speed back up again

Just leave the stock DV on and forget about the wanky noise!!!!

[mozzzy_2000]

That flutter is the air bouncing back and forward between the impeller wheel and the throttle body. This places a fair ammount of extra load on the turbo bearings / shaft (as ir almost forces the turbo to spin backwards) plus increases lag as the turbo slows to less RPM and takes longer to speed back up again

Just leave the stock DV on and forget about the wanky noise!!!!

Yeah I was going to say what you are discribing is either turbo flutter or surging and the DV is actually meant to prevent it. I've just recently installed the APR R1 DV and the increase in performance over the stock DV is immense. Whilst my stock bosch DV was in perfect condition it is clear that its performance is sub par. The APR DV holds the boost far better through the gears and almost eliminates the turbo lag behind gear shifts and this has an overall effect of faster acceleration. It is very noticable.

[Kai]

That flutter is the air bouncing back and forward between the impeller wheel and the throttle body. This places a fair ammount of extra load on the turbo bearings / shaft (as ir almost forces the turbo to spin backwards) plus increases lag as the turbo slows to less RPM and takes longer to speed back up again

Just leave the stock DV on and forget about the wanky noise!!!!

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.

[MR-GTI]

Boys Boys boys..

I think a few of you have miss diagnosed the problem and are going off in another direction..

For the sake of not causing an argument I will give you some back ground.
I have been playing with cars for over 20yrs.
I know how a Turbo works and I know how and why flutter is created.
So I'm not ignorant..nor am I an inexperienced child..

The flutter has nothing to do with it..it will not stop the car from boosting and definitely will not make it drop off.

This is an uncomplicated issue... so one more time for the Dummies !!
The engine drops on and off boost when up in the rev range..
It was not there before never has been regardless of adding the Pod ect..but it is there now.. It has nothing to do with using a Pod filter or blocking off the DV..
Sure I agree maybe by blocking off the DV it might has played havoc with the air flow and sensors.. that's why I'm asking..
I'm thinking it might be possible that one of the mechanics that just serviced it might have accidentally disconnected or unplugged a vac line..

I have played and built many cars over the years, some being turboed, I have raced and owned cars that have run sub 11sec quarters.. so I would like to think I have more than 1/2 an idea about cars and their workings

I'll admit I'm not up to scratch with the new technology as I'm from the OLDSKOOL Blow Through and Suck through Turbo set ups, with carbies and simply fuel injection set ups..So yes I will admit I do not know everything...

All I'm saying is it is very easy to judge someone when you don't know the history or the facts, and I do not hold that again anyone.

So thank you all for you input and advice. I will sort this out and let those who don't think that I'm a 16yr old playing with a High tech cars, know the result.

Thanks.

Regs MR-GTI

[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!!!

--------------------

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