boost gauge turbo flutter

[V8Sam]

hello guys,

done a bit of searching around and im not sure if its boost surge or flutter?

so i thought id start a fresh.

recently the car had an airtec intercooler fitted, as it turns out the battery was leaking over one of the older intercoolers causing a hole in it hence the boost leak. see previous posts.

how ever, ever since fitting it, as the car builds up boost as normal the gauge needle can be seen heading up to 20 psi (which it normally boost at) but then once its there it flutters up and down incredibly so the needle is just a blur hence the 'flutter' term im using.

you can hear it dumping at the equivalent rate of needle flutter, whilst this is happening the car really holds back on power.

occasionally it boosts up fine and it runs perfectly. infact it runs very well, and very powerful.

so, here is the question.

whats do you think could be causing this?

(unfortunately i cant do any logs as my laptop only runs whilst on mains power)

also, is this bad for the car? (silly question maybe?) obviously trying to stay off boost as much as possible, and that seems fine driving round town, but the car is needed. so no real choice.

 

[Stuart B]

DV Flutter - its usually a faulty Diverter Valve

 

[V8Sam]

faulty diverter valve? or the pipes that are to it? or both you think?

i think its a forge type one.

will try and take it out and plug it up see if it improves.

 

[GeorgieS3]

I would replace with the oem valve mate, I had this exact same problem.

 

[V8Sam]

can a oem one fit in badger 5 tip?

 

[Stuart B]

yes of course, Bill virtually demands we all use OEM types

maybe the spring is broken in your Forge DV don't they need servicing every year?

 

[V8Sam]

not sure?

might have a spare spring somewhere though now you reminded me.

ill look in the morning

 

[Stuart B]

You need silicon grease too and sometimes a piston if I remember rightly, but as others said just get a 710n or a 710p OEM DV. About £30 and will last for 10 years. The service kits are the same price.

 

[SHUk]

Try swooping the n75

 

[V8Sam]

Don’t have a spare n75.

Will try one of my forge Dv off my b5 s4 to see if that cures it.

If so I’ll go grab a oem one

 

[Vishal Tween]

I had a forge DV fitted to my K03 MK5 gti running stage 2+. Useless thing. When it was failing the car topped out at 155bhp on the dyno. The curve double dipped!

Swapped to Rev G and the car run sweet as a nut!

 

[nobbybonez]

same, had a forge one fluttering and changed for oem, all sorted.

 

[Alex C]

...the car builds up boost as normal the gauge needle can be seen heading up to 20 psi (which it normally boost at) but then once its there it flutters up and down incredibly so the needle is just a blur hence the 'flutter' term im using.

you can hear it dumping at the equivalent rate of needle flutter, whilst this is happening the car really holds back on power.

the boost gauge needle 'flutters' between what and what? 0psi to 20psi? 15psi? to 25psi?
has the DV valve been installed the wrong way around? some people like to do this...
does it still have the N249 valve?

don't take the DV out and plug it up - that'll damage the turbo

 

[V8Sam]

Between 18-22 ish.

Dv hasn’t been moved at all.

Why would you want to install it the wrong way round?

Infact how can you even install it wrong way round?

 

[Alex C]

? the valve has an inlet and an outlet - swap them around

http://forums.vwvortex.com/showthread.php?1358727-stock-diverter-valve-in-reverse-position

 

[desertstorm]

Is the turbo surging. If the intercooler has much better flow than the old one it may be allowing the turbo to surge. Does it start producing boost any sooner than before ?

 

[V8Sam]

Nope

Runs as normal
Untill boost is on

Then it flutters

If you are very gentle with the power it holds it to full boost with no problems.

But 8/10 times it flutters and the power stutters with it

Like I said will swap my b5s4 dv over at weekend if it stops I’ll get an oem one and keep you updated

 

[SHUk]

N75 valve

 

[V8Sam]

how would the n75 cause the stuttering?

also whats the benifit/point of running a dv in reverse?

 

[Stuart B]

Unplug the N75 and see if it still stutters, it will be low boost but might help highlight the area.

I think mostly myths and old wives tails, although I thought I could see some logic in it, being the pressure from the charge pipe is being diverted to the TIP, the flat faced bottom of the DV is facing that pressure rather than the side of the valve maybe the charge pipe pressure will open it quicker? Some people said it makes a nicer sound.

 

[SHUk]

N75 controls boost being the boost solenoid

 

[V8Sam]

little update on this.

changed dv over for a known working forge one, that came off my s4 same issue.

any other ideas floating about?

 

[superkarl]

Sounds like surge to me

 

[<tuffty/>]

If it's surge and not compressor stall then changing a dv will not help

<tuffty/>

 

[V8Sam]

so, are the symptoms of boost surge any different to what was mentioned? bearing in mind it only happens when on boost and not when letting off. which i would assume is when compressor stalling is normally heard.

how can you go about rectifying this? what would cause it to happen? just a new intercooler being fitted enough?

 

[<tuffty/>]

Fluttering under boost is generally surge.. . Fitting a fmic shouldn't cause it directly but it's plausible the increased flow capability could allow the engine to generate more airflow sooner and create surge

It maybe that your map needs a tweak to sort boost out to prevent surge

<tuffty/>

 

[V8Sam]

pretty much the conclusion we came to then.

not much info on the map its running as its was done a while ago. and by a previous owner.

 

[Stuart B]

I would try to change the N75 you can pick up a second hand one for a few quid.

 

[superkarl]

pretty much the conclusion we came to then.

not much info on the map its running as its was done a while ago. and by a previous owner.

There’s your problem

 

[V8Sam]

but never used to play up like this, since fitting the FMIC it has. so map tweek is looking like the option to go down.