S3 screeching turbo/ dump valve

[sirebank]

[img]images/graemlins/s3addict.gif[/img] Anybody experienced problems with their standard dump valve on a modified S3? Bought my chipped + Milltekked S3 from an Audi dealer. At revs between 3 to 3.5k there is a screeching from the engine which, I suspect, is the dump valve. I have taken the car back to Audi, who say the turbo is now outputting 2.78bar but the standard valve is only good for 2bar. However, has anyone experienced the screeching noise but found it was due to something other than the dump valve? [img]images/graemlins/audiS4black.gif[/img]

[wazza]

[img]images/graemlins/s3addict.gif[/img] turbo is now outputting 2.78bar

Are you sure? [img]images/graemlins/blush.gif[/img]

[sirebank]

When you say "Are you sure?" I presume you refer to the 2.78bar output. I am sure that it is the value they told me, I am not sure how they measured it/ how accurate it is. It is not a word of mouth error as the mechanic had written the value on the job sheet. [img]images/graemlins/confused.gif[/img] I take it from your question that this is quite a high value? What would you think was a reasonable value for a modified S3 engine? Thanks for your interest.

[S3Bangs]

I'd like to believe acceptable values would be between 1.3 - 1.8Bar.. [img]images/graemlins/nodder.gif[/img] , depending on the tuner.
2.78 seems a tad high tho! [img]images/graemlins/shocked.gif[/img]

[wazza]

If it is was running at 2.78 bar, I would be worried to drive the car [img]images/graemlins/crazy.gif[/img].
(is that the Big Bang theory Andy usually gets [img]images/graemlins/tung2.gif[/img])
As Tony said, a modded S3 is between 1.3 and 1.7 bar.

[sirebank]

Just had a chat with Kim Collins. Apparently, the value Audi is quoting is total pressure, not increase in pressure. [img]images/graemlins/blush.gif[/img] Therefore, pressure boost would be 1.78bar. Sounds a bit more plausible, doesn't it?
Anyway, anybody experienced the screeching noise, then?

[wazza]

Thank God for that [img]images/graemlins/blush.gif[/img]
And yes, my car (S4) has that screeching noise. It is booked in (again) next Tuesday.
The last two times I took the car in, the noise has not appeared on the test drive as it is intermittent.
Does yours happen all the time?

[DuncS3]

The screeching (on a S3) is IMO normally your airbox/induction system sucking in all that air as your hit boost (you mention 3-3.5K) - it is normal on chipped S3s, assuming we are talking about the same thing. If you had bought the car standard, you would of noticed the difference, i.e. didnt 'screech' before. I know mine does it and other chipped S3s do it to...The noise should be coming from the left hand engine bay if it is the same thing...

Dunc [img]images/graemlins/s3addict.gif[/img]

[wazza]

My S4 is standard and I can hear it.
I even had Mitch in the car once to listen to it and he said get it checked out [img]images/graemlins/nodder.gif[/img].

[sirebank]

Does yours happen all the time?

Yes, except when the engine is cold on a really cold morning (-2deg C), when I get noticably less boost pressure anyway.

A local tuner (not audi specialist) speculated that it could be the hose between air inlet and turbo, first distorting to oval as the engine warms up and then vibrating with a 'reed' effect. Sounds vaguely plausible - especially with regad to an intermittent fault. [img]images/graemlins/smirk.gif[/img]

[DuncS3]

Mine was chipped by APR (originally) and the screeching only happened after they done it (like a day later). I was a bit worried at first as it was a 'new' noise, until I went in an AMD chipped car which sounded exactly the same. It was actually SitaS3 who told me what it was..how he knows I dunno. Point about standard and chipped, was that when running more boost, you were sucking in more air, hence more noticeable...

Maybe some of the other chipped S3 people can comment, incase its different for them?

Dunc [img]images/graemlins/s3addict.gif[/img]

[sitas3]

how he knows I dunno.

I know because mine was/is doing the same. As you know Duncan, I complained many times about this, and was told by both AMD and Wayside Audi in MK that because of the extra boost pressure, this sucks more air in via the airbox, and the noise is a result of this. One thing you could check is the elephant trunk type hose that starts on the airbox and fastens onto the turbo - this can collapse on some cars that have been chipped and the solution is to place a sleeve inside near to the turbo end. This scenario is demonstrated in a captured film, on the forge website Here

Hope this helps..


BTW, Chipped S3's use DV's more.. My second is starting to go (not as bad as last time, but Warbling/chattering noise can sometimes be heard - unless there's a bird in my car somewhere [img]images/graemlins/confused.gif[/img] Two new DV's are now on order from VAGPARTS)