[urq] Wastegate "Chirp" is not a myth? So say the boys from UK and CAN

Sat Sep 15 13:40:19 PDT 2012

So what is then, wastegate flutter or compressor stall?  As per both of your
responces on this matter.  
Oh wait, you just conveniently erased it from the bottom.. ;)  Not to worry,
I added it back in for reference.
Can you make up your mind finally?  That coffee is not working....

Regards
Martin, chirping and fluttering apparently, must be getting old

  _____  

From: Scott Justusson [mailto:qshipq at aol.com] 
Sent: 15-Sep-12 11:54
To: martin at quattro.ca; urq at audifans.com
Subject: Re: [urq] Wastegate "Chirp" is *not* a myth? So say the boys from
UK and CAN

I guess this topic should have been on the trivia contest at urq25!  I say
'yuk' when I hear nonsense about turbo theory and operation.  You or the
laddie across the pond are welcome to write up a rebuttal to *any* accepted
tribute to this phenomenon.  I look forward to the Wiki correctlon too!  Use
the video I referenced, but I'll warn you it won't help!  It's so easy to
test this phenom without any pizzo(tm) electronic sensors, it becomes
nothing more than perpetuating a myth.

Martin, the BOV or BPV could be 200mm, and compressor stall will still be
measurable, and it's also audible in both your vids.  If this was indeed a
WG phenom, then you could change the sound by WG variables, boost profile,
WGFV application, wastegate size, wastegate exit, backpressure, etc.
Amazing when all those variables change, remove a bypass valve, and the
compressor stall will still be present and audible.  Try putting a
sound/heat shield on the WG, and make the same run....

Martin, you couldn't have this more wrong.  Come on out to Steamboat, we can
show you compressor stall in stock Scars (because of altitude and constant
tire load of low cf).  The videos you present on a closed test track, could
even look better! ;)

I hope you and the esteemed gent from the UK carry this on intensely, so we
can isolate the two dissenters on  the *only* forum on the net that gives
the impression that this wastegate chatter myth, may be in fact:  True?!  

Carry on...  Please!   My coffee is tasting better with some chuckles this
morning!

Scott "chipin' away in his junk urq's

-----Original Message-----
From: Martin Pajak <martin at quattro.ca>
To: 'Scott Justusson' <qshipq at aol.com>; urq <urq at audifans.com>
Sent: Sat, Sep 15, 2012 10:26 am
Subject: RE: [urq] Wastegate "Chirp"

I guess you can't read either, really Scott??  I have a 50mm Tial BOV
In my vid it is not from behind, but side.

Yuk is a word I would use when looking at your old blue '83..  ;)
It was for sale again not long ago.  Poor thing... someone should just put
it out of its misery.

Good luck with this thread, I'll just go out an drive my car, for real.

Regards
Martin

From: Scott Justusson [mailto:qshipq at aol.com] 
Sent: 15-Sep-12 10:39
To: martin at quattro.ca; urq at audifans.com
Subject: Re: [urq] Wastegate "Chirp" on Rally, SCCA and IMSA Race Cars

Yuk again. Your vid shows compressor stall too. Add more bypass valves, you
can make it go away, take the bypass valve out, you can increase the stall
sound. What most don't realize is that pressure spike under load is
*massive*, more than a 1in, 2in, and even 3in bypass valve can dump fast
enough to prevent some stall when the throttle slams shut. I've measured
peak spikes on a k2610vt in the 70-100psi range. That's gonna make a lotta
noise if you then take a 650hp S1 with a monster turbo, and slam the
throttle shut as it's ramping up, under load. 

Look at any groupB rally vid. You can never hear the sound from behind the
car, where the WG dumps, you ALWAYS hear it as the car comes at you. That's
because it's happening at the compressor side, not the exhaust. Take all
10minutes of that video below, and point me to WG 'chirp' or WG flutter. 

You guys are making my coffee taste funny, but appreciate the chuckles

Really Martin?! 

SJ

  _____  

From: Scott Justusson [mailto:qshipq at aol.com <mailto:qshipq at aol.com?> ] 
Sent: 15-Sep-12 10:00
To: martin at quattro.ca; urq at audifans.com
Subject: Re: [urq] Wastegate "Chirp" on Rally, SCCA and IMSA Race Cars

Yuk. Wastegate 'flutter' is not the 'chirp' being referred to. Wastegate
flutter (an open throttle pheonomenon) can't be heard on any rally car, even
if you left the WG exhaust open to atmo. Go :40sec into this vid, then tray
again at 5:50-6:10... Better yet, watch all 10 minutes and find an instance
of WG chatter, I sure couldn't do it. But I'm sure you guys know better.....
https://www.youtube.com/watch?v=ejIhA2UhfNA

Come on boys, I mean... Really!?!?

Scott 'chipin' J

-----Original Message-----
From: Martin Pajak <martin at quattro.ca>
To: phil <phil at isham-research.co.uk>; urq <urq at audifans.com>
Sent: Sat, Sep 15, 2012 8:26 am
Subject: Re: [urq] Wastegate "Chirp" on Rally, SCCA and IMSA Race Cars

Hi Phil,

Must be something to it, I have a stock wastegate, a big 50mm Tial dump

valve (setup with proper spring for nice pssssh, it is open at idle).

3071r turbo with mushroom HKS filter.  Yet I still get the chirping sound

from the exhaust side of the engine, in addition to the whoosh from the dump

(so I do not think it is a stall).  You can sort of hear it here, but it is

much better in real life.

 <http://www.youtube.com/watch?v=qIyj8El8jkA>
http://www.youtube.com/watch?v=qIyj8El8jkA

Cheers

Martin Pajak

 <http://www.quattro.ca/> http://www.quattro.ca 

1982 Audi Ur-quattro, SQ project

1983 Audi 80 quattro, Euro 2-Tür

1983 Audi Ur-quattro, Stock Helios Blue

1984 Audi Ur-quattro, 20vt with 6-speed

1993 Audi 90 CS quattro, 2.5 TDI with 6-speed

1993 Audi 80 quattro Avant, 2.5 TDI with 6-speed

-----Original Message-----

From:  <mailto:urq-bounces at audifans.com> urq-bounces at audifans.com [
<mailto:urq-bounces at audifans.com?> mailto:urq-bounces at audifans.com] On
Behalf

Of Phil Payne

Sent: 15-Sep-12 03:56

To: 'Scott Justusson';  <mailto:ub3ratl4sf00 at gmail.com>
ub3ratl4sf00 at gmail.com;  <mailto:koenigj at comcast.net> koenigj at comcast.net;

 <mailto:urq at audifans.com> urq at audifans.com

Subject: Re: [urq] Wastegate "Chirp" on Rally, SCCA and IMSA Race Cars

Well, here we go again.  I once had a long history of disagreeing with

Scott.

The chatter that I hear is almost always wastegate.  I've had Snap-off

piezo-electric microphones all over the engine bay and that's where it's

coming from.

However, I do very much agree with the problems that turbo stall can cause

on turbos - especially the K24.  What exacerbates this problem (in the UK)

is that the dominant turbo rebuilder ( <http://www.aet-turbos.co.uk/>
http://www.aet-turbos.co.uk/ - good

guys) won't accept a turbo with a broken shaft as an exchange item.  Having

seen them strip one, I can understand why.

I also agree with the comments about bypass valve capacity.

I've got other reservations.  Over here, Bailey is a dominant supplier of

bypass (and blow-off) valves, but their product has a non-linear opening

characteristic that I believe results in some back pressure before it opens.

The unit Audi fitted to the ur-quattro 20V (035 145 710) has a much smoother

opening profile but - as Scott implies - does have a restricted capacity.

Nevertheless - I do agree that fitting such a valve increases turbo lifetime

and is in general a very good, cheap and easily reversed modification.  For

most untweaked 10Vs I recommend the 20V part (number above) but do make sure

that you don't impede airflow over the turbo and exhaust manifold when you

fit it.

-----Original Message-----

From:  <mailto:urq-bounces at audifans.com> urq-bounces at audifans.com [
<mailto:urq-bounces at audifans.com?> mailto:urq-bounces at audifans.com] On
Behalf

Of Scott Justusson

Sent: 15 September 2012 04:22

To:  <mailto:ub3ratl4sf00 at gmail.com> ub3ratl4sf00 at gmail.com;
<mailto:koenigj at comcast.net> koenigj at comcast.net;  <mailto:urq at audifans.com>
urq at audifans.com

Subject: Re: [urq] Wastegate "Chirp" on Rally, SCCA and IMSA Race Cars

Except all WRC and ProRally urq's chattered, from day 1, btwitnessedt.

Read: Only the later cars had the recirc setup.  In the early cars and even

the reference below, it was not 'wastegate' chatter it was always compressor

stall from a turbo spooling up and the throttle slamming shut.  There were

no bypass valves in the early cars, so with big turbos, you heard the

compressor stall.  On Buffum's drives back in the early 80's, you would hear

that chirping 5 miinutes before you even saw the car.

We actually get a lot of it quite noticeable at Steamboat with the 20vt

k24's.  When I discussed it with Ned Ritchie years ago, we figured it was

the turbo working beyond the ability of the bypass valve to dump at altitude

(with tires on ice spinning up under load), that caused turbo stall.  If you

really like that noise, put a cone filter in place of the airbox, you will

hear compressor stall during street driving.  Or put a restrictor in the

bypass valve, or plug the bypass valve all together.

All that said, it's not a healthy noise for turbo longevity, especially on a

k24, btblewthat up at steamboat in my 10vt k24 urq.  That small shaft can't

take the thrust load of the stall.

Cheers, hey Roland, and my .02

Scott J

chirping 20vt 4kq cone filter

84 urq

83 urq

[urq] Wastegate "Chirp" is *not* a myth? So say the boys from UK and CAN

[urq] Wastegate "Chirp" is not a myth? So say the boys from UK and CAN