[urq] Wastegate "Chirp" is *not* a myth? So say the boys from UK and CAN
djdawson2 at aol.com
djdawson2 at aol.com
Sat Sep 15 20:45:25 PDT 2012
Guys,
I've had plenty of reasons to debate Scotty J in the past, and there's been more than a few times that we didn't see eye to eye.
But the thought that this is wastegate chirp? Seriously?
Think about this logically for a second. The WG only opens when the pressure in the exhaust manifold - between the head and the turbine - surpasses the WG spring's ability to hold it shut. This is typically wide open throttle, or close to it. Watch any of these videos, and it seems like it should be more than obvious that this is a lift-throttle phenomenon... not wide open.
My 930's WG noise is very obvious, and couldn't possibly be confused with compressor stall. The only thing is does is get plenty loud when it begins to open, as it vents to atmosphere through a small muffler. It continues to get louder as the rpm's build... sounds quite a lot like an exhaust leak on a NA engine.
When trying to fully understand the compressor surge I was experiencing using a GT3076R on my 2.2 20v, I too locked my WG shut by placing a solid object inside the WG cover such that it could not possibly open. I then tested VERY carefully to determine if my WG control had anything to do with my perceived surge issue. It did not. But more important to this discussion, my compressor still made that beautiful chirping sound as I lifted... no WG behavior was even possible.
BTW, worth noting that my intake consisted of a very large K&N inlet, flowing through 4 inch plumbing, through a "flow straightener" (suggested by the original UrS intake design), and into a Porsche 928 MAF. With this intake, all of this compressor noise was very noticeable, quite loud in fact... ask anyone who listened to Chad Clark scream that car around the Steamboat track.
As I progressed with this engine, I ditched the little OE Bosch BPV with a billet unit using 1 1/4 inch plumbing. This did reduce the chirp, but did not entirely eliminate it.
Long story short... I can't imagine how you guys could possibly think this is WG noise. The pressure spike after the throttle plate slaps shut ought to be enough evidence to convince anyone. I have not measured that spike, but every time I blew pressure hoses, it was when I lifted to shift gears.
Anyway... best of luck on this discussion.
Dave
-----Original Message-----
From: Scott Justusson <qshipq at aol.com>
To: urq <urq at audifans.com>
Sent: Sat, Sep 15, 2012 6:53 pm
Subject: Re: [urq] Wastegate "Chirp" is *not* a myth? So say the boys from UK and CAN
There was a time when I too thought compressor stall was wastegate flutter. I
found Ned was correct during a great beer discussion on this very topic many
years ago. On the suggestion of a well respected turbo builder several years
ago, I clamped a wastegate shut, and found the chirp (as heard in the group B
vid, and your vids) was compressor stall, nothing else. Then I took a 470whp
quattro and actually tested various 'leaks' (BOV, BPV, and respective boost
references to the WG/IM), and found everything in your video, and everything in
the group B vids, and attributed the chirps to compressor stall. Where I got
misled drinking the "myth Koolaid" many years back, is that *a compressor stall
event does not require a fully 'closed' throttle*. In fact, the bigger the
turbo and/or the smaller the engine, only a small amount of 'lift throttle'
creates the stall when under load.
When I tested this phenom, I used a Fluke meter with peak and hold memory
pressure guages mounted before and after the intercooler, and measured some
pretty impressive boost spikes. On the 470hp quattro, I also tested various
preloads of the largest adjustable HKS non-recirc BPV. With small changes in
preload, I could tune the compressor stall events, the amount of boost spike,
and the resulting sounds. Adding in 2 HKS BPV, I still measured compressor
stall pressure spikes of over 2:1 (PR:Boost spike) ratios on that engine
I'm sorry if I cut something off that you somehow think 'helped' you. I was
going to start down the road of the difference between BOV and a BPV, but
decided your videos both clearly demonstrate compressor stall events. Reprased:
"Your videos also ("too" - as along with the groupB vid) shows clearly
compressor stall events." Not "in addition to wastegate flutter", just
compressor stall events.
Sorry if it wasn't clear enough for you. If you would like to point me to
wastegate flutter events in the groupB vid or yours, please do reference the
video and a time base control for me to listen for them. I assure you, I have
the right video and audio equipment to decipher something even close.
Or, we could just look to the group B vid, ask Roland if this is what he was
speaking to, and call "compressor stall" what made those cool sounds. It's
unclear to me that you agree the 10min vid I referenced clearly demonstrates
compressor stall events by the dozens. If you agree, then we can move on to
your specific application and claims on your car, starting with the difference
between a BOV and BPV functions, respectively
Thanks for hangin in there Martin, I'm sure you and Phil can clarify your claims
better than you have.
Best Chirps from the Chicago stall
Scott J
-----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 4:25 pm
Subject: RE: [urq] Wastegate "Chirp" is *not* a myth? So say the boys from UK
and CAN
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]
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
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