[A4] A4 Digest, Vol 36, Issue 17

Brandon Rogers brogers at terrix.com
Mon Oct 30 12:05:38 EST 2006

I'm pretty sure the WG is _closed_ at idle so that as you accelerate you
can build boost (if it were open much of the exhaust gases would bypass
the turbo and you would not be able to build much boost), and as revs
climb and boost builds the WG starts to open to keep from overspinning
the turbo. And that said - Audi/VW use boost controllers in the form of
the WGFV - Waste Gate Frequency Valve.  Depending on the software you
have the ECU tells it when to keep the WG closed and when to open it up.

'84 urquattro 20Vt
'01.5 S4
'98 A4 1.8Tq

-----Original Message-----
From: a4-bounces at audifans.com [mailto:a4-bounces at audifans.com] On Behalf
Of Greg Megara
Sent: Thursday, October 26, 2006 9:00 AM
To: a4 at audifans.com
Subject: Re: [A4] A4 Digest, Vol 36, Issue 17

I don't have any experience with high altitude turbo engines, but I
thought this might be helpful: Turbo-prop aircraft generally
"turbo-normalize" their engines, meaning that the boost allows the
engine to operate as it would at sea level; there is no overboosting. If
you were to use a boost controller (I found someone who installed one in
an s4:
http://home.pacbell.net/gj_os/evcinstl.html) you may be able to do the
same thing on a ko4 1.8t engine in order to minimize lag. Cars usually
idle with the wastegate full open, being able to keep it slightly closed
to normalize the engine to sea-level conditions sounds like it would
minimize turbo lag to me.

Does that sound right to anyone?

I have a ko4 1.8t and it's balls to the wall fun. Get a good clutch to
go with it so you can dump on it, and you'll be in the low 6's for 0-60.
I also recommend a carbon-fiber hood---it reduces weight on the nose of
the car and taking corners feels more balanced with less understeer.



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