modified new s4 questions

[Brett Dikeman]

Can't offer any S4tt experience, but the question sounds general
enough that I think I can offer a little help....just take it with a
grain of salt :-)

  8:21 PM -0700 4/16/02, Brian O' wrote:

>anybody else out there have a tweeked s4 ?? i think we are having
>bov problems.
>  it seems to loose boost after letting off full throttle before
>entering a turn.

Blowoff valves, or bypass valves?  Big, important difference.  If
they're blowoff valves(sure sounds like it), yeah, you're going to
have all sorts of problems, like, oh, say, raw fuel getting dumped
into the exhaust; all that metered air going off into nowhere causes
super, super rich running, and the ECU may pick up on this and think
something is really wrong.  Blowoff valves have no business being on
anything except purpose-built racecars with custom ECUs, whole 9
yards...


>  it will reset itself after shutting it down and restarting. its got
>apr 93+100 2 stage chip, k+n cone intake, apr down pipes and test
>pipes, uuc ver 1 cat back, h+r supercup type coil overs and big reds
>in front. went to mid ohio over the weekend and it keep shutting
>down. i put the boost guage on it tonight and it pulls 12 lbs in 1-4
>and reaches about 14 in 5th and 6th, not that that matters in those
>gears !! i thought our old 1.8 a4 did 14 lbs in lower gears, 12 just
>does not seen right for the s4 with these mods, anyone ?? bueller ???

If the ECU is shutting the car down or limiting boost, something is
-very- wrong(never ignore this or continue to push the car!)...and
there should be a fault code stored.  If you're racing an S4 from a
serious standpoint, then I strongly suggest you get the VAG-COM
program+adapter...at $200, it's a steal if you already have a laptop,
for the kinds of information it can provide; if you don't have a
laptop, they can be had pretty cheaply on ebay and other places(it
doesn't take much to run VAG-COM.)  Even does logging...and there's a
LOT of accessible data in the ECUS of cars made in the last half
decade since ODB-II was introduced.

If you're running -bypass- valves and they are toasted(not uncommon
on the S4, as I'm sure you know), you stand a very good chance of
overspinning the turbos, -particularly- with a chip.  Muchos $$$, so
I wouldn't try to race or push the car hard until you figure out
what's going on with some detective work.

Bypass valves are easily tested by removing from the car and applying
a vacuum to the control port and seeing if it holds the vacuum;
release the vacuum, and try both blowing through both ports(should be
no leakage whatsoever) and pushing the valve open with your
finger(should be stiff resistance.)  If it fails any of these checks,
toss it.

Hope this helps.

Brett
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