[BiturboS4] RE: Hesitation

Edwards, Dave Dave_Edwards at iOra.com
Thu Oct 24 19:10:11 EDT 2002

On Wed, 2002-10-23 at 16:45, California Fields wrote:

> in the gas pedal (like a turbo lag or something).  It's kind of hard
> to explain but does this sound normal?  Here's an example of the
> delayed
> response:  I'm cruising along in 3rd gear at about 3k rpm...I abruptly
> the throttle down from about 10% (cruising) to half way and hold it....the
> lurches forward with strong force but then the power backs off a
bit...kind of
> like there was an initial spike of pressure but then it equilibrates to a
> plateau of power (still accelerating strong but just not AS strong)...kind
> like I pulled back on the throttle when I really hadn't.  Is this a normal

I'd take a long, hard look at your bypass valves.

I was having the same symptoms on my stock S4 Avant; dealer said, "Oh, they
all do that after 15k miles or so..." Uh huh, sure. So I bought myself two
new bypass valves, installed them, and voila! The lumpy, irregular power
delivery is gone...

I'd imagine that the symptoms would be even more noticeable with a chipped
car and higher boost levels.


2001 S4 Avant 6spd

I agree - sounds like sticking valves. If you still have the stock Bosch
valves, get rid of them, like yesterday. I'll add two more points:

1) Don't expect a chipped car to be a smooth as a stock one. ECU mapping is
a compromise and you've gone for performance at the expense of some things.
2) If the chip is not mapped to cope with changes in the exhaust system then
indeed it can suffer, mainly by running too lean. This should not be much of
a problem with the cat-back (which IMO just changes the noise, not much
else), but certainly is with the full system.


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