re. Stebro [was: 4kq Exhaust time]

[Ben Swann]

On Tuesday, March 26, 2002 9:20 AM, Marc Swanson
[SMTP:mswanson at mswanson.com] wrote:
> > There is a reason Stebro went with the 2.5 or so(forget exactly, but I
have
> > the specs somewhere).  They tested larger diameters on the 5000 Turbo
> > including 3".  They lost too much velocity in the system resulting in
> > drivability problems.
>
> I don't buy it.  I can believe this on an NA car which needs a certain
amount
> of backpressure, but on turbos all necessary backpressure is created by
the
> turbo.  To quote Corky Bell from his book Maximum Boost:    "The best
turbo
> exhaust system is no exhaust system at all".
>
>
> -Marc-
> 87 4ktq
> 88 90q
>
Mark,

I don't see how he can say that outright.  There are issues like resonance
and scavenging.  I believe this issue is addressed in VW performance and
tuning.  You can have too much of a good thing, especially if the car will
be driven on the street/real world conditions.  Yes I am talking about
turbo systems, where they discussed that in turbo systems and too large of
an exhaust could hurt, especially low end torque.

Of course I could be full of it and just recall seeing this, but usually I
remember these things.

I think the parameters of exhaust systems will change drastically when you
are designing for racing.

I wouldn't want to argue with an expert though.

Probably the Stebro is a good compromise for street/performance use.  Right
now the smallest diameter on the exhaust system in my 5ktq is the downpipe,
so I'd think that would be the next thing to address.

Ben