re. Stebro [was: 4kq Exhaust time]

[Robert Deis]

On Tue, 26 Mar 2002 auditude at get.net wrote:

> > 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.  3" is way too much they concluded
> > unless the car would be driven wide open all the time.

Curious- I know several 2.0 turbo drivers that use 3" with all-around
better performance than 2.5" systems.  Wonder why that is..

> I thought with a turbo, the less backpressure the better.

Correct.  The turbine itself provides all the back pressure you need for
off-boost performance.

Given the choice, running the turbine exhaust straight to atmosphere would
give you the best results, but that's normally not practical because of
noise and emmissions.

So, since you need a pipe for other reasons, you'd want to choose one that
causes the least impediment to the system- which again leads to "bigger is
better" up to the point where you lose so much flow velocity that the
exhaust gasses begin to cool, get more dense, and become difficult to push
through the pipe.

I'd expect a high-end hit, though, not a drivability hit- that's most
interesting...  Exhaust mechanics are deceptively complicated.

> What does the whole system include that the cat-back doesn't?  They provide high-
> flow cats?

Downpipe and test pipe, at least. Maybe cat instead of test pipe.

--
------------------------------------------------------------------------------
  Rob Deis                  "Let the people know beforehand what the law
  MiB3347                      is and what they are to expect."
  rdeis at io.com                              -- 18th Congress, Rec. 75